Merge branch 'main', update to changes

The regular confirmation prompt is shown then with a "Save modified
project settings" checkbox.

release/datafiles/userdef/userdef_default_theme.c

@@ -899,6 +899,33 @@ const bTheme U_theme_default = {
     .outline_width = 1,
     .facedot_size = 4,
   },
+  .space_project_settings = {
+    .back = RGBA(0x30303000),
+    .title = RGBA(0xeeeeeeff),
+    .text = RGBA(0xe6e6e6ff),
+    .text_hi = RGBA(0xffffffff),
+    .header = RGBA(0x303030b3),
+    .header_text = RGBA(0xeeeeeeff),
+    .header_text_hi = RGBA(0xffffffff),
+    .tab_active = RGBA(0x303030ff),
+    .tab_inactive = RGBA(0x1d1d1dff),
+    .tab_back = RGBA(0x181818ff),
+    .tab_outline = RGBA(0x3d3d3dff),
+    .button = RGBA(0x1d1d1dff),
+    .button_title = RGBA(0xffffffff),
+    .button_text = RGBA(0xccccccff),
+    .button_text_hi = RGBA(0xffffffff),
+    .navigation_bar = RGBA(0x303030ff),
+    .execution_buts = RGBA(0x303030ff),
+    .panelcolors = {
+      .header = RGBA(0x3d3d3dff),
+      .back = RGBA(0x3d3d3dff),
+      .sub_back = RGBA(0x0000001f),
+    },
+    .vertex_size = 3,
+    .outline_width = 1,
+    .facedot_size = 4,
+  },
   .space_console = {
     .back = RGBA(0x1d1d1d00),
     .title = RGBA(0xeeeeeeff),

release/scripts/presets/interface_theme/Blender_Light.xml

@@ -1160,6 +1160,40 @@
         </space>
       </ThemePreferences>
     </preferences>
+    <project_settings>
+      <ThemeProjectSettings>
+        <space>
+          <ThemeSpaceGeneric
+            back="#b3b3b3"
+            title="#181818"
+            text="#000000"
+            text_hi="#ffffff"
+            header="#b3b3b3ff"
+            header_text="#000000"
+            header_text_hi="#ffffff"
+            button="#7272727f"
+            button_title="#000000"
+            button_text="#000000"
+            button_text_hi="#000000"
+            navigation_bar="#b3b3b3ff"
+            execution_buts="#b3b3b3ff"
+            tab_active="#6697e6"
+            tab_inactive="#535353"
+            tab_back="#404040ff"
+            tab_outline="#3c3c3c"
+            >
+            <panelcolors>
+              <ThemePanelColors
+                header="#b3b3b300"
+                back="#a3a3a3cc"
+                sub_back="#00000024"
+                >
+              </ThemePanelColors>
+            </panelcolors>
+          </ThemeSpaceGeneric>
+        </space>
+      </ThemeProjectSettings>
+    </project_settings>
     <console>
       <ThemeConsole
         line_output="#71a8ff"

release/scripts/startup/bl_ui/__init__.py

@@ -70,6 +70,7 @@ _modules = [
     "space_nla",
     "space_node",
     "space_outliner",
+    "space_project_settings",
     "space_properties",
     "space_sequencer",
     "space_spreadsheet",

release/scripts/startup/bl_ui/space_project_settings.py

@@ -0,0 +1,212 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+import bpy
+from bpy.types import Header, Menu, Panel
+from bpy.app.translations import pgettext_iface as iface_
+from bl_ui.utils import CenterAlignMixIn
+
+
+# -----------------------------------------------------------------------------
+# Main Header
+
+class PROJECTSETTINGS_HT_header(Header):
+    bl_space_type = 'PROJECT_SETTINGS'
+
+    @staticmethod
+    def draw_buttons(layout, context):
+        project = context.project
+
+        layout.operator_context = 'EXEC_AREA'
+
+        is_dirty = project and project.is_dirty
+
+        # Show '*' to let users know the settings have been modified.
+        layout.operator(
+            "project.save_settings",
+            text=iface_("Save Settings") + (" *" if is_dirty else ""),
+            translate=False,
+        )
+
+    def draw(self, context):
+        layout = self.layout
+        layout.operator_context = 'EXEC_AREA'
+
+        layout.template_header()
+
+        PROJECTSETTINGS_MT_editor_menus.draw_collapsible(context, layout)
+
+        layout.separator_spacer()
+
+        self.draw_buttons(layout, context)
+
+
+# -----------------------------------------------------------------------------
+# Main Navigation Bar
+
+class PROJECTSETTINGS_PT_navigation_bar(Panel):
+    bl_label = "Project Settings Navigation"
+    bl_space_type = 'PROJECT_SETTINGS'
+    bl_region_type = 'NAVIGATION_BAR'
+    bl_options = {'HIDE_HEADER'}
+
+    def draw(self, context):
+        layout = self.layout
+
+        space_data = context.space_data
+        project = context.project
+
+        col = layout.column()
+        col.enabled = project is not None
+
+        col.scale_x = 1.3
+        col.scale_y = 1.3
+        col.prop(space_data, "active_section", expand=True)
+
+
+class PROJECTSETTINGS_MT_editor_menus(Menu):
+    bl_idname = "PROJECTSETTINGS_MT_editor_menus"
+    bl_label = ""
+
+    def draw(self, _context):
+        layout = self.layout
+        layout.menu("PROJECTSETTINGS_MT_view")
+
+
+class PROJECTSETTINGS_MT_view(Menu):
+    bl_label = "View"
+
+    def draw(self, _context):
+        layout = self.layout
+
+        layout.menu("INFO_MT_area")
+
+
+class PROJECTSETTINGS_MT_advanced_operations(Menu):
+    bl_label = "Advanced Project Settings Operations"
+
+    def draw(self, _context):
+        layout = self.layout
+
+        layout.operator("project.delete_setup")
+
+
+class PROJECTSETTINGS_PT_save_project_settings(Panel):
+    bl_label = "Save Project Settings"
+    bl_space_type = 'PROJECT_SETTINGS'
+    bl_region_type = 'EXECUTE'
+    bl_options = {'HIDE_HEADER'}
+
+    @classmethod
+    def poll(cls, context):
+        # Hide when header is visible
+        for region in context.area.regions:
+            if region.type == 'HEADER' and region.height <= 1:
+                return True
+
+        return False
+
+    def draw(self, context):
+        layout = self.layout.row()
+        layout.operator_context = 'EXEC_AREA'
+
+        layout.menu("PROJECTSETTINGS_MT_advanced_operations", text="", icon='COLLAPSEMENU')
+
+        PROJECTSETTINGS_HT_header.draw_buttons(layout, context)
+
+
+class PROJECTSETTINGS_PT_no_project(Panel):
+    bl_space_type = 'PROJECT_SETTINGS'
+    bl_region_type = 'WINDOW'
+    # Special hardcoded context.
+    bl_context = "no_project"
+    bl_label = "No Project"
+    bl_options = {'HIDE_HEADER'}
+
+    @classmethod
+    def poll(cls, context):
+        return (context.project is None)
+
+    def draw(self, context):
+        layout = self.layout
+
+        layout.label(text="No active project.", icon='INFO')
+        col = layout.column(align=True)
+        col.label(text="Open/store a file inside of a project directory, or set up a new project")
+        col.label(text="by choosing a project directory.")
+
+        row = layout.row()
+        split = row.split(factor=0.3)
+        split.operator("project.new", text="Set up Project...")
+
+
+class PROJECTSETTINGS_PT_setup(CenterAlignMixIn, Panel):
+    bl_space_type = 'PROJECT_SETTINGS'
+    bl_region_type = 'WINDOW'
+    bl_context = "general"
+    bl_label = "Setup"
+    bl_options = {'HIDE_HEADER'}
+
+    def draw_centered(self, context, layout):
+        project = context.project
+
+        layout.prop(project, "name")
+        layout.prop(project, "root_path", text="Location")
+
+
+class PROJECTSETTINGS_PT_asset_libraries(Panel):
+    bl_space_type = 'PROJECT_SETTINGS'
+    bl_region_type = 'WINDOW'
+    bl_context = "asset_libraries"
+    bl_label = "Asset Libraries"
+
+    def draw(self, context):
+        layout = self.layout
+        layout.use_property_split = False
+        layout.use_property_decorate = False
+
+        project = context.project
+
+        box = layout.box()
+        split = box.split(factor=0.35)
+        name_col = split.column()
+        path_col = split.column()
+
+        row = name_col.row(align=True)  # Padding
+        row.separator()
+        row.label(text="Name")
+
+        row = path_col.row(align=True)  # Padding
+        row.separator()
+        row.label(text="Path")
+
+        for i, library in enumerate(project.asset_libraries):
+            row = name_col.row()
+            row.alert = not library.name
+            row.prop(library, "name", text="")
+
+            row = path_col.row()
+            subrow = row.row()
+            subrow.alert = not library.path
+            subrow.prop(library, "path", text="")
+            row.operator("project.custom_asset_library_remove", text="", icon='X', emboss=False).index = i
+
+        row = box.row()
+        row.alignment = 'RIGHT'
+        row.operator("project.custom_asset_library_add", text="", icon='ADD', emboss=False)
+
+
+classes = (
+    PROJECTSETTINGS_HT_header,
+    PROJECTSETTINGS_MT_editor_menus,
+    PROJECTSETTINGS_MT_view,
+    PROJECTSETTINGS_MT_advanced_operations,
+    PROJECTSETTINGS_PT_navigation_bar,
+    PROJECTSETTINGS_PT_save_project_settings,
+    PROJECTSETTINGS_PT_no_project,
+    PROJECTSETTINGS_PT_setup,
+    PROJECTSETTINGS_PT_asset_libraries,
+)
+
+if __name__ == "__main__":  # only for live edit.
+    from bpy.utils import register_class
+    for cls in classes:
+        register_class(cls)

release/scripts/startup/bl_ui/space_topbar.py

@@ -278,6 +278,10 @@ class TOPBAR_MT_file(Menu):
         layout.operator("wm.revert_mainfile")
         layout.menu("TOPBAR_MT_file_recover")
 
+        if context.preferences.experimental.use_blender_projects:
+            props = layout.operator("project.new", text="Set up Project...")
+            props.open_settings_after = True
+
         layout.separator()
 
         layout.operator_context = 'EXEC_AREA' if context.blend_data.is_saved else 'INVOKE_AREA'
@@ -629,6 +633,8 @@ class TOPBAR_MT_edit(Menu):
 
         layout.separator()
 
+        if context.preferences.experimental.use_blender_projects:
+            layout.operator("screen.project_settings_show", text="Project Settings...")
         layout.operator("screen.userpref_show",
                         text="Preferences...", icon='PREFERENCES')
 
@@ -735,7 +741,7 @@ class TOPBAR_MT_help(Menu):
 class TOPBAR_MT_file_context_menu(Menu):
     bl_label = "File Context Menu"
 
-    def draw(self, _context):
+    def draw(self, context):
         layout = self.layout
 
         layout.operator_context = 'INVOKE_AREA'
@@ -754,6 +760,8 @@ class TOPBAR_MT_file_context_menu(Menu):
 
         layout.separator()
 
+        if context.preferences.experimental.use_blender_projects:
+            layout.operator("screen.project_settings_show", text="Project Settings...")
         layout.operator("screen.userpref_show",
                         text="Preferences...", icon='PREFERENCES')
 

release/scripts/startup/bl_ui/space_userpref.py

@@ -10,6 +10,7 @@ from bpy.app.translations import (
     pgettext_iface as iface_,
     pgettext_tip as tip_,
 )
+from bl_ui.utils import CenterAlignMixIn
 
 
 # -----------------------------------------------------------------------------
@@ -147,40 +148,6 @@ class USERPREF_PT_save_preferences(Panel):
         USERPREF_HT_header.draw_buttons(layout, context)
 
 
-# -----------------------------------------------------------------------------
-# Min-In Helpers
-
-# Panel mix-in.
-class CenterAlignMixIn:
-    """
-    Base class for panels to center align contents with some horizontal margin.
-    Deriving classes need to implement a ``draw_centered(context, layout)`` function.
-    """
-
-    def draw(self, context):
-        layout = self.layout
-        width = context.region.width
-        ui_scale = context.preferences.system.ui_scale
-        # No horizontal margin if region is rather small.
-        is_wide = width > (350 * ui_scale)
-
-        layout.use_property_split = True
-        layout.use_property_decorate = False  # No animation.
-
-        row = layout.row()
-        if is_wide:
-            row.label()  # Needed so col below is centered.
-
-        col = row.column()
-        col.ui_units_x = 50
-
-        # Implemented by sub-classes.
-        self.draw_centered(context, col)
-
-        if is_wide:
-            row.label()  # Needed so col above is centered.
-
-
 # -----------------------------------------------------------------------------
 # Interface Panels
 
@@ -1290,6 +1257,10 @@ class ThemeGenericClassGenerator:
             if theme_area.identifier in {'USER_INTERFACE', 'STYLE', 'BONE_COLOR_SETS'}:
                 continue
 
+            prefs = bpy.context.preferences
+            if not prefs.experimental.use_blender_projects and theme_area.identifier == 'PROJECT_SETTINGS':
+                continue
+
             panel_id = "USERPREF_PT_theme_" + theme_area.identifier.lower()
             # Generate panel-class from theme_area
             yield type(panel_id, (PreferenceThemeSpacePanel, ThemePanel, Panel), {
@@ -2348,6 +2319,7 @@ class USERPREF_PT_experimental_prototypes(ExperimentalPanel, Panel):
                 ({"property": "use_full_frame_compositor"}, ("blender/blender/issues/88150", "#88150")),
                 ({"property": "enable_eevee_next"}, ("blender/blender/issues/93220", "#93220")),
                 ({"property": "enable_workbench_next"}, ("blender/blender/issues/101619", "#101619")),
+                ({"property": "use_blender_projects"}, None),
             ),
         )
 

release/scripts/startup/bl_ui/utils.py

@@ -36,3 +36,40 @@ class PresetPanel:
         layout.operator_context = 'EXEC_DEFAULT'
 
         Menu.draw_preset(self, context)
+
+
+# -----------------------------------------------------------------------------
+# Mix-In Helpers
+
+# Panel mix-in.
+class CenterAlignMixIn:
+    """
+    Base class for panels to center align contents with some horizontal margin.
+    Deriving classes need to implement a ``draw_centered(context, layout)`` function.
+
+    Used by Preferences and Project Settings, and optimized for their display. May not work that
+    well in other cases.
+    """
+
+    def draw(self, context):
+        layout = self.layout
+        width = context.region.width
+        ui_scale = context.preferences.system.ui_scale
+        # No horizontal margin if region is rather small.
+        is_wide = width > (350 * ui_scale)
+
+        layout.use_property_split = True
+        layout.use_property_decorate = False  # No animation.
+
+        row = layout.row()
+        if is_wide:
+            row.label()  # Needed so col below is centered.
+
+        col = row.column()
+        col.ui_units_x = 50
+
+        # Implemented by sub-classes.
+        self.draw_centered(context, col)
+
+        if is_wide:
+            row.label()  # Needed so col above is centered.

source/blender/asset_system/intern/asset_library.cc

@@ -12,8 +12,8 @@
 #include "AS_asset_library.hh"
 #include "AS_asset_representation.hh"
 
+#include "BKE_asset_library_custom.h"
 #include "BKE_main.h"
-#include "BKE_preferences.h"
 
 #include "BLI_fileops.h"
 #include "BLI_path_util.h"
@@ -74,8 +74,8 @@ std::string AS_asset_library_root_path_from_library_ref(
 std::string AS_asset_library_find_suitable_root_path_from_path(
     const blender::StringRefNull input_path)
 {
-  if (bUserAssetLibrary *preferences_lib = BKE_preferences_asset_library_containing_path(
-          &U, input_path.c_str())) {
+  if (CustomAssetLibraryDefinition *preferences_lib = BKE_asset_library_custom_containing_path(
+          &U.asset_libraries, input_path.c_str())) {
     return preferences_lib->path;
   }
 
@@ -267,15 +267,17 @@ Vector<AssetLibraryReference> all_valid_asset_library_refs()
     result.append(library_ref);
   }
   int i;
-  LISTBASE_FOREACH_INDEX (const bUserAssetLibrary *, asset_library, &U.asset_libraries, i) {
+  LISTBASE_FOREACH_INDEX (
+      const CustomAssetLibraryDefinition *, asset_library, &U.asset_libraries, i) {
     if (!BLI_is_dir(asset_library->path)) {
       continue;
     }
     AssetLibraryReference library_ref{};
     library_ref.custom_library_index = i;
-    library_ref.type = ASSET_LIBRARY_CUSTOM;
+    library_ref.type = ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES;
     result.append(library_ref);
   }
+  /* TODO project libraries */
 
   AssetLibraryReference library_ref{};
   library_ref.custom_library_index = -1;

source/blender/asset_system/intern/asset_library_service.cc

@@ -4,9 +4,14 @@
  * \ingroup asset_system
  */
 
-#include "BKE_blender.h"
-#include "BKE_preferences.h"
+#include <memory>
+#include <string>
 
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender.h"
+#include "BKE_blender_project.h"
+
+#include "BLI_path_util.h"
 #include "BLI_string_ref.hh"
 
 #include "DNA_asset_types.h"
@@ -82,8 +87,9 @@ AssetLibrary *AssetLibraryService::get_asset_library(
     }
     case ASSET_LIBRARY_ALL:
       return get_asset_library_all(bmain);
-    case ASSET_LIBRARY_CUSTOM: {
-      bUserAssetLibrary *custom_library = find_custom_asset_library_from_library_ref(
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES:
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT: {
+      CustomAssetLibraryDefinition *custom_library = find_custom_asset_library_from_library_ref(
           library_reference);
       if (!custom_library) {
         return nullptr;
@@ -199,29 +205,81 @@ AssetLibrary *AssetLibraryService::get_asset_library_all(const Main *bmain)
   return all_library_.get();
 }
 
-bUserAssetLibrary *AssetLibraryService::find_custom_asset_library_from_library_ref(
+CustomAssetLibraryDefinition *AssetLibraryService::find_custom_asset_library_from_library_ref(
     const AssetLibraryReference &library_reference)
 {
-  BLI_assert(library_reference.type == ASSET_LIBRARY_CUSTOM);
+  BLI_assert(ELEM(library_reference.type,
+                  ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES,
+                  ASSET_LIBRARY_CUSTOM_FROM_PROJECT));
   BLI_assert(library_reference.custom_library_index >= 0);
 
-  return BKE_preferences_asset_library_find_from_index(&U, library_reference.custom_library_index);
+  switch (eAssetLibraryType(library_reference.type)) {
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES: {
+      return BKE_asset_library_custom_find_from_index(&U.asset_libraries,
+                                                      library_reference.custom_library_index);
+    }
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT: {
+      BlenderProject *project = BKE_project_active_get();
+      if (!project) {
+        return NULL;
+      }
+
+      ListBase *project_libraries = BKE_project_custom_asset_libraries_get(project);
+      return BKE_asset_library_custom_find_from_index(project_libraries,
+                                                      library_reference.custom_library_index);
+    }
+    case ASSET_LIBRARY_ALL:
+    case ASSET_LIBRARY_LOCAL:
+    case ASSET_LIBRARY_ESSENTIALS:
+      break;
+  }
+
+  BLI_assert_unreachable();
+  return NULL;
 }
 
 std::string AssetLibraryService::root_path_from_library_ref(
     const AssetLibraryReference &library_reference)
 {
-  if (ELEM(library_reference.type, ASSET_LIBRARY_ALL, ASSET_LIBRARY_LOCAL)) {
-    return "";
+  switch (eAssetLibraryType(library_reference.type)) {
+    case ASSET_LIBRARY_ALL:
+    case ASSET_LIBRARY_LOCAL:
+    case ASSET_LIBRARY_ESSENTIALS:
+      return "";
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES: {
+      CustomAssetLibraryDefinition *user_library = find_custom_asset_library_from_library_ref(
+          library_reference);
+      if (!user_library) {
+        return "";
+      }
+
+      return user_library->path;
+    }
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT: {
+      CustomAssetLibraryDefinition *project_library = find_custom_asset_library_from_library_ref(
+          library_reference);
+      if (!project_library) {
+        return "";
+      }
+
+      /* Project asset libraries typically use relative paths (relative to project root directory).
+       */
+      if (BLI_path_is_rel(project_library->path)) {
+        const BlenderProject *project = BKE_project_active_get();
+        const char *project_root_path = BKE_project_root_path_get(project);
+        char path[1024]; /* FILE_MAX */
+        BLI_path_join(path, sizeof(path), project_root_path, project_library->path);
+        return path;
+      }
+
+      return project_library->path;
+    }
+    default:
+      BLI_assert_unreachable();
+      break;
   }
 
-  bUserAssetLibrary *custom_library = find_custom_asset_library_from_library_ref(
-      library_reference);
-  if (!custom_library || !custom_library->path[0]) {
-    return "";
-  }
-
-  return custom_library->path;
+  return "";
 }
 
 void AssetLibraryService::allocate_service_instance()

source/blender/asset_system/intern/asset_library_service.hh

@@ -14,7 +14,6 @@
 #include <memory>
 
 struct AssetLibraryReference;
-struct bUserAssetLibrary;
 
 namespace blender::asset_system {
 
@@ -59,7 +58,7 @@ class AssetLibraryService {
   static void destroy();
 
   static std::string root_path_from_library_ref(const AssetLibraryReference &library_reference);
-  static bUserAssetLibrary *find_custom_asset_library_from_library_ref(
+  static CustomAssetLibraryDefinition *find_custom_asset_library_from_library_ref(
       const AssetLibraryReference &library_reference);
 
   AssetLibrary *get_asset_library(const Main *bmain,

source/blender/asset_system/tests/asset_catalog_test.cc

@@ -4,7 +4,7 @@
 #include "AS_asset_catalog.hh"
 #include "AS_asset_catalog_tree.hh"
 
-#include "BKE_preferences.h"
+#include "BKE_asset_library_custom.h"
 
 #include "BLI_fileops.h"
 #include "BLI_path_util.h"
@@ -93,8 +93,8 @@ class AssetCatalogTest : public AssetLibraryTestBase {
     BLI_path_slash_native(cdf_in_subdir.data());
 
     /* Set up a temporary asset library for testing. */
-    bUserAssetLibrary *asset_lib_pref = BKE_preferences_asset_library_add(
-        &U, "Test", registered_asset_lib.c_str());
+    CustomAssetLibraryDefinition *asset_lib_pref = BKE_asset_library_custom_add(
+        &U.asset_libraries, "Test", registered_asset_lib.c_str());
     ASSERT_NE(nullptr, asset_lib_pref);
     ASSERT_TRUE(BLI_dir_create_recursive(asset_lib_subdir.c_str()));
 
@@ -145,7 +145,7 @@ class AssetCatalogTest : public AssetLibraryTestBase {
     /* Test that the "red herring" CDF has not been touched. */
     EXPECT_EQ(0, BLI_file_size(cdf_in_subdir.c_str()));
 
-    BKE_preferences_asset_library_remove(&U, asset_lib_pref);
+    BKE_asset_library_custom_remove(&U.asset_libraries, asset_lib_pref);
   }
 };
 

source/blender/blenkernel/BKE_asset_library_custom.h

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ *
+ * API to manage a list of #CustomAssetLibraryDefinition items.
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "BLI_compiler_attrs.h"
+#include "BLI_utildefines.h"
+
+struct CustomAssetLibraryDefinition;
+struct ListBase;
+
+struct CustomAssetLibraryDefinition *BKE_asset_library_custom_add(
+    struct ListBase *custom_libraries,
+    const char *name CPP_ARG_DEFAULT(nullptr),
+    const char *path CPP_ARG_DEFAULT(nullptr)) ATTR_NONNULL(1);
+/**
+ * Unlink and free a library preference member.
+ * \note Free's \a library itself.
+ */
+void BKE_asset_library_custom_remove(struct ListBase *custom_libraries,
+                                     struct CustomAssetLibraryDefinition *library) ATTR_NONNULL();
+
+void BKE_asset_library_custom_name_set(struct ListBase *custom_libraries,
+                                       struct CustomAssetLibraryDefinition *library,
+                                       const char *name) ATTR_NONNULL();
+
+/**
+ * Set the library path, ensuring it is pointing to a directory.
+ * Single blend files can only act as "Current File" library; libraries on disk
+ * should always be directories. Blindly sets the path without additional checks. The asset system
+ * can ignore libraries that it can't resolve to a valid location. If the path does not exist,
+ * that's fine; it can created as directory if necessary later.
+ */
+void BKE_asset_library_custom_path_set(struct CustomAssetLibraryDefinition *library,
+                                       const char *path) ATTR_NONNULL();
+
+struct CustomAssetLibraryDefinition *BKE_asset_library_custom_find_from_index(
+    const struct ListBase *custom_libraries, int index) ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
+struct CustomAssetLibraryDefinition *BKE_asset_library_custom_find_from_name(
+    const struct ListBase *custom_libraries, const char *name)
+    ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
+
+/**
+ * Return the #CustomAssetLibraryDefinition that contains the given file/directory path. The given
+ * path can be the library's top-level directory, or any path inside that directory.
+ *
+ * When more than one asset libraries match, the first matching one is returned (no smartness when
+ * there nested asset libraries).
+ *
+ * Return NULL when no such asset library is found. */
+struct CustomAssetLibraryDefinition *BKE_asset_library_custom_containing_path(
+    const struct ListBase *custom_libraries, const char *path)
+    ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
+
+int BKE_asset_library_custom_get_index(
+    const struct ListBase /*#CustomAssetLibraryDefinition*/ *custom_libraries,
+    const struct CustomAssetLibraryDefinition *library) ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
+#ifdef __cplusplus
+}
+#endif

source/blender/blenkernel/BKE_blender_project.h

@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#pragma once
+
+#include "DNA_space_types.h"
+
+#include "BLI_compiler_attrs.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* C-handle for #bke::BlenderProject. */
+typedef struct BlenderProject BlenderProject;
+
+/** See #bke::ProjectSettings::create_settings_directory(). */
+bool BKE_project_create_settings_directory(const char *project_root_path) ATTR_NONNULL();
+/** See #bke::ProjectSettings::delete_settings_directory(). */
+bool BKE_project_delete_settings_directory(BlenderProject *project) ATTR_NONNULL();
+
+BlenderProject *BKE_project_active_get(void) ATTR_WARN_UNUSED_RESULT;
+/**
+ * \note: When unsetting an active project, the previously active one will be destroyed, so
+ *        pointers may dangle.
+ */
+void BKE_project_active_unset(void);
+/**
+ * Check if \a path references a project root directory. Will return false for paths pointing into
+ * the project root directory.
+ */
+bool BKE_project_is_path_project_root(const char *path) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
+/**
+ * Check if \a path points to or into a project root path (i.e. if one of the ancestors of the
+ * referenced file/directory is a project root directory).
+ */
+bool BKE_project_contains_path(const char *path) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
+
+/**
+ * Attempt to load and activate a project based on the given path. If the path doesn't lead
+ * into a project, the active project is unset. Note that the project will be unset on any
+ * failure when loading the project.
+ *
+ * \note: When setting an active project, the previously active one will be destroyed, so
+ * pointers may dangle.
+ */
+BlenderProject *BKE_project_active_load_from_path(const char *path) ATTR_NONNULL();
+
+bool BKE_project_settings_save(const BlenderProject *project) ATTR_NONNULL();
+
+const char *BKE_project_root_path_get(const BlenderProject *project) ATTR_WARN_UNUSED_RESULT
+    ATTR_NONNULL();
+/**
+ * \param name The new name to set, expected to be 0 terminated.
+ */
+void BKE_project_name_set(const BlenderProject *project_handle, const char *name) ATTR_NONNULL();
+const char *BKE_project_name_get(const BlenderProject *project) ATTR_WARN_UNUSED_RESULT
+    ATTR_NONNULL();
+ListBase *BKE_project_custom_asset_libraries_get(const BlenderProject *project)
+    ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
+void BKE_project_tag_has_unsaved_changes(const BlenderProject *project) ATTR_NONNULL();
+/**
+ * Check if the project is marked as having unsaved changes. For convenience this allows passing
+ * null as the project (returns false then), so a call like
+ * `BKE_project_has_unsaved_changes(CTX_wm_project())` can be done without having to null-check the
+ * project first.
+ */
+bool BKE_project_has_unsaved_changes(const BlenderProject *project) ATTR_WARN_UNUSED_RESULT;
+
+#ifdef __cplusplus
+}
+#endif

source/blender/blenkernel/BKE_blender_project.hh

@@ -0,0 +1,204 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#pragma once
+
+#include <memory>
+
+#include "BLI_listbase.h"
+#include "BLI_string_ref.hh"
+#include "BLI_utility_mixins.hh"
+
+struct BlenderProject;
+
+namespace blender::io::serialize {
+class DictionaryValue;
+}
+
+namespace blender::bke {
+
+class ProjectSettings;
+struct CustomAssetLibraries;
+
+/**
+ * Entry point / API for core Blender project management.
+ *
+ * Responsibilities:
+ * - Own and give access to the active project.
+ * - Manage the .blender_project/ directory.
+ * - Store and manage (including reading & writing) of the .blender_project/settings.json file. The
+ *   implementation of this can be found in the internal #ProjectSettings class.
+ * - Tag for unsaved changes as needed.
+ */
+class BlenderProject {
+  friend class ProjectSettings;
+
+  /* Path to the project root using native slashes plus a trailing slash. */
+  std::string root_path_;
+  std::unique_ptr<ProjectSettings> settings_;
+
+ public:
+  inline static const StringRefNull SETTINGS_DIRNAME = ".blender_project";
+  inline static const StringRefNull SETTINGS_FILENAME = "settings.json";
+
+ public:
+  static auto get_active [[nodiscard]] () -> BlenderProject *;
+  static auto set_active(std::unique_ptr<BlenderProject> settings) -> BlenderProject *;
+
+  /**
+   * Read project settings from the given \a path, which may point to some directory or file inside
+   * of the project directory. Both Unix and Windows style slashes are allowed. Path is expected to
+   * be normalized.
+   *
+   * Attempt to read project data from the given \a project_path, which may be either a project
+   * root directory or the .blender_project directory, and load it into runtime data. Letting the
+   * returned #unique_pointer run out of scope cleanly destructs the runtime project data.
+   *
+   * \note Does NOT set the loaded project active.
+   *
+   * \return The loaded project or null on failure.
+   */
+  static auto load_from_path(StringRef project_path) -> std::unique_ptr<BlenderProject>;
+
+  /**
+   * Initializes a blender project by creating a .blender_project directory at the given \a
+   * project_root_path.
+   * Both Unix and Windows style slashes are allowed.
+   *
+   * \return True if the settings directory was created, or already existed. False on failure.
+   */
+  static auto create_settings_directory(StringRef project_root_path) -> bool;
+  /**
+   * Remove the .blender_project directory with all of its contents at the given \a
+   * project_root_path. If this is the path of the active project, it is marked as having changed
+   * but it is not unloaded. Runtime project data is still valid at this point.
+   *
+   * \return True on success.
+   */
+  static auto delete_settings_directory(StringRef project_root_path) -> bool;
+
+  /**
+   * Check if the directory given by \a path contains a .blender_project directory and should thus
+   * be considered a project root directory.
+   */
+  static auto path_is_project_root(StringRef path) -> bool;
+
+  /**
+   * Check if \a path points into a project and return the root directory path of that project (the
+   * one containing the .blender_project directory). Walks "upwards" through the path and returns
+   * the first project found, so if a project is nested inside another one, the nested project is
+   * used.
+   * Both Unix and Windows style slashes are allowed.
+   *
+   * \return The project root path or an empty path if not found. The referenced string points into
+   *         the input \a path, so slashes are not converted in the returned value.
+   */
+  static auto project_root_path_find_from_path [[nodiscard]] (StringRef path) -> StringRef;
+
+  /* --- Non-static member functions. --- */
+
+  BlenderProject(StringRef project_root_path, std::unique_ptr<ProjectSettings> settings);
+
+  /**
+   * Version of the static #delete_settings_directory() that deletes the settings directory of this
+   * project. Always tags as having unsaved changes after successful deletion.
+   */
+  auto delete_settings_directory() -> bool;
+
+  auto root_path [[nodiscard]] () const -> StringRefNull;
+  auto get_settings [[nodiscard]] () const -> ProjectSettings &;
+
+ private:
+  static auto active_project_ptr() -> std::unique_ptr<BlenderProject> &;
+  /**
+   * Get the project root path from a path that is either already the project root, or the
+   * .blender_project directory. Returns the path with native slashes plus a trailing slash.
+   */
+  static auto project_path_to_native_project_root_path(StringRef project_path) -> std::string;
+  /**
+   * Get the .blender_project directory path from a project root path. Returns the path with native
+   * slashes plus a trailing slash. Assumes the path already ends with a native trailing slash.
+   */
+  static auto project_root_path_to_settings_path(StringRef project_root_path) -> std::string;
+  /**
+   * Returns the path with native slashes.
+   * Assumes the path already ends with a native trailing slash.
+   */
+  static auto project_root_path_to_settings_filepath(StringRef project_root_path) -> std::string;
+};
+
+/**
+ * Runtime representation of the project settings (`.blender_project/settings.json`) with IO
+ * functionality.
+ */
+class ProjectSettings {
+  std::string project_name_;
+  std::unique_ptr<CustomAssetLibraries> asset_libraries_;
+
+  bool has_unsaved_changes_ = false;
+
+ public:
+  /**
+   * Read project settings from the given \a project_path, which may be either a project root
+   * directory or the .blender_project directory.
+   * Both Unix and Windows style slashes are allowed. Path is expected to be normalized.
+   *
+   * \return The read project settings or null in case of failure.
+   */
+  static auto load_from_disk [[nodiscard]] (StringRef project_path)
+  -> std::unique_ptr<ProjectSettings>;
+  /**
+   * Read project settings from the given \a path, which may point to some directory or file inside
+   * of the project directory. Both Unix and Windows style slashes are allowed. Path is expected to
+   * be normalized.
+   *
+   * \return The read project settings or null in case of failure.
+   */
+  static auto load_from_path [[nodiscard]] (StringRef path) -> std::unique_ptr<ProjectSettings>;
+
+  /** Explicit constructor and destructor needed to manage the CustomAssetLibraries unique_ptr. */
+  ProjectSettings();
+  /* Implementation defaulted. */
+  ~ProjectSettings();
+
+  /**
+   * Write project settings to the given \a project_path, which may be either a project root
+   * directory or the .blender_project directory. The .blender_project directory must exist.
+   * Both Unix and Windows style slashes are allowed. Path is expected to be normalized.
+   *
+   * \return True on success. If the .blender_project directory doesn't exist, that's treated
+   *         as failure.
+   */
+  auto save_to_disk(StringRef project_path) -> bool;
+
+  void project_name(StringRef new_name);
+  auto project_name [[nodiscard]] () const -> StringRefNull;
+  auto asset_library_definitions() const -> const ListBase &;
+  auto asset_library_definitions() -> ListBase &;
+  /**
+   * Forcefully tag the project settings for having unsaved changes. This needs to be done if
+   * project settings data is modified directly by external code, not via a project settings API
+   * function. The API functions set the tag for all changes they manage.
+   */
+  void tag_has_unsaved_changes();
+  /**
+   * Returns true if there were any changes done to the settings that have not been written to
+   * disk yet. Project settings API functions that change data set this, however when external
+   * code modifies project settings data it may have to manually set the tag, see
+   * #tag_has_unsaved_changes().
+   */
+  auto has_unsaved_changes [[nodiscard]] () const -> bool;
+
+ private:
+  auto to_dictionary() const -> std::unique_ptr<io::serialize::DictionaryValue>;
+};
+
+}  // namespace blender::bke
+
+inline ::BlenderProject *BKE_project_c_handle(blender::bke::BlenderProject *project)
+{
+  return reinterpret_cast<::BlenderProject *>(project);
+}

source/blender/blenkernel/BKE_context.h

@@ -27,6 +27,7 @@ extern "C" {
 
 struct ARegion;
 struct Base;
+struct BlenderProject;
 struct CacheFile;
 struct Collection;
 struct Depsgraph;
@@ -186,6 +187,7 @@ struct ARegion *CTX_wm_menu(const bContext *C);
 struct wmGizmoGroup *CTX_wm_gizmo_group(const bContext *C);
 struct wmMsgBus *CTX_wm_message_bus(const bContext *C);
 struct ReportList *CTX_wm_reports(const bContext *C);
+struct BlenderProject *CTX_wm_project(void);
 
 struct View3D *CTX_wm_view3d(const bContext *C);
 struct RegionView3D *CTX_wm_region_view3d(const bContext *C);
@@ -205,6 +207,7 @@ struct SpaceUserPref *CTX_wm_space_userpref(const bContext *C);
 struct SpaceClip *CTX_wm_space_clip(const bContext *C);
 struct SpaceTopBar *CTX_wm_space_topbar(const bContext *C);
 struct SpaceSpreadsheet *CTX_wm_space_spreadsheet(const bContext *C);
+struct SpaceProjectSettings *CTX_wm_space_project_settings(const bContext *C);
 
 void CTX_wm_manager_set(bContext *C, struct wmWindowManager *wm);
 void CTX_wm_window_set(bContext *C, struct wmWindow *win);

source/blender/blenkernel/BKE_preferences.h

@@ -13,55 +13,11 @@ extern "C" {
 #include "BLI_compiler_attrs.h"
 
 struct UserDef;
-struct bUserAssetLibrary;
 
 /** Name of the asset library added by default. Needs translation with `DATA_()` still. */
 #define BKE_PREFS_ASSET_LIBRARY_DEFAULT_NAME N_("User Library")
 
-struct bUserAssetLibrary *BKE_preferences_asset_library_add(struct UserDef *userdef,
-                                                            const char *name,
-                                                            const char *path) ATTR_NONNULL(1);
-/**
- * Unlink and free a library preference member.
- * \note Free's \a library itself.
- */
-void BKE_preferences_asset_library_remove(struct UserDef *userdef,
-                                          struct bUserAssetLibrary *library) ATTR_NONNULL();
-
-void BKE_preferences_asset_library_name_set(struct UserDef *userdef,
-                                            struct bUserAssetLibrary *library,
-                                            const char *name) ATTR_NONNULL();
-
-/**
- * Set the library path, ensuring it is pointing to a directory.
- * Single blend files can only act as "Current File" library; libraries on disk
- * should always be directories. If the path does not exist, that's fine; it can
- * created as directory if necessary later.
- */
-void BKE_preferences_asset_library_path_set(struct bUserAssetLibrary *library, const char *path)
-    ATTR_NONNULL();
-
-struct bUserAssetLibrary *BKE_preferences_asset_library_find_from_index(
-    const struct UserDef *userdef, int index) ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
-struct bUserAssetLibrary *BKE_preferences_asset_library_find_from_name(
-    const struct UserDef *userdef, const char *name) ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
-
-/**
- * Return the bUserAssetLibrary that contains the given file/directory path. The given path can be
- * the library's top-level directory, or any path inside that directory.
- *
- * When more than one asset libraries match, the first matching one is returned (no smartness when
- * there nested asset libraries).
- *
- * Return NULL when no such asset library is found. */
-struct bUserAssetLibrary *BKE_preferences_asset_library_containing_path(
-    const struct UserDef *userdef, const char *path) ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
-
-int BKE_preferences_asset_library_get_index(const struct UserDef *userdef,
-                                            const struct bUserAssetLibrary *library)
-    ATTR_NONNULL() ATTR_WARN_UNUSED_RESULT;
-
-void BKE_preferences_asset_library_default_add(struct UserDef *userdef) ATTR_NONNULL();
+void BKE_preferences_custom_asset_library_default_add(struct UserDef *userdef) ATTR_NONNULL();
 
 #ifdef __cplusplus
 }

source/blender/blenkernel/CMakeLists.txt

@@ -72,12 +72,15 @@ set(SRC
   intern/armature_selection.cc
   intern/armature_update.c
   intern/asset.cc
+  intern/asset_library_custom.cc
   intern/attribute.cc
   intern/attribute_access.cc
   intern/attribute_math.cc
   intern/autoexec.c
   intern/blender.c
   intern/blender_copybuffer.c
+  intern/blender_project.cc
+  intern/blender_project_settings.cc
   intern/blender_undo.cc
   intern/blender_user_menu.c
   intern/blendfile.cc
@@ -321,12 +324,15 @@ set(SRC
   BKE_armature.h
   BKE_armature.hh
   BKE_asset.h
+  BKE_asset_library_custom.h
   BKE_attribute.h
   BKE_attribute.hh
   BKE_attribute_math.hh
   BKE_autoexec.h
   BKE_blender.h
   BKE_blender_copybuffer.h
+  BKE_blender_project.h
+  BKE_blender_project.hh
   BKE_blender_undo.h
   BKE_blender_user_menu.h
   BKE_blender_version.h
@@ -824,7 +830,7 @@ if(WITH_GTESTS)
   set(TEST_SRC
     intern/action_test.cc
     intern/armature_test.cc
-    intern/asset_metadata_test.cc
+    intern/blender_project_test.cc
     intern/bpath_test.cc
     intern/cryptomatte_test.cc
     intern/curves_geometry_test.cc
@@ -842,6 +848,7 @@ if(WITH_GTESTS)
   )
   set(TEST_INC
     ../editors/include
+    ../blenloader/tests
   )
   include(GTestTesting)
   blender_add_test_lib(bf_blenkernel_tests "${TEST_SRC}" "${INC};${TEST_INC}" "${INC_SYS}" "${LIB}")

source/blender/blenkernel/intern/asset_library_custom.cc

@@ -0,0 +1,113 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include <string.h>
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_fileops.h"
+#include "BLI_listbase.h"
+#include "BLI_path_util.h"
+#include "BLI_string.h"
+#include "BLI_string_utf8.h"
+#include "BLI_string_utils.h"
+
+#include "BKE_appdir.h"
+
+#include "BLT_translation.h"
+
+#include "DNA_asset_types.h"
+#include "DNA_userdef_types.h"
+
+#include "BKE_asset_library_custom.h"
+
+using namespace blender;
+
+/* -------------------------------------------------------------------- */
+/** \name Asset Libraries
+ * \{ */
+
+CustomAssetLibraryDefinition *BKE_asset_library_custom_add(ListBase *custom_libraries,
+                                                           const char *name,
+                                                           const char *path)
+{
+  CustomAssetLibraryDefinition *library = MEM_cnew<CustomAssetLibraryDefinition>(
+      "CustomAssetLibraryDefinition");
+
+  BLI_addtail(custom_libraries, library);
+
+  if (name) {
+    BKE_asset_library_custom_name_set(custom_libraries, library, name);
+  }
+  if (path) {
+    BLI_strncpy(library->path, path, sizeof(library->path));
+  }
+  library->import_method = ASSET_IMPORT_APPEND_REUSE;
+
+  return library;
+}
+
+void BKE_asset_library_custom_remove(ListBase *custom_libraries,
+                                     CustomAssetLibraryDefinition *library)
+{
+  BLI_freelinkN(custom_libraries, library);
+}
+
+void BKE_asset_library_custom_name_set(ListBase *custom_libraries,
+                                       CustomAssetLibraryDefinition *library,
+                                       const char *name)
+{
+  BLI_strncpy_utf8(library->name, name, sizeof(library->name));
+  BLI_uniquename(custom_libraries,
+                 library,
+                 name,
+                 '.',
+                 offsetof(CustomAssetLibraryDefinition, name),
+                 sizeof(library->name));
+}
+
+void BKE_asset_library_custom_path_set(CustomAssetLibraryDefinition *library, const char *path)
+{
+  BLI_strncpy(library->path, path, sizeof(library->path));
+}
+
+CustomAssetLibraryDefinition *BKE_asset_library_custom_find_from_index(
+    const ListBase *custom_libraries, int index)
+{
+  return static_cast<CustomAssetLibraryDefinition *>(BLI_findlink(custom_libraries, index));
+}
+
+CustomAssetLibraryDefinition *BKE_asset_library_custom_find_from_name(
+    const ListBase *custom_libraries, const char *name)
+{
+  return static_cast<CustomAssetLibraryDefinition *>(
+      BLI_findstring(custom_libraries, name, offsetof(CustomAssetLibraryDefinition, name)));
+}
+
+CustomAssetLibraryDefinition *BKE_asset_library_custom_containing_path(
+    const ListBase *custom_libraries, const char *path)
+{
+  LISTBASE_FOREACH (CustomAssetLibraryDefinition *, asset_lib_pref, custom_libraries) {
+    if (BLI_path_contains(asset_lib_pref->path, path)) {
+      return asset_lib_pref;
+    }
+  }
+  return NULL;
+}
+
+int BKE_asset_library_custom_get_index(const ListBase *custom_libraries,
+                                       const CustomAssetLibraryDefinition *library)
+{
+  return BLI_findindex(custom_libraries, library);
+}
+
+/** \} */

source/blender/blenkernel/intern/blender_project.cc

@@ -0,0 +1,311 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "BKE_asset_library_custom.h"
+
+#include "BLI_path_util.h"
+#include "BLI_string.h"
+
+#include "BLI_fileops.h"
+
+#include "BKE_blender_project.h"
+#include "BKE_blender_project.hh"
+
+namespace blender::bke {
+
+BlenderProject::BlenderProject(const StringRef project_root_path,
+                               std::unique_ptr<ProjectSettings> settings)
+    : settings_(std::move(settings))
+{
+  root_path_ = BlenderProject::project_path_to_native_project_root_path(project_root_path);
+  BLI_assert(root_path_.back() == SEP);
+}
+
+/* ---------------------------------------------------------------------- */
+/** \name Active project management (static storage)
+ * \{ */
+
+/* Construct on First Use idiom. */
+std::unique_ptr<BlenderProject> &BlenderProject::active_project_ptr()
+{
+  static std::unique_ptr<BlenderProject> active_;
+  return active_;
+}
+
+BlenderProject *BlenderProject::set_active(std::unique_ptr<BlenderProject> project)
+{
+  std::unique_ptr<BlenderProject> &active = active_project_ptr();
+  if (project) {
+    active = std::move(project);
+  }
+  else {
+    active = nullptr;
+  }
+
+  return active.get();
+}
+
+BlenderProject *BlenderProject::get_active()
+{
+  std::unique_ptr<BlenderProject> &active = active_project_ptr();
+  return active.get();
+}
+
+/** \} */
+
+/* ---------------------------------------------------------------------- */
+/** \name Project and project settings management.
+ * \{ */
+
+std::unique_ptr<BlenderProject> BlenderProject::load_from_path(StringRef project_path)
+{
+  const StringRef project_root_path = project_root_path_find_from_path(project_path);
+
+  std::unique_ptr<bke::ProjectSettings> project_settings = bke::ProjectSettings::load_from_path(
+      project_root_path);
+  if (!project_settings) {
+    return nullptr;
+  }
+
+  return std::make_unique<BlenderProject>(project_root_path, std::move(project_settings));
+}
+
+bool BlenderProject::create_settings_directory(StringRef project_path)
+{
+  std::string project_root_path = project_path_to_native_project_root_path(project_path);
+  std::string settings_path = project_root_path_to_settings_path(project_root_path);
+
+  return BLI_dir_create_recursive(settings_path.c_str());
+}
+
+bool BlenderProject::delete_settings_directory(StringRef project_path)
+{
+  std::string project_root_path = project_path_to_native_project_root_path(project_path);
+  std::string settings_path = project_root_path_to_settings_path(project_root_path);
+
+  /* Returns 0 on success. */
+  if (BLI_delete(settings_path.c_str(), true, true)) {
+    return false;
+  }
+
+  BlenderProject *active_project = get_active();
+  if (active_project &&
+      BLI_path_cmp_normalized(project_root_path.c_str(), active_project->root_path().c_str())) {
+    active_project->settings_->tag_has_unsaved_changes();
+  }
+  return true;
+}
+
+bool BlenderProject::delete_settings_directory()
+{
+  if (!delete_settings_directory(root_path_)) {
+    return false;
+  }
+
+  settings_->tag_has_unsaved_changes();
+  return true;
+}
+
+/** \} */
+
+/* ---------------------------------------------------------------------- */
+/** \name Simple getters & setters
+ * \{ */
+
+StringRefNull BlenderProject::root_path() const
+{
+  return root_path_;
+}
+
+ProjectSettings &BlenderProject::get_settings() const
+{
+  BLI_assert(settings_ != nullptr);
+  return *settings_;
+}
+
+/** \} */
+
+/* ---------------------------------------------------------------------- */
+/** \name Path stuff
+ * \{ */
+
+StringRef BlenderProject::project_root_path_find_from_path(StringRef path)
+{
+  /* There are two versions of the path used here: One copy that is converted to native slashes,
+   * and the unmodified original path from the input. */
+
+  std::string path_native = path;
+  BLI_path_slash_native(path_native.data());
+
+  StringRef cur_path = path;
+
+  while (cur_path.size()) {
+    std::string cur_path_native = StringRef(path_native.c_str(), cur_path.size());
+    if (path_is_project_root(cur_path_native)) {
+      return path.substr(0, cur_path.size());
+    }
+
+    /* Walk "up the path" (check the parent next). */
+    const int64_t pos_last_slash = cur_path_native.find_last_of(SEP);
+    if (pos_last_slash == StringRef::not_found) {
+      break;
+    }
+    cur_path = cur_path.substr(0, pos_last_slash);
+  }
+
+  return "";
+}
+
+static StringRef path_strip_trailing_native_slash(StringRef path)
+{
+  const int64_t pos_before_trailing_slash = path.find_last_not_of(SEP);
+  return (pos_before_trailing_slash == StringRef::not_found) ?
+             path :
+             path.substr(0, pos_before_trailing_slash + 1);
+}
+
+bool BlenderProject::path_is_project_root(StringRef path)
+{
+  path = path_strip_trailing_native_slash(path);
+  return BLI_exists(std::string(path + SEP_STR + SETTINGS_DIRNAME).c_str());
+}
+
+std::string BlenderProject::project_path_to_native_project_root_path(StringRef project_path)
+{
+  std::string project_path_native = project_path;
+  BLI_path_slash_native(project_path_native.data());
+
+  const StringRef path_no_trailing_slashes = path_strip_trailing_native_slash(project_path_native);
+  if (path_no_trailing_slashes.endswith(SETTINGS_DIRNAME)) {
+    return StringRef(path_no_trailing_slashes).drop_suffix(SETTINGS_DIRNAME.size());
+  }
+
+  return std::string(path_no_trailing_slashes) + SEP;
+}
+
+std::string BlenderProject::project_root_path_to_settings_path(StringRef project_root_path)
+{
+  BLI_assert(project_root_path.back() == SEP);
+  return project_root_path + SETTINGS_DIRNAME + SEP;
+}
+
+std::string BlenderProject::project_root_path_to_settings_filepath(StringRef project_root_path)
+{
+  BLI_assert(project_root_path.back() == SEP);
+  return project_root_path_to_settings_path(project_root_path) + SETTINGS_FILENAME;
+}
+
+/** \} */
+
+}  // namespace blender::bke
+
+/* ---------------------------------------------------------------------- */
+/** \name C-API
+ * \{ */
+
+using namespace blender;
+
+bool BKE_project_create_settings_directory(const char *project_root_path)
+{
+  return bke::BlenderProject::create_settings_directory(project_root_path);
+}
+
+bool BKE_project_delete_settings_directory(BlenderProject *project_handle)
+{
+  bke::BlenderProject *project = reinterpret_cast<bke::BlenderProject *>(project_handle);
+  return project->delete_settings_directory();
+}
+
+BlenderProject *BKE_project_active_get(void)
+{
+  return reinterpret_cast<BlenderProject *>(bke::BlenderProject::get_active());
+}
+
+void BKE_project_active_unset(void)
+{
+  bke::BlenderProject::set_active(nullptr);
+}
+
+bool BKE_project_is_path_project_root(const char *path)
+{
+  return bke::BlenderProject::path_is_project_root(path);
+}
+
+bool BKE_project_contains_path(const char *path)
+{
+  const StringRef found_root_path = bke::BlenderProject::project_root_path_find_from_path(path);
+  return !found_root_path.is_empty();
+}
+
+BlenderProject *BKE_project_active_load_from_path(const char *path)
+{
+  /* Project should be unset if the path doesn't contain a project root. Unset in the beginning so
+   * early exiting behaves correctly. */
+  BKE_project_active_unset();
+
+  std::unique_ptr<bke::BlenderProject> project = bke::BlenderProject::load_from_path(path);
+
+  return reinterpret_cast<::BlenderProject *>(bke::BlenderProject::set_active(std::move(project)));
+}
+
+bool BKE_project_settings_save(const BlenderProject *project_handle)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  bke::ProjectSettings &settings = project->get_settings();
+  return settings.save_to_disk(project->root_path());
+}
+
+const char *BKE_project_root_path_get(const BlenderProject *project_handle)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  return project->root_path().c_str();
+}
+
+void BKE_project_name_set(const BlenderProject *project_handle, const char *name)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  project->get_settings().project_name(name);
+}
+
+const char *BKE_project_name_get(const BlenderProject *project_handle)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  return project->get_settings().project_name().c_str();
+}
+
+ListBase *BKE_project_custom_asset_libraries_get(const BlenderProject *project_handle)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  bke::ProjectSettings &settings = project->get_settings();
+  return &settings.asset_library_definitions();
+}
+
+void BKE_project_tag_has_unsaved_changes(const BlenderProject *project_handle)
+{
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  bke::ProjectSettings &settings = project->get_settings();
+  settings.tag_has_unsaved_changes();
+}
+
+bool BKE_project_has_unsaved_changes(const BlenderProject *project_handle)
+{
+  if (!project_handle) {
+    return false;
+  }
+
+  const bke::BlenderProject *project = reinterpret_cast<const bke::BlenderProject *>(
+      project_handle);
+  const bke::ProjectSettings &settings = project->get_settings();
+  return settings.has_unsaved_changes();
+}
+
+/** \} */

source/blender/blenkernel/intern/blender_project_settings.cc

@@ -0,0 +1,318 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include <fstream>
+#include <memory>
+#include <string>
+
+#include "BLI_fileops.h"
+#include "BLI_listbase.h"
+#include "BLI_serialize.hh"
+
+#include "BKE_asset_library_custom.h"
+
+#include "DNA_asset_types.h"
+
+#include "BKE_blender_project.hh"
+
+namespace serialize = blender::io::serialize;
+
+namespace blender::bke {
+
+/* ---------------------------------------------------------------------- */
+
+struct CustomAssetLibraries : NonCopyable {
+  ListBase asset_libraries = {nullptr, nullptr}; /* CustomAssetLibraryDefinition */
+
+  CustomAssetLibraries() = default;
+  CustomAssetLibraries(ListBase asset_libraries);
+  CustomAssetLibraries(CustomAssetLibraries &&);
+  ~CustomAssetLibraries();
+  auto operator=(CustomAssetLibraries &&) -> CustomAssetLibraries &;
+};
+
+CustomAssetLibraries::CustomAssetLibraries(ListBase asset_libraries)
+    : asset_libraries(asset_libraries)
+{
+}
+
+CustomAssetLibraries::CustomAssetLibraries(CustomAssetLibraries &&other)
+{
+  *this = std::move(other);
+}
+
+CustomAssetLibraries &CustomAssetLibraries::operator=(CustomAssetLibraries &&other)
+{
+  asset_libraries = other.asset_libraries;
+  BLI_listbase_clear(&other.asset_libraries);
+  return *this;
+}
+
+CustomAssetLibraries::~CustomAssetLibraries()
+{
+  LISTBASE_FOREACH_MUTABLE (CustomAssetLibraryDefinition *, library, &asset_libraries) {
+    BKE_asset_library_custom_remove(&asset_libraries, library);
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+/** \name settings.json Reading (Deserializing)
+ * \{ */
+
+struct ExtractedSettings {
+  std::string project_name;
+  ListBase asset_libraries = {nullptr, nullptr}; /* CustomAssetLibraryDefinition */
+};
+
+static std::unique_ptr<serialize::Value> read_settings_file(StringRef settings_filepath)
+{
+  std::ifstream is;
+  is.open(settings_filepath);
+  if (is.fail()) {
+    return nullptr;
+  }
+
+  serialize::JsonFormatter formatter;
+  /* Will not be a dictionary in case of error (corrupted file). */
+  std::unique_ptr<serialize::Value> deserialized_values = formatter.deserialize(is);
+  is.close();
+
+  if (deserialized_values->type() != serialize::eValueType::Dictionary) {
+    return nullptr;
+  }
+
+  return deserialized_values;
+}
+
+static std::unique_ptr<ExtractedSettings> extract_settings(
+    const serialize::DictionaryValue &dictionary)
+{
+  using namespace serialize;
+
+  std::unique_ptr extracted_settings = std::make_unique<ExtractedSettings>();
+
+  const DictionaryValue::Lookup attributes = dictionary.create_lookup();
+
+  /* "project": */ {
+    const DictionaryValue::LookupValue *project_value = attributes.lookup_ptr("project");
+    BLI_assert(project_value != nullptr);
+
+    const DictionaryValue *project_dict = (*project_value)->as_dictionary_value();
+    const StringValue *project_name_value =
+        project_dict->create_lookup().lookup("name")->as_string_value();
+    if (project_name_value) {
+      extracted_settings->project_name = project_name_value->value();
+    }
+  }
+  /* "asset_libraries": */ {
+    const DictionaryValue::LookupValue *asset_libraries_value = attributes.lookup_ptr(
+        "asset_libraries");
+    if (asset_libraries_value) {
+      const ArrayValue *asset_libraries_array = (*asset_libraries_value)->as_array_value();
+      if (!asset_libraries_array) {
+        throw std::runtime_error(
+            "Unexpected asset_library format in settings.json, expected array");
+      }
+
+      for (const ArrayValue::Item &element : asset_libraries_array->elements()) {
+        const DictionaryValue *object_value = element->as_dictionary_value();
+        if (!object_value) {
+          throw std::runtime_error(
+              "Unexpected asset_library entry in settings.json, expected dictionary entries only");
+        }
+        const DictionaryValue::Lookup element_lookup = object_value->create_lookup();
+        const DictionaryValue::LookupValue *name_value = element_lookup.lookup_ptr("name");
+        if (name_value && (*name_value)->type() != eValueType::String) {
+          throw std::runtime_error(
+              "Unexpected asset_library entry in settings.json, expected name to be string");
+        }
+        const DictionaryValue::LookupValue *path_value = element_lookup.lookup_ptr("path");
+        if (path_value && (*path_value)->type() != eValueType::String) {
+          throw std::runtime_error(
+              "Unexpected asset_library entry in settings.json, expected path to be string");
+        }
+
+        /* TODO this isn't really extracting, should be creating data from the settings be a
+         * separate step? */
+        CustomAssetLibraryDefinition *library = BKE_asset_library_custom_add(
+            &extracted_settings->asset_libraries);
+        /* Name or path may not be set, this is fine. */
+        if (name_value) {
+          std::string name = (*name_value)->as_string_value()->value();
+          BKE_asset_library_custom_name_set(
+              &extracted_settings->asset_libraries, library, name.c_str());
+        }
+        if (path_value) {
+          std::string path = (*path_value)->as_string_value()->value();
+          BKE_asset_library_custom_path_set(library, path.c_str());
+        }
+      }
+    }
+  }
+
+  return extracted_settings;
+}
+
+/** \} */
+
+/* ---------------------------------------------------------------------- */
+/** \name settings.json Writing (Serializing)
+ * \{ */
+
+std::unique_ptr<serialize::DictionaryValue> ProjectSettings::to_dictionary() const
+{
+  using namespace serialize;
+
+  std::unique_ptr<DictionaryValue> root = std::make_unique<DictionaryValue>();
+  DictionaryValue::Items &root_attributes = root->elements();
+
+  /* "project": */ {
+    std::unique_ptr<DictionaryValue> project_dict = std::make_unique<DictionaryValue>();
+    DictionaryValue::Items &project_attributes = project_dict->elements();
+    project_attributes.append_as("name", new StringValue(project_name_));
+    root_attributes.append_as("project", std::move(project_dict));
+  }
+  /* "asset_libraries": */ {
+    if (!BLI_listbase_is_empty(&asset_libraries_->asset_libraries)) {
+      std::unique_ptr<ArrayValue> asset_libs_array = std::make_unique<ArrayValue>();
+      ArrayValue::Items &asset_libs_elements = asset_libs_array->elements();
+      LISTBASE_FOREACH (
+          const CustomAssetLibraryDefinition *, library, &asset_libraries_->asset_libraries) {
+        std::unique_ptr<DictionaryValue> library_dict = std::make_unique<DictionaryValue>();
+        DictionaryValue::Items &library_attributes = library_dict->elements();
+
+        library_attributes.append_as("name", new StringValue(library->name));
+        library_attributes.append_as("path", new StringValue(library->path));
+        asset_libs_elements.append_as(std::move(library_dict));
+      }
+      root_attributes.append_as("asset_libraries", std::move(asset_libs_array));
+    }
+  }
+
+  return root;
+}
+
+static void write_settings_file(StringRef settings_filepath,
+                                std::unique_ptr<serialize::DictionaryValue> dictionary)
+{
+  using namespace serialize;
+
+  JsonFormatter formatter;
+
+  std::ofstream os;
+  os.open(settings_filepath, std::ios::out | std::ios::trunc);
+  formatter.serialize(os, *dictionary);
+  os.close();
+}
+
+/** \} */
+
+/* ---------------------------------------------------------------------- */
+
+std::unique_ptr<ProjectSettings> ProjectSettings::load_from_disk(StringRef project_path)
+{
+  const std::string project_root_path = BlenderProject::project_path_to_native_project_root_path(
+      project_path);
+
+  if (!BLI_exists(project_root_path.c_str())) {
+    return nullptr;
+  }
+  if (!BlenderProject::path_is_project_root(project_root_path.c_str())) {
+    return nullptr;
+  }
+
+  const std::string settings_filepath = BlenderProject::project_root_path_to_settings_filepath(
+      project_root_path);
+  std::unique_ptr<serialize::Value> values = read_settings_file(settings_filepath);
+  std::unique_ptr<ExtractedSettings> extracted_settings = nullptr;
+  if (values) {
+    BLI_assert(values->as_dictionary_value() != nullptr);
+    extracted_settings = extract_settings(*values->as_dictionary_value());
+  }
+
+  std::unique_ptr loaded_settings = std::make_unique<ProjectSettings>();
+  if (extracted_settings) {
+    loaded_settings->project_name_ = extracted_settings->project_name;
+    /* Moves ownership. */
+    loaded_settings->asset_libraries_ = std::make_unique<CustomAssetLibraries>(
+        extracted_settings->asset_libraries);
+  }
+
+  return loaded_settings;
+}
+
+std::unique_ptr<ProjectSettings> ProjectSettings::load_from_path(StringRef path)
+{
+  StringRef project_root = BlenderProject::project_root_path_find_from_path(path);
+  if (project_root.is_empty()) {
+    return nullptr;
+  }
+
+  return bke::ProjectSettings::load_from_disk(project_root);
+}
+
+bool ProjectSettings::save_to_disk(StringRef project_path)
+{
+  const std::string project_root_path = BlenderProject::project_path_to_native_project_root_path(
+      project_path);
+
+  if (!BLI_exists(project_root_path.c_str())) {
+    return false;
+  }
+  if (!BlenderProject::path_is_project_root(project_root_path.c_str())) {
+    return false;
+  }
+
+  const std::string settings_filepath = BlenderProject::project_root_path_to_settings_filepath(
+      project_root_path);
+  std::unique_ptr settings_as_dict = to_dictionary();
+  write_settings_file(settings_filepath, std::move(settings_as_dict));
+
+  has_unsaved_changes_ = false;
+
+  return true;
+}
+
+/* ---------------------------------------------------------------------- */
+
+ProjectSettings::ProjectSettings() : asset_libraries_(std::make_unique<CustomAssetLibraries>())
+{
+}
+
+ProjectSettings::~ProjectSettings() = default;
+
+void ProjectSettings::project_name(StringRef new_name)
+{
+  project_name_ = new_name;
+  has_unsaved_changes_ = true;
+}
+
+StringRefNull ProjectSettings::project_name() const
+{
+  return project_name_;
+}
+
+const ListBase &ProjectSettings::asset_library_definitions() const
+{
+  return asset_libraries_->asset_libraries;
+}
+
+ListBase &ProjectSettings::asset_library_definitions()
+{
+  return asset_libraries_->asset_libraries;
+}
+
+void ProjectSettings::tag_has_unsaved_changes()
+{
+  has_unsaved_changes_ = true;
+}
+
+bool ProjectSettings::has_unsaved_changes() const
+{
+  return has_unsaved_changes_;
+}
+
+}  // namespace blender::bke

source/blender/blenkernel/intern/blender_project_test.cc

@@ -0,0 +1,325 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2022 Blender Foundation. All rights reserved. */
+
+#include "BKE_appdir.h"
+#include "BKE_blender_project.h"
+#include "BKE_blender_project.hh"
+#include "BKE_main.h"
+
+#include "BLI_fileops.h"
+#include "BLI_function_ref.hh"
+#include "BLI_path_util.h"
+#include "BLI_vector.hh"
+
+#include "BLO_readfile.h"
+
+#include "blendfile_loading_base_test.h"
+
+#include "testing/testing.h"
+
+namespace blender::bke::tests {
+
+struct SVNFiles {
+  const std::string svn_root = blender::tests::flags_test_asset_dir();
+  const std::string project_root_rel = "blender_project/the_project";
+  const std::string project_root = svn_root + "/blender_project/the_project";
+};
+
+class ProjectTest : public testing::Test {
+  /* RAII helper to delete the created directories reliably after testing or on errors. */
+  struct ProjectDirectoryRAIIWrapper {
+    std::string project_path_;
+    /* Path with OS preferred slashes ('/' on Unix, '\' on Windows). Important for some file
+     * operations. */
+    std::string native_project_path_;
+    std::string base_path_;
+
+    ProjectDirectoryRAIIWrapper(StringRefNull base_path, StringRefNull relative_project_path)
+    {
+      BLI_assert_msg(ELEM(base_path.back(), SEP, ALTSEP),
+                     "Expected base_path to have trailing slash");
+      std::string project_path = base_path + relative_project_path;
+
+      native_project_path_ = project_path;
+      BLI_path_slash_native(native_project_path_.data());
+      if (native_project_path_.back() != SEP) {
+        native_project_path_ += SEP;
+      }
+
+      /** Assert would be preferable but that would only run in debug builds, and #ASSERT_TRUE()
+       * doesn't support printing a message. */
+      if (BLI_exists(native_project_path_.c_str())) {
+        throw std::runtime_error("Can't execute test, temporary path '" + project_path +
+                                 "' already exists");
+      }
+
+      BLI_dir_create_recursive(native_project_path_.c_str());
+      if (!BLI_exists(native_project_path_.c_str())) {
+        throw std::runtime_error("Can't execute test, failed to create path '" +
+                                 native_project_path_ + "'");
+      }
+
+      base_path_ = base_path;
+      project_path_ = project_path;
+      BLI_assert(StringRef{&project_path_[base_path.size()]} == relative_project_path);
+    }
+
+    ~ProjectDirectoryRAIIWrapper()
+    {
+      if (!project_path_.empty()) {
+        /* Cut the path off at the first slash after the base path, so we delete the directory
+         * created for the test. */
+        const size_t first_slash_pos = native_project_path_.find_first_of(SEP, base_path_.size());
+        std::string path_to_delete = native_project_path_;
+        if (first_slash_pos != std::string::npos) {
+          path_to_delete.erase(first_slash_pos);
+        }
+        BLI_delete(path_to_delete.c_str(), true, true);
+        BLI_assert(!BLI_exists(native_project_path_.c_str()));
+      }
+    }
+  };
+
+ public:
+  /* Run the test on multiple paths or variations of the same path. Useful to test things like
+   * unicode paths, with or without trailing slash, non-native slashes, etc. The callback gets both
+   * the unmodified path (possibly with non-native slashes), and the path converted to native
+   * slashes passed. Call functions under test with the former, and use the latter to check the
+   * results with BLI_fileops.h functions */
+  void test_foreach_project_path(FunctionRef<void(StringRefNull /* project_path */,
+                                                  StringRefNull /* project_path_native */)> fn)
+  {
+    const Vector<StringRefNull> subpaths = {
+        "temporary-project-root",
+        "test-temporary-unicode-dir-новый/temporary-project-root",
+        /* Same but with trailing slash. */
+        "test-temporary-unicode-dir-новый/temporary-project-root/",
+        /* Windows style slash. */
+        "test-temporary-unicode-dir-новый\\temporary-project-root",
+        /* Windows style trailing slash. */
+        "test-temporary-unicode-dir-новый\\temporary-project-root\\",
+    };
+
+    BKE_tempdir_init("");
+
+    const std::string tempdir = BKE_tempdir_session();
+    for (StringRefNull subpath : subpaths) {
+      ProjectDirectoryRAIIWrapper temp_project_path(tempdir, subpath);
+      fn(temp_project_path.project_path_, temp_project_path.native_project_path_);
+    }
+  }
+
+  void TearDown() override
+  {
+    BKE_project_active_unset();
+  }
+};
+
+TEST_F(ProjectTest, settings_create)
+{
+  test_foreach_project_path([](StringRefNull project_path, StringRefNull project_path_native) {
+    if (!BlenderProject::create_settings_directory(project_path)) {
+      /* Not a regular test failure, this may fail if there is a permission issue for example. */
+      FAIL() << "Failed to create project directory in '" << project_path
+             << "', check permissions";
+    }
+    std::string project_settings_dir = project_path_native + SEP_STR +
+                                       BlenderProject::SETTINGS_DIRNAME;
+    EXPECT_TRUE(BLI_exists(project_settings_dir.c_str()) &&
+                BLI_is_dir(project_settings_dir.c_str()))
+        << project_settings_dir + " was not created";
+  });
+}
+
+/* Load the project by pointing to the project root directory (as opposed to the .blender_project
+ * directory). */
+TEST_F(ProjectTest, load_from_project_root_path)
+{
+  test_foreach_project_path([](StringRefNull project_path, StringRefNull project_path_native) {
+    BlenderProject::create_settings_directory(project_path);
+
+    std::unique_ptr project = BlenderProject::load_from_path(project_path);
+    EXPECT_NE(project, nullptr);
+    EXPECT_EQ(project->root_path(), project_path_native);
+    EXPECT_EQ(project->get_settings().project_name(), "");
+  });
+}
+
+/* Load the project by pointing to the .blender_project directory (as opposed to the project root
+ * directory). */
+TEST_F(ProjectTest, load_from_project_settings_path)
+{
+  test_foreach_project_path([](StringRefNull project_path, StringRefNull project_path_native) {
+    BlenderProject::create_settings_directory(project_path);
+
+    std::unique_ptr project = BlenderProject::load_from_path(
+        project_path + (ELEM(project_path.back(), SEP, ALTSEP) ? "" : SEP_STR) +
+        BlenderProject::SETTINGS_DIRNAME);
+    EXPECT_NE(project, nullptr);
+    EXPECT_EQ(project->root_path(), project_path_native);
+    EXPECT_EQ(project->get_settings().project_name(), "");
+  });
+}
+
+static void project_settings_match_expected_from_svn(const ProjectSettings &project_settings)
+{
+  EXPECT_EQ(project_settings.project_name(), "Ružena");
+
+  const ListBase &asset_libraries = project_settings.asset_library_definitions();
+  CustomAssetLibraryDefinition *first = (CustomAssetLibraryDefinition *)asset_libraries.first;
+  EXPECT_STREQ(first->name, "Lorem Ipsum");
+  EXPECT_STREQ(first->path, "assets");
+  EXPECT_EQ(first->next, asset_libraries.last);
+  CustomAssetLibraryDefinition *last = (CustomAssetLibraryDefinition *)asset_libraries.last;
+  EXPECT_EQ(last->prev, asset_libraries.first);
+  EXPECT_STREQ(last->name, "Материалы");
+  EXPECT_STREQ(last->path, "новый\\assets");
+}
+
+TEST_F(ProjectTest, settings_json_read)
+{
+  SVNFiles svn_files{};
+  std::unique_ptr from_project_settings = ProjectSettings::load_from_disk(svn_files.project_root);
+  EXPECT_NE(from_project_settings, nullptr);
+  project_settings_match_expected_from_svn(*from_project_settings);
+}
+
+TEST_F(ProjectTest, settings_json_write)
+{
+  SVNFiles svn_files{};
+  std::unique_ptr from_project_settings = ProjectSettings::load_from_disk(svn_files.project_root);
+
+  /* Take the settings read from the SVN files and write it to /tmp/ projects. */
+  test_foreach_project_path(
+      [&from_project_settings](StringRefNull to_project_path, StringRefNull) {
+        BlenderProject::create_settings_directory(to_project_path);
+
+        if (!from_project_settings->save_to_disk(to_project_path)) {
+          FAIL();
+        }
+
+        /* Now check if the settings written to disk match the expectations. */
+        std::unique_ptr written_settings = ProjectSettings::load_from_disk(to_project_path);
+        EXPECT_NE(written_settings, nullptr);
+        project_settings_match_expected_from_svn(*written_settings);
+      });
+}
+
+TEST_F(ProjectTest, settings_read_change_write)
+{
+  SVNFiles svn_files{};
+  std::unique_ptr from_project_settings = ProjectSettings::load_from_disk(svn_files.project_root);
+
+  EXPECT_FALSE(from_project_settings->has_unsaved_changes());
+
+  /* Take the settings read from the SVN files and write it to /tmp/ projects. */
+  test_foreach_project_path(
+      [&from_project_settings](StringRefNull to_project_path, StringRefNull) {
+        BlenderProject::create_settings_directory(to_project_path);
+
+        from_project_settings->project_name("новый");
+        EXPECT_TRUE(from_project_settings->has_unsaved_changes());
+
+        if (!from_project_settings->save_to_disk(to_project_path)) {
+          FAIL();
+        }
+        EXPECT_FALSE(from_project_settings->has_unsaved_changes());
+
+        /* Now check if the settings written to disk match the expectations. */
+        std::unique_ptr written_settings = ProjectSettings::load_from_disk(to_project_path);
+        EXPECT_NE(written_settings, nullptr);
+        EXPECT_EQ(written_settings->project_name(), "новый");
+        EXPECT_FALSE(from_project_settings->has_unsaved_changes());
+      });
+}
+
+TEST_F(ProjectTest, project_root_path_find_from_path)
+{
+  /* Test the temporarily created directories with their various path formats. */
+  test_foreach_project_path([](StringRefNull project_path, StringRefNull /*project_path_native*/) {
+    /* First test without a .blender_project directory present. */
+    EXPECT_EQ(BlenderProject::project_root_path_find_from_path(project_path), "");
+
+    BlenderProject::create_settings_directory(project_path);
+    EXPECT_EQ(BlenderProject::project_root_path_find_from_path(project_path), project_path);
+  });
+
+  SVNFiles svn_files{};
+
+  /* Test the prepared project directory from the libs SVN repository. */
+  EXPECT_EQ(BlenderProject::project_root_path_find_from_path(svn_files.project_root +
+                                                             "/some_project_file.blend"),
+            svn_files.project_root);
+  EXPECT_EQ(BlenderProject::project_root_path_find_from_path(
+                svn_files.project_root +
+                "/unicode_subdirectory_новый/another_subdirectory/some_nested_project_file.blend"),
+            svn_files.project_root);
+}
+
+class BlendfileProjectLoadingTest : public BlendfileLoadingBaseTest {
+};
+
+/* Test if loading the blend file loads the project data as expected. */
+TEST_F(BlendfileProjectLoadingTest, load_blend_file)
+{
+  EXPECT_EQ(BKE_project_active_get(), nullptr);
+
+  if (!blendfile_load("blender_project/the_project/some_project_file.blend")) {
+    FAIL();
+  }
+
+  ::BlenderProject *svn_project = BKE_project_active_load_from_path(bfile->main->filepath);
+  EXPECT_NE(svn_project, nullptr);
+  EXPECT_EQ(BKE_project_active_get(), svn_project);
+  EXPECT_STREQ("Ružena", BKE_project_name_get(svn_project));
+  /* Note: The project above will be freed once a different active project is set. So get the path
+   * for future comparisons. */
+  std::string svn_project_path = BKE_project_root_path_get(svn_project);
+
+  blendfile_free();
+
+  /* Check if loading a different .blend updates the project properly */
+  if (!blendfile_load("blender_project/the_project/unicode_subdirectory_новый/"
+                      "another_subdirectory/some_nested_project_file.blend")) {
+    FAIL();
+  }
+  ::BlenderProject *svn_project_from_nested = BKE_project_active_load_from_path(
+      bfile->main->filepath);
+  EXPECT_NE(svn_project_from_nested, nullptr);
+  EXPECT_EQ(BKE_project_active_get(), svn_project_from_nested);
+  EXPECT_STREQ(svn_project_path.c_str(), BKE_project_root_path_get(svn_project_from_nested));
+  EXPECT_STREQ("Ružena", BKE_project_name_get(svn_project_from_nested));
+  blendfile_free();
+
+  /* Check if loading a .blend that's not in the project unsets the project properly. */
+  if (!blendfile_load("blender_project/not_a_project_file.blend")) {
+    FAIL();
+  }
+  BKE_project_active_load_from_path(bfile->main->filepath);
+  EXPECT_EQ(BKE_project_active_get(), nullptr);
+}
+
+TEST_F(ProjectTest, project_load_and_delete)
+{
+  test_foreach_project_path([](StringRefNull project_path, StringRefNull project_path_native) {
+    BlenderProject::create_settings_directory(project_path);
+
+    ::BlenderProject *project = BKE_project_active_load_from_path(project_path.c_str());
+    EXPECT_NE(project, nullptr);
+    EXPECT_FALSE(BKE_project_has_unsaved_changes(project));
+
+    std::string project_settings_dir = project_path_native + SEP_STR +
+                                       BlenderProject::SETTINGS_DIRNAME;
+
+    EXPECT_TRUE(BLI_exists(project_settings_dir.c_str()));
+    if (!BKE_project_delete_settings_directory(project)) {
+      FAIL();
+    }
+    /* Runtime project should still exist, but with unsaved changes. */
+    EXPECT_NE(project, nullptr);
+    EXPECT_TRUE(BKE_project_has_unsaved_changes(project));
+    EXPECT_FALSE(BLI_exists(project_settings_dir.c_str()));
+  });
+}
+
+}  // namespace blender::bke::tests

source/blender/blenkernel/intern/blendfile.cc

@@ -30,6 +30,7 @@
 #include "BKE_addon.h"
 #include "BKE_appdir.h"
 #include "BKE_blender.h"
+#include "BKE_blender_project.h"
 #include "BKE_blender_version.h"
 #include "BKE_blendfile.h"
 #include "BKE_bpath.h"
@@ -455,6 +456,16 @@ static void setup_app_blend_file_data(bContext *C,
   }
 }
 
+static void setup_app_project_data(BlendFileData *bfd, const struct BlendFileReadParams *params)
+{
+  if (!U.experimental.use_blender_projects) {
+    return;
+  }
+  if ((params->skip_flags & BLO_READ_SKIP_DATA) == 0) {
+    BKE_project_active_load_from_path(bfd->main->filepath);
+  }
+}
+
 static void handle_subversion_warning(Main *main, BlendFileReadReport *reports)
 {
   if (main->minversionfile > BLENDER_FILE_VERSION ||
@@ -481,6 +492,7 @@ void BKE_blendfile_read_setup_ex(bContext *C,
       BLO_update_defaults_startup_blend(bfd->main, startup_app_template);
     }
   }
+  setup_app_project_data(bfd, params);
   setup_app_blend_file_data(C, bfd, params, reports);
   BLO_blendfiledata_free(bfd);
 }
@@ -695,7 +707,7 @@ UserDef *BKE_blendfile_userdef_from_defaults(void)
   /* Default studio light. */
   BKE_studiolight_default(userdef->light_param, userdef->light_ambient);
 
-  BKE_preferences_asset_library_default_add(userdef);
+  BKE_preferences_custom_asset_library_default_add(userdef);
 
   return userdef;
 }

source/blender/blenkernel/intern/context.cc

@@ -30,6 +30,7 @@
 
 #include "BLT_translation.h"
 
+#include "BKE_blender_project.h"
 #include "BKE_context.h"
 #include "BKE_layer.h"
 #include "BKE_main.h"
@@ -763,6 +764,11 @@ ReportList *CTX_wm_reports(const bContext *C)
   return nullptr;
 }
 
+BlenderProject *CTX_wm_project(void)
+{
+  return BKE_project_active_get();
+}
+
 View3D *CTX_wm_view3d(const bContext *C)
 {
   ScrArea *area = CTX_wm_area(C);
@@ -929,6 +935,15 @@ SpaceSpreadsheet *CTX_wm_space_spreadsheet(const bContext *C)
   return nullptr;
 }
 
+SpaceProjectSettings *CTX_wm_space_project_settings(const bContext *C)
+{
+  ScrArea *area = CTX_wm_area(C);
+  if (area && area->spacetype == SPACE_PROJECT_SETTINGS) {
+    return static_cast<SpaceProjectSettings *>(area->spacedata.first);
+  }
+  return nullptr;
+}
+
 void CTX_wm_manager_set(bContext *C, wmWindowManager *wm)
 {
   C->wm.manager = wm;

source/blender/blenkernel/intern/preferences.c

@@ -2,28 +2,17 @@
 
 /** \file
  * \ingroup bke
- *
- * User defined asset library API.
  */
 
-#include <string.h>
-
-#include "DNA_asset_types.h"
-
-#include "MEM_guardedalloc.h"
-
-#include "BLI_fileops.h"
-#include "BLI_listbase.h"
 #include "BLI_path_util.h"
-#include "BLI_string.h"
-#include "BLI_string_utf8.h"
-#include "BLI_string_utils.h"
 
 #include "BKE_appdir.h"
+#include "BKE_asset_library_custom.h"
 #include "BKE_preferences.h"
 
 #include "BLT_translation.h"
 
+#include "DNA_asset_types.h"
 #include "DNA_userdef_types.h"
 
 #define U BLI_STATIC_ASSERT(false, "Global 'U' not allowed, only use arguments passed in!")
@@ -32,80 +21,7 @@
 /** \name Asset Libraries
  * \{ */
 
-bUserAssetLibrary *BKE_preferences_asset_library_add(UserDef *userdef,
-                                                     const char *name,
-                                                     const char *path)
-{
-  bUserAssetLibrary *library = MEM_callocN(sizeof(*library), "bUserAssetLibrary");
-
-  BLI_addtail(&userdef->asset_libraries, library);
-
-  if (name) {
-    BKE_preferences_asset_library_name_set(userdef, library, name);
-  }
-  if (path) {
-    BLI_strncpy(library->path, path, sizeof(library->path));
-  }
-  library->import_method = ASSET_IMPORT_APPEND_REUSE;
-
-  return library;
-}
-
-void BKE_preferences_asset_library_remove(UserDef *userdef, bUserAssetLibrary *library)
-{
-  BLI_freelinkN(&userdef->asset_libraries, library);
-}
-
-void BKE_preferences_asset_library_name_set(UserDef *userdef,
-                                            bUserAssetLibrary *library,
-                                            const char *name)
-{
-  BLI_strncpy_utf8(library->name, name, sizeof(library->name));
-  BLI_uniquename(&userdef->asset_libraries,
-                 library,
-                 name,
-                 '.',
-                 offsetof(bUserAssetLibrary, name),
-                 sizeof(library->name));
-}
-
-void BKE_preferences_asset_library_path_set(bUserAssetLibrary *library, const char *path)
-{
-  BLI_strncpy(library->path, path, sizeof(library->path));
-  if (BLI_is_file(library->path)) {
-    BLI_path_parent_dir(library->path);
-  }
-}
-
-bUserAssetLibrary *BKE_preferences_asset_library_find_from_index(const UserDef *userdef, int index)
-{
-  return BLI_findlink(&userdef->asset_libraries, index);
-}
-
-bUserAssetLibrary *BKE_preferences_asset_library_find_from_name(const UserDef *userdef,
-                                                                const char *name)
-{
-  return BLI_findstring(&userdef->asset_libraries, name, offsetof(bUserAssetLibrary, name));
-}
-
-bUserAssetLibrary *BKE_preferences_asset_library_containing_path(const UserDef *userdef,
-                                                                 const char *path)
-{
-  LISTBASE_FOREACH (bUserAssetLibrary *, asset_lib_pref, &userdef->asset_libraries) {
-    if (BLI_path_contains(asset_lib_pref->path, path)) {
-      return asset_lib_pref;
-    }
-  }
-  return NULL;
-}
-
-int BKE_preferences_asset_library_get_index(const UserDef *userdef,
-                                            const bUserAssetLibrary *library)
-{
-  return BLI_findindex(&userdef->asset_libraries, library);
-}
-
-void BKE_preferences_asset_library_default_add(UserDef *userdef)
+void BKE_preferences_custom_asset_library_default_add(UserDef *userdef)
 {
   char documents_path[FILE_MAXDIR];
 
@@ -114,8 +30,8 @@ void BKE_preferences_asset_library_default_add(UserDef *userdef)
     return;
   }
 
-  bUserAssetLibrary *library = BKE_preferences_asset_library_add(
-      userdef, DATA_(BKE_PREFS_ASSET_LIBRARY_DEFAULT_NAME), NULL);
+  CustomAssetLibraryDefinition *library = BKE_asset_library_custom_add(
+      &userdef->asset_libraries, DATA_(BKE_PREFS_ASSET_LIBRARY_DEFAULT_NAME), NULL);
 
   /* Add new "Default" library under '[doc_path]/Blender/Assets'. */
   BLI_path_join(library->path, sizeof(library->path), documents_path, N_("Blender"), N_("Assets"));

source/blender/blenloader/intern/readfile.cc

@@ -2675,6 +2675,7 @@ static void lib_link_workspace_layout_restore(IDNameLib_Map *id_map,
           case SPACE_USERPREF:
           case SPACE_TOPBAR:
           case SPACE_STATUSBAR:
+          case SPACE_PROJECT_SETTINGS:
           case SPACE_EMPTY:
             /* Nothing to do here. */
             break;

source/blender/blenloader/intern/versioning_userdef.c

@@ -22,6 +22,7 @@
 #include "DNA_windowmanager_types.h"
 
 #include "BKE_addon.h"
+#include "BKE_asset_library_custom.h"
 #include "BKE_blender_version.h"
 #include "BKE_colorband.h"
 #include "BKE_idprop.h"
@@ -100,6 +101,7 @@ static void do_versions_theme(const UserDef *userdef, bTheme *btheme)
    */
   {
     /* Keep this block, even when empty. */
+    btheme->space_project_settings = btheme->space_preferences;
   }
 
 #undef FROM_DEFAULT_V4_UCHAR
@@ -680,7 +682,7 @@ void blo_do_versions_userdef(UserDef *userdef)
 
   if (!USER_VERSION_ATLEAST(292, 9)) {
     if (BLI_listbase_is_empty(&userdef->asset_libraries)) {
-      BKE_preferences_asset_library_default_add(userdef);
+      BKE_preferences_custom_asset_library_default_add(userdef);
     }
   }
 
@@ -733,11 +735,11 @@ void blo_do_versions_userdef(UserDef *userdef)
      * since it doesn't handle translations and ignores user changes. But this was an alpha build
      * (experimental) feature and the name is just for display in the UI anyway. So it doesn't have
      * to work perfectly at all. */
-    LISTBASE_FOREACH (bUserAssetLibrary *, asset_library, &userdef->asset_libraries) {
+    LISTBASE_FOREACH (CustomAssetLibraryDefinition *, asset_library, &userdef->asset_libraries) {
       /* Ignores translations, since that would depend on the current preferences (global `U`). */
       if (STREQ(asset_library->name, "Default")) {
-        BKE_preferences_asset_library_name_set(
-            userdef, asset_library, BKE_PREFS_ASSET_LIBRARY_DEFAULT_NAME);
+        BKE_asset_library_custom_name_set(
+            &userdef->asset_libraries, asset_library, BKE_PREFS_ASSET_LIBRARY_DEFAULT_NAME);
       }
     }
   }
@@ -774,7 +776,7 @@ void blo_do_versions_userdef(UserDef *userdef)
   }
 
   if (!USER_VERSION_ATLEAST(305, 10)) {
-    LISTBASE_FOREACH (bUserAssetLibrary *, asset_library, &userdef->asset_libraries) {
+    LISTBASE_FOREACH (CustomAssetLibraryDefinition *, asset_library, &userdef->asset_libraries) {
       asset_library->import_method = ASSET_IMPORT_APPEND_REUSE;
     }
   }

source/blender/blenloader/intern/writefile.cc

@@ -94,6 +94,8 @@
 #include "BLI_threads.h"
 #include "MEM_guardedalloc.h" /* MEM_freeN */
 
+#include "BKE_blender_project.h"
+#include "BKE_blender_project.hh"
 #include "BKE_blender_version.h"
 #include "BKE_bpath.h"
 #include "BKE_global.h" /* for G */
@@ -922,8 +924,9 @@ static void write_userdef(BlendWriter *writer, const UserDef *userdef)
     BLO_write_struct(writer, bPathCompare, path_cmp);
   }
 
-  LISTBASE_FOREACH (const bUserAssetLibrary *, asset_library_ref, &userdef->asset_libraries) {
-    BLO_write_struct(writer, bUserAssetLibrary, asset_library_ref);
+  LISTBASE_FOREACH (
+      const CustomAssetLibraryDefinition *, asset_library_ref, &userdef->asset_libraries) {
+    BLO_write_struct(writer, CustomAssetLibraryDefinition, asset_library_ref);
   }
 
   LISTBASE_FOREACH (const uiStyle *, style, &userdef->uistyles) {
@@ -1506,6 +1509,11 @@ bool BLO_write_file(Main *mainvar,
     }
   }
 
+  /* Update active project information based on the new file location. */
+  if (U.experimental.use_blender_projects) {
+    BKE_project_active_load_from_path(filepath);
+  }
+
   /* actual file writing */
   const bool err = write_file_handle(
       mainvar, &ww, nullptr, nullptr, write_flags, use_userdef, thumb);

source/blender/editors/CMakeLists.txt

@@ -21,6 +21,7 @@ if(WITH_BLENDER)
   add_subdirectory(metaball)
   add_subdirectory(object)
   add_subdirectory(physics)
+  add_subdirectory(project)
   add_subdirectory(render)
   add_subdirectory(scene)
   add_subdirectory(sculpt_paint)
@@ -37,6 +38,7 @@ if(WITH_BLENDER)
   add_subdirectory(space_nla)
   add_subdirectory(space_node)
   add_subdirectory(space_outliner)
+  add_subdirectory(space_project_settings)
   add_subdirectory(space_script)
   add_subdirectory(space_sequencer)
   add_subdirectory(space_spreadsheet)

source/blender/editors/asset/ED_asset_library.h

@@ -37,6 +37,8 @@ AssetLibraryReference ED_asset_library_reference_from_enum_value(int value);
 const struct EnumPropertyItem *ED_asset_library_reference_to_rna_enum_itemf(
     bool include_generated);
 
+struct CustomAssetLibraryDefinition *ED_asset_library_find_custom_library_from_reference(
+    const AssetLibraryReference *library_ref);
 #ifdef __cplusplus
 }
 #endif

source/blender/editors/asset/intern/asset_library_reference.cc

@@ -4,8 +4,15 @@
  * \ingroup edasset
  */
 
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender_project.h"
+#include "BKE_context.h"
+
+#include "DNA_userdef_types.h"
+
 #include "BLI_hash.hh"
 
+#include "ED_asset_library.h"
 #include "asset_library_reference.hh"
 
 namespace blender::ed::asset {
@@ -18,14 +25,15 @@ AssetLibraryReferenceWrapper::AssetLibraryReferenceWrapper(const AssetLibraryRef
 bool operator==(const AssetLibraryReferenceWrapper &a, const AssetLibraryReferenceWrapper &b)
 {
   return (a.type == b.type) &&
-         ((a.type == ASSET_LIBRARY_CUSTOM) ? (a.custom_library_index == b.custom_library_index) :
-                                             true);
+         (ELEM(a.type, ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES, ASSET_LIBRARY_CUSTOM_FROM_PROJECT) ?
+              (a.custom_library_index == b.custom_library_index) :
+              true);
 }
 
 uint64_t AssetLibraryReferenceWrapper::hash() const
 {
   uint64_t hash1 = DefaultHash<decltype(type)>{}(type);
-  if (type != ASSET_LIBRARY_CUSTOM) {
+  if (!ELEM(type, ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES, ASSET_LIBRARY_CUSTOM_FROM_PROJECT)) {
     return hash1;
   }
 
@@ -34,3 +42,25 @@ uint64_t AssetLibraryReferenceWrapper::hash() const
 }
 
 }  // namespace blender::ed::asset
+
+CustomAssetLibraryDefinition *ED_asset_library_find_custom_library_from_reference(
+    const AssetLibraryReference *library_ref)
+{
+  switch (library_ref->type) {
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES:
+      return BKE_asset_library_custom_find_from_index(&U.asset_libraries,
+                                                      library_ref->custom_library_index);
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT: {
+      BlenderProject *project = CTX_wm_project();
+      if (project) {
+        return BKE_asset_library_custom_find_from_index(
+            BKE_project_custom_asset_libraries_get(project), library_ref->custom_library_index);
+      }
+      break;
+    }
+    case ASSET_LIBRARY_LOCAL:
+      return nullptr;
+  }
+
+  return nullptr;
+}

source/blender/editors/asset/intern/asset_library_reference_enum.cc

@@ -11,7 +11,9 @@
 
 #include "BLI_listbase.h"
 
-#include "BKE_preferences.h"
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender_project.h"
+#include "BKE_context.h"
 
 #include "DNA_userdef_types.h"
 
@@ -23,17 +25,15 @@
 
 int ED_asset_library_reference_to_enum_value(const AssetLibraryReference *library)
 {
-  /* Simple case: Predefined repository, just set the value. */
-  if (library->type < ASSET_LIBRARY_CUSTOM) {
+  /* Simple case: Predefined library, just set the value. */
+  if (library->type < ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES) {
     return library->type;
   }
 
   /* Note that the path isn't checked for validity here. If an invalid library path is used, the
    * Asset Browser can give a nice hint on what's wrong. */
-  const bUserAssetLibrary *user_library = BKE_preferences_asset_library_find_from_index(
-      &U, library->custom_library_index);
-  if (user_library) {
-    return ASSET_LIBRARY_CUSTOM + library->custom_library_index;
+  if (ED_asset_library_find_custom_library_from_reference(library)) {
+    return library->type + library->custom_library_index;
   }
 
   return ASSET_LIBRARY_LOCAL;
@@ -44,32 +44,63 @@ AssetLibraryReference ED_asset_library_reference_from_enum_value(int value)
   AssetLibraryReference library;
 
   /* Simple case: Predefined repository, just set the value. */
-  if (value < ASSET_LIBRARY_CUSTOM) {
+  if (value < ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES) {
     library.type = value;
     library.custom_library_index = -1;
     BLI_assert(ELEM(value, ASSET_LIBRARY_ALL, ASSET_LIBRARY_LOCAL, ASSET_LIBRARY_ESSENTIALS));
     return library;
   }
 
-  const bUserAssetLibrary *user_library = BKE_preferences_asset_library_find_from_index(
-      &U, value - ASSET_LIBRARY_CUSTOM);
+  const eAssetLibraryType type = (value < ASSET_LIBRARY_CUSTOM_FROM_PROJECT) ?
+                                     ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES :
+                                     ASSET_LIBRARY_CUSTOM_FROM_PROJECT;
 
-  /* Note that there is no check if the path exists here. If an invalid library path is used, the
-   * Asset Browser can give a nice hint on what's wrong. */
-  if (!user_library) {
-    library.type = ASSET_LIBRARY_ALL;
-    library.custom_library_index = -1;
-  }
-  else {
-    const bool is_valid = (user_library->name[0] && user_library->path[0]);
-    if (is_valid) {
-      library.custom_library_index = value - ASSET_LIBRARY_CUSTOM;
-      library.type = ASSET_LIBRARY_CUSTOM;
+  const CustomAssetLibraryDefinition *custom_library = nullptr;
+
+  library.type = type;
+  library.custom_library_index = value - type;
+
+  {
+    custom_library = ED_asset_library_find_custom_library_from_reference(&library);
+
+    /* Note that there is no check if the path exists here. If an invalid library path is used, the
+     * Asset Browser can give a nice hint on what's wrong. */
+    const bool is_valid = custom_library && (custom_library->name[0] && custom_library->path[0]);
+    if (!is_valid) {
+      library.custom_library_index = -1;
     }
   }
+
   return library;
 }
 
+static void add_custom_asset_library_enum_items(
+    const ListBase * /*CustomAssetLibraryDefinition*/ libraries,
+    const eAssetLibraryType library_type,
+    EnumPropertyItem **items,
+    int *totitem)
+{
+  int i;
+  LISTBASE_FOREACH_INDEX (CustomAssetLibraryDefinition *, custom_library, libraries, i) {
+    /* Note that the path itself isn't checked for validity here. If an invalid library path is
+     * used, the Asset Browser can give a nice hint on what's wrong. */
+    const bool is_valid = (custom_library->name[0] && custom_library->path[0]);
+    if (!is_valid) {
+      continue;
+    }
+
+    AssetLibraryReference library_reference;
+    library_reference.type = library_type;
+    library_reference.custom_library_index = i;
+
+    const int enum_value = ED_asset_library_reference_to_enum_value(&library_reference);
+    /* Use library path as description, it's a nice hint for users. */
+    EnumPropertyItem tmp = {
+        enum_value, custom_library->name, ICON_NONE, custom_library->name, custom_library->path};
+    RNA_enum_item_add(items, totitem, &tmp);
+  }
+}
+
 const EnumPropertyItem *ED_asset_library_reference_to_rna_enum_itemf(const bool include_generated)
 {
   EnumPropertyItem *item = nullptr;
@@ -97,29 +128,21 @@ const EnumPropertyItem *ED_asset_library_reference_to_rna_enum_itemf(const bool
     RNA_enum_items_add(&item, &totitem, generated_items);
   }
 
-  /* Add separator if needed. */
-  if (!BLI_listbase_is_empty(&U.asset_libraries)) {
+  BlenderProject *project = CTX_wm_project();
+  if (project && !BLI_listbase_is_empty(BKE_project_custom_asset_libraries_get(project))) {
     RNA_enum_item_add_separator(&item, &totitem);
+
+    add_custom_asset_library_enum_items(BKE_project_custom_asset_libraries_get(project),
+                                        ASSET_LIBRARY_CUSTOM_FROM_PROJECT,
+                                        &item,
+                                        &totitem);
   }
 
-  int i;
-  LISTBASE_FOREACH_INDEX (bUserAssetLibrary *, user_library, &U.asset_libraries, i) {
-    /* Note that the path itself isn't checked for validity here. If an invalid library path is
-     * used, the Asset Browser can give a nice hint on what's wrong. */
-    const bool is_valid = (user_library->name[0] && user_library->path[0]);
-    if (!is_valid) {
-      continue;
-    }
+  if (!BLI_listbase_is_empty(&U.asset_libraries)) {
+    RNA_enum_item_add_separator(&item, &totitem);
 
-    AssetLibraryReference library_reference;
-    library_reference.type = ASSET_LIBRARY_CUSTOM;
-    library_reference.custom_library_index = i;
-
-    const int enum_value = ED_asset_library_reference_to_enum_value(&library_reference);
-    /* Use library path as description, it's a nice hint for users. */
-    EnumPropertyItem tmp = {
-        enum_value, user_library->name, ICON_NONE, user_library->name, user_library->path};
-    RNA_enum_item_add(&item, &totitem, &tmp);
+    add_custom_asset_library_enum_items(
+        &U.asset_libraries, ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES, &item, &totitem);
   }
 
   RNA_enum_item_end(&item, &totitem);

source/blender/editors/asset/intern/asset_list.cc

@@ -14,15 +14,15 @@
 
 #include "AS_asset_library.hh"
 
+#include "BKE_blender_project.h"
 #include "BKE_context.h"
 
 #include "BLI_map.hh"
+#include "BLI_path_util.h"
 #include "BLI_utility_mixins.hh"
 
 #include "DNA_space_types.h"
 
-#include "BKE_preferences.h"
-
 #include "WM_api.h"
 
 /* XXX uses private header of file-space. */
@@ -31,6 +31,7 @@
 
 #include "ED_asset_handle.h"
 #include "ED_asset_indexer.h"
+#include "ED_asset_library.h"
 #include "ED_asset_list.h"
 #include "ED_asset_list.hh"
 #include "asset_library_reference.hh"
@@ -373,7 +374,8 @@ std::optional<eFileSelectType> AssetListStorage::asset_library_reference_to_file
     case ASSET_LIBRARY_ALL:
       return FILE_ASSET_LIBRARY_ALL;
     case ASSET_LIBRARY_ESSENTIALS:
-    case ASSET_LIBRARY_CUSTOM:
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES:
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT:
       return FILE_ASSET_LIBRARY;
     case ASSET_LIBRARY_LOCAL:
       return FILE_MAIN_ASSET;

source/blender/editors/asset/intern/asset_ops.cc

@@ -7,11 +7,11 @@
 #include "AS_asset_library.h"
 #include "AS_asset_library.hh"
 
+#include "BKE_asset_library_custom.h"
 #include "BKE_bpath.h"
 #include "BKE_context.h"
 #include "BKE_lib_id.h"
 #include "BKE_main.h"
-#include "BKE_preferences.h"
 #include "BKE_report.h"
 
 #include "BLI_fileops.h" /* MSVC needs this for `PATH_MAX` */
@@ -679,7 +679,7 @@ static void ASSET_OT_catalogs_save(struct wmOperatorType *ot)
 /* -------------------------------------------------------------------- */
 
 static bool could_be_asset_bundle(const Main *bmain);
-static const bUserAssetLibrary *selected_asset_library(struct wmOperator *op);
+static const CustomAssetLibraryDefinition *selected_asset_library(struct wmOperator *op);
 static bool is_contained_in_selected_asset_library(struct wmOperator *op, const char *filepath);
 static bool set_filepath_for_asset_lib(const Main *bmain, struct wmOperator *op);
 static bool has_external_files(Main *bmain, struct ReportList *reports);
@@ -701,8 +701,8 @@ static bool asset_bundle_install_poll(bContext *C)
   }
 
   /* Check whether this file is already located inside any asset library. */
-  const struct bUserAssetLibrary *asset_lib = BKE_preferences_asset_library_containing_path(
-      &U, bmain->filepath);
+  const struct CustomAssetLibraryDefinition *asset_lib = BKE_asset_library_custom_containing_path(
+      &U.asset_libraries, bmain->filepath);
   if (asset_lib) {
     return false;
   }
@@ -773,7 +773,7 @@ static int asset_bundle_install_exec(bContext *C, wmOperator *op)
     return operator_result;
   }
 
-  const bUserAssetLibrary *lib = selected_asset_library(op);
+  const CustomAssetLibraryDefinition *lib = selected_asset_library(op);
   BLI_assert_msg(lib, "If the asset library is not known, how did we get here?");
   BKE_reportf(op->reports,
               RPT_INFO,
@@ -833,18 +833,18 @@ static bool could_be_asset_bundle(const Main *bmain)
   return fnmatch("*_bundle.blend", bmain->filepath, FNM_CASEFOLD) == 0;
 }
 
-static const bUserAssetLibrary *selected_asset_library(struct wmOperator *op)
+static const CustomAssetLibraryDefinition *selected_asset_library(struct wmOperator *op)
 {
   const int enum_value = RNA_enum_get(op->ptr, "asset_library_ref");
   const AssetLibraryReference lib_ref = ED_asset_library_reference_from_enum_value(enum_value);
-  const bUserAssetLibrary *lib = BKE_preferences_asset_library_find_from_index(
-      &U, lib_ref.custom_library_index);
+  const CustomAssetLibraryDefinition *lib = BKE_asset_library_custom_find_from_index(
+      &U.asset_libraries, lib_ref.custom_library_index);
   return lib;
 }
 
 static bool is_contained_in_selected_asset_library(struct wmOperator *op, const char *filepath)
 {
-  const bUserAssetLibrary *lib = selected_asset_library(op);
+  const CustomAssetLibraryDefinition *lib = selected_asset_library(op);
   if (!lib) {
     return false;
   }
@@ -858,7 +858,7 @@ static bool is_contained_in_selected_asset_library(struct wmOperator *op, const
 static bool set_filepath_for_asset_lib(const Main *bmain, struct wmOperator *op)
 {
   /* Find the directory path of the selected asset library. */
-  const bUserAssetLibrary *lib = selected_asset_library(op);
+  const CustomAssetLibraryDefinition *lib = selected_asset_library(op);
   if (lib == nullptr) {
     return false;
   }

source/blender/editors/include/ED_project.h

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup editors
+ *
+ * Editor level functions for Blender projects.
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct BlenderProject;
+struct Main;
+struct ReportList;
+
+void ED_operatortypes_project(void);
+
+/** Sets the project name to the directory name it is located in and registers a "Project Library"
+ * asset library pointing to `//assets/`. */
+void ED_project_set_defaults(struct BlenderProject *project);
+/**
+ * High level project creation (create project + load if needed + write default settings if
+ * needed).
+ *
+ * Initializes a new project in \a project_root_dir by creating the `.blender_project/` directory
+ * there. The new project will only be loaded if \a bmain represents a file within the project
+ * directory.
+ *
+ * \return True on success.
+ */
+bool ED_project_new(const struct Main *bmain,
+                    const char *project_root_dir,
+                    struct ReportList *reports);
+
+#ifdef __cplusplus
+}
+#endif

source/blender/editors/include/ED_screen.h

@@ -28,6 +28,7 @@ struct Depsgraph;
 struct IDProperty;
 struct Main;
 struct MenuType;
+struct ReportList;
 struct Scene;
 struct SpaceLink;
 struct WorkSpace;
@@ -492,6 +493,9 @@ int ED_screen_animation_play(struct bContext *C, int sync, int mode);
 bScreen *ED_screen_animation_playing(const struct wmWindowManager *wm);
 bScreen *ED_screen_animation_no_scrub(const struct wmWindowManager *wm);
 
+/** \return True on success. */
+bool ED_project_settings_window_show(struct bContext *C, struct ReportList *reports);
+
 /* screen keymaps */
 /* called in spacetypes.c */
 void ED_operatortypes_screen(void);

source/blender/editors/include/ED_space_api.h

@@ -46,6 +46,7 @@ void ED_spacetype_clip(void);
 void ED_spacetype_statusbar(void);
 void ED_spacetype_topbar(void);
 void ED_spacetype_spreadsheet(void);
+void ED_spacetype_project_settings(void);
 
 /** \} */
 

source/blender/editors/interface/interface_handlers.cc

@@ -675,7 +675,7 @@ static bool ui_rna_is_userdef(PointerRNA *ptr, PropertyRNA *prop)
               &RNA_AddonPreferences,
               &RNA_KeyConfigPreferences,
               &RNA_KeyMapItem,
-              &RNA_UserAssetLibrary);
+              &RNA_CustomAssetLibraryDefinition);
 }
 
 bool UI_but_is_userdef(const uiBut *but)

source/blender/editors/interface/interface_template_search_menu.cc

@@ -634,6 +634,7 @@ static MenuSearch_Data *menu_items_from_ui_create(
           SPACE_MENU_MAP(SPACE_NODE, "NODE_MT_editor_menus");
           SPACE_MENU_MAP(SPACE_CONSOLE, "CONSOLE_MT_editor_menus");
           SPACE_MENU_MAP(SPACE_USERPREF, "USERPREF_MT_editor_menus");
+          SPACE_MENU_MAP(SPACE_PROJECT_SETTINGS, "PROJECTSETTINGS_MT_editor_menus");
           SPACE_MENU_MAP(SPACE_CLIP,
                          (((const SpaceClip *)sl)->mode == SC_MODE_TRACKING) ?
                              "CLIP_MT_tracking_editor_menus" :

source/blender/editors/interface/resources.cc

@@ -122,6 +122,9 @@ const uchar *UI_ThemeGetColorPtr(bTheme *btheme, int spacetype, int colorid)
         case SPACE_USERPREF:
           ts = &btheme->space_preferences;
           break;
+        case SPACE_PROJECT_SETTINGS:
+          ts = &btheme->space_project_settings;
+          break;
         case SPACE_CONSOLE:
           ts = &btheme->space_console;
           break;

source/blender/editors/project/CMakeLists.txt

@@ -0,0 +1,28 @@
+
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set(INC
+  .
+  ../include
+  ../../blenkernel
+  ../../blenlib
+  ../../blentranslation
+  ../../makesdna
+  ../../makesrna
+  ../../windowmanager
+  ../../../../intern/guardedalloc
+)
+
+set(INC_SYS
+)
+
+set(SRC
+    project.cc
+    project_ops.cc
+)
+
+set(LIB
+  bf_blenkernel
+)
+
+blender_add_lib(bf_editor_project "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")

source/blender/editors/project/project.cc

@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup edproject
+ */
+
+#include "BLI_path_util.h"
+#include "BLI_string.h"
+#include "BLI_string_ref.hh"
+
+#include "BLT_translation.h"
+
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender_project.h"
+#include "BKE_blender_project.hh"
+#include "BKE_context.h"
+#include "BKE_main.h"
+#include "BKE_report.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "ED_project.h"
+
+using namespace blender;
+
+/** Name of the asset library added by default. Needs translation with `DATA_()`. */
+inline static const char *DEFAULT_ASSET_LIBRARY_NAME = N_("Project Library");
+inline static const char *DEFAULT_ASSET_LIBRARY_PATH = "//assets/";
+
+void ED_project_set_defaults(BlenderProject *project)
+{
+  char project_root_dir[FILE_MAXDIR];
+  BLI_strncpy(project_root_dir, BKE_project_root_path_get(project), sizeof(project_root_dir));
+
+  /* Set directory name as default project name. */
+  char dirname[FILE_MAXFILE];
+  BLI_path_slash_rstrip(project_root_dir);
+  BLI_split_file_part(project_root_dir, dirname, sizeof(dirname));
+  BKE_project_name_set(project, dirname);
+
+  ListBase *libraries = BKE_project_custom_asset_libraries_get(project);
+  BKE_asset_library_custom_add(
+      libraries, DATA_(DEFAULT_ASSET_LIBRARY_NAME), DEFAULT_ASSET_LIBRARY_PATH);
+}
+
+bool ED_project_new(const Main *bmain, const char *project_root_dir, ReportList *reports)
+{
+  if (!BKE_project_create_settings_directory(project_root_dir)) {
+    BKE_reportf(reports,
+                RPT_ERROR,
+                "Failed to create project with unknown error. Is the directory read-only?");
+    return false;
+  }
+
+  std::unique_ptr<bke::BlenderProject> loaded_project = bke::BlenderProject::load_from_path(
+      project_root_dir);
+
+  /* Some default settings for the project. */
+  if (loaded_project) {
+    BlenderProject *loaded_project_c = BKE_project_c_handle(loaded_project.get());
+
+    ED_project_set_defaults(loaded_project_c);
+    /* Write defaults to the hard drive. */
+    BKE_project_settings_save(loaded_project_c);
+  }
+
+  BKE_reportf(reports, RPT_INFO, "Project created and loaded successfully");
+
+  const char *blend_path = BKE_main_blendfile_path(bmain);
+  const bool blend_is_in_project = blend_path[0] &&
+                                   BLI_path_contains(project_root_dir, blend_path);
+  if (blend_is_in_project) {
+    bke::BlenderProject::set_active(std::move(loaded_project));
+  }
+  else {
+    BKE_reportf(reports,
+                RPT_WARNING,
+                "The current file is not located inside of the new project. This means the new "
+                "project is not active");
+  }
+
+  return true;
+}

source/blender/editors/project/project_ops.cc

@@ -0,0 +1,298 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup edproject
+ */
+
+#include <climits>
+
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender_project.h"
+#include "BKE_context.h"
+#include "BKE_main.h"
+#include "BKE_report.h"
+
+#include "BLI_path_util.h"
+
+#include "BLT_translation.h"
+
+#include "DNA_space_types.h"
+
+#include "RNA_access.h"
+#include "RNA_define.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "ED_project.h"
+#include "ED_screen.h"
+
+using namespace blender;
+
+static bool has_active_project_poll(bContext *C)
+{
+  const BlenderProject *active_project = CTX_wm_project();
+  CTX_wm_operator_poll_msg_set(C, TIP_("No active project loaded"));
+  return active_project != NULL;
+}
+
+/* -------------------------------------------------------------------- */
+/** \name New project operator
+ * \{ */
+
+static bool new_project_poll(bContext *C)
+{
+  if (!U.experimental.use_blender_projects) {
+    CTX_wm_operator_poll_msg_set(C, "Experimental project support is not enabled");
+    return false;
+  }
+  return true;
+}
+
+static int new_project_exec(bContext *C, wmOperator *op)
+{
+  const Main *bmain = CTX_data_main(C);
+
+  if (!RNA_struct_property_is_set(op->ptr, "directory")) {
+    BKE_report(op->reports, RPT_ERROR, "No path defined for creating a new project in");
+    return OPERATOR_CANCELLED;
+  }
+  char project_root_dir[FILE_MAXDIR];
+  RNA_string_get(op->ptr, "directory", project_root_dir);
+
+  if (!ED_project_new(bmain, project_root_dir, op->reports)) {
+    return OPERATOR_CANCELLED;
+  }
+
+  PropertyRNA *prop_open_settings = RNA_struct_find_property(op->ptr, "open_settings_after");
+  if (RNA_property_is_set(op->ptr, prop_open_settings) &&
+      RNA_property_boolean_get(op->ptr, prop_open_settings)) {
+    ED_project_settings_window_show(C, op->reports);
+  }
+
+  WM_main_add_notifier(NC_PROJECT, NULL);
+  /* Update the window title. */
+  WM_main_add_notifier(NC_WM | ND_DATACHANGED, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+static int new_project_invoke(bContext *C, wmOperator *op, const wmEvent * /*event*/)
+{
+  const Main *bmain = CTX_data_main(C);
+  const char *blendfile_path = BKE_main_blendfile_path(bmain);
+  if (blendfile_path[0]) {
+    /* Open at the .blend file location if any. */
+    RNA_string_set(op->ptr, "directory", blendfile_path);
+  }
+
+  WM_event_add_fileselect(C, op);
+  return OPERATOR_RUNNING_MODAL;
+}
+
+static void PROJECT_OT_new(wmOperatorType *ot)
+{
+  ot->name = "New Project";
+  ot->idname = "PROJECT_OT_new";
+  ot->description = "Choose a directory to use as the root of a project";
+
+  ot->invoke = new_project_invoke;
+  ot->exec = new_project_exec;
+  /* omit window poll so this can work in background mode */
+  ot->poll = new_project_poll;
+
+  WM_operator_properties_filesel(ot,
+                                 FILE_TYPE_FOLDER,
+                                 FILE_BLENDER,
+                                 FILE_OPENFILE,
+                                 WM_FILESEL_DIRECTORY,
+                                 FILE_DEFAULTDISPLAY,
+                                 FILE_SORT_DEFAULT);
+
+  PropertyRNA *prop;
+  prop = RNA_def_boolean(ot->srna,
+                         "open_settings_after",
+                         false,
+                         "",
+                         "Open the project settings window after successfully creating a project");
+  RNA_def_property_flag(prop, PROP_HIDDEN);
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Write Project Settings Operator
+ * \{ */
+
+static int save_settings_exec(bContext * /*C*/, wmOperator * /*op*/)
+{
+  BlenderProject *active_project = CTX_wm_project();
+
+  if (!BKE_project_settings_save(active_project)) {
+    return OPERATOR_CANCELLED;
+  }
+
+  return OPERATOR_FINISHED;
+}
+
+static void PROJECT_OT_save_settings(wmOperatorType *ot)
+{
+  ot->name = "Save Project Settings";
+  ot->idname = "PROJECT_OT_save_settings";
+  ot->description = "Make the current changes to the project settings permanent";
+
+  ot->invoke = WM_operator_confirm;
+  ot->poll = has_active_project_poll;
+  ot->exec = save_settings_exec;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Delete project setup operator
+ * \{ */
+
+static int delete_project_setup_exec(bContext *C, wmOperator *op)
+{
+  if (!BKE_project_delete_settings_directory(CTX_wm_project())) {
+    BKE_report(op->reports,
+               RPT_ERROR,
+               "Failed to delete project settings. Is the project directory read-only?");
+    return OPERATOR_CANCELLED;
+  }
+  BKE_project_active_unset();
+
+  WM_main_add_notifier(NC_PROJECT, NULL);
+  /* Update the window title. */
+  WM_event_add_notifier_ex(CTX_wm_manager(C), CTX_wm_window(C), NC_WM | ND_DATACHANGED, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+static void PROJECT_OT_delete_setup(wmOperatorType *ot)
+{
+  ot->name = "Delete Project Setup";
+  ot->idname = "PROJECT_OT_delete_setup";
+  ot->description =
+      "Remove the configuration of the current project with all settings, but keep project files "
+      "(such as .blend files) untouched";
+
+  ot->invoke = WM_operator_confirm;
+  ot->exec = delete_project_setup_exec;
+  /* omit window poll so this can work in background mode */
+  ot->poll = has_active_project_poll;
+}
+
+/** \} */
+/* -------------------------------------------------------------------- */
+/** \name Add Custom Asset Library
+ * \{ */
+
+static int custom_asset_library_add_exec(bContext * /*C*/, wmOperator *op)
+{
+  BlenderProject *project = CTX_wm_project();
+
+  char path[FILE_MAXDIR];
+  char dirname[FILE_MAXFILE];
+
+  RNA_string_get(op->ptr, "directory", path);
+
+  BLI_path_slash_rstrip(path);
+  /* Always keep project paths relative for now. Adds the "//" prefix which usually denotes a path
+   * that's relative to the current .blend, for now use it for project relative paths as well. */
+  BLI_path_rel(path, BKE_project_root_path_get(project));
+  BLI_split_file_part(path, dirname, sizeof(dirname));
+
+  ListBase *asset_libraries = BKE_project_custom_asset_libraries_get(project);
+  /* NULL is a valid directory path here. A library without path will be created then. */
+  BKE_asset_library_custom_add(asset_libraries, dirname, path);
+  BKE_project_tag_has_unsaved_changes(project);
+
+  WM_main_add_notifier(NC_ASSET | ND_ASSET_LIBRARY, NULL);
+  WM_main_add_notifier(NC_PROJECT, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+static int custom_asset_library_add_invoke(bContext *C, wmOperator *op, const wmEvent * /*event*/)
+{
+  if (!RNA_struct_property_is_set(op->ptr, "directory")) {
+    WM_event_add_fileselect(C, op);
+    return OPERATOR_RUNNING_MODAL;
+  }
+
+  return custom_asset_library_add_exec(C, op);
+}
+
+/* Similar to #PREFERENCES_OT_asset_library_add. */
+static void PROJECT_OT_custom_asset_library_add(wmOperatorType *ot)
+{
+  ot->name = "Add Asset Library";
+  ot->idname = "PROJECT_OT_custom_asset_library_add";
+  ot->description = "Register a directory to be used by the Asset Browser as source of assets";
+
+  ot->exec = custom_asset_library_add_exec;
+  ot->invoke = custom_asset_library_add_invoke;
+  ot->poll = has_active_project_poll;
+
+  ot->flag = OPTYPE_INTERNAL;
+
+  WM_operator_properties_filesel(ot,
+                                 FILE_TYPE_FOLDER,
+                                 FILE_SPECIAL,
+                                 FILE_OPENFILE,
+                                 WM_FILESEL_DIRECTORY,
+                                 FILE_DEFAULTDISPLAY,
+                                 FILE_SORT_DEFAULT);
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Remove Custom Asset Library
+ * \{ */
+
+static int custom_asset_library_remove_exec(bContext * /*C*/, wmOperator *op)
+{
+  const int index = RNA_int_get(op->ptr, "index");
+
+  BlenderProject *project = CTX_wm_project();
+  ListBase *asset_libraries = BKE_project_custom_asset_libraries_get(project);
+  CustomAssetLibraryDefinition *library = BKE_asset_library_custom_find_from_index(asset_libraries,
+                                                                                   index);
+  BKE_asset_library_custom_remove(asset_libraries, library);
+  BKE_project_tag_has_unsaved_changes(project);
+
+  WM_main_add_notifier(NC_ASSET | ND_ASSET_LIBRARY, NULL);
+  WM_main_add_notifier(NC_PROJECT, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+/* Similar to #PREFERENCES_OT_asset_library_remove. */
+static void PROJECT_OT_custom_asset_library_remove(wmOperatorType *ot)
+{
+  ot->name = "Remove Asset Library";
+  ot->idname = "PROJECT_OT_custom_asset_library_remove";
+  ot->description =
+      "Unregister a path to a .blend file, so the Asset Browser will not attempt to show it "
+      "anymore";
+
+  ot->exec = custom_asset_library_remove_exec;
+  ot->poll = has_active_project_poll;
+
+  ot->flag = OPTYPE_INTERNAL;
+
+  RNA_def_int(ot->srna, "index", 0, 0, INT_MAX, "Index", "", 0, 1000);
+}
+
+/** \} */
+
+void ED_operatortypes_project()
+{
+  WM_operatortype_append(PROJECT_OT_new);
+  WM_operatortype_append(PROJECT_OT_save_settings);
+  WM_operatortype_append(PROJECT_OT_delete_setup);
+  WM_operatortype_append(PROJECT_OT_custom_asset_library_add);
+  WM_operatortype_append(PROJECT_OT_custom_asset_library_remove);
+}

source/blender/editors/screen/screen_ops.c

@@ -5039,7 +5039,14 @@ static void SCREEN_OT_back_to_previous(struct wmOperatorType *ot)
 /** \name Show User Preferences Operator
  * \{ */
 
-static int userpref_show_exec(bContext *C, wmOperator *op)
+/**
+ * Shared window opening logic for preferences and project settings.
+ * \return True on success.
+ */
+static bool settings_window_show(bContext *C,
+                                 eSpace_Type space_type,
+                                 const char *window_title,
+                                 ReportList *reports)
 {
   wmWindow *win_cur = CTX_wm_window(C);
   /* Use eventstate, not event from _invoke, so this can be called through exec(). */
@@ -5047,6 +5054,43 @@ static int userpref_show_exec(bContext *C, wmOperator *op)
   int sizex = (500 + UI_NAVIGATION_REGION_WIDTH) * UI_DPI_FAC;
   int sizey = 520 * UI_DPI_FAC;
 
+  /* changes context! */
+  if (WM_window_open(C,
+                     window_title,
+                     event->xy[0],
+                     event->xy[1],
+                     sizex,
+                     sizey,
+                     space_type,
+                     false,
+                     false,
+                     true,
+                     WIN_ALIGN_LOCATION_CENTER) != NULL) {
+    /* The header only contains the editor switcher and looks empty.
+     * So hiding in the temp window makes sense. */
+    ScrArea *area = CTX_wm_area(C);
+    ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_HEADER);
+    if (region) {
+      region->flag |= RGN_FLAG_HIDDEN;
+      ED_region_visibility_change_update(C, area, region);
+    }
+
+    /* And also show the region with "Load & Save" buttons. */
+    region = BKE_area_find_region_type(area, RGN_TYPE_EXECUTE);
+    if (region) {
+      region->flag &= ~RGN_FLAG_HIDDEN;
+      ED_region_visibility_change_update(C, area, region);
+    }
+
+    return true;
+  }
+
+  BKE_report(reports, RPT_ERROR, "Failed to open window!");
+  return false;
+}
+
+static int userpref_show_exec(bContext *C, wmOperator *op)
+{
   PropertyRNA *prop = RNA_struct_find_property(op->ptr, "section");
   if (prop && RNA_property_is_set(op->ptr, prop)) {
     /* Set active section via RNA, so it can fail properly. */
@@ -5059,34 +5103,10 @@ static int userpref_show_exec(bContext *C, wmOperator *op)
     RNA_property_update(C, &pref_ptr, active_section_prop);
   }
 
-  /* changes context! */
-  if (WM_window_open(C,
-                     IFACE_("Blender Preferences"),
-                     event->xy[0],
-                     event->xy[1],
-                     sizex,
-                     sizey,
-                     SPACE_USERPREF,
-                     false,
-                     false,
-                     true,
-                     WIN_ALIGN_LOCATION_CENTER) != NULL) {
-    /* The header only contains the editor switcher and looks empty.
-     * So hiding in the temp window makes sense. */
-    ScrArea *area = CTX_wm_area(C);
-    ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_HEADER);
-
-    region->flag |= RGN_FLAG_HIDDEN;
-    ED_region_visibility_change_update(C, area, region);
-
-    /* And also show the region with "Load & Save" buttons. */
-    region = BKE_area_find_region_type(area, RGN_TYPE_EXECUTE);
-    region->flag &= ~RGN_FLAG_HIDDEN;
-    ED_region_visibility_change_update(C, area, region);
-
+  if (settings_window_show(C, SPACE_USERPREF, IFACE_("Blender Preferences"), op->reports)) {
     return OPERATOR_FINISHED;
   }
-  BKE_report(op->reports, RPT_ERROR, "Failed to open window!");
+
   return OPERATOR_CANCELLED;
 }
 
@@ -5114,6 +5134,62 @@ static void SCREEN_OT_userpref_show(struct wmOperatorType *ot)
 
 /** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Show Project Settings Operator
+ * \{ */
+
+bool ED_project_settings_window_show(bContext *C, ReportList *reports)
+{
+  return settings_window_show(
+      C, SPACE_PROJECT_SETTINGS, IFACE_("Blender Project Settings"), reports);
+}
+
+static int project_settings_show_exec(bContext *C, wmOperator *op)
+{
+  if (!ED_project_settings_window_show(C, op->reports)) {
+    return OPERATOR_CANCELLED;
+  }
+
+  PropertyRNA *prop = RNA_struct_find_property(op->ptr, "section");
+  SpaceProjectSettings *space_project = CTX_wm_space_project_settings(C);
+  if (space_project && prop && RNA_property_is_set(op->ptr, prop)) {
+    /* Set active section via RNA, so it can fail properly. */
+
+    bScreen *screen = CTX_wm_screen(C);
+    PointerRNA space_ptr;
+    RNA_pointer_create(&screen->id, &RNA_SpaceProjectSettings, space_project, &space_ptr);
+    PropertyRNA *active_section_prop = RNA_struct_find_property(&space_ptr, "active_section");
+
+    RNA_property_enum_set(&space_ptr, active_section_prop, RNA_property_enum_get(op->ptr, prop));
+    RNA_property_update(C, &space_ptr, active_section_prop);
+  }
+
+  return OPERATOR_FINISHED;
+}
+
+static void SCREEN_OT_project_settings_show(struct wmOperatorType *ot)
+{
+  /* identifiers */
+  ot->name = "Open Project Settings...";
+  ot->description = "Edit configuration for the active Blender project";
+  ot->idname = "SCREEN_OT_project_settings_show";
+
+  /* api callbacks */
+  ot->exec = project_settings_show_exec;
+  ot->poll = ED_operator_screenactive_nobackground; /* Not in background as this opens a window. */
+
+  PropertyRNA *prop;
+  prop = RNA_def_enum(ot->srna,
+                      "section",
+                      rna_enum_project_settings_section_items,
+                      0,
+                      "",
+                      "Section to activate in the project settings");
+  RNA_def_property_flag(prop, PROP_HIDDEN);
+}
+
+/** \} */
+
 /* -------------------------------------------------------------------- */
 /** \name Show Drivers Editor Operator
  * \{ */
@@ -5702,6 +5778,7 @@ void ED_operatortypes_screen(void)
   WM_operatortype_append(SCREEN_OT_screenshot);
   WM_operatortype_append(SCREEN_OT_screenshot_area);
   WM_operatortype_append(SCREEN_OT_userpref_show);
+  WM_operatortype_append(SCREEN_OT_project_settings_show);
   WM_operatortype_append(SCREEN_OT_drivers_editor_show);
   WM_operatortype_append(SCREEN_OT_info_log_show);
   WM_operatortype_append(SCREEN_OT_region_blend);

source/blender/editors/space_api/CMakeLists.txt

@@ -22,6 +22,7 @@ set(SRC
 
 set(LIB
   bf_editor_geometry
+  bf_editor_project
   bf_editor_space_action
   bf_editor_space_buttons
   bf_editor_space_clip
@@ -33,6 +34,7 @@ set(LIB
   bf_editor_space_nla
   bf_editor_space_node
   bf_editor_space_outliner
+  bf_editor_space_project_settings
   bf_editor_space_script
   bf_editor_space_sequencer
   bf_editor_space_spreadsheet

source/blender/editors/space_api/spacetypes.c

@@ -43,6 +43,7 @@
 #include "ED_object.h"
 #include "ED_paint.h"
 #include "ED_physics.h"
+#include "ED_project.h"
 #include "ED_render.h"
 #include "ED_scene.h"
 #include "ED_screen.h"
@@ -82,9 +83,11 @@ void ED_spacetypes_init(void)
   ED_spacetype_statusbar();
   ED_spacetype_topbar();
   ED_spacetype_spreadsheet();
+  ED_spacetype_project_settings();
 
   /* Register operator types for screen and all spaces. */
   ED_operatortypes_userpref();
+  ED_operatortypes_project();
   ED_operatortypes_workspace();
   ED_operatortypes_scene();
   ED_operatortypes_screen();

source/blender/editors/space_file/file_draw.c

@@ -1157,13 +1157,17 @@ static void file_draw_invalid_library_hint(const bContext *C,
   {
     UI_icon_draw(sx, sy - UI_UNIT_Y, ICON_INFO);
 
+    uiBlock *block = UI_block_begin(C, region, __func__, UI_EMBOSS);
+
     const char *suggestion = TIP_(
         "Asset Libraries are local directories that can contain .blend files with assets inside.\n"
-        "Manage Asset Libraries from the File Paths section in Preferences");
+        "Manage Asset Libraries from the File Paths section in the Preferences or in the Project "
+        "Settings.");
     file_draw_string_multiline(
         sx + UI_UNIT_X, sy, suggestion, width - UI_UNIT_X, line_height, text_col, NULL, &sy);
 
-    uiBlock *block = UI_block_begin(C, region, __func__, UI_EMBOSS);
+    const short but_offset_y = line_height + UI_UNIT_Y * 1.2f;
+    const short but_width = UI_UNIT_X * 8;
     uiBut *but = uiDefIconTextButO(block,
                                    UI_BTYPE_BUT,
                                    "SCREEN_OT_userpref_show",
@@ -1171,13 +1175,26 @@ static void file_draw_invalid_library_hint(const bContext *C,
                                    ICON_PREFERENCES,
                                    NULL,
                                    sx + UI_UNIT_X,
-                                   sy - line_height - UI_UNIT_Y * 1.2f,
-                                   UI_UNIT_X * 8,
+                                   sy - but_offset_y,
+                                   but_width,
                                    UI_UNIT_Y,
                                    NULL);
     PointerRNA *but_opptr = UI_but_operator_ptr_get(but);
     RNA_enum_set(but_opptr, "section", USER_SECTION_FILE_PATHS);
 
+    but = uiDefButO(block,
+                    UI_BTYPE_BUT,
+                    "SCREEN_OT_project_settings_show",
+                    WM_OP_INVOKE_DEFAULT,
+                    NULL,
+                    sx + UI_UNIT_X + but_width + UI_UNIT_X,
+                    sy - but_offset_y,
+                    but_width,
+                    UI_UNIT_Y,
+                    NULL);
+    but_opptr = UI_but_operator_ptr_get(but);
+    RNA_enum_set(but_opptr, "section", PROJECT_SETTINGS_SECTION_ASSET_LIBRARIES);
+
     UI_block_end(C, block);
     UI_block_draw(C, block);
   }

source/blender/editors/space_file/filelist.cc

@@ -48,6 +48,7 @@
 #endif
 
 #include "BKE_asset.h"
+#include "BKE_blender_project.h"
 #include "BKE_context.h"
 #include "BKE_global.h"
 #include "BKE_icons.h"
@@ -55,12 +56,12 @@
 #include "BKE_lib_id.h"
 #include "BKE_main.h"
 #include "BKE_main_idmap.h"
-#include "BKE_preferences.h"
 #include "BLO_readfile.h"
 
 #include "DNA_asset_types.h"
 #include "DNA_space_types.h"
 
+#include "ED_asset_library.h"
 #include "ED_datafiles.h"
 #include "ED_fileselect.h"
 #include "ED_screen.h"
@@ -1052,12 +1053,18 @@ static bool filelist_compare_asset_libraries(const AssetLibraryReference *librar
   if (library_a->type != library_b->type) {
     return false;
   }
-  if (library_a->type == ASSET_LIBRARY_CUSTOM) {
+
+  const bool is_custom_library = ELEM(
+      library_a->type, ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES, ASSET_LIBRARY_CUSTOM_FROM_PROJECT);
+  if (is_custom_library) {
+    if (library_a->custom_library_index != library_b->custom_library_index) {
+      return false;
+    }
+
     /* Don't only check the index, also check that it's valid. */
-    bUserAssetLibrary *library_ptr_a = BKE_preferences_asset_library_find_from_index(
-        &U, library_a->custom_library_index);
-    return (library_ptr_a != nullptr) &&
-           (library_a->custom_library_index == library_b->custom_library_index);
+    if (!ED_asset_library_find_custom_library_from_reference(library_a)) {
+      return false;
+    }
   }
 
   return true;
@@ -1198,6 +1205,10 @@ static int filelist_geticon_ex(const FileList *filelist,
 {
   const eFileSel_File_Types typeflag = (eFileSel_File_Types)file->typeflag;
 
+  if ((typeflag & FILE_TYPE_DIR) && (typeflag & FILE_TYPE_BLENDER_PROJECT)) {
+    return ICON_FUND;
+  }
+
   if ((typeflag & FILE_TYPE_DIR) &&
       !(ignore_libdir && (typeflag & (FILE_TYPE_BLENDERLIB | FILE_TYPE_BLENDER)))) {
     if (FILENAME_IS_PARENT(file->relpath)) {
@@ -3045,6 +3056,12 @@ static int filelist_readjob_list_dir(FileListReadJob *job_params,
         }
       }
 
+      if ((entry->typeflag & FILE_TYPE_DIR) && !(entry->typeflag & FILE_TYPE_BLENDER)) {
+        if (BKE_project_is_path_project_root(target)) {
+          entry->typeflag |= FILE_TYPE_BLENDER_PROJECT;
+        }
+      }
+
 #ifndef WIN32
       /* Set linux-style dot files hidden too. */
       if (is_hidden_dot_filename(entry->relpath, entry)) {

source/blender/editors/space_file/filesel.cc

@@ -24,6 +24,7 @@
 #endif
 
 #include "AS_asset_representation.hh"
+#include "AS_asset_library.hh"
 
 #include "DNA_screen_types.h"
 #include "DNA_space_types.h"
@@ -41,13 +42,15 @@
 #include "BLT_translation.h"
 
 #include "BKE_appdir.h"
+#include "BKE_asset_library_custom.h"
+#include "BKE_blender_project.h"
 #include "BKE_context.h"
 #include "BKE_idtype.h"
 #include "BKE_main.h"
-#include "BKE_preferences.h"
 
 #include "BLF_api.h"
 
+#include "ED_asset_library.h"
 #include "ED_fileselect.h"
 #include "ED_screen.h"
 
@@ -416,37 +419,30 @@ static void fileselect_refresh_asset_params(FileAssetSelectParams *asset_params)
 {
   AssetLibraryReference *library = &asset_params->asset_library_ref;
   FileSelectParams *base_params = &asset_params->base_params;
-  bUserAssetLibrary *user_library = nullptr;
 
-  /* Ensure valid repository, or fall-back to local one. */
-  if (library->type == ASSET_LIBRARY_CUSTOM) {
-    BLI_assert(library->custom_library_index >= 0);
-
-    user_library = BKE_preferences_asset_library_find_from_index(&U,
-                                                                 library->custom_library_index);
-    if (!user_library) {
-      library->type = ASSET_LIBRARY_ALL;
-    }
+  /* Ensure valid asset library, or fall-back to local one. */
+  if (!ED_asset_library_find_custom_library_from_reference(library)) {
+    library->type = ASSET_LIBRARY_ALL;
   }
 
+  std::string root_path = AS_asset_library_root_path_from_library_ref(*library);
+  BLI_strncpy(base_params->dir, root_path.c_str(), sizeof(base_params->dir));
+
   switch (eAssetLibraryType(library->type)) {
-    case ASSET_LIBRARY_ESSENTIALS:
+      case ASSET_LIBRARY_ESSENTIALS:
       BLI_strncpy(base_params->dir,
                   blender::asset_system::essentials_directory_path().c_str(),
                   sizeof(base_params->dir));
       base_params->type = FILE_ASSET_LIBRARY;
       break;
     case ASSET_LIBRARY_ALL:
-      base_params->dir[0] = '\0';
       base_params->type = FILE_ASSET_LIBRARY_ALL;
       break;
     case ASSET_LIBRARY_LOCAL:
-      base_params->dir[0] = '\0';
       base_params->type = FILE_MAIN_ASSET;
       break;
-    case ASSET_LIBRARY_CUSTOM:
-      BLI_assert(user_library);
-      BLI_strncpy(base_params->dir, user_library->path, sizeof(base_params->dir));
+    case ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES:
+    case ASSET_LIBRARY_CUSTOM_FROM_PROJECT:
       base_params->type = FILE_ASSET_LIBRARY;
       break;
   }

source/blender/editors/space_node/link_drag_search.cc

@@ -244,10 +244,11 @@ static void gather_search_link_ops_for_all_assets(const bContext &C,
                                                   Vector<SocketLinkOperation> &search_link_ops)
 {
   int i;
-  LISTBASE_FOREACH_INDEX (const bUserAssetLibrary *, asset_library, &U.asset_libraries, i) {
+  LISTBASE_FOREACH_INDEX (
+      const CustomAssetLibraryDefinition *, asset_library, &U.asset_libraries, i) {
     AssetLibraryReference library_ref{};
     library_ref.custom_library_index = i;
-    library_ref.type = ASSET_LIBRARY_CUSTOM;
+    library_ref.type = ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES;
     /* Skip local assets to avoid duplicates when the asset is part of the local file library. */
     gather_search_link_ops_for_asset_library(
         C, node_tree, socket, library_ref, true, search_link_ops);

source/blender/editors/space_project_settings/CMakeLists.txt

@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+set(INC
+  ../include
+  ../../blenfont
+  ../../blenkernel
+  ../../blenlib
+  ../../blenloader
+  ../../blentranslation
+  ../../depsgraph
+  ../../makesdna
+  ../../makesrna
+  ../../windowmanager
+  ../../../../intern/guardedalloc
+
+  # dna_type_offsets.h
+  ${CMAKE_CURRENT_BINARY_DIR}/../../makesdna/intern
+  # RNA_prototypes.h
+  ${CMAKE_BINARY_DIR}/source/blender/makesrna
+)
+
+set(SRC
+  space_project_settings.cc
+)
+
+set(LIB
+)
+
+blender_add_lib(bf_editor_space_project_settings "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")
+
+# RNA_prototypes.h dna_type_offsets.h
+ add_dependencies(bf_editor_space_project_settings bf_rna)
+ add_dependencies(bf_editor_space_project_settings bf_dna)

source/blender/editors/space_project_settings/space_project_settings.cc

@@ -0,0 +1,258 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "BKE_screen.h"
+
+#include "BLI_string.h"
+#include "BLI_string_ref.hh"
+
+#include "BLO_read_write.h"
+
+#include "DNA_screen_types.h"
+#include "DNA_space_types.h"
+
+#include "ED_screen.h"
+#include "ED_space_api.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "RNA_access.h"
+#include "RNA_enum_types.h"
+
+#include "UI_interface.h"
+
+using namespace blender;
+
+static SpaceLink *project_settings_create(const ScrArea *area, const Scene * /*scene*/)
+{
+  SpaceProjectSettings *project_settings_space = MEM_cnew<SpaceProjectSettings>(
+      "project settings space");
+  project_settings_space->spacetype = SPACE_PROJECT_SETTINGS;
+
+  {
+    /* Header. */
+    ARegion *region = MEM_cnew<ARegion>("project settings header");
+    BLI_addtail(&project_settings_space->regionbase, region);
+    region->regiontype = RGN_TYPE_HEADER;
+    /* Ignore preference "USER_HEADER_BOTTOM" here (always show bottom for new types). */
+    region->alignment = RGN_ALIGN_BOTTOM;
+  }
+
+  {
+    /* navigation region */
+    ARegion *region = MEM_cnew<ARegion>("project settings navigation region");
+    BLI_addtail(&project_settings_space->regionbase, region);
+    region->regiontype = RGN_TYPE_NAV_BAR;
+    region->alignment = RGN_ALIGN_LEFT;
+
+    /* Use smaller size when opened in area like properties editor (same as preferences do). */
+    if (area->winx && area->winx < 3.0f * UI_NAVIGATION_REGION_WIDTH * UI_DPI_FAC) {
+      region->sizex = UI_NARROW_NAVIGATION_REGION_WIDTH;
+    }
+  }
+  {
+    /* execution region */
+    ARegion *region = MEM_cnew<ARegion>("project settings execution region");
+    BLI_addtail(&project_settings_space->regionbase, region);
+    region->regiontype = RGN_TYPE_EXECUTE;
+    region->alignment = RGN_ALIGN_BOTTOM | RGN_SPLIT_PREV;
+    region->flag |= RGN_FLAG_DYNAMIC_SIZE | RGN_FLAG_HIDDEN;
+  }
+
+  {
+    /* Main window. */
+    ARegion *region = MEM_cnew<ARegion>("project settings main region");
+    BLI_addtail(&project_settings_space->regionbase, region);
+    region->regiontype = RGN_TYPE_WINDOW;
+  }
+
+  return reinterpret_cast<SpaceLink *>(project_settings_space);
+}
+
+static void project_settings_free(SpaceLink * /*sl*/)
+{
+}
+
+static void project_settings_init(wmWindowManager * /*wm*/, ScrArea * /*area*/)
+{
+}
+
+static SpaceLink *project_settings_duplicate(SpaceLink *sl)
+{
+  const SpaceProjectSettings *sproject_settings_old = reinterpret_cast<SpaceProjectSettings *>(sl);
+  SpaceProjectSettings *sproject_settings_new = reinterpret_cast<SpaceProjectSettings *>(
+      MEM_dupallocN(sproject_settings_old));
+
+  return reinterpret_cast<SpaceLink *>(sproject_settings_new);
+}
+
+static void project_settings_listener(const wmSpaceTypeListenerParams *params)
+{
+  const wmNotifier *wmn = params->notifier;
+  ScrArea *area = params->area;
+
+  switch (wmn->category) {
+    case NC_PROJECT:
+      ED_area_tag_redraw(area);
+      break;
+  }
+}
+
+static void project_settings_operatortypes(void)
+{
+}
+
+static void project_settings_keymap(struct wmKeyConfig * /*keyconf*/)
+{
+}
+
+static void project_settings_blend_write(BlendWriter *writer, SpaceLink *sl)
+{
+  BLO_write_struct(writer, SpaceProjectSettings, sl);
+}
+
+/* add handlers, stuff you only do once or on area/region changes */
+static void project_settings_main_region_init(wmWindowManager *wm, ARegion *region)
+{
+  /* do not use here, the properties changed in user-preferences do a system-wide refresh,
+   * then scroller jumps back */
+  // region->v2d.flag &= ~V2D_IS_INIT;
+
+  region->v2d.scroll = V2D_SCROLL_RIGHT | V2D_SCROLL_VERTICAL_HIDE;
+
+  ED_region_panels_init(wm, region);
+}
+
+static void project_settings_main_region_layout(const bContext *C, ARegion *region)
+{
+  SpaceProjectSettings *sproject_settings = CTX_wm_space_project_settings(C);
+
+  char id_lower[64];
+  const char *contexts[2] = {id_lower, NULL};
+
+  if (!CTX_wm_project()) {
+    /* Special context for when there is no project. UI can draw a special panel then. */
+    STRNCPY(id_lower, "no_project");
+  }
+  else {
+    /* Avoid duplicating identifiers, use existing RNA enum. */
+    const EnumPropertyItem *items = rna_enum_project_settings_section_items;
+    int i = RNA_enum_from_value(items, sproject_settings->active_section);
+    /* Enum value not found: File is from the future. */
+    if (i == -1) {
+      i = 0;
+    }
+    StringRefNull id = items[i].identifier;
+    BLI_assert(id.size() < (int64_t)sizeof(id_lower));
+    STRNCPY(id_lower, id.c_str());
+    BLI_str_tolower_ascii(id_lower, strlen(id_lower));
+  }
+
+  ED_region_panels_layout_ex(C, region, &region->type->paneltypes, contexts, NULL);
+}
+
+static void project_settings_main_region_listener(const wmRegionListenerParams * /*params*/)
+{
+}
+
+static void project_settings_header_region_init(wmWindowManager * /*wm*/, ARegion *region)
+{
+  ED_region_header_init(region);
+}
+
+static void project_settings_header_region_listener(const wmRegionListenerParams * /*params*/)
+{
+}
+
+/* add handlers, stuff you only do once or on area/region changes */
+static void project_settings_navigation_region_init(wmWindowManager *wm, ARegion *region)
+{
+  region->v2d.scroll = V2D_SCROLL_RIGHT | V2D_SCROLL_VERTICAL_HIDE;
+
+  ED_region_panels_init(wm, region);
+}
+
+static void project_settings_navigation_region_draw(const bContext *C, ARegion *region)
+{
+  ED_region_panels(C, region);
+}
+
+static void project_settings_navigation_region_listener(const wmRegionListenerParams * /*params*/)
+{
+}
+
+/* add handlers, stuff you only do once or on area/region changes */
+static void project_settings_execute_region_init(wmWindowManager *wm, ARegion *region)
+{
+  ED_region_panels_init(wm, region);
+  region->v2d.keepzoom |= V2D_LOCKZOOM_X | V2D_LOCKZOOM_Y;
+}
+
+static void project_settings_execute_region_listener(const wmRegionListenerParams * /*params*/)
+{
+}
+
+void ED_spacetype_project_settings()
+{
+  SpaceType *st = MEM_cnew<SpaceType>("spacetype project settings");
+
+  st->spaceid = SPACE_PROJECT_SETTINGS;
+  STRNCPY(st->name, "Project Settings");
+
+  st->create = project_settings_create;
+  st->free = project_settings_free;
+  st->init = project_settings_init;
+  st->duplicate = project_settings_duplicate;
+  st->listener = project_settings_listener;
+  st->operatortypes = project_settings_operatortypes;
+  st->keymap = project_settings_keymap;
+  st->blend_write = project_settings_blend_write;
+
+  ARegionType *art;
+
+  /* regions: main window */
+  art = MEM_cnew<ARegionType>("spacetype project settings region");
+  art->regionid = RGN_TYPE_WINDOW;
+  art->keymapflag = ED_KEYMAP_UI;
+
+  art->init = project_settings_main_region_init;
+  art->layout = project_settings_main_region_layout;
+  art->draw = ED_region_panels_draw;
+  art->listener = project_settings_main_region_listener;
+  BLI_addhead(&st->regiontypes, art);
+
+  /* regions: header */
+  art = MEM_cnew<ARegionType>("spacetype project settings header region");
+  art->regionid = RGN_TYPE_HEADER;
+  art->prefsizey = HEADERY;
+  art->keymapflag = ED_KEYMAP_UI | ED_KEYMAP_VIEW2D | ED_KEYMAP_HEADER;
+
+  art->listener = project_settings_header_region_listener;
+  art->init = project_settings_header_region_init;
+  art->draw = ED_region_header;
+  BLI_addhead(&st->regiontypes, art);
+
+  /* regions: navigation window */
+  art = MEM_cnew<ARegionType>("spacetype project settings navigation region");
+  art->regionid = RGN_TYPE_NAV_BAR;
+  art->prefsizex = UI_NAVIGATION_REGION_WIDTH;
+  art->keymapflag = ED_KEYMAP_UI | ED_KEYMAP_NAVBAR;
+
+  art->init = project_settings_navigation_region_init;
+  art->draw = project_settings_navigation_region_draw;
+  art->listener = project_settings_navigation_region_listener;
+  BLI_addhead(&st->regiontypes, art);
+
+  /* regions: execution window */
+  art = MEM_cnew<ARegionType>("spacetype project settings execute region");
+  art->regionid = RGN_TYPE_EXECUTE;
+  art->prefsizey = HEADERY;
+  art->keymapflag = ED_KEYMAP_UI;
+
+  art->init = project_settings_execute_region_init;
+  art->layout = ED_region_panels_layout;
+  art->draw = ED_region_panels_draw;
+  art->listener = project_settings_execute_region_listener;
+  BLI_addhead(&st->regiontypes, art);
+
+  BKE_spacetype_register(st);
+}

source/blender/editors/space_userpref/userpref_ops.c

@@ -16,9 +16,9 @@
 #endif
 #include "BLI_path_util.h"
 
+#include "BKE_asset_library_custom.h"
 #include "BKE_context.h"
 #include "BKE_main.h"
-#include "BKE_preferences.h"
 
 #include "BKE_report.h"
 
@@ -134,7 +134,8 @@ static int preferences_asset_library_add_exec(bContext *UNUSED(C), wmOperator *o
   BLI_split_file_part(path, dirname, sizeof(dirname));
 
   /* NULL is a valid directory path here. A library without path will be created then. */
-  const bUserAssetLibrary *new_library = BKE_preferences_asset_library_add(&U, dirname, path);
+  CustomAssetLibraryDefinition *new_library = BKE_asset_library_custom_add(
+      &U.asset_libraries, dirname, path);
   /* Activate new library in the UI for further setup. */
   U.active_asset_library = BLI_findindex(&U.asset_libraries, new_library);
   U.runtime.is_dirty = true;
@@ -158,6 +159,7 @@ static int preferences_asset_library_add_invoke(bContext *C,
   return preferences_asset_library_add_exec(C, op);
 }
 
+/* Similar to #PROJECT_OT_custom_asset_library_add. */
 static void PREFERENCES_OT_asset_library_add(wmOperatorType *ot)
 {
   ot->name = "Add Asset Library";
@@ -196,23 +198,23 @@ static bool preferences_asset_library_remove_poll(bContext *C)
 static int preferences_asset_library_remove_exec(bContext *UNUSED(C), wmOperator *op)
 {
   const int index = RNA_int_get(op->ptr, "index");
-  bUserAssetLibrary *library = BLI_findlink(&U.asset_libraries, index);
+  CustomAssetLibraryDefinition *library = BLI_findlink(&U.asset_libraries, index);
   if (!library) {
     return OPERATOR_CANCELLED;
   }
 
-  BKE_preferences_asset_library_remove(&U, library);
+  BKE_asset_library_custom_remove(&U.asset_libraries, library);
   const int count_remaining = BLI_listbase_count(&U.asset_libraries);
   /* Update active library index to be in range. */
   CLAMP(U.active_asset_library, 0, count_remaining - 1);
   U.runtime.is_dirty = true;
-
   /* Trigger refresh for the Asset Browser. */
   WM_main_add_notifier(NC_SPACE | ND_SPACE_ASSET_PARAMS, NULL);
 
   return OPERATOR_FINISHED;
 }
 
+/* Similar to #PROJECT_OT_custom_asset_library_add. */
 static void PREFERENCES_OT_asset_library_remove(wmOperatorType *ot)
 {
   ot->name = "Remove Asset Library";

source/blender/editors/util/CMakeLists.txt

@@ -72,6 +72,7 @@ set(SRC
   ../include/ED_paint.h
   ../include/ED_particle.h
   ../include/ED_physics.h
+  ../include/ED_project.h
   ../include/ED_render.h
   ../include/ED_scene.h
   ../include/ED_screen.h

source/blender/makesdna/DNA_asset_types.h

@@ -2,6 +2,9 @@
 
 /** \file
  * \ingroup DNA
+ *
+ * Only contains types that need writing to files or that are accessed directly via RNA (as opposed
+ * to being opaque types accessed via an API).
  */
 
 #pragma once
@@ -92,11 +95,12 @@ typedef enum eAssetLibraryType {
   ASSET_LIBRARY_ESSENTIALS = 3,
 
   /** Display assets from custom asset libraries, as defined in the preferences
-   * (#bUserAssetLibrary). The name will be taken from #FileSelectParams.asset_library_ref.idname
-   * then.
-   * In RNA, we add the index of the custom library to this to identify it by index. So keep
-   * this last! */
-  ASSET_LIBRARY_CUSTOM = 100,
+   * (#CustomAssetLibraryDefinition). In RNA, we add the index of the custom library to this to
+   * identify it by index. */
+  ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES = 100,
+  /** Same as #ASSET_LIBRARY_CUSTOM_FROM_PREFERENCES, but the library is defined for a specific
+     project only. */
+  ASSET_LIBRARY_CUSTOM_FROM_PROJECT = 500,
 } eAssetLibraryType;
 
 typedef enum eAssetImportMethod {
@@ -111,23 +115,36 @@ typedef enum eAssetImportMethod {
 } eAssetImportMethod;
 
 /**
- * Information to identify an asset library. May be either one of the predefined types (current
- * 'Main', builtin library, project library), or a custom type as defined in the Preferences.
- *
- * If the type is set to #ASSET_LIBRARY_CUSTOM, `custom_library_index` must be set to identify the
- * custom library. Otherwise it is not used.
+ * Information to identify an asset library. May be either one of the predefined types ("Current
+ * File" builtin library), or a custom type as defined in the Preferences/Project.
  */
 typedef struct AssetLibraryReference {
+  /* If set to #ASSET_LIBRARY_CUSTOM_XXX, `custom_library_index` must be set to identify
+   * the custom library. Otherwise it is not used. */
   short type; /* eAssetLibraryType */
   char _pad1[2];
   /**
-   * If showing a custom asset library (#ASSET_LIBRARY_CUSTOM), this is the index of the
-   * #bUserAssetLibrary within #UserDef.asset_libraries.
+   * If showing a custom asset library (#ASSET_LIBRARY_CUSTOM_XXX), this is the index of the
+   * #CustomAssetLibraryDefinition within its owner (preferences or project settings).
    * Should be ignored otherwise (but better set to -1 then, for sanity and debugging).
    */
   int custom_library_index;
 } AssetLibraryReference;
 
+/**
+ * Custom asset libraries can be registered in the preferences or project settings. This is the
+ * container to hold these settings.
+ */
+typedef struct CustomAssetLibraryDefinition {
+  struct CustomAssetLibraryDefinition *next, *prev;
+
+  char name[64];   /* MAX_NAME */
+  char path[1024]; /* FILE_MAX */
+
+  short import_method; /* eAssetImportMethod */
+  char _pad[6];
+} CustomAssetLibraryDefinition;
+
 /**
  * To be replaced by #AssetRepresentation!
  *

source/blender/makesdna/DNA_space_types.h

@@ -1091,6 +1091,8 @@ typedef enum eFileSel_File_Types {
   FILE_TYPE_VOLUME = (1 << 19),
 
   FILE_TYPE_ASSET = (1 << 28),
+  /** Directory is a Blender project root directory. */
+  FILE_TYPE_BLENDER_PROJECT = (1 << 29),
   /** An FS directory (i.e. S_ISDIR on its path is true). */
   FILE_TYPE_DIR = (1 << 30),
   FILE_TYPE_BLENDERLIB = (1u << 31),
@@ -1732,6 +1734,30 @@ typedef struct SpaceUserPref {
 
 /** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Project Settings
+ * \{ */
+
+typedef struct SpaceProjectSettings {
+  SpaceLink *next, *prev;
+  /** Storage of regions for inactive spaces. */
+  ListBase regionbase;
+  char spacetype;
+  char link_flag;
+  char _pad0[6];
+  /* End 'SpaceLink' header. */
+
+  char active_section; /* eSpaceProjectSettings_Section */
+  char _pad1[7];
+} SpaceProjectSettings;
+
+typedef enum eSpaceProjectSettings_Section {
+  PROJECT_SETTINGS_SECTION_GENERAL = 0,
+  PROJECT_SETTINGS_SECTION_ASSET_LIBRARIES = 1,
+} eSpaceProjectSettings_Section;
+
+/** \} */
+
 /* -------------------------------------------------------------------- */
 /** \name Motion Tracking
  * \{ */
@@ -2076,9 +2102,10 @@ typedef enum eSpace_Type {
   SPACE_CLIP = 20,
   SPACE_TOPBAR = 21,
   SPACE_STATUSBAR = 22,
-  SPACE_SPREADSHEET = 23
+  SPACE_SPREADSHEET = 23,
+  SPACE_PROJECT_SETTINGS = 24
 
-#define SPACE_TYPE_NUM (SPACE_SPREADSHEET + 1)
+#define SPACE_TYPE_NUM (SPACE_PROJECT_SETTINGS + 1)
 } eSpace_Type;
 
 /* use for function args */

source/blender/makesdna/DNA_userdef_types.h

@@ -488,6 +488,7 @@ typedef struct bTheme {
   ThemeSpace space_outliner;
   ThemeSpace space_node;
   ThemeSpace space_preferences;
+  ThemeSpace space_project_settings;
   ThemeSpace space_console;
   ThemeSpace space_clip;
   ThemeSpace space_topbar;
@@ -572,16 +573,6 @@ enum {
   USER_MENU_TYPE_PROP = 4,
 };
 
-typedef struct bUserAssetLibrary {
-  struct bUserAssetLibrary *next, *prev;
-
-  char name[64];   /* MAX_NAME */
-  char path[1024]; /* FILE_MAX */
-
-  short import_method; /* eAssetImportMethod */
-  char _pad0[6];
-} bUserAssetLibrary;
-
 typedef struct SolidLight {
   int flag;
   float smooth;
@@ -658,7 +649,8 @@ typedef struct UserDef_Experimental {
   char use_sculpt_texture_paint;
   char enable_workbench_next;
   char use_new_volume_nodes;
-  char _pad[6];
+  char use_blender_projects;
+  char _pad[5];
   /** `makesdna` does not allow empty structs. */
 } UserDef_Experimental;
 
@@ -778,7 +770,7 @@ typedef struct UserDef {
   struct ListBase autoexec_paths;
   /** #bUserMenu. */
   struct ListBase user_menus;
-  /** #bUserAssetLibrary */
+  /** #CustomAssetLibraryDefinition */
   struct ListBase asset_libraries;
 
   char keyconfigstr[64];

source/blender/makesdna/intern/dna_rename_defs.h

@@ -41,6 +41,7 @@ DNA_STRUCT_RENAME(Lamp, Light)
 DNA_STRUCT_RENAME(SpaceButs, SpaceProperties)
 DNA_STRUCT_RENAME(SpaceIpo, SpaceGraph)
 DNA_STRUCT_RENAME(SpaceOops, SpaceOutliner)
+DNA_STRUCT_RENAME(bUserAssetLibrary, CustomAssetLibraryDefinition)
 DNA_STRUCT_RENAME_ELEM(BPoint, alfa, tilt)
 DNA_STRUCT_RENAME_ELEM(BezTriple, alfa, tilt)
 DNA_STRUCT_RENAME_ELEM(Bone, curveInX, curve_in_x)

source/blender/makesrna/RNA_enum_items.h

@@ -208,6 +208,8 @@ DEF_ENUM(rna_enum_context_mode_items)
 
 DEF_ENUM(rna_enum_preference_section_items)
 
+DEF_ENUM(rna_enum_project_settings_section_items)
+
 DEF_ENUM(rna_enum_attribute_type_items)
 DEF_ENUM(rna_enum_color_attribute_type_items)
 DEF_ENUM(rna_enum_attribute_type_with_auto_items)

source/blender/makesrna/intern/CMakeLists.txt

@@ -20,6 +20,7 @@ set(DEFSRC
   rna_armature.c
   rna_asset.c
   rna_attribute.c
+  rna_blender_project.c
   rna_boid.c
   rna_brush.c
   rna_cachefile.c

source/blender/makesrna/intern/makesrna.c

@@ -4494,6 +4494,7 @@ static RNAProcessItem PROCESS_ITEMS[] = {
     {"rna_armature.c", "rna_armature_api.c", RNA_def_armature},
     {"rna_attribute.c", NULL, RNA_def_attribute},
     {"rna_asset.c", NULL, RNA_def_asset},
+    {"rna_blender_project.c", NULL, RNA_def_blender_project},
     {"rna_boid.c", NULL, RNA_def_boid},
     {"rna_brush.c", NULL, RNA_def_brush},
     {"rna_cachefile.c", NULL, RNA_def_cachefile},

source/blender/makesrna/intern/rna_asset.c

@@ -20,6 +20,7 @@
 #  include "AS_asset_library.h"
 
 #  include "BKE_asset.h"
+#  include "BKE_asset_library_custom.h"
 #  include "BKE_context.h"
 #  include "BKE_idprop.h"
 
@@ -29,6 +30,9 @@
 #  include "ED_asset.h"
 #  include "ED_fileselect.h"
 
+#  include "WM_api.h"
+#  include "WM_types.h"
+
 #  include "RNA_access.h"
 
 static char *rna_AssetMetaData_path(const PointerRNA *UNUSED(ptr))
@@ -266,6 +270,35 @@ void rna_AssetMetaData_catalog_id_update(struct bContext *C, struct PointerRNA *
   AS_asset_library_refresh_catalog_simplename(asset_library, asset_data);
 }
 
+static void rna_CustomAssetLibraryDefinition_name_set(PointerRNA *ptr, const char *value)
+{
+  CustomAssetLibraryDefinition *library = (CustomAssetLibraryDefinition *)ptr->data;
+
+  /* We can't cleanly access the owning listbase here, but reconstructing the list from the link is
+   * fine. */
+  ListBase asset_libraries = BLI_listbase_from_link((Link *)library);
+  BKE_asset_library_custom_name_set(&asset_libraries, library, value);
+}
+
+static void rna_CustomAssetLibraryDefinition_path_set(PointerRNA *ptr, const char *value)
+{
+  CustomAssetLibraryDefinition *library = (CustomAssetLibraryDefinition *)ptr->data;
+
+  char dirpath[FILE_MAX];
+  BLI_strncpy(dirpath, value, sizeof(dirpath));
+  if (BLI_is_file(dirpath)) {
+    BLI_path_parent_dir(dirpath);
+  }
+  BKE_asset_library_custom_path_set(library, dirpath);
+}
+
+void rna_AssetLibrary_settings_update(Main *UNUSED(bmain),
+                                      Scene *UNUSED(scene),
+                                      PointerRNA *UNUSED(ptr))
+{
+  WM_main_add_notifier(NC_ASSET | ND_ASSET_LIBRARY, NULL);
+}
+
 static PointerRNA rna_AssetHandle_file_data_get(PointerRNA *ptr)
 {
   AssetHandle *asset_handle = ptr->data;
@@ -497,6 +530,55 @@ static void rna_def_asset_library_reference(BlenderRNA *brna)
       srna, "Asset Library Reference", "Identifier to refer to the asset library");
 }
 
+static void rna_def_asset_library_reference_custom(BlenderRNA *brna)
+{
+  StructRNA *srna;
+  PropertyRNA *prop;
+
+  srna = RNA_def_struct(brna, "CustomAssetLibraryDefinition", NULL);
+  RNA_def_struct_clear_flag(srna, STRUCT_UNDO);
+  RNA_def_struct_ui_text(
+      srna, "Asset Library", "Settings to define a reusable library for Asset Browsers to use");
+
+  prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
+  RNA_def_property_ui_text(
+      prop, "Name", "Identifier (not necessarily unique) for the asset library");
+  RNA_def_property_string_funcs(prop, NULL, NULL, "rna_CustomAssetLibraryDefinition_name_set");
+  RNA_def_struct_name_property(srna, prop);
+  RNA_def_property_update(prop, 0, "rna_AssetLibrary_settings_update");
+
+  prop = RNA_def_property(srna, "path", PROP_STRING, PROP_DIRPATH);
+  RNA_def_property_ui_text(
+      prop, "Path", "Path to a directory with .blend files to use as an asset library");
+  RNA_def_property_string_funcs(prop, NULL, NULL, "rna_CustomAssetLibraryDefinition_path_set");
+  RNA_def_property_update(prop, 0, "rna_AssetLibrary_settings_update");
+
+  static const EnumPropertyItem import_method_items[] = {
+      {ASSET_IMPORT_LINK, "LINK", 0, "Link", "Import the assets as linked data-block"},
+      {ASSET_IMPORT_APPEND,
+       "APPEND",
+       0,
+       "Append",
+       "Import the assets as copied data-block, with no link to the original asset data-block"},
+      {ASSET_IMPORT_APPEND_REUSE,
+       "APPEND_REUSE",
+       0,
+       "Append (Reuse Data)",
+       "Import the assets as copied data-block while avoiding multiple copies of nested, "
+       "typically heavy data. For example the textures of a material asset, or the mesh of an "
+       "object asset, don't have to be copied every time this asset is imported. The instances of "
+       "the asset share the data instead"},
+      {0, NULL, 0, NULL, NULL},
+  };
+  prop = RNA_def_property(srna, "import_method", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, import_method_items);
+  RNA_def_property_ui_text(
+      prop,
+      "Default Import Method",
+      "Determine how the asset will be imported, unless overridden by the Asset Browser");
+  RNA_def_property_update(prop, 0, "rna_AssetLibrary_settings_update");
+}
+
 PropertyRNA *rna_def_asset_library_reference_common(struct StructRNA *srna,
                                                     const char *get,
                                                     const char *set)
@@ -515,6 +597,7 @@ void RNA_def_asset(BlenderRNA *brna)
   rna_def_asset_tag(brna);
   rna_def_asset_data(brna);
   rna_def_asset_library_reference(brna);
+  rna_def_asset_library_reference_custom(brna);
   rna_def_asset_handle(brna);
   rna_def_asset_catalog_path(brna);
 

source/blender/makesrna/intern/rna_blender_project.c

@@ -0,0 +1,158 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup RNA
+ */
+
+#include "RNA_define.h"
+
+#include "rna_internal.h"
+
+#ifdef RNA_RUNTIME
+
+#  include "BKE_asset_library_custom.h"
+#  include "BKE_blender_project.h"
+
+#  include "BLT_translation.h"
+
+#  include "WM_api.h"
+
+static void rna_BlenderProject_update(Main *UNUSED(bmain),
+                                      Scene *UNUSED(scene),
+                                      PointerRNA *UNUSED(ptr))
+{
+  /* TODO evaluate which props should send which notifiers. */
+  /* Force full redraw of all windows. */
+  WM_main_add_notifier(NC_WINDOW, NULL);
+}
+
+static void rna_BlenderProject_name_get(PointerRNA *ptr, char *value)
+{
+  BlenderProject *project = ptr->data;
+  if (!project) {
+    value[0] = '\0';
+    return;
+  }
+
+  strcpy(value, BKE_project_name_get(project));
+}
+
+static int rna_BlenderProject_name_length(PointerRNA *ptr)
+{
+  BlenderProject *project = ptr->data;
+  if (!project) {
+    return 0;
+  }
+
+  return strlen(BKE_project_name_get(project));
+}
+
+static void rna_BlenderProject_name_set(PointerRNA *ptr, const char *value)
+{
+  BlenderProject *project = ptr->data;
+
+  if (!project) {
+    return;
+  }
+
+  BKE_project_name_set(project, value);
+}
+
+static void rna_BlenderProject_root_path_get(PointerRNA *ptr, char *value)
+{
+  BlenderProject *project = ptr->data;
+  if (!project) {
+    value[0] = '\0';
+    return;
+  }
+
+  strcpy(value, BKE_project_root_path_get(project));
+}
+
+static int rna_BlenderProject_root_path_length(PointerRNA *ptr)
+{
+  BlenderProject *project = ptr->data;
+  if (!project) {
+    return 0;
+  }
+
+  return strlen(BKE_project_root_path_get(project));
+}
+
+static void rna_BlenderProject_root_path_set(PointerRNA *UNUSED(ptr), const char *UNUSED(value))
+{
+  /* Property is not editable, see #rna_BlenderProject_root_path_editable(). */
+  BLI_assert_unreachable();
+}
+
+static int rna_BlenderProject_root_path_editable(PointerRNA *UNUSED(ptr), const char **r_info)
+{
+  /* Path is never editable (setting up a project is an operation), but return a nicer disabled
+   * hint. */
+  *r_info = N_("Project location cannot be changed, displayed for informal purposes only");
+  return 0;
+}
+
+static void rna_BlenderProject_asset_libraries_begin(CollectionPropertyIterator *iter,
+                                                     PointerRNA *ptr)
+{
+  BlenderProject *project = ptr->data;
+  ListBase *asset_libraries = BKE_project_custom_asset_libraries_get(project);
+  rna_iterator_listbase_begin(iter, asset_libraries, NULL);
+}
+
+static bool rna_BlenderProject_is_dirty_get(PointerRNA *ptr)
+{
+  const BlenderProject *project = ptr->data;
+  return BKE_project_has_unsaved_changes(project);
+}
+
+#else
+
+void RNA_def_blender_project(BlenderRNA *brna)
+{
+  StructRNA *srna = RNA_def_struct(brna, "BlenderProject", NULL);
+  RNA_def_struct_ui_text(srna, "Blender Project", "");
+
+  PropertyRNA *prop;
+
+  prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_funcs(prop,
+                                "rna_BlenderProject_name_get",
+                                "rna_BlenderProject_name_length",
+                                "rna_BlenderProject_name_set");
+  RNA_def_property_ui_text(prop, "Name", "The identifier for the project");
+  RNA_def_struct_name_property(srna, prop);
+  RNA_def_property_update(prop, 0, "rna_BlenderProject_update");
+
+  prop = RNA_def_property(srna, "root_path", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_funcs(prop,
+                                "rna_BlenderProject_root_path_get",
+                                "rna_BlenderProject_root_path_length",
+                                "rna_BlenderProject_root_path_set");
+  RNA_def_property_editable_func(prop, "rna_BlenderProject_root_path_editable");
+  RNA_def_property_ui_text(prop, "Location", "The location of the project on disk");
+
+  prop = RNA_def_property(srna, "asset_libraries", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_struct_type(prop, "CustomAssetLibraryDefinition");
+  RNA_def_property_collection_funcs(prop,
+                                    "rna_BlenderProject_asset_libraries_begin",
+                                    "rna_iterator_listbase_next",
+                                    "rna_iterator_listbase_end",
+                                    "rna_iterator_listbase_get",
+                                    NULL,
+                                    NULL,
+                                    NULL,
+                                    NULL);
+  RNA_def_property_ui_text(prop, "Asset Libraries", "");
+
+  prop = RNA_def_property(srna, "is_dirty", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_funcs(prop, "rna_BlenderProject_is_dirty_get", NULL);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(
+      prop,
+      "Dirty",
+      "Project settings have changed since read from disk. Save the settings to keep them");
+}
+
+#endif

source/blender/makesrna/intern/rna_context.c

@@ -203,6 +203,15 @@ static PointerRNA rna_Context_preferences_get(PointerRNA *UNUSED(ptr))
   return newptr;
 }
 
+static PointerRNA rna_Context_project_get(PointerRNA *UNUSED(ptr))
+{
+  struct BlenderProject *project = CTX_wm_project();
+
+  PointerRNA newptr;
+  RNA_pointer_create(NULL, &RNA_BlenderProject, project, &newptr);
+  return newptr;
+}
+
 static int rna_Context_mode_get(PointerRNA *ptr)
 {
   bContext *C = (bContext *)ptr->data;
@@ -338,6 +347,11 @@ void RNA_def_context(BlenderRNA *brna)
   RNA_def_property_struct_type(prop, "Preferences");
   RNA_def_property_pointer_funcs(prop, "rna_Context_preferences_get", NULL, NULL, NULL);
 
+  prop = RNA_def_property(srna, "project", PROP_POINTER, PROP_NONE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_struct_type(prop, "BlenderProject");
+  RNA_def_property_pointer_funcs(prop, "rna_Context_project_get", NULL, NULL, NULL);
+
   prop = RNA_def_property(srna, "mode", PROP_ENUM, PROP_NONE);
   RNA_def_property_enum_items(prop, rna_enum_context_mode_items);
   RNA_def_property_clear_flag(prop, PROP_EDITABLE);

source/blender/makesrna/intern/rna_internal.h

@@ -142,6 +142,7 @@ void RNA_def_animviz(struct BlenderRNA *brna);
 void RNA_def_armature(struct BlenderRNA *brna);
 void RNA_def_attribute(struct BlenderRNA *brna);
 void RNA_def_asset(struct BlenderRNA *brna);
+void RNA_def_blender_project(struct BlenderRNA *brna);
 void RNA_def_boid(struct BlenderRNA *brna);
 void RNA_def_brush(struct BlenderRNA *brna);
 void RNA_def_cachefile(struct BlenderRNA *brna);

source/blender/makesrna/intern/rna_screen.c

@@ -186,6 +186,10 @@ static const EnumPropertyItem *rna_Area_ui_type_itemf(bContext *C,
       continue;
     }
 
+    if (!U.experimental.use_blender_projects && (item_from->value == SPACE_PROJECT_SETTINGS)) {
+      continue;
+    }
+
     SpaceType *st = item_from->identifier[0] ? BKE_spacetype_from_id(item_from->value) : NULL;
     int totitem_prev = totitem;
     if (st && st->space_subtype_item_extend != NULL) {

source/blender/makesrna/intern/rna_space.c

@@ -171,11 +171,16 @@ const EnumPropertyItem rna_enum_space_type_items[] = {
      ICON_SPREADSHEET,
      "Spreadsheet",
      "Explore geometry data in a table"},
+    {SPACE_PROJECT_SETTINGS,
+     "PROJECT_SETTINGS",
+     ICON_PREFERENCES,
+     "Project Settings",
+     "Edit persistent configuration settings for the active project"},
     {SPACE_USERPREF,
      "PREFERENCES",
      ICON_PREFERENCES,
      "Preferences",
-     "Edit persistent configuration settings"},
+     "Edit persistent configuration settings for personal use"},
     {0, NULL, 0, NULL, NULL},
 };
 
@@ -528,6 +533,12 @@ static const EnumPropertyItem rna_enum_curve_display_handle_items[] = {
     {0, NULL, 0, NULL, NULL},
 };
 
+const EnumPropertyItem rna_enum_project_settings_section_items[] = {
+    {PROJECT_SETTINGS_SECTION_GENERAL, "GENERAL", 0, "General", ""},
+    {PROJECT_SETTINGS_SECTION_ASSET_LIBRARIES, "ASSET_LIBRARIES", 0, "Asset Libraries", ""},
+    {0, NULL, 0, NULL, NULL},
+};
+
 #ifdef RNA_RUNTIME
 
 #  include "AS_asset_representation.h"
@@ -551,7 +562,6 @@ static const EnumPropertyItem rna_enum_curve_display_handle_items[] = {
 #  include "BKE_layer.h"
 #  include "BKE_nla.h"
 #  include "BKE_paint.h"
-#  include "BKE_preferences.h"
 #  include "BKE_scene.h"
 #  include "BKE_screen.h"
 #  include "BKE_workspace.h"
@@ -611,6 +621,8 @@ static StructRNA *rna_Space_refine(struct PointerRNA *ptr)
       return &RNA_SpaceConsole;
     case SPACE_USERPREF:
       return &RNA_SpacePreferences;
+    case SPACE_PROJECT_SETTINGS:
+      return &RNA_SpaceProjectSettings;
     case SPACE_CLIP:
       return &RNA_SpaceClipEditor;
     case SPACE_SPREADSHEET:
@@ -7246,6 +7258,20 @@ static void rna_def_space_userpref(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Filter", "Search term for filtering in the UI");
 }
 
+static void rna_def_space_project_settings(BlenderRNA *brna)
+{
+  StructRNA *srna;
+
+  srna = RNA_def_struct(brna, "SpaceProjectSettings", "Space");
+  RNA_def_struct_ui_text(srna, "Space Project Settings", "Blender project space data");
+
+  PropertyRNA *prop;
+
+  prop = RNA_def_property(srna, "active_section", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_project_settings_section_items);
+  RNA_def_property_ui_text(prop, "Active Section", "Choose the category of options to display");
+}
+
 static void rna_def_node_tree_path(BlenderRNA *brna)
 {
   StructRNA *srna;
@@ -8176,6 +8202,7 @@ void RNA_def_space(BlenderRNA *brna)
   rna_def_console_line(brna);
   rna_def_space_info(brna);
   rna_def_space_userpref(brna);
+  rna_def_space_project_settings(brna);
   rna_def_node_tree_path(brna);
   rna_def_space_node(brna);
   rna_def_space_clip(brna);

source/blender/makesrna/intern/rna_userdef.c

@@ -163,7 +163,6 @@ static const EnumPropertyItem rna_enum_preference_gpu_backend_items[] = {
 #  include "BKE_object.h"
 #  include "BKE_paint.h"
 #  include "BKE_pbvh.h"
-#  include "BKE_preferences.h"
 #  include "BKE_screen.h"
 
 #  include "DEG_depsgraph.h"
@@ -317,18 +316,6 @@ static void rna_userdef_language_update(Main *UNUSED(bmain),
   USERDEF_TAG_DIRTY;
 }
 
-static void rna_userdef_asset_library_name_set(PointerRNA *ptr, const char *value)
-{
-  bUserAssetLibrary *library = (bUserAssetLibrary *)ptr->data;
-  BKE_preferences_asset_library_name_set(&U, library, value);
-}
-
-static void rna_userdef_asset_library_path_set(PointerRNA *ptr, const char *value)
-{
-  bUserAssetLibrary *library = (bUserAssetLibrary *)ptr->data;
-  BKE_preferences_asset_library_path_set(library, value);
-}
-
 static void rna_userdef_script_autoexec_update(Main *UNUSED(bmain),
                                                Scene *UNUSED(scene),
                                                PointerRNA *ptr)
@@ -2562,6 +2549,21 @@ static void rna_def_userdef_theme_space_userpref(BlenderRNA *brna)
   rna_def_userdef_theme_spaces_main(srna);
 }
 
+static void rna_def_userdef_theme_space_project_settings(BlenderRNA *brna)
+{
+  StructRNA *srna;
+
+  /* space_userpref */
+
+  srna = RNA_def_struct(brna, "ThemeProjectSettings", NULL);
+  RNA_def_struct_sdna(srna, "ThemeSpace");
+  RNA_def_struct_clear_flag(srna, STRUCT_UNDO);
+  RNA_def_struct_ui_text(
+      srna, "Theme Project Settings", "Theme settings for the Blender project settings editor");
+
+  rna_def_userdef_theme_spaces_main(srna);
+}
+
 static void rna_def_userdef_theme_space_console(BlenderRNA *brna)
 {
   StructRNA *srna;
@@ -3902,6 +3904,8 @@ static void rna_def_userdef_themes(BlenderRNA *brna)
       {11, "PROPERTIES", ICON_PROPERTIES, "Properties", ""},
       {12, "OUTLINER", ICON_OUTLINER, "Outliner", ""},
       {14, "PREFERENCES", ICON_PREFERENCES, "Preferences", ""},
+      /* TODO icon */
+      {24, "PROJECT_SETTINGS", ICON_PREFERENCES, "Project Settings", ""},
       {15, "INFO", ICON_INFO, "Info", ""},
       {16, "FILE_BROWSER", ICON_FILEBROWSER, "File Browser", ""},
       {17, "CONSOLE", ICON_CONSOLE, "Python Console", ""},
@@ -4014,6 +4018,12 @@ static void rna_def_userdef_themes(BlenderRNA *brna)
   RNA_def_property_struct_type(prop, "ThemePreferences");
   RNA_def_property_ui_text(prop, "Preferences", "");
 
+  prop = RNA_def_property(srna, "project_settings", PROP_POINTER, PROP_NONE);
+  RNA_def_property_flag(prop, PROP_NEVER_NULL);
+  RNA_def_property_pointer_sdna(prop, NULL, "space_project_settings");
+  RNA_def_property_struct_type(prop, "ThemeProjectSettings");
+  RNA_def_property_ui_text(prop, "Project Settings", "");
+
   prop = RNA_def_property(srna, "console", PROP_POINTER, PROP_NONE);
   RNA_def_property_flag(prop, PROP_NEVER_NULL);
   RNA_def_property_pointer_sdna(prop, NULL, "space_console");
@@ -4300,6 +4310,7 @@ static void rna_def_userdef_dothemes(BlenderRNA *brna)
   rna_def_userdef_theme_space_outliner(brna);
   rna_def_userdef_theme_space_info(brna);
   rna_def_userdef_theme_space_userpref(brna);
+  rna_def_userdef_theme_space_project_settings(brna);
   rna_def_userdef_theme_space_console(brna);
   rna_def_userdef_theme_space_clip(brna);
   rna_def_userdef_theme_space_topbar(brna);
@@ -6111,56 +6122,6 @@ static void rna_def_userdef_keymap(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Key Config", "The name of the active key configuration");
 }
 
-static void rna_def_userdef_filepaths_asset_library(BlenderRNA *brna)
-{
-  StructRNA *srna;
-  PropertyRNA *prop;
-
-  srna = RNA_def_struct(brna, "UserAssetLibrary", NULL);
-  RNA_def_struct_sdna(srna, "bUserAssetLibrary");
-  RNA_def_struct_clear_flag(srna, STRUCT_UNDO);
-  RNA_def_struct_ui_text(
-      srna, "Asset Library", "Settings to define a reusable library for Asset Browsers to use");
-
-  prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
-  RNA_def_property_ui_text(
-      prop, "Name", "Identifier (not necessarily unique) for the asset library");
-  RNA_def_property_string_funcs(prop, NULL, NULL, "rna_userdef_asset_library_name_set");
-  RNA_def_struct_name_property(srna, prop);
-  RNA_def_property_update(prop, 0, "rna_userdef_update");
-
-  prop = RNA_def_property(srna, "path", PROP_STRING, PROP_DIRPATH);
-  RNA_def_property_ui_text(
-      prop, "Path", "Path to a directory with .blend files to use as an asset library");
-  RNA_def_property_string_funcs(prop, NULL, NULL, "rna_userdef_asset_library_path_set");
-  RNA_def_property_update(prop, 0, "rna_userdef_update");
-
-  static const EnumPropertyItem import_method_items[] = {
-      {ASSET_IMPORT_LINK, "LINK", 0, "Link", "Import the assets as linked data-block"},
-      {ASSET_IMPORT_APPEND,
-       "APPEND",
-       0,
-       "Append",
-       "Import the assets as copied data-block, with no link to the original asset data-block"},
-      {ASSET_IMPORT_APPEND_REUSE,
-       "APPEND_REUSE",
-       0,
-       "Append (Reuse Data)",
-       "Import the assets as copied data-block while avoiding multiple copies of nested, "
-       "typically heavy data. For example the textures of a material asset, or the mesh of an "
-       "object asset, don't have to be copied every time this asset is imported. The instances of "
-       "the asset share the data instead"},
-      {0, NULL, 0, NULL, NULL},
-  };
-  prop = RNA_def_property(srna, "import_method", PROP_ENUM, PROP_NONE);
-  RNA_def_property_enum_items(prop, import_method_items);
-  RNA_def_property_ui_text(
-      prop,
-      "Default Import Method",
-      "Determine how the asset will be imported, unless overridden by the Asset Browser");
-  RNA_def_property_update(prop, 0, "rna_userdef_update");
-}
-
 static void rna_def_userdef_filepaths(BlenderRNA *brna)
 {
   PropertyRNA *prop;
@@ -6341,10 +6302,8 @@ static void rna_def_userdef_filepaths(BlenderRNA *brna)
   RNA_def_property_enum_items(prop, preview_type_items);
   RNA_def_property_ui_text(prop, "File Preview Type", "What type of blend preview to create");
 
-  rna_def_userdef_filepaths_asset_library(brna);
-
   prop = RNA_def_property(srna, "asset_libraries", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_struct_type(prop, "UserAssetLibrary");
+  RNA_def_property_struct_type(prop, "CustomAssetLibraryDefinition");
   RNA_def_property_ui_text(prop, "Asset Libraries", "");
 
   prop = RNA_def_property(srna, "active_asset_library", PROP_INT, PROP_NONE);
@@ -6468,6 +6427,12 @@ static void rna_def_userdef_experimental(BlenderRNA *brna)
   RNA_def_property_ui_text(
       prop, "Override Templates", "Enable library override template in the python API");
 
+  prop = RNA_def_property(srna, "use_blender_projects", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_ui_text(prop,
+                           "Blender Projects",
+                           "Enable support for Blender project directories, consisting out of "
+                           "multiple .blend files and dedicated project settings");
+
   prop = RNA_def_property(srna, "enable_eevee_next", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "enable_eevee_next", 1);
   RNA_def_property_ui_text(prop, "EEVEE Next", "Enable the new EEVEE codebase, requires restart");

source/blender/python/intern/bpy_rna_callback.c

@@ -239,6 +239,9 @@ static eSpace_Type rna_Space_refine_reverse(StructRNA *srna)
   if (srna == &RNA_SpacePreferences) {
     return SPACE_USERPREF;
   }
+  if (srna == &RNA_SpaceProjectSettings) {
+    return SPACE_PROJECT_SETTINGS;
+  }
   if (srna == &RNA_SpaceClipEditor) {
     return SPACE_CLIP;
   }

source/blender/windowmanager/WM_types.h

@@ -355,6 +355,8 @@ typedef struct wmNotifier {
 #define NC_ASSET (27 << 24)
 /* Changes to the active viewer path. */
 #define NC_VIEWER_PATH (28 << 24)
+/* Changes related to the active project. */
+#define NC_PROJECT (29 << 24)
 
 /* data type, 256 entries is enough, it can overlap */
 #define NOTE_DATA 0x00FF0000
@@ -496,6 +498,9 @@ typedef struct wmNotifier {
  * reloading of asset libraries & their catalogs should happen. That only happens on explicit user
  * action. */
 #define ND_ASSET_CATALOGS (4 << 16)
+/* Some settings of an asset library were changed, and UIs showing asset library information should
+ * redraw. */
+#define ND_ASSET_LIBRARY (5 << 16)
 
 /* subtype, 256 entries too */
 #define NOTE_SUBTYPE 0x0000FF00

source/blender/windowmanager/intern/wm_draw.c

@@ -567,6 +567,7 @@ static const char *wm_area_name(ScrArea *area)
     SPACE_NAME(SPACE_CLIP);
     SPACE_NAME(SPACE_TOPBAR);
     SPACE_NAME(SPACE_STATUSBAR);
+    SPACE_NAME(SPACE_PROJECT_SETTINGS);
     default:
       return "Unknown Space";
   }
@@ -1357,6 +1358,9 @@ void wm_draw_update(bContext *C)
 
   BKE_image_free_unused_gpu_textures();
 
+  /* Subscribe to messages when drawing, #ED_region_do_draw() does the same on region level. */
+  wm_messages_subscribe(wm);
+
   LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
 #ifdef WIN32
     GHOST_TWindowState state = GHOST_GetWindowState(win->ghostwin);

source/blender/windowmanager/intern/wm_files.cc

@@ -61,6 +61,7 @@
 #include "BKE_appdir.h"
 #include "BKE_autoexec.h"
 #include "BKE_blender.h"
+#include "BKE_blender_project.h"
 #include "BKE_blendfile.h"
 #include "BKE_callbacks.h"
 #include "BKE_context.h"
@@ -160,7 +161,8 @@ void WM_file_tag_modified(void)
 bool wm_file_or_session_data_has_unsaved_changes(const Main *bmain, const wmWindowManager *wm)
 {
   return !wm->file_saved || ED_image_should_save_modified(bmain) ||
-         AS_asset_library_has_any_unsaved_catalogs();
+         AS_asset_library_has_any_unsaved_catalogs() ||
+         BKE_project_has_unsaved_changes(CTX_wm_project());
 }
 
 /** \} */
@@ -3187,6 +3189,16 @@ static int wm_save_as_mainfile_exec(bContext *C, wmOperator *op)
     return OPERATOR_CANCELLED;
   }
 
+  const BlenderProject *active_project = CTX_wm_project();
+  if (active_project && !BKE_project_contains_path(path)) {
+    BKE_reportf(
+        op->reports,
+        RPT_WARNING,
+        "File saved outside of the active project's path (\"%s\"). Active project changed.",
+        BKE_project_root_path_get(active_project));
+    /* Don't cancel. Otherwise there's no way to save files outside of the active project. */
+  }
+
   const int fileflags_orig = G.fileflags;
   int fileflags = G.fileflags;
 
@@ -3597,6 +3609,7 @@ void wm_test_autorun_warning(bContext *C)
  * \{ */
 
 static char save_images_when_file_is_closed = true;
+static char save_project_settings_when_file_is_closed = true;
 
 static void wm_block_file_close_cancel(bContext *C, void *arg_block, void * /*arg_data*/)
 {
@@ -3639,6 +3652,12 @@ static void wm_block_file_close_save(bContext *C, void *arg_block, void *arg_dat
     }
   }
 
+  BlenderProject *project = CTX_wm_project();
+  if (project && BKE_project_has_unsaved_changes(project) &&
+      save_project_settings_when_file_is_closed) {
+    BKE_project_settings_save(project);
+  }
+
   bool file_has_been_saved_before = BKE_main_blendfile_path(bmain)[0] != '\0';
 
   if (file_has_been_saved_before) {
@@ -3776,6 +3795,30 @@ static uiBlock *block_create__close_file_dialog(struct bContext *C,
     has_extra_checkboxes = true;
   }
 
+  if (BKE_project_has_unsaved_changes(CTX_wm_project())) {
+    /* Only the first checkbox should get extra separation. */
+    if (!has_extra_checkboxes) {
+      uiItemS(layout);
+    }
+
+    uiDefButBitC(block,
+                 UI_BTYPE_CHECKBOX,
+                 1,
+                 0,
+                 "Save modified project settings",
+                 0,
+                 0,
+                 0,
+                 UI_UNIT_Y,
+                 &save_project_settings_when_file_is_closed,
+                 0,
+                 0,
+                 0,
+                 0,
+                 "");
+    has_extra_checkboxes = true;
+  }
+
   if (AS_asset_library_has_any_unsaved_catalogs()) {
     static char save_catalogs_when_file_is_closed;
 

source/blender/windowmanager/intern/wm_window.c

@@ -28,6 +28,7 @@
 
 #include "BLT_translation.h"
 
+#include "BKE_blender_project.h"
 #include "BKE_context.h"
 #include "BKE_global.h"
 #include "BKE_icons.h"
@@ -42,6 +43,7 @@
 #include "RNA_enum_types.h"
 
 #include "WM_api.h"
+#include "WM_message.h"
 #include "WM_types.h"
 #include "wm.h"
 #include "wm_draw.h"
@@ -464,6 +466,8 @@ void wm_window_close(bContext *C, wmWindowManager *wm, wmWindow *win)
 
 void wm_window_title(wmWindowManager *wm, wmWindow *win)
 {
+#define MAX_PROJECT_NAME_HINT (MAX_NAME + 4)
+
   if (WM_window_is_temp_screen(win)) {
     /* Nothing to do for 'temp' windows,
      * because #WM_window_open always sets window title. */
@@ -472,11 +476,23 @@ void wm_window_title(wmWindowManager *wm, wmWindow *win)
     /* this is set to 1 if you don't have startup.blend open */
     const char *blendfile_path = BKE_main_blendfile_path_from_global();
     if (blendfile_path[0] != '\0') {
-      char str[sizeof(((Main *)NULL)->filepath) + 24];
+      char project_name_hint[MAX_PROJECT_NAME_HINT] = "";
+      char str[sizeof(((Main *)NULL)->filepath) + sizeof(project_name_hint) + 24];
+
+      struct BlenderProject *project = CTX_wm_project();
+      if (project) {
+        const char *name = BKE_project_name_get(project);
+        BLI_snprintf(project_name_hint,
+                     sizeof(project_name_hint),
+                     "%s - ",
+                     (name && name[0]) ? name : IFACE_("Unnamed project"));
+      }
+
       BLI_snprintf(str,
                    sizeof(str),
-                   "Blender%s [%s%s]",
+                   "Blender%s [%s%s%s]",
                    wm->file_saved ? "" : "*",
+                   project_name_hint,
                    blendfile_path,
                    G_MAIN->recovered ? " (Recovered)" : "");
       GHOST_SetTitle(win->ghostwin, str);
@@ -490,6 +506,8 @@ void wm_window_title(wmWindowManager *wm, wmWindow *win)
      * terminate request (e.g. OS Shortcut Alt+F4, Command+Q, (...), or session end). */
     GHOST_SetWindowModifiedState(win->ghostwin, (bool)!wm->file_saved);
   }
+
+#undef MAX_PROJECT_NAME_HINT
 }
 
 void WM_window_set_dpi(const wmWindow *win)
@@ -1596,6 +1614,35 @@ void wm_window_process_events(const bContext *C)
   }
 }
 
+/* -------------------------------------------------------------------- */
+/** \name WM level message bus subscribers
+ * \{ */
+
+static void wm_msg_windows_title_update_fn(bContext *C,
+                                           wmMsgSubscribeKey *UNUSED(msg_key),
+                                           wmMsgSubscribeValue *UNUSED(msg_val))
+{
+  wmWindowManager *wm = CTX_wm_manager(C);
+  LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
+    wm_window_title(wm, win);
+  }
+}
+
+void wm_messages_subscribe(wmWindowManager *wm)
+{
+  WM_msgbus_clear_by_owner(wm->message_bus, wm);
+
+  wmMsgSubscribeValue msg_sub_value_update_win_titles = {0};
+  msg_sub_value_update_win_titles.owner = wm;
+  msg_sub_value_update_win_titles.notify = wm_msg_windows_title_update_fn;
+
+  /* Update window titles on project name change. */
+  WM_msg_subscribe_rna_anon_prop(
+      wm->message_bus, BlenderProject, name, &msg_sub_value_update_win_titles);
+}
+
+/** \} */
+
 /* -------------------------------------------------------------------- */
 /** \name Ghost Init/Exit
  * \{ */

source/blender/windowmanager/wm_window.h

@@ -23,6 +23,8 @@ void wm_ghost_init(bContext *C);
 void wm_ghost_init_background(void);
 void wm_ghost_exit(void);
 
+void wm_messages_subscribe(wmWindowManager *wm);
+
 /**
  * This one should correctly check for apple top header...
  * done for Cocoa: returns window contents (and not frame) max size.