source/blender/editors/include/UI_interface_c.hh

@@ -712,6 +712,21 @@ int UI_popup_menu_invoke(bContext *C, const char *idname, ReportList *reports) A
  * E.g. WM might need to do this for exiting files correctly.
  */
 void UI_popup_menu_retval_set(const uiBlock *block, int retval, bool enable);
+/**
+ * Set a dummy panel in the popup `block` to support using layout panels, the panel is linked
+ * to the popup `region` so layout panels state can be persistent until the popup is closed.
+ */
+void UI_popup_dummy_panel_set(ARegion *region, uiBlock *block);
+/** Toggles layout panel open state and returns the new state. */
+bool UI_layout_panel_toggle_open(const bContext *C, struct LayoutPanelHeader *header);
+void UI_panel_drag_collapse_handler_add(const bContext *C, const bool was_open);
+LayoutPanelHeader *UI_layout_panel_header_under_mouse(const Panel &panel, const int my);
+/** Apply scroll to layout panels when the main panel is used in popups. */
+void UI_layout_panel_popup_scroll_apply(Panel *panel, const float dy);
+void UI_draw_layout_panels_backdrop(const ARegion *region,
+                                    const Panel *panel,
+                                    const float radius,
+                                    float subpanel_backcolor[4]);
 /**
  * Setting the button makes the popup open from the button instead of the cursor.
  */

source/blender/editors/interface/interface.cc

@@ -2096,6 +2096,15 @@ void UI_block_draw(const bContext *C, uiBlock *block)
                           UI_panel_should_show_background(region, block->panel->type),
                           region->flag & RGN_FLAG_SEARCH_FILTER_ACTIVE);
   }
+  /* Shared layout panel backdrop style between redo region and popups. */
+  if (block->panel && ELEM(region->regiontype, RGN_TYPE_HUD, RGN_TYPE_TEMPORARY)) {
+    /* TODO: Add as theme color. */
+    float subpanel_backcolor[4]{0.2f, 0.3f, 0.33f, 0.05f};
+    const bTheme *btheme = UI_GetTheme();
+    const float aspect = block->panel->runtime->block->aspect;
+    const float radius = btheme->tui.panel_roundness * U.widget_unit * 0.5f / aspect;
+    UI_draw_layout_panels_backdrop(region, block->panel, radius, subpanel_backcolor);
+  }
 
   BLF_batch_draw_begin();
   UI_icon_draw_cache_begin();

source/blender/editors/interface/interface_handlers.cc

@@ -55,6 +55,7 @@
 #include "ED_undo.hh"
 
 #include "UI_interface.hh"
+#include "UI_interface_c.hh"
 #include "UI_string_search.hh"
 
 #include "BLF_api.hh"
@@ -10124,6 +10125,8 @@ static void ui_menu_scroll_apply_offset_y(ARegion *region, uiBlock *block, float
 
   /* remember scroll offset for refreshes */
   block->handle->scrolloffset += dy;
+  /* Apply popup scroll delta to layout panels too. */
+  UI_layout_panel_popup_scroll_apply(block->panel, dy);
 
   /* apply scroll offset */
   LISTBASE_FOREACH (uiBut *, bt, &block->buttons) {
@@ -11428,6 +11431,25 @@ static int ui_handle_menus_recursive(bContext *C,
           C, event, submenu, level + 1, is_parent_inside || inside, is_menu, false);
     }
   }
+  else if (event->val == KM_PRESS && event->type == LEFTMOUSE) {
+    LISTBASE_FOREACH (uiBlock *, block, &menu->region->uiblocks) {
+      if (block->panel) {
+        int mx = event->xy[0];
+        int my = event->xy[1];
+        ui_window_to_block(menu->region, block, &mx, &my);
+        if (!IN_RANGE(float(mx), block->rect.xmin, block->rect.xmax)) {
+          break;
+        }
+        LayoutPanelHeader *header = UI_layout_panel_header_under_mouse(*block->panel, my);
+        if (header) {
+          ED_region_tag_redraw(menu->region);
+          ED_region_tag_refresh_ui(menu->region);
+          UI_panel_drag_collapse_handler_add(C, !UI_layout_panel_toggle_open(C, header));
+          retval = WM_UI_HANDLER_BREAK;
+        }
+      }
+    }
+  }
 
   /* now handle events for our own menu */
   if (retval == WM_UI_HANDLER_CONTINUE || event->type == TIMER) {

source/blender/editors/interface/interface_panel.cc

@@ -38,6 +38,7 @@
 #include "ED_screen.hh"
 
 #include "UI_interface.hh"
+#include "UI_interface_c.hh"
 #include "UI_interface_icons.hh"
 #include "UI_resources.hh"
 #include "UI_view2d.hh"
@@ -1162,6 +1163,36 @@ static int layout_panel_y_offset()
   return UI_style_get_dpi()->panelspace;
 }
 
+void UI_draw_layout_panels_backdrop(const ARegion *region,
+                                    const Panel *panel,
+                                    const float radius,
+                                    float subpanel_backcolor[4])
+{
+  /* Draw backdrops for layout panels. */
+  for (const LayoutPanelBody &body : panel->runtime->layout_panels.bodies) {
+
+    rctf panel_blockspace = panel->runtime->block->rect;
+    panel_blockspace.ymax = panel->runtime->block->rect.ymax + body.end_y;
+    panel_blockspace.ymin = panel->runtime->block->rect.ymax + body.start_y;
+    BLI_rctf_translate(&panel_blockspace, 0, -layout_panel_y_offset());
+
+    /* If the layout panel is at the end of the root panel, it's bottom corners are rounded. */
+    const bool is_main_panel_end = panel_blockspace.ymin - panel->runtime->block->rect.ymin < 10;
+    if (is_main_panel_end) {
+      panel_blockspace.ymin = panel->runtime->block->rect.ymin;
+      UI_draw_roundbox_corner_set(UI_CNR_BOTTOM_RIGHT | UI_CNR_BOTTOM_LEFT);
+    }
+    else {
+      UI_draw_roundbox_corner_set(UI_CNR_NONE);
+    }
+
+    rcti panel_pixelspace = ui_to_pixelrect(region, panel->runtime->block, &panel_blockspace);
+    rctf panel_pixelspacef;
+    BLI_rctf_rcti_copy(&panel_pixelspacef, &panel_pixelspace);
+    UI_draw_roundbox_4fv(&panel_pixelspacef, true, radius, subpanel_backcolor);
+  }
+}
+
 static void panel_draw_aligned_backdrop(const ARegion *region,
                                         const Panel *panel,
                                         const rcti *rect,
@@ -1200,31 +1231,9 @@ static void panel_draw_aligned_backdrop(const ARegion *region,
     box_rect.ymax = rect->ymax;
     UI_draw_roundbox_4fv(&box_rect, true, radius, panel_backcolor);
 
-    /* Draw backdrops for layout panels. */
-    for (const LayoutPanelBody &body : panel->runtime->layout_panels.bodies) {
-      float subpanel_backcolor[4];
-      UI_GetThemeColor4fv(TH_PANEL_SUB_BACK, subpanel_backcolor);
-
-      rctf panel_blockspace = panel->runtime->block->rect;
-      panel_blockspace.ymax = panel->runtime->block->rect.ymax + body.end_y;
-      panel_blockspace.ymin = panel->runtime->block->rect.ymax + body.start_y;
-      BLI_rctf_translate(&panel_blockspace, 0, -layout_panel_y_offset());
-
-      /* If the layout panel is at the end of the root panel, it's bottom corners are rounded. */
-      const bool is_main_panel_end = panel_blockspace.ymin - panel->runtime->block->rect.ymin < 10;
-      if (is_main_panel_end) {
-        panel_blockspace.ymin = panel->runtime->block->rect.ymin;
-        UI_draw_roundbox_corner_set(UI_CNR_BOTTOM_RIGHT | UI_CNR_BOTTOM_LEFT);
-      }
-      else {
-        UI_draw_roundbox_corner_set(UI_CNR_NONE);
-      }
-
-      rcti panel_pixelspace = ui_to_pixelrect(region, panel->runtime->block, &panel_blockspace);
-      rctf panel_pixelspacef;
-      BLI_rctf_rcti_copy(&panel_pixelspacef, &panel_pixelspace);
-      UI_draw_roundbox_4fv(&panel_pixelspacef, true, radius, subpanel_backcolor);
-    }
+    float subpanel_backcolor[4];
+    UI_GetThemeColor4fv(TH_PANEL_SUB_BACK, subpanel_backcolor);
+    UI_draw_layout_panels_backdrop(region, panel, radius, subpanel_backcolor);
   }
 
   /* Panel header backdrops for non sub-panels. */
@@ -1931,7 +1940,7 @@ static void ui_do_drag(const bContext *C, const wmEvent *event, Panel *panel)
 /** \name Region Level Panel Interaction
  * \{ */
 
-static LayoutPanelHeader *get_layout_panel_header_under_mouse(const Panel &panel, const int my)
+LayoutPanelHeader *UI_layout_panel_header_under_mouse(const Panel &panel, const int my)
 {
   for (LayoutPanelHeader &header : panel.runtime->layout_panels.headers) {
     if (IN_RANGE(float(my - panel.runtime->block->rect.ymax + layout_panel_y_offset()),
@@ -1956,7 +1965,7 @@ static uiPanelMouseState ui_panel_mouse_state_get(const uiBlock *block,
   if (IN_RANGE(float(my), block->rect.ymax, block->rect.ymax + PNL_HEADER)) {
     return PANEL_MOUSE_INSIDE_HEADER;
   }
-  if (get_layout_panel_header_under_mouse(*panel, my) != nullptr) {
+  if (UI_layout_panel_header_under_mouse(*panel, my) != nullptr) {
     return PANEL_MOUSE_INSIDE_LAYOUT_PANEL_HEADER;
   }
 
@@ -1984,8 +1993,10 @@ static void ui_panel_drag_collapse(const bContext *C,
                                    const uiPanelDragCollapseHandle *dragcol_data,
                                    const int xy_dst[2])
 {
-  ARegion *region = CTX_wm_region(C);
-
+  ARegion *region = CTX_wm_menu(C);
+  if (!region) {
+    region = CTX_wm_region(C);
+  }
   LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
     float xy_a_block[2] = {float(dragcol_data->xy_init[0]), float(dragcol_data->xy_init[1])};
     float xy_b_block[2] = {float(xy_dst[0]), float(xy_dst[1])};
@@ -2015,6 +2026,7 @@ static void ui_panel_drag_collapse(const bContext *C,
             &header.open_owner_ptr,
             RNA_struct_find_property(&header.open_owner_ptr, header.open_prop_name.c_str()));
         ED_region_tag_redraw(region);
+        ED_region_tag_refresh_ui(region);
       }
     }
 
@@ -2080,7 +2092,7 @@ static int ui_panel_drag_collapse_handler(bContext *C, const wmEvent *event, voi
   return retval;
 }
 
-static void ui_panel_drag_collapse_handler_add(const bContext *C, const bool was_open)
+void UI_panel_drag_collapse_handler_add(const bContext *C, const bool was_open)
 {
   wmWindow *win = CTX_wm_window(C);
   const wmEvent *event = win->eventstate;
@@ -2097,32 +2109,32 @@ static void ui_panel_drag_collapse_handler_add(const bContext *C, const bool was
                           eWM_EventHandlerFlag(0));
 }
 
+bool UI_layout_panel_toggle_open(const bContext *C, LayoutPanelHeader *header)
+{
+  const bool is_open = RNA_boolean_get(&header->open_owner_ptr, header->open_prop_name.c_str());
+  RNA_boolean_set(&header->open_owner_ptr, header->open_prop_name.c_str(), !is_open);
+  RNA_property_update(
+      const_cast<bContext *>(C),
+      &header->open_owner_ptr,
+      RNA_struct_find_property(&header->open_owner_ptr, header->open_prop_name.c_str()));
+  return !is_open;
+}
+
 static void ui_handle_layout_panel_header(
     const bContext *C, const uiBlock *block, const int /*mx*/, const int my, const int event_type)
 {
   Panel *panel = block->panel;
   BLI_assert(panel->type != nullptr);
 
-  LayoutPanelHeader *header = get_layout_panel_header_under_mouse(*panel, my);
+  LayoutPanelHeader *header = UI_layout_panel_header_under_mouse(*panel, my);
   if (header == nullptr) {
     return;
   }
-
-  const bool is_open = RNA_boolean_get(&header->open_owner_ptr, header->open_prop_name.c_str());
-  if (is_open) {
-    RNA_boolean_set(&header->open_owner_ptr, header->open_prop_name.c_str(), false);
-  }
-  else {
-    RNA_boolean_set(&header->open_owner_ptr, header->open_prop_name.c_str(), true);
-  }
-  RNA_property_update(
-      const_cast<bContext *>(C),
-      &header->open_owner_ptr,
-      RNA_struct_find_property(&header->open_owner_ptr, header->open_prop_name.c_str()));
+  const bool new_state = UI_layout_panel_toggle_open(C, header);
   ED_region_tag_redraw(CTX_wm_region(C));
 
   if (event_type == LEFTMOUSE) {
-    ui_panel_drag_collapse_handler_add(C, is_open);
+    UI_panel_drag_collapse_handler_add(C, !new_state);
   }
 }
 
@@ -2188,7 +2200,7 @@ static void ui_handle_panel_header(const bContext *C,
     SET_FLAG_FROM_TEST(panel->flag, !UI_panel_is_closed(panel), PNL_CLOSED);
 
     if (event_type == LEFTMOUSE) {
-      ui_panel_drag_collapse_handler_add(C, UI_panel_is_closed(panel));
+      UI_panel_drag_collapse_handler_add(C, UI_panel_is_closed(panel));
     }
 
     /* Set panel custom data (modifier) active when expanding sub-panels, but not top-level

source/blender/editors/interface/interface_region_popup.cc

@@ -576,6 +576,38 @@ static void ui_popup_block_remove(bContext *C, uiPopupBlockHandle *handle)
   }
 }
 
+void UI_layout_panel_popup_scroll_apply(Panel *panel, const float dy)
+{
+  if (!panel || dy == 0.0f) {
+    return;
+  }
+  for (LayoutPanelBody &body : panel->runtime->layout_panels.bodies) {
+    body.start_y += dy;
+    body.end_y += dy;
+  }
+  for (LayoutPanelHeader &headcer : panel->runtime->layout_panels.headers) {
+    headcer.start_y += dy;
+    headcer.end_y += dy;
+  }
+}
+
+void UI_popup_dummy_panel_set(ARegion *region, uiBlock *block)
+{
+  Panel *&panel = region->runtime.popup_block_panel;
+  if (!panel) {
+    /* Dummy popup panel type. */
+    static PanelType panel_type = []() {
+      PanelType type{};
+      type.flag = PANEL_TYPE_NO_HEADER;
+      return type;
+    }();
+    panel = BKE_panel_new(&panel_type);
+  }
+  panel->runtime->layout_panels.clear();
+  block->panel = panel;
+  panel->runtime->block = block;
+}
+
 uiBlock *ui_popup_block_refresh(bContext *C,
                                 uiPopupBlockHandle *handle,
                                 ARegion *butregion,
@@ -753,7 +785,14 @@ uiBlock *ui_popup_block_refresh(bContext *C,
     region->winrct.ymax = block->rect.ymax + UI_POPUP_MENU_TOP;
 
     UI_block_translate(block, -region->winrct.xmin, -region->winrct.ymin);
+    /* Popups can change size, fix scroll offset if a panel was closed. */
+    float ymin = FLT_MAX;
+    LISTBASE_FOREACH (uiBut *, bt, &block->buttons) {
+      ymin = min_ff(ymin, bt->rect.ymin);
+    }
 
+    handle->scrolloffset = std::clamp<float>(
+        handle->scrolloffset, 0.0f, std::max<float>(block->rect.ymin - ymin, 0.0f));
     /* apply scroll offset */
     if (handle->scrolloffset != 0.0f) {
       LISTBASE_FOREACH (uiBut *, bt, &block->buttons) {
@@ -762,6 +801,8 @@ uiBlock *ui_popup_block_refresh(bContext *C,
       }
     }
   }
+  /* Apply popup scroll offset to layout panels. */
+  UI_layout_panel_popup_scroll_apply(block->panel, handle->scrolloffset);
 
   if (block_old) {
     block->oldblock = block_old;
@@ -875,6 +916,10 @@ void ui_popup_block_free(bContext *C, uiPopupBlockHandle *handle)
     handle->popup_create_vars.arg_free(handle->popup_create_vars.arg);
   }
 
+  if (handle->region->runtime.popup_block_panel) {
+    BKE_panel_free(handle->region->runtime.popup_block_panel);
+  }
+
   ui_popup_block_remove(C, handle);
 
   MEM_freeN(handle);

source/blender/makesdna/DNA_screen_types.h

@@ -454,6 +454,9 @@ typedef struct ARegion_Runtime {
 
   /** Maps #uiBlock::name to uiBlock for faster lookups. */
   struct GHash *block_name_map;
+
+  /* Dummy panel used in popups so they can support layout panels. */
+  Panel *popup_block_panel;
 } ARegion_Runtime;
 
 typedef struct ARegion {

source/blender/windowmanager/intern/wm_operators.cc

@@ -1391,6 +1391,7 @@ static uiBlock *wm_block_create_redo(bContext *C, ARegion *region, void *arg_op)
   BLI_assert(op->type->flag & OPTYPE_REGISTER);
 
   UI_block_func_handle_set(block, wm_block_redo_cb, arg_op);
+  UI_popup_dummy_panel_set(region, block);
   uiLayout *layout = UI_block_layout(
       block, UI_LAYOUT_VERTICAL, UI_LAYOUT_PANEL, 0, 0, width, UI_UNIT_Y, 0, style);
 
@@ -1476,6 +1477,7 @@ static uiBlock *wm_block_dialog_create(bContext *C, ARegion *region, void *user_
   uiBlock *block = UI_block_begin(C, region, __func__, UI_EMBOSS);
   UI_block_flag_disable(block, UI_BLOCK_LOOP);
   UI_block_theme_style_set(block, UI_BLOCK_THEME_STYLE_POPUP);
+  UI_popup_dummy_panel_set(region, block);
 
   if (data->mouse_move_quit) {
     UI_block_flag_enable(block, UI_BLOCK_MOVEMOUSE_QUIT);