scripts/modules/bl_i18n_utils/bl_extract_messages.py

@@ -588,6 +588,7 @@ def dump_py_messages_from_files(msgs, reports, files, settings):
                   ),
         "message": (),
         "heading": (),
+        "placeholder": ((("text_ctxt",), _ctxt_to_ctxt),),
     }
 
     context_kw_set = {}
@@ -621,7 +622,8 @@ def dump_py_messages_from_files(msgs, reports, files, settings):
         for arg_pos, (arg_kw, arg) in enumerate(func.parameters.items()):
             if (not arg.is_output) and (arg.type == 'STRING'):
                 for msgid, msgctxts in context_kw_set.items():
-                    if arg_kw in msgctxts:
+                    # The msgid can be missing if it is used in only some UILayout functions but not all
+                    if arg_kw in msgctxts and msgid in func_translate_args[func_id]:
                         func_translate_args[func_id][msgid][1][arg_kw] = arg_pos
     # The report() func of operators.
     for func_id, func in bpy.types.Operator.bl_rna.functions.items():

source/blender/editors/include/UI_interface_c.hh

@@ -933,6 +933,11 @@ void UI_but_disable(uiBut *but, const char *disabled_hint);
 
 void UI_but_type_set_menu_from_pulldown(uiBut *but);
 
+/**
+ * Set at hint that describes the expected value when empty.
+ */
+void UI_but_placeholder_set(uiBut *but, const char *placeholder_text) ATTR_NONNULL(1);
+
 /**
  * Special button case, only draw it when used actively, for outliner etc.
  *
@@ -2775,7 +2780,8 @@ void uiItemFullR(uiLayout *layout,
                  int value,
                  eUI_Item_Flag flag,
                  const char *name,
-                 int icon);
+                 int icon,
+                 const char *placeholder = nullptr);
 /**
  * Use a wrapper function since re-implementing all the logic in this function would be messy.
  */

source/blender/editors/interface/interface.cc

@@ -61,6 +61,7 @@
 #include "WM_types.hh"
 
 #include "RNA_access.hh"
+#include "RNA_enum_types.hh"
 
 #ifdef WITH_PYTHON
 #  include "BPY_extern_run.h"
@@ -3477,6 +3478,10 @@ static void ui_but_free(const bContext *C, uiBut *but)
     MEM_freeN(but->hold_argN);
   }
 
+  if (but->placeholder) {
+    MEM_freeN(but->placeholder);
+  }
+
   ui_but_free_type_specific(but);
 
   if (but->active) {
@@ -5906,6 +5911,36 @@ void UI_but_disable(uiBut *but, const char *disabled_hint)
   but->disabled_info = disabled_hint;
 }
 
+void UI_but_placeholder_set(uiBut *but, const char *placeholder_text)
+{
+  MEM_SAFE_FREE(but->placeholder);
+  but->placeholder = BLI_strdup_null(placeholder_text);
+}
+
+const char *ui_but_placeholder_get(uiBut *but)
+{
+  const char *placeholder = (but->placeholder) ? but->placeholder : nullptr;
+
+  if (!placeholder && but->rnaprop) {
+    if (but->type == UI_BTYPE_SEARCH_MENU) {
+      StructRNA *type = RNA_property_pointer_type(&but->rnapoin, but->rnaprop);
+      const short idcode = RNA_type_to_ID_code(type);
+      if (idcode != 0) {
+        RNA_enum_name(rna_enum_id_type_items, idcode, &placeholder);
+        placeholder = CTX_IFACE_(BLT_I18NCONTEXT_ID_ID, placeholder);
+      }
+    }
+    else if (but->type == UI_BTYPE_TEXT) {
+      const char *identifier = RNA_property_identifier(but->rnaprop);
+      if (STR_ELEM(identifier, "search_filter", "filter_text", "filter_search")) {
+        placeholder = CTX_IFACE_(BLT_I18NCONTEXT_ID_WINDOWMANAGER, "Search");
+      }
+    }
+  }
+
+  return placeholder;
+}
+
 void UI_but_type_set_menu_from_pulldown(uiBut *but)
 {
   BLI_assert(but->type == UI_BTYPE_PULLDOWN);

source/blender/editors/interface/interface_intern.hh

@@ -175,6 +175,8 @@ struct uiBut {
   char strdata[UI_MAX_NAME_STR] = "";
   char drawstr[UI_MAX_DRAW_STR] = "";
 
+  char *placeholder = nullptr;
+
   rctf rect = {}; /* block relative coords */
 
   char *poin = nullptr;
@@ -742,6 +744,11 @@ void ui_but_active_string_clear_and_exit(bContext *C, uiBut *but) ATTR_NONNULL()
 void ui_but_set_string_interactive(bContext *C, uiBut *but, const char *value);
 uiBut *ui_but_drag_multi_edit_get(uiBut *but);
 
+/**
+ * Get the hint that describes the expected value when empty.
+ */
+const char *ui_but_placeholder_get(uiBut *but);
+
 void ui_def_but_icon(uiBut *but, int icon, int flag);
 /**
  * Avoid using this where possible since it's better not to ask for an icon in the first place.

source/blender/editors/interface/interface_layout.cc

@@ -2055,7 +2055,8 @@ void uiItemFullR(uiLayout *layout,
                  int value,
                  eUI_Item_Flag flag,
                  const char *name,
-                 int icon)
+                 int icon,
+                 const char *placeholder)
 {
   uiBlock *block = layout->root->block;
   char namestr[UI_MAX_NAME_STR];
@@ -2468,6 +2469,10 @@ void uiItemFullR(uiLayout *layout,
     UI_but_flag_enable(but, UI_BUT_LIST_ITEM);
   }
 
+  if (but && placeholder) {
+    UI_but_placeholder_set(but, placeholder);
+  }
+
 #ifdef UI_PROP_DECORATE
   if (ui_decorate.use_prop_decorate) {
     uiBut *but_decorate = ui_decorate.but ? ui_decorate.but->next :

source/blender/editors/interface/interface_widgets.cc

@@ -2187,6 +2187,22 @@ static void widget_draw_text(const uiFontStyle *fstyle,
     }
   }
 
+  /* Show placeholder text if the input is empty and not being edited. */
+  if (!drawstr[0] && !but->editstr && ELEM(but->type, UI_BTYPE_TEXT, UI_BTYPE_SEARCH_MENU)) {
+    const char *placeholder = ui_but_placeholder_get(but);
+    if (placeholder && placeholder[0]) {
+      uiFontStyleDraw_Params params{};
+      params.align = align;
+      uiFontStyle style = *fstyle;
+      style.shadow = 0;
+      uchar col[4];
+      copy_v4_v4_uchar(col, wcol->text);
+      col[3] *= 0.33f;
+      UI_fontstyle_draw_ex(
+          &style, rect, placeholder, strlen(placeholder), col, &params, nullptr, nullptr, nullptr);
+    }
+  }
+
   /* part text right aligned */
   if (drawstr_right) {
     uchar col[4];

source/blender/makesrna/intern/rna_ui_api.cc

@@ -84,6 +84,7 @@ static void rna_uiItemR(uiLayout *layout,
                         const char *text_ctxt,
                         bool translate,
                         int icon,
+                        const char *placeholder,
                         bool expand,
                         bool slider,
                         int toggle,
@@ -109,6 +110,7 @@ static void rna_uiItemR(uiLayout *layout,
 
   /* Get translated name (label). */
   name = rna_translate_ui_text(name, text_ctxt, nullptr, prop, translate);
+  placeholder = rna_translate_ui_text(placeholder, text_ctxt, nullptr, prop, translate);
 
   if (slider) {
     flag |= UI_ITEM_R_SLIDER;
@@ -140,7 +142,7 @@ static void rna_uiItemR(uiLayout *layout,
     flag |= UI_ITEM_R_CHECKBOX_INVERT;
   }
 
-  uiItemFullR(layout, ptr, prop, index, 0, flag, name, icon);
+  uiItemFullR(layout, ptr, prop, index, 0, flag, name, icon, placeholder);
 }
 
 static void rna_uiItemR_with_popover(uiLayout *layout,
@@ -1147,6 +1149,8 @@ void RNA_api_ui_layout(StructRNA *srna)
   RNA_def_function_ui_description(func, "Item. Exposes an RNA item and places it into the layout");
   api_ui_item_rna_common(func);
   api_ui_item_common(func);
+  RNA_def_string(
+      func, "placeholder", nullptr, 0, "", "Hint describing the expected value when empty");
   RNA_def_boolean(func, "expand", false, "", "Expand button to show more detail");
   RNA_def_boolean(func, "slider", false, "", "Use slider widget for numeric values");
   RNA_def_int(func,