source/blender/editors/interface/interface.cc

@@ -3477,6 +3477,10 @@ 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 +5910,17 @@ void UI_but_disable(uiBut *but, const char *disabled_hint)
   but->disabled_info = disabled_hint;
 }
 
+void UI_but_placeholder(uiBut *but, const char *placeholder_text)
+{
+  if (but->placeholder) {
+    MEM_SAFE_FREE(but->placeholder);
+    but->placeholder = nullptr;
+  }
+  if (placeholder_text && placeholder_text[0]) {
+    but->placeholder = BLI_strdup(placeholder_text);
+  }
+}
+
 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;

source/blender/editors/interface/interface_widgets.cc

@@ -2187,6 +2187,46 @@ static void widget_draw_text(const uiFontStyle *fstyle,
     }
   }
 
+  if (strlen(drawstr) == 0 && !but->editstr &&
+      ELEM(but->type, UI_BTYPE_TEXT, UI_BTYPE_SEARCH_MENU))
+  {
+
+    /* Custom placeholder text here just while testing. */
+    const char *placeholder = (but->placeholder) ? but->placeholder : "Placeholder";
+    switch (but->icon) {
+      case ICON_VIEWZOOM:
+        placeholder = "Search";
+        break;
+      case ICON_SCENE_DATA:
+        placeholder = "Scene";
+        break;
+      case ICON_OBJECT_DATA:
+        placeholder = "Object";
+        break;
+      case ICON_SEQUENCE:
+        placeholder = "Movie Clip";
+        break;
+    }
+    
+    uiFontStyleDraw_Params params{};
+    params.align = align;
+    uiFontStyle style = *fstyle;
+    style.italic = true;
+    uchar col[4];
+    copy_v4_v4_uchar(col, wcol->text);
+    col[3] *= 0.4f;
+    int font_xofs, font_yofs;
+    UI_fontstyle_draw_ex(&style,
+                         rect,
+                         placeholder,
+                         strlen(placeholder),
+                         col,
+                         &params,
+                         &font_xofs,
+                         &font_yofs,
+                         nullptr);
+  }
+
   /* part text right aligned */
   if (drawstr_right) {
     uchar col[4];