Core: added ImDrawListSharedData::TextHook called by AddText(), and ImGuiItemFlags_NoTextSelect, to allow implementing text selection externally.

docs/CHANGELOG.txt

@@ -96,6 +96,10 @@ Other Changes:
 - Multi-Select:
   - Fixed `ImGuiSelectionBasicStorage::GetNextSelectedItem()` reading one past the
     end of storage when trailing items are unselected (#9604) [@MilosLord]
+- Text: added `ImDrawListSharedData::TextHook` (internal), called by `ImDrawList::AddText()`
+  with the font, position, clip rectangle and string of every text run before its glyphs
+  are emitted, and `ImGuiItemFlags_NoTextSelect` to let such a hook skip items. Enables
+  text selection/copy of any displayed text without changes to widget code.
 - ImVec2: added a check for cases where a custom `IM_VEC2_CLASS_EXTRA` macro
   adds an extra `operator=` to ImVec2. This isn't supported but should not
   be needed as you should have a constructor to convert from your type to ImVec2.

imgui.h

@@ -1330,6 +1330,8 @@ enum ImGuiItemFlags_
     //   - If you use MixedMode and the simplest solution is to ensure LiveEdit is off but widgets where this applies.
     //---------------------------------------------------------------------------------
     ImGuiItemFlags_MixedValue               = 1 << 9,   // false    // [BETA] Represent a mixed/indeterminate value. Replace value label with "-" and apply edits on validation.
+
+    ImGuiItemFlags_NoTextSelect             = 1 << 10,  // false    // Text drawn while set is ignored by text selection implemented via ImDrawListSharedData::TextHook: not highlighted, not copied, and a click on it does not start a selection.
 };
 
 // Flags for ImGui::InputText()

imgui_draw.cpp

@@ -2977,6 +2977,8 @@ void ImDrawList::AddText(ImFont* font, float font_size, const ImVec2& pos, ImU32
         clip_rect.z = ImMin(clip_rect.z, cpu_fine_clip_rect->z);
         clip_rect.w = ImMin(clip_rect.w, cpu_fine_clip_rect->w);
     }
+    if (_Data->TextHook != NULL)
+        _Data->TextHook(this, font, font_size, pos, clip_rect, text_begin, text_end, wrap_width, _Data->TextHookUserData);
     font->RenderText(this, font_size, pos, col, clip_rect, text_begin, text_end, wrap_width, (cpu_fine_clip_rect != NULL) ? ImDrawTextFlags_CpuFineClip : ImDrawTextFlags_None);
 }
 

imgui_internal.h

@@ -975,6 +975,8 @@ struct IMGUI_API ImDrawListSharedData
     ImVector<ImVec2> TempBuffer;                // Temporary write buffer
     ImVector<ImDrawList*> DrawLists;            // All draw lists associated to this ImDrawListSharedData
     ImGuiContext*   Context;                    // [OPTIONAL] Link to Dear ImGui context. 99% of ImDrawList/ImFontAtlas can function without an ImGui context, but this facilitate handling one legacy edge case.
+    void          (*TextHook)(ImDrawList* draw_list, ImFont* font, float font_size, const ImVec2& pos, const ImVec4& clip_rect, const char* text_begin, const char* text_end, float wrap_width, void* user_data); // [OPTIONAL] Called by AddText() before the glyphs are emitted: anything it draws ends up underneath the text. text_end may be NULL.
+    void*           TextHookUserData;
 
     // Lookup tables
     ImVec2          ArcFastVtx[IM_DRAWLIST_ARCFAST_TABLE_SIZE]; // Sample points on the quarter of the circle.