Fixed CTRL+Tab dimming background assert when target window has a callback in the last ImDrawCmd. (#4857, #5937)

docs/CHANGELOG.txt

@@ -42,6 +42,8 @@ Breaking changes:
 
 Other changes:
 
+- Fixed CTRL+Tab dimming background assert when target window has a callback
+  in the last ImDrawCmd. (#4857, #5937)
 - InputText: Fixed a case where deactivation frame would write to underlying
   buffer or call CallbackResize although unnecessary, in a frame where the
   return value was false.

imgui.cpp

@@ -4917,14 +4917,14 @@ static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32
         ImDrawList* draw_list = window->RootWindow->DrawList;
         if (draw_list->CmdBuffer.Size == 0)
             draw_list->AddDrawCmd();
-        draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // Ensure ImDrawCmd are not merged
+        draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // FIXME: Need to stricty ensure ImDrawCmd are not merged (ElemCount==6 checks below will verify that)
         draw_list->AddRectFilled(viewport_rect.Min, viewport_rect.Max, col);
         ImDrawCmd cmd = draw_list->CmdBuffer.back();
         IM_ASSERT(cmd.ElemCount == 6);
         draw_list->CmdBuffer.pop_back();
         draw_list->CmdBuffer.push_front(cmd);
-        draw_list->PopClipRect();
         draw_list->AddDrawCmd(); // We need to create a command as CmdBuffer.back().IdxOffset won't be correct if we append to same command.
+        draw_list->PopClipRect();
     }
 }