ImDrawData: Fixed an issue where TotalVtxCount/TotalIdxCount does not match the sum of individual ImDrawList's buffer sizes. (#6716)

Amend dbeeeae59

docs/CHANGELOG.txt

@@ -48,6 +48,8 @@ Other changes:
   through proper navigation logic: honor scrolling and selection. (#1079, #1131)
 - Sliders: Fixed an integer overflow and div-by-zero in SliderInt() when
   v_max=INT_MAX (#6675, #6679) [@jbarthelmes]
+- ImDrawData: Fixed an issue where TotalVtxCount/TotalIdxCount does not match the sum
+  of individual ImDrawList's buffer sizes when a dimming/modal background is rendered. (#6716)
 - ImDrawList: Fixed OOB access in _CalcCircleAutoSegmentCount when passing excessively
   large radius to AddCircle(). (#6657, #5317) [@EggsyCRO, @jdpatdiscord]
 - Debug Tools: Metrics: Fixed "Drawlists" section and per-viewport equivalent

imgui.cpp

@@ -5011,8 +5011,6 @@ static void AddWindowToDrawData(ImGuiWindow* window, int layer)
     ImGuiViewportP* viewport = window->Viewport;
     IM_ASSERT(viewport != NULL);
     g.IO.MetricsRenderWindows++;
-    if (window->Flags & ImGuiWindowFlags_DockNodeHost)
-        window->DrawList->ChannelsMerge();
     ImGui::AddDrawListToDrawDataEx(&viewport->DrawDataP, viewport->DrawDataBuilder.Layers[layer], window->DrawList);
     for (int i = 0; i < window->DC.ChildWindows.Size; i++)
     {
@@ -5349,6 +5347,17 @@ void ImGui::Render()
             AddDrawListToDrawDataEx(&viewport->DrawDataP, viewport->DrawDataBuilder.Layers[0], GetBackgroundDrawList(viewport));
     }
 
+    for (int n = 0; n != g.WindowsFocusOrder.Size; n++)
+    {
+        ImGuiWindow* window = g.Windows[n];
+        if (window->Flags & ImGuiWindowFlags_DockNodeHost)
+            window->DrawList->ChannelsMerge();
+    }
+
+    // Draw modal/window whitening backgrounds
+    if (first_render_of_frame)
+        RenderDimmedBackgrounds();
+
     // Add ImDrawList to render
     ImGuiWindow* windows_to_render_top_most[2];
     windows_to_render_top_most[0] = (g.NavWindowingTarget && !(g.NavWindowingTarget->Flags & ImGuiWindowFlags_NoBringToFrontOnFocus)) ? g.NavWindowingTarget->RootWindowDockTree : NULL;
@@ -5364,10 +5373,6 @@ void ImGui::Render()
         if (windows_to_render_top_most[n] && IsWindowActiveAndVisible(windows_to_render_top_most[n])) // NavWindowingTarget is always temporarily displayed as the top-most window
             AddRootWindowToDrawData(windows_to_render_top_most[n]);
 
-    // Draw modal/window whitening backgrounds
-    if (first_render_of_frame)
-        RenderDimmedBackgrounds();
-
     // Draw software mouse cursor if requested by io.MouseDrawCursor flag
     if (g.IO.MouseDrawCursor && first_render_of_frame && g.MouseCursor != ImGuiMouseCursor_None)
         RenderMouseCursor(g.IO.MousePos, g.Style.MouseCursorScale, g.MouseCursor, IM_COL32_WHITE, IM_COL32_BLACK, IM_COL32(0, 0, 0, 48));