Misc: Made multiple calls to Render() during the same frame early out faster.

docs/CHANGELOG.txt

@@ -54,6 +54,7 @@ Other changes:
   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]
+- Misc: Made multiple calls to Render() during the same frame early out faster.
 - Debug Tools: Metrics: Fixed "Drawlists" section and per-viewport equivalent
   appearing empty (regression in 1.89.8).
 - Demo: Demonstrate out-of-order rendering using ImDrawListSplitter.

imgui.cpp

@@ -5077,15 +5077,15 @@ void ImGui::Render()
 
     if (g.FrameCountEnded != g.FrameCount)
         EndFrame();
-    const bool first_render_of_frame = (g.FrameCountRendered != g.FrameCount);
+    if (g.FrameCountRendered == g.FrameCount)
+        return;
     g.FrameCountRendered = g.FrameCount;
-    g.IO.MetricsRenderWindows = 0;
 
+    g.IO.MetricsRenderWindows = 0;
     CallContextHooks(&g, ImGuiContextHookType_RenderPre);
 
     // Draw modal/window whitening backgrounds
-    if (first_render_of_frame)
+    RenderDimmedBackgrounds();
-        RenderDimmedBackgrounds();
 
     // Add background ImDrawList (for each active viewport)
     for (int n = 0; n != g.Viewports.Size; n++)
@@ -5112,7 +5112,7 @@ void ImGui::Render()
             AddRootWindowToDrawData(windows_to_render_top_most[n]);
 
     // Draw software mouse cursor if requested by io.MouseDrawCursor flag
-    if (g.IO.MouseDrawCursor && first_render_of_frame && g.MouseCursor != ImGuiMouseCursor_None)
+    if (g.IO.MouseDrawCursor && 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));
 
     // Setup ImDrawData structures for end-user