Focus: fixed fallback "Debug" window temporarily taking focus and setting io.WantCaptureKeyboard for a frame. (#9243)

docs/CHANGELOG.txt

diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 43a7f78..d812e8b 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -92,6 +92,8 @@
   - Implemented a custom tweak to extend hit-testing bounding box when window is sitting
     at the edge of a viewport (e.g. fullscreen or docked window), so that e.g. mouse the
     mouse at the extreme of the screen will reach the scrollbar. (#9276)
+- Focus: fixed fallback "Debug" window temporarily taking focus and setting io.WantCaptureKeyboard
+  for one frame on e.g. application boot if no other windows are submitted. (#9243)
 - Demo: fixed IMGUI_DEMO_MARKER locations for examples applets. (#9261, #3689) [@pthom]
 - Backends:
   - SDLGPU3: removed unnecessary call to SDL_WaitForGPUIdle when releasing

imgui.cpp

diff --git a/imgui.cpp b/imgui.cpp
index 3638f6b..d716a5a 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -5985,10 +5985,14 @@
     }
     g.WantTextInputNextFrame = ime_data->WantTextInput ? 1 : 0;
 
-    // Hide implicit/fallback "Debug" window if it hasn't been used
+    // Hide and unfocus implicit/fallback "Debug" window if it hasn't been used
     g.WithinFrameScopeWithImplicitWindow = false;
-    if (g.CurrentWindow && !g.CurrentWindow->WriteAccessed)
+    if (g.CurrentWindow && g.CurrentWindow->IsFallbackWindow && g.CurrentWindow->WriteAccessed == false)
+    {
         g.CurrentWindow->Active = false;
+        if (g.NavWindow && g.NavWindow->RootWindow == g.CurrentWindow)
+            FocusWindow(NULL);
+    }
     End();
 
     // Update navigation: Ctrl+Tab, wrap-around requests