Viewports: Fixed active InputText() from preventing viewports to merge. (#4212)

docs/CHANGELOG.txt

@@ -208,6 +208,7 @@ Docking+Viewports Branch:
 
 - Viewports: Fixed a CTRL+TAB crash with viewports enabled when the window list needs to appears in
   its own viewport (regression from 1.86). (#4023, #787)
+- Viewports: Fixed active InputText() from preventing viewports to merge. (#4212)
 - (Breaking) Removed ImGuiPlatformIO::Platform_SetImeInputPos() in favor of newly standardized
   io.SetPlatformImeDataFn() function. Should not affect more than default backends.
 

imgui.cpp

@@ -12925,7 +12925,8 @@ static void ImGui::WindowSelectViewport(ImGuiWindow* window)
     {
         // Merge into host viewport?
         // We cannot test window->ViewportOwned as it set lower in the function.
-        bool try_to_merge_into_host_viewport = (window->Viewport && window == window->Viewport->Window && g.ActiveId == 0);
+        // Testing (g.ActiveId == 0 || g.ActiveIdAllowOverlap) to avoid merging during a short-term widget interaction. Main intent was to avoid during resize (see #4212)
+        bool try_to_merge_into_host_viewport = (window->Viewport && window == window->Viewport->Window && (g.ActiveId == 0 || g.ActiveIdAllowOverlap));
         if (try_to_merge_into_host_viewport)
             UpdateTryMergeWindowIntoHostViewports(window);
     }