Viewport: Fixed a situation when the implicit Debug window can hold on a zombie viewport which platform window is not properly destroyed. (#1542)

imgui.cpp

@@ -3955,29 +3955,29 @@ void ImGui::UpdatePlatformWindows()
     {
         ImGuiViewportP* viewport = g.Viewports[i];
         viewport->LastPos = viewport->Pos;
-        if (viewport->LastFrameActive < g.FrameCount)
+
-        {
+        // Destroy platform window if the viewport hasn't been submitted or if it is hosting a hidden window (the implicit Debug window will be registered its viewport then be disabled)
-            if (viewport->LastFrameActive < g.FrameCount - 1)
+        bool destroy_platform_window = false;
+        destroy_platform_window |= (viewport->LastFrameActive < g.FrameCount - 1);
+        destroy_platform_window |= (viewport->Window && !IsWindowActiveAndVisible(viewport->Window));
+        if (destroy_platform_window)
         {
-                if (g.PlatformIO.Renderer_DestroyWindow)
+            if (viewport->CreatedPlatformWindow && g.PlatformIO.Renderer_DestroyWindow)
                 g.PlatformIO.Renderer_DestroyWindow(viewport);
-                if (g.PlatformIO.Platform_DestroyWindow)
+            if (viewport->CreatedPlatformWindow && g.PlatformIO.Platform_DestroyWindow)
                 g.PlatformIO.Platform_DestroyWindow(viewport);
             viewport->CreatedPlatformWindow = false;
             IM_ASSERT(viewport->RendererUserData == NULL);
             IM_ASSERT(viewport->PlatformUserData == NULL && viewport->PlatformHandle == NULL);
-            }
             continue;
         }
+        if (viewport->LastFrameActive < g.FrameCount)
+            continue;
 
         // New windows that appears directly in a new viewport won't always have a size on their frame
         if (viewport->Size.x <= 0 || viewport->Size.y <= 0)
             continue;
 
-        // Ignore viewport that are hosting a hidden window (also check the Active flag, as the implicit Debug window will be registering its viewport then immediately disabled)
-        if (viewport->Window && !IsWindowActiveAndVisible(viewport->Window))
-            continue;
-
         // Update viewport flags
         if (viewport->Window != NULL)
         {