Added function to get viewport size of the game window when in editor. This allows for certain functions to behave correctly.

Source/Editor/Editor.cs

@@ -1408,6 +1408,23 @@ namespace FlaxEditor
             }
         }
 
+        internal void Internal_GetGameWindowViewportSize(out Float2 result)
+        {
+            result = new Float2(1280, 720);
+            var gameWin = Windows.GameWin;
+            if (gameWin?.Root?.RootWindow is WindowRootControl root)
+            {
+                // Handle case when Game window is not selected in tab view
+                var dockedTo = gameWin.ParentDockPanel;
+                if (dockedTo != null && dockedTo.SelectedTab != gameWin && dockedTo.SelectedTab != null)
+                    result = dockedTo.SelectedTab.Size * root.DpiScale;
+                else
+                    result = gameWin.Viewport.Size * root.DpiScale;
+
+                result = Float2.Round(result);
+            }
+        }
+
         internal bool Internal_OnAppExit()
         {
             // In editor play mode (when main window is not closed) just skip engine exit and leave the play mode