On Windows, GtkLauncher.exe starts up with two Gdk-CRITICAL **: IA__gdk_window_create_similar_surface: assertion `GDK_IS_WINDOW (window)' failed warnings, and doesn't draw anything in its WebKitWebView. This is coming from createSurfaceForBackingStore() in WidgetBackingStoreCairo.cpp, which tries to call gtk_widget_get_window() before the widget is realized.
Created attachment 125378 [details] Create the backing store after WebKitWebView is realized The widget backing store was created in size_allocate() before the widget was realized. This wasn't a problem for GtkWidgetBackingStoreX11, but WidgetBackingStoreCairo's constructor needs the widget's GDK window, which is is created in realize(). Fixes the WebKitWebView not painting on platforms that use WidgetBackingStoreCairo, e.g. win32. Gdk-CRITICAL **: IA__gdk_window_create_similar_surface: assertion `GDK_IS_WINDOW (window)' failed
Comment on attachment 125378 [details] Create the backing store after WebKitWebView is realized Please check if my patch at https://bugs.webkit.org/show_bug.cgi?id=77743 fixes this issue. It should delay the backing store creation until mapping.
I can confirm that the patch in bug 77743 also fixes it, thanks! *** This bug has been marked as a duplicate of bug 77743 ***