Currently when creating hidden window and showing it later the content does not get repainted automatically (unless something else triggers the repaint). It would be helpful if there was a way from embedder to tell the flutter HWND to repaint itself.

It could be either custom message (i.e. WM_FLUTTER_REQUEST_REDRAW = WM_USER) or parent could simply forward its WM_SHOWWINDOW to flutter HWND and flutter would trigger redraw on WM_SHOWWINDOW.