private void HandlePintaCoreActionsImageCanvasSizeActivated(object sender, EventArgs e)
{
ResizeCanvasDialog dialog = new ResizeCanvasDialog ();
dialog.ParentWindow = main_window.GdkWindow;
dialog.WindowPosition = Gtk.WindowPosition.CenterOnParent;
int response = dialog.Run ();
if (response == (int)Gtk.ResponseType.Ok)
dialog.SaveChanges ();
dialog.Destroy ();
}