Use deprecated gdk_device_grab instead of gdk_seat_grab because the
check needs to be done before showing the window and gdk_seat_grab
requires the window to be visible.

The remote event happens after the loss of focus from the shortcut has
already hidden the menu. This means that unless a delay is used, you
cannot toggle the menu and it will be shown every time.

Closes #8

Closes #12

This reverts commit 363c0102.