On Quartz the drawing region must be padded out to a multiple of 4 px
on regular displays and 8 px on Retina ones. Failing to do so used to
cause smearing on multi-monitor mixed-DPI systems but that seems to
have been fixed. There remains a visible flicker in animations.
Padding the GdkWindow width as well as the content frame and cairo
surface causes the frame clock to get frozen if multiple calls to
gtk_window_resize use the same size because
gdk_window_move_resize_internal sees a difference between the window
size and the requested size (the latter isn't padded out) and freezes updates. GdkQuartzNSWindow
windowDidResize is supposed to thaw them, but because the padded-out
width set for the frame doesn't change the window isn't resized and
the frame clock is never thawed.
Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/7188
41bd9e4290