bug#42406: Mouse-wheel scrolling can be flickering

[Konrad Podczeck]

With this patch, toolbar, frame-title, menu and scroll-bars display correctly, 
but the text-area of a frame is just white, i.e., no text appears.

Konrad
> Am 16.12.2020 um 22:31 schrieb Alan Third <alan@idiocy.org>:
> 
> On Tue, Dec 15, 2020 at 03:06:03PM +0100, Konrad Podczeck wrote:
>> Just to clarify, despite of the title of this bug, it is not a
>> flickering, but the mouse-wheel scrolling preformance decreases with
>> the number of open frames, in the sense that it becomes more and
>> more sticky.
> 
> I don't think the attached patch will fix this, but it may improve
> things a little. Can you please try it?
> 
> -- 
> Alan Third
> <0001-Improve-drawing-performance-on-macOS.patch>