bug#32932: 27.0.50; render bugs on macOS Mojave

[Robert Pluim]

>>>>> On Sat, 25 Jan 2020 15:37:41 +0200, Eli Zaretskii <eliz@gnu.org> said:

    >> Date: Sat, 25 Jan 2020 12:44:01 +0000
    >> From: Alan Third <alan@idiocy.org>
    >> Cc: 32932@debbugs.gnu.org
    >> 
    >> So we have a trade off here of slower performance, which may or may
    >> not be an issue, against drawing anomalies. I’m beginning to feel it’s
    >> probably better to just get rid of the drawing issues and live with
    >> the performance hit. I know that for me the performance difference is
    >> not going to be noticeable at all.

    Eli> I think your tendency is the correct way of handling this issue: first
    Eli> be correct, then fast.

The redraw problems have been starting to annoy me recently. Iʼll take
correctness over speed as well.

(Iʼve not found any inspired solution to the speed issue. I *have*
found various ways to kill Emacs, though :-) )

Robert