bug#30699: 26.0.91; buffer contents flicker on macOS frames when frames are resized

[Eli Zaretskii]

> Date: Tue, 6 Mar 2018 22:55:02 +0000
> From: Alan Third <alan@idiocy.org>
> Cc: 30699@debbugs.gnu.org, aaronjensen@gmail.com
> 
> In theory if you call NSDisableScreenUpdates before the blanking of
> the frame, then call NSEnableScreenUpdates after drawing the contents
> of the frame, both should appear as one action (we don’t see the blank
> frame at all).

Where does the frame blanking happen in the NS build?

> I’ve tried adding calls to NSDisableScreenUpdates and
> NSEnableScreenUpdates in redisplay_internal, just to see if it works,
> but I couldn’t get it to work at all: I always saw the blanked frame.
> Either these functions don’t work as advertised or there’s something
> else going on. It’s quite probable I’ve misunderstood
> redisplay_internal.

If you tell me where did you try to add these calls and perhaps also
what was your mental model of what redisplay_internal does when you
did that, I might be able to help you add this in the right places
(assuming the idea is workable, and I trust your expertise on that).