bug#32932: 27.0.50; render bugs on macOS Mojave

[Alan Third]

On Mon, Oct 29, 2018 at 10:56:34PM -0700, Aaron Jensen wrote:
> I’ve got a consistent repro on my config with this patch. If I start
> emacs then open a dired buffer in a dir that has images in it, then
> hit return on one of the images, the current line goes blank while the
> image loads. If I kill the buffer and reopen the same one it does not
> repro.
> 
> I cannot reproduce this in emacs -Q as it’s much faster than whatever
> my config is doing whenever I open an image.

I was hoping I’d manage to get something going with this but it’s
completely fine here. Does the line blank, then redraw, then the image
loads in its new buffer?

Something is blanking the line. There are only so many places where
that happens so in theory it should be relatively straight‐forward to
find the place in question. Perhaps start by commenting out the
NSRectFill commands in ns_clear_frame and ns_clear_frame_area.
-- 
Alan Third