bug#63187: 30.0.50; Tail of longer lines painted after end of nearby lines on macOS

[Kai Ma]

> On Jun 25, 2023, at 20:46, Alan Third <alan@idiocy.org> wrote:
> 
>>> 
>>> modified src/nsterm.m @@ -10622,7 +10622,7 @@ - (void) display
>>> {
>>>   NSTRACE_WHEN (NSTRACE_GROUP_FOCUS, "[EmacsLayer display]");
>>> 
>>> -  if (context)
>>> +  if (context && context != [NSGraphicsContext currentContext])
>>>     {
>>>       [self releaseContext];
>>> 
>>> 
>>> ...
>>> 
>>> Actually...
>>> 
>>> That change should probably be made anyway. If the NS run loop kicks
>>> in between an ns_focus call and an ns_unfocus call, it could call
>>> display and our display function will happily destroy the existing
>>> context without creating a new one, so any *subsequent* drawing
>>> operations, up until ns_unfocus, will be lost.
>> 
>> OK, I'm adding this to my current build.
>> 
>> Is this in line with the type of issue I'm seeing where scrolling
>> works but the ghosting either replicates (or scrolls with it?) In
>> other words, what would you expect to see in this scenario? Would it
>> just stop painting entirely?
> 
> 
> Kai, it might be worth trying just that change above, while keeping
> the call to performSelectorInMainThread and see if it fixes anything
> for you.

Unfortunately, the problem persists (as in the YouTube video) if 
performSelectorInMainThread is present.