bug#73752: 29.4; Ligatures are randomly rendered with extra spaces

[Yixuan Chen <xuan@xlk.me>]

On 10/30/24 21:39, Tim Ruffing wrote:
> I'm not sure if I have the time to verify this in the coming days, I'd
> appreciate if some of the other affected users could give it a try.

I'm sorry I wasn't following this thread closely for the last few days. 
I'm currently busy with a submission due in two weeks so I don't have 
continuous time to investigate the problem using GDB before Nov. 14.

> I can't recall that it ever flipped suddenly from good to
> bad *when the affected ligatures was in the visible array of the
> buffer*. But I'm not so sure if this has really never flipped from good
> to bad during a session, when the ligature was not visible.

I'm pretty certain it doesn't happen to a line spontaneously. I usually 
encounter this behavior (with a probability) when
1. after a font changes, like what the script I submitted did.
2. after switching to a different buffer, even if both buffers contains 
ligatures and uses the same font/fontset setting (though maybe one of 
the buffers contains certain characters with bold/italic/etc font 
attributes, I don't recall it exactly).
3. (maybe) after scrolling down/up the buffer into a position where a 
line contains ligatures appears.

Best,
Yixuan