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

[Yixuan Chen <xuan@xlk.me>]

On 10/27/24 15:14, Eli Zaretskii wrote:
>> Date: Sun, 27 Oct 2024 13:46:55 -0400
>> Cc: visuweshm@gmail.com, luangruo@yahoo.com, 73752@debbugs.gnu.org
>> From: Yixuan Chen <xuan@xlk.me>
>>
>>> Sorry, I still don't understand.  Your code does
>>>
>>>     (highlight-lines-matching-regexp (cdr face) (car face))
>>>
>>> This potentially shows each line in a different face, and thus can
>>> affect the metrics of the SPC character glyph which is what the
>>> indentation is made of.  So why is this a problem, let alone a bug?
>>
>> The problem is executing that line at 10PM today may render the font one
>> way, while executing that line at 6AM tomorrow (with exactly the same
>> "face" variable) may render the font a different way, even if all the
>> other variables remains the same.
> 
> But you modify the faces in a random fashion, so why is this a
> surprise that it is not deterministic?

Just in case my last explanation wasn't clear enough: by "with exactly 
the same face variable", I'm saying that when the randomizer picks the 
same font attribute (the same everything), there is a chance it will 
render that line differently.