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

[Tim Ruffing <dev@real-or-random.org>]

> > pp is calling Emacs to print to its stderr.  If that is redirected
> > somewhere else you won't see the output.
> 

Ah, this was the right hint. I'm using emacs in daemon mode, started
from systemd, so I can inspect stderr via journalctl.

------

Broken rendering for ligature "===" starting at pos 1290 (emacs happens
to be in daemon mode)

[...]
 39  480: COMP[19 (0..0)] pos=1290 w=20 a+d=20+6 face=39 MB
 40  500: COMP[19 (1..1)] pos=1291 w=20 a+d=20+6 face=39 MB
 41  520: COMP[19 (2..2)] pos=1292 w=20 a+d=20+6 face=39 MB
[...]

$ pp composition_gstring_from_id(19)
 
 [[#<font-object "-UKWN-Iosevka Term SS04-regular-normal-normal-*-20-*-*-*-d-0-iso10646-1"> 61 61 61] 19 [0 0 61 5852 10 1 11 11 -4 [0 0 20]] [1 1 61 5896 10 -1 11 11 -4 [0 0 20]] [2 2 61 5891 10 -1 9 11 -4 [0 0 20]]]

-------

Proper rendering (emacs happens to be not in daemon mode):

 39  390: COMP[13 (0..0)] pos=1290 w=10 a+d=20+6 face=39 MB
 40  400: COMP[13 (1..1)] pos=1291 w=10 a+d=20+6 face=39 MB
 41  410: COMP[13 (2..2)] pos=1292 w=10 a+d=20+6 face=39 MB

$ pp composition_gstring_from_id(13) 

 [[#<font-object "-UKWN-Iosevka Term SS04-regular-normal-normal-*-20-*-*-*-d-0-iso10646-1"> 61 61 61] 13 [0 0 61 5852 10 1 11 11 -4 nil] [1 1 61 5896 10 -1 11 11 -4 nil] [2 2 61 5891 10 -1 9 11 -4 nil]] 


Both sessions are still running. I Hope this helps. Let me know if need
more remote hands.


Best,
Tim