bug#54646: 29.0.50; set-fontset-font and font clipping issues

[Eli Zaretskii]

> From: Visuwesh <visuweshm@gmail.com>
> Date: Thu, 31 Mar 2022 09:07:30 +0530
> 
> I cannot seem to reproduce this from emacs -Q, nor do I see this issue
> when I start Emacs up (I use the daemon if that makes a difference [2]).
> [...]
> It naturally shows up after using Emacs for a while, sometimes reopening
> the frame fixes the clipping problems, sometimes I have to reevaluate
> the set-fontset-font form to fix it.  And this issue isn't font-specific
> as well: I had the same problem with "Noto Serif."  I would highly any
> hints towards nailing the problem down; I'm really out of ideas.

When it happens, does it help to do the below?

  M-: (clear-composition-cache) RET

Also, does this happen with buffer text or on the mode line?  If it
happens with buffer text, try these two experiments when it happens:

  . move the cursor with C-f across the problematically-displayed
    text, and see whether the display becomes correct and/or whether
    you see some display artifacts, like "ghosts" of the cursor block
    left behind;
  . go to the problematically-displayed text and type "C-u C-x =",
    then compare what you see with the results of "C-u C-x =" for
    the same text when it is correctly displayed

> [2] Modifying the fontset in `server-after-make-frame-hook' does not
>     make a difference.  I don't see the issue when I do not use the
>     daemon but I believe I haven't run the non-daemon session long
>     enough.

Then please try running such a non-daemon session longer.  It is
important to know whether this is at all related to daemon.

If it only happens with daemon sessions, I'll ask you to describe in
more detail how you use those sessions.  In particular, do you use
both GUI and TTY emacsclient frames in the same session, do you edit
Tamil text in TTY frames, do you connect to the same server from
different remote hosts, or display frames on clients that use
different font for Tamil?  Any other detail in your routine usage
might give a clue.

Thanks.