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

[Visuwesh <visuweshm@gmail.com>]

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[வியாழன் மார்ச் 31, 2022] Eli Zaretskii wrote:

>> From: Visuwesh <visuweshm@gmail.com>
>> Cc: 54646@debbugs.gnu.org
>> Date: Thu, 31 Mar 2022 12:33:47 +0530
>> 
>> >   . 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
>> >
>> 
>> The *Help* buffer also has incorrectly shaped text.
>
> That's not what I meant.  I meant to save the information from *Help*
> when the text is displayed incorrectly, and then compare it with what
> "C-u C-x =" produces when the same text is displayed correctly
> (presumably, if you restart Emacs?).
>

I have attached three text files that have the content of the *Help*
buffer in the three cases:

    · correct: from emacs -Q which does not exhibit the problem.

    · incorrect: from an non-daemon Emacs session that exhibits the
      problem.

    · correct_config: from a fresh Emacs session with my init.el loaded
      that does not exhibit the problem.

>> >> [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.
>> >
>> 
>> Yes, I will do and see if there are any changes.
>
> Thanks.

Looks like this issue has nothing to do with me using the daemon.  If I
go about using Emacs like I usually do, it reproduces in a non-daemon
session as well.  Here's all the things I did in this session (AFAICR):

    · Started a process in the background using the doas TRAMP method.

    · Scrolled around in my init.el file which has Tamil text in the
      hopes of reproducing the issue.  I also increased and decreased
      the buffer text size a few times.

    · Opened gnus and sent the previous reply.  I'm currently writing
      the mail from an Emacs session that exhibits the problem.

Also, the mode line text is rendered similar to the text in-buffer:


[-- Attachment #2: screenshot_202203311415.png --]
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So far M-: (clear-composition-cache) has not helped.


[-- Attachment #4: emacs -Q C-u C-x = --]
[-- Type: text/plain, Size: 1231 bytes --]

             position: 5673 of 5691 (100%), column: 49
            character: க (displayed as க) (codepoint 2965, #o5625, #xb95)
              charset: unicode (Unicode (ISO10646))
code point in charset: 0x0B95
               script: tamil
               syntax: w 	which means: word
             category: .:Base, L:Strong L2R
             to input: type "C-x 8 RET b95" or "C-x 8 RET TAMIL LETTER KA"
          buffer code: #xE0 #xAE #x95
            file code: #xE0 #xAE #x95 (encoded by coding system utf-8-unix)
              display: composed to form "க்" (see below)

Composed with the following character(s) "்" using this font:
  ftcrhb:-Goss-Kurinto Seri-regular-normal-normal-*-13-*-*-*-*-0-iso10646-1
by these glyphs:
  [0 1 2965 23479 11 0 12 7 0 nil]
  [0 1 3021 23505 0 -1 1 10 -8 [-5 0 0]]
with these character(s):
  ் (#xbcd) TAMIL SIGN VIRAMA

Character code properties: customize what to show
  name: TAMIL LETTER KA
  general-category: Lo (Letter, Other)
  decomposition: (2965) ('க')

There are text properties here:
  dired-filename       t
  fontified            t
  help-echo            "mouse-2: visit this file in other window"
  mouse-face           highlight

[-- Attachment #5: emacs personal config C-u C-x = --]
[-- Type: text/plain, Size: 1231 bytes --]

             position: 5505 of 5523 (100%), column: 46
            character: க (displayed as க) (codepoint 2965, #o5625, #xb95)
              charset: unicode (Unicode (ISO10646))
code point in charset: 0x0B95
               script: tamil
               syntax: w 	which means: word
             category: .:Base, L:Strong L2R
             to input: type "C-x 8 RET b95" or "C-x 8 RET TAMIL LETTER KA"
          buffer code: #xE0 #xAE #x95
            file code: #xE0 #xAE #x95 (encoded by coding system utf-8-unix)
              display: composed to form "க்" (see below)

Composed with the following character(s) "்" using this font:
  ftcrhb:-Goss-Kurinto Seri-regular-normal-normal-*-14-*-*-*-*-0-iso10646-1
by these glyphs:
  [0 1 2965 23479 12 0 12 8 0 nil]
  [0 1 3021 23505 0 -1 1 11 -9 [-6 0 0]]
with these character(s):
  ் (#xbcd) TAMIL SIGN VIRAMA

Character code properties: customize what to show
  name: TAMIL LETTER KA
  general-category: Lo (Letter, Other)
  decomposition: (2965) ('க')

There are text properties here:
  dired-filename       t
  fontified            t
  help-echo            "mouse-2: visit this file in other window"
  mouse-face           highlight

[-- Attachment #6: emacs problematic C-u C-x = --]
[-- Type: text/plain, Size: 1247 bytes --]

             position: 5505 of 5523 (100%), column: 46
            character: க (displayed as க) (codepoint 2965, #o5625, #xb95)
              charset: unicode (Unicode (ISO10646))
code point in charset: 0x0B95
               script: tamil
               syntax: w 	which means: word
             category: .:Base, L:Strong L2R
             to input: type "C-x 8 RET b95" or "C-x 8 RET TAMIL LETTER KA"
          buffer code: #xE0 #xAE #x95
            file code: #xE0 #xAE #x95 (encoded by coding system utf-8-unix)
              display: composed to form "க்" (see below)

Composed with the following character(s) "்" using this font:
  ftcrhb:-Goss-Kurinto Seri-regular-normal-normal-*-14-*-*-*-*-0-iso10646-1
by these glyphs:
  [0 1 2965 23479 12 0 12 8 0 [0 0 20]]
  [0 1 3021 23505 0 -1 1 11 -9 [-14 0 0]]
with these character(s):
  ் (#xbcd) TAMIL SIGN VIRAMA

Character code properties: customize what to show
  name: TAMIL LETTER KA
  general-category: Lo (Letter, Other)
  decomposition: (2965) ('க')

There are text properties here:
  dired-filename       t
  fontified            t
  help-echo            "mouse-2: visit this file in other window"
  mouse-face           highlight

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