bug#53729: 29.0.50; Tamil text not shaped in modeline

[Visuwesh]

[புதன், பிப்ரவரி 16 2022] Visuwesh wrote:

> [செவ்வாய், பிப்ரவரி 15 2022] Eli Zaretskii wrote:
>
>>> From: Visuwesh <visuweshm@gmail.com>
>>> Cc: 53729@debbugs.gnu.org
>>> Date: Tue, 15 Feb 2022 07:17:12 +0530
>>> 
>>> > Looks like the rendering of the file name is affected by the non-Tamil
>>> > text that follows it?
>>> >
>>> 
>>> And it looks like it is not just any non-Tamil text that affects it but
>>> only image like extensions?  For example, if the extension is .txt, .sh,
>>> .c, .el, .svg, .djvu, then the buffer name is shaped properly.  But if I
>>> use the extensions .tiff, .png, .jpeg, .pdf, .jpg, then the buffer name
>>> is not shaped.  The file I renamed was a bash script.
>>
>> The display code which renders this doesn't know anything about the
>> meaning of the extensions, it only cares about the characters it needs
>> to display.  So if image-file extensions tend to cause this, it's
>> because of the characters that are part of the extensions, or maybe
>> because having an image file visited by the buffer affects the mode
>> line in some other way that causes this issue.
>>
>>> > But I cannot reproduce this on my system, so it is hard to tell what
>>> > is going on here.
>>> 
>>> That is really unfortunate.
>>
>> Maybe someone else can reproduce this?
>
> I will try reproducing it in latest master by the end of this week, and
> maybe Emacs 28 pretest on Windows (compiling master on Windows is
> unfortunately not feasible for me), and report back.  I will also see if
> I can ask someone else to reproduce this in Linux.

I have not tried reproducing it in other systems but I did try latest
master, and the text is still not shaped.  However, I just noticed that
I missed this warning message that was written to stdout (which is
mostly why I did not notice it) when I close Emacs:

    Warning: Missing charsets in String to FontSet conversion

I tried quickly grepping for "Missing charsets" and "Warning: " in Emacs
git repo but I don't see this particular warning in the results.

[ I realise that a lot of time could have been saved if I was more
  attentive, sorry about that.  ]