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

[Eli Zaretskii <eliz@gnu.org>]

> From: Visuwesh <visuweshm@gmail.com>
> Cc: 53729@debbugs.gnu.org
> Date: Thu, 03 Feb 2022 07:15:01 +0530
> 
> > on the mode line, the buffer is shown in bold, so perhaps there's a
> > problem with the bold variant of the Noto Serif Tamil font?  If you
> > type the same text in a buffer, but give it the 'bold' face, do you
> > see the same problem with buffer text as on the mode line?
> 
> No, when I give it the bold face and insert it in a buffer, the text is
> shaped properly.  Then, I tried setting mode-line-format to
> "அக்கிச்சிறகுகள்" and '(:propertize "அக்கிச்சிறகுகள்" face bold) and in both
> cases, the text is shaped properly.  I'm not sure where the problem is
> anymore.  I attached screenshots of the same as well.

Strange.  I guess the only way of investigating this is to step with
GDB into the code which renders the mode line, and see which font
specifically is being used there?

Btw, do I understand correctly that the problem you see is the
incorrect location of the dot-like diacriticals above the letters?  Or
is the problem something else?  (I don't read the Tamil script.)