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

[Eli Zaretskii <eliz@gnu.org>]

> From: Visuwesh <visuweshm@gmail.com>
> Cc: rpluim@gmail.com,  54646@debbugs.gnu.org
> Date: Fri, 01 Apr 2022 22:10:54 +0530
> 
> > WHat is different between the two cases in this data?  Does the call
> > to font->driver->text_extents produce different data in 'metrics',
> > perhaps?  Do the values in pos[i] structure differ?  Something else?
> 
> TBH, I'm not even sure if I am comparing the data for the same set of
> characters but AFAICT the values don't seem to differ.  Is there a way
> to print the concerned character so I can make better comparisons?

The character codepoints are in the chars[] array, AFAIR.

If the input to HarfBuzz is identical, but the output isn't, it points
to a HarfBuzz bug.

> I don't think it is of any help but I attached two text files: bad-case
> and good-case.  bad-case has all the data for the clipped text, and
> good-case for the non-clipped text (for the same font size, at least I
> hope so...).

It's hard to understand what you printed out, or where is the
difference.  It is best to print only the data for the characters for
which you see display problems, because all the rest is just clutter.
And in any case, please print the character with the data, otherwise
it is impossible to know what to compare.