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bug#54646: 29.0.50; set-fontset-font and font clipping issues
From: |
Visuwesh |
Subject: |
bug#54646: 29.0.50; set-fontset-font and font clipping issues |
Date: |
Sat, 11 Jun 2022 19:24:16 +0530 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
[வெள்ளி ஏப்ரல் 22, 2022] Eli Zaretskii wrote:
Hello Eli, Robert
>> From: Visuwesh <visuweshm@gmail.com>
>> Cc: rpluim@gmail.com, 54646@debbugs.gnu.org
>> Date: Fri, 22 Apr 2022 16:16:07 +0530
>>
>> >> and the GOOD case for bb9 bbf is
>> >>
>> >> lbearing 1 rbearing 28 width 28 ascent 9 descent 5
>> >> 1 bb9 bbf xadvance 1809 yadvance 0 xoffset 0 yoffset 0
>> >> xpos 0 yoff 0 wadjust 28
>> >>
>> >> and the BAD case is
>> >>
>> >> lbearing 1 rbearing 28 width 28 ascent 9 descent 5
>> >> 1 bb9 bbf xadvance 3193 yadvance 0 xoffset 0 yoffset 0
>> >> xpos 0 yoff 0 wadjust 50
>> >
>> > This looks like HarfBuzz is feeding us incorrect data for some reason,
>> > but I cannot imagine what that reason could be, sorry.
>>
>> Could it be some kind of cache? Because when Emacs rendered the entire
>> webpage, I was unable to reproduce the issue.
>
> When Emacs have rendered the entire page, we no longer call HarfBuzz,
> because the composition data is indeed cached by Emacs.
>
> The print-outs you produced are from calling HarfBuzz, so our caching
> cannot affect that, AFAIU.
I think this might be a cairo+pango problem. My suspicion is due to
this bug report https://github.com/harfbuzz/harfbuzz/issues/1892 --
although I don't see the problem with English text as shown in the
screenshots.
I tried to turn off font metrics in cairo by applying the following
patch,
cairo-hint-metrics.diff
Description: Text Data
but that did not solve the issue.
However, I have been using the xft+harfbuzz combo for a ~week now and I
can say with confidence that I don't experience this strange issue. I
would highly appreciate it if the decision to remove the xft backend
could be delayed until a solution comes up [1]. Although the font
rendering is worse, the text stays readable at all font sizes.
[1] ./configure --with-cairo says,
configure: WARNING: This configuration uses libXft, which has a number of
font rendering issues, and is being considered for removal in the
next release of Emacs. Please consider using Cairo graphics +
HarfBuzz text shaping instead (they are auto-detected if the
relevant development headers are installed).
- bug#54646: 29.0.50; set-fontset-font and font clipping issues,
Visuwesh <=