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bug#51495: 29.0.50; [PATCH] Avoid fonts with incomplete coverage of MATH
From: |
Kévin Le Gouguec |
Subject: |
bug#51495: 29.0.50; [PATCH] Avoid fonts with incomplete coverage of MATHEMATICAL chars |
Date: |
Fri, 29 Oct 2021 23:40:39 +0200 |
Hello,
This is a followup to a discussion on help-gnu-emacs[1] which revealed
that script-representative-chars does not account for problematic fonts
like KpMath[2] which provide only partial coverage for the MATHEMATICAL
SCRIPT codepoints U+1D49C–U+1D4CF (𝒜–𝓏).
To be more specific, this font only covers MATHEMATICAL SCRIPT CAPITAL
codepoints and does not cover MATHEMATICAL SCRIPT SMALL codepoints.
Since setup-default-fontset only puts MATHEMATICAL SCRIPT CAPITAL A in
script-representative-chars, Emacs fails to ensure that the fonts
returned by Fontconfig also provide glyphs for SMALL codepoints.
As soon as I get a bug number, I'll followup with a patch (reviewed by
Eli[3]) that deals with the situation by adding both ends of each
"math-subgroup" to script-representative-chars, using lists rather than
vectors to make each codepoint mandatory.
>From the discussion, it seems that this problem is not very common (the
gap in KpMath seems very uncommon[2]), and has multiple workarounds
(uninstalling the font, tweaking fontconfig rules, tweaking fontsets),
so although the patch applies to both master and emacs-28, I guess there
is no pressing need to have this on the release branch, and master would
be more appropriate?
Thank you for your time.
[1] help-gnu-emacs <878s02u5m6.fsf@gmail.com>
https://lists.gnu.org/archive/html/help-gnu-emacs/2021-09/msg00150.html
[2] http://mirrors.ctan.org/fonts/kpfonts-otf/doc/unimath-kpfonts.pdf
§ 15.1.7, 15.1.8
[3] help-gnu-emacs <83k0jjcsal.fsf@gnu.org>
https://lists.gnu.org/archive/html/help-gnu-emacs/2021-09/msg00192.html
In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo
version 1.16.0)
of 2021-10-26 built on amdahl30
Repository revision: f56408a6f0152cd46d1ea8a0985fbfeeb839ea06
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: openSUSE Tumbleweed
- bug#51495: 29.0.50; [PATCH] Avoid fonts with incomplete coverage of MATHEMATICAL chars,
Kévin Le Gouguec <=