After bug 1170782, we only use the typo metrics when the USE_TYPO_METRICS bit is explicitly set (http://www.microsoft.com/typography/otspec/os2.htm#fss). This is not the case in some old versions of math fonts, causing excessive line spacing. Users and packagers must upgrade to the latest version. Latin Modern Math: Debian: Fixed in testing (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=799731) Ubuntu: Fixed in Xenial Xerus (https://bugs.launchpad.net/ubuntu/+source/lmodern/+bug/1502701) Fedora: Fixed in version 24 openSuse: https://bugzilla.opensuse.org/show_bug.cgi?id=948624
The square root sign is much too high in Firefox 43+ as you can see at http://jsfiddle.net/mpopp75/6d7dju8q/ Also the denominator of the fraction is too high so maybe the problem lays in displacing fractions.
Are you able to tell which math font you use? I suspect this is https://bugzilla.mozilla.org/show_bug.cgi?id=1170782 ; some old versions do not have the USE_TYPO_METRICS flag properly set.
I haven't set a font so it must be what Firefox (on Linux64) uses by default.
Default fonts are at https://dxr.mozilla.org/mozilla-central/source/modules/libpref/init/all.js#1929 What do you get with this testcase? (You can also use the inspector on the <math> tag to check the font-family)
The font I used is Latin Modern Math. Other fonts (at least some) display nicely, like for example DejaVu Sans.
The latest version (1.959) should not have the bug: http://www.gust.org.pl/projects/e-foundry/lm-math/download/index_html Some Linux distros (e.g. Debian) still have an old version: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=799731
(In reply to Frédéric Wang (:fredw) from comment #5) > Some Linux distros (e.g. Debian) still have an old version: > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=799731 The bug just got closed in Debian sid today, so hopefully it will be the cases in other Debian-based distributions such as Ubuntu and Mint. Apparently, the latest build for Fedora 24 also have version 1.959 (http://koji.fedoraproject.org/koji/rpminfo?rpmID=6858749). I open an enhancement request in openSuse.
Summary: Math formula display issue in Firefox 43+ → Incorrect math rendering with old OpenType fonts after bug 1170782
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