FAQ: add entry about color emoji Xft bug

This has been asked many times on IRC and the mailinglist. Make it easier to
find information about this particular Xft issue by adding it to the FAQ.
dev
Hiltjo Posthuma 2019-05-17 13:00:10 +02:00
parent f1546cf9c1
commit caa1d8fbea
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FAQ
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@ -165,3 +165,30 @@ Apply [1].
[1] http://st.suckless.org/patches/delkey
## BadLength X error in Xft when trying to render emoji
Xft makes st crash when rendering color emojis with the following error:
"X Error of failed request: BadLength (poly request too large or internal Xlib length error)"
Major opcode of failed request: 139 (RENDER)
Minor opcode of failed request: 20 (RenderAddGlyphs)
Serial number of failed request: 1595
Current serial number in output stream: 1818"
This is a known bug in Xft (not st) which happens on some platforms and
combination of particular fonts and fontconfig settings.
See also:
https://gitlab.freedesktop.org/xorg/lib/libxft/issues/6
https://bugs.freedesktop.org/show_bug.cgi?id=107534
https://bugzilla.redhat.com/show_bug.cgi?id=1498269
The solution is to remove color emoji fonts or disable this in the fontconfig
XML configuration. As an ugly workaround (which may work only on newer
fontconfig versions (FC_COLOR)), the following code can be used to mask color
fonts:
FcPatternAddBool(fcpattern, FC_COLOR, FcFalse);
Please don't bother reporting this bug to st, but notify the upstream Xft
developers about fixing this bug.