fc-match -v reports rgba:1 instead of rgba:2 with BGR display

[Mikko Rantalainen]

I have a BGR display so I really would like to have BGR subpixel rendering. I'm having major trouble getting fc-match to emit correct info.

$ fc-match -v | grep -E 'rgba|lcdfilter|antialias|hintstyle|dpi'
 antialias: True(w)
 hintstyle: 2(i)(w)
 dpi: 75(f)(s)
 rgba: 1(i)(w)
 lcdfilter: 1(i)(w)

$ ls -l /etc/fonts/conf.d/10*
lrwxrwxrwx 1 root root 31 2016-08-16 22:18 /etc/fonts/conf.d/10-antialias.conf -> ../conf.avail/10-antialias.conf
lrwxrwxrwx 1 root root 30 2019-06-14 12:27 /etc/fonts/conf.d/10-autohint.conf -> ../conf.avail/10-autohint.conf
lrwxrwxrwx 1 root root 29 2016-08-16 22:18 /etc/fonts/conf.d/10-hinting.conf -> ../conf.avail/10-hinting.conf
lrwxrwxrwx 1 root root 36 2016-08-16 22:18 /etc/fonts/conf.d/10-hinting-slight.conf -> ../conf.avail/10-hinting-slight.conf
lrwxrwxrwx 1 root root 40 2016-08-16 22:18 /etc/fonts/conf.d/10-scale-bitmap-fonts.conf -> ../conf.avail/10-scale-bitmap-fonts.conf
lrwxrwxrwx 1 root root 35 2019-06-13 12:16 /etc/fonts/conf.d/10-sub-pixel-bgr.conf -> ../conf.avail/10-sub-pixel-bgr.conf

$ strace -e trace=file fc-match -v 2>&1 | grep "open.*bgr"
open("/etc/fonts/conf.d/10-sub-pixel-bgr.conf", O_RDONLY|O_CLOEXEC) = 5

$ gsettings list-recursively | grep bgr
com.canonical.unity-greeter xft-rgba 'bgr'
org.cinnamon.settings-daemon.plugins.xsettings rgba-order 'bgr'
org.gnome.settings-daemon.plugins.xsettings rgba-order 'bgr'
org.cinnamon.settings-daemon.plugins.xsettings rgba-order 'bgr'
org.gnome.settings-daemon.plugins.xsettings rgba-order 'bgr'
org.mate.font-rendering rgba-order 'bgr'

Is there some documented reason that fc-match fails to report correct subpixel order given this config? Is there some another configuration file that I must modify or create to get fc-match to correctly declare BGR subpixel structure?

Also, the dpi above is incorrect too, the correct value would be near 96.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: fontconfig 2.11.94-0ubuntu1.1
ProcVersionSignature: Ubuntu 4.15.0-51.55~16.04.1-lowlatency 4.15.18
Uname: Linux 4.15.0-51-lowlatency x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: MATE
Date: Tue Jun 25 16:50:15 2019
InstallationDate: Installed on 2015-02-23 (1583 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
SourcePackage: fontconfig
UpgradeStatus: Upgraded to xenial on 2016-06-10 (1110 days ago)

[Sebastien Bacher (seb128)]

Thank you for your bug report, it might be worth reporting upstream on https://gitlab.freedesktop.org/fontconfig/fontconfig/issues