Bug#866820: firefox-esr: FF doesn't show downloadable Droid Sans Mono WOFF font

[Evgeny Zubok]

Package: firefox-esr
Version: 45.9.0esr-1, 52.2.0esr-1~deb9u1
Severity: normal

I'm not sure whether this bug is Debian-specific or not.

Preface.
========

What we have here.

1. Debian stable (stretch).

2. Firefox 45.9.0esr-1 or Firefox 52.2.0esr-1~deb9u1 from Debian
repository.

3. A clear profile for both browsers without add-ons and any custom
preferences.

4. Fontconfig from Debian repository without custom configuration files
in ~/.config/fontconfig/ and ~/.fonts.conf and only with Debian supplied
configurations in /etc/fonts/.

5. Droid Sans Mono font isn't installed on my machine.

I. A Problem
============

The page that demonstarates an issue:

https://www.linux.org.ru/add_comment.jsp?topic=13504587&replyto=13506095

Field of text with 1111111111/WWWWWWWWWW (ten symbols) should be printed
with downloaded Droid Sans Mono font. The glyphs in both strings should
be placed one upon another. This element (<code>) uses font-family:
"Droid Sans Mono",monospace,sans-serif. These strings look correct in
Chromium browser from Debian repository.

A text in the edit box (<textarea>) also should be monospaced. The
element has style font-family: "Droid Sans Mono",sans-serif.

CSS has the following font-face declaration at very beginning:

@font-face {
  font-family:'Droid Sans Mono';
  src:url("/font/droidsansmono/DroidSansMono-webfont.eot");
  src:url("/font/droidsansmono/DroidSansMono-webfont.eot?#iefix") format("embedded-opentype"),
      url("/font/droidsansmono/DroidSansMono-webfont.woff") format("woff"),
      url("/font/droidsansmono/DroidSansMono-webfont.ttf") format("truetype"),
      url("/font/droidsansmono/DroidSansMono-webfont.svg#droid_sans_monoregular") format("svg");
  font-weight:normal;
  font-style:normal
}

According to the WebDeveloper's Network tab, the
DroidSansMono-webfont.woff is downloaded succesfully. Note that the
configuration options for dowloadable fonts have its default values:

browser.display.use_document_fonts = 1
gfx.downloadable_fonts.disable_cache = false 
gfx.downloadable_fonts.enabled = true
gfx.downloadable_fonts.fallback_delay = 3000
gfx.downloadable_fonts.woff2.enabled = true
gfx.font_loader.delay = 8000
gfx.font_loader.families_per_slice = 3
gfx.font_loader.interval = 50


II. What I tried to resolve an issue
====================================

1. I wrote a subtitution rule for fontconfig.

~/.config/fontconfig/fonts.conf:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "../fonts.dtd">

<fontconfig>
  <alias binding="same">
    <family>Droid Sans Mono</family>
    <accept>
      <family>DejaVu Sans Mono</family>
    </accept>
  </alias>

  <alias binding="same">
    <family>@font-face:Droid Sans Mono</family>
    <accept>
      <family>DejaVu Sans Mono</family>
    </accept>
  </alias>
</fontconfig>

Verification:

$ fc-match "Droid Sans Mono" 
DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"

$ fc-match '@font\-face\:Droid Sans Mono'
DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"


2. I tried to on/off the gfx.font_rendering.fontconfig.fontlist.enabled
property followed by restart of FF. Also without any success.


-- System Information:
Debian Release: 9.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 4.9.0-3-686-pae (SMP w/2 CPU cores)
Locale: LANG=ru_RU.UTF-8, LC_CTYPE=ru_RU.UTF-8 (charmap=UTF-8), LANGUAGE=ru_RU.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Init: sysvinit (via /sbin/init)

Versions of packages firefox-esr depends on:
ii  debianutils               4.8.1.1
ii  fontconfig                2.11.0-6.7+b1
ii  libasound2                1.1.3-5
ii  libatk1.0-0               2.22.0-1
ii  libc6                     2.24-11+deb9u1
ii  libcairo2                 1.14.8-1
ii  libdbus-1-3               1.10.18-1
ii  libdbus-glib-1-2          0.108-2
ii  libevent-2.0-5            2.0.21-stable-3
ii  libffi6                   3.2.1-6
ii  libfontconfig1            2.11.0-6.7+b1
ii  libfreetype6              2.6.3-3.2
ii  libgcc1                   1:6.3.0-18
ii  libgdk-pixbuf2.0-0        2.36.5-2
ii  libglib2.0-0              2.50.3-2
ii  libgtk2.0-0               2.24.31-2
ii  libhunspell-1.4-0         1.4.1-2+b2
ii  libnspr4                  2:4.12-6
ii  libnss3                   2:3.26.2-1.1
ii  libpango-1.0-0            1.40.5-1
ii  libsqlite3-0              3.16.2-5
ii  libstartup-notification0  0.12-4+b2
ii  libstdc++6                6.3.0-18
ii  libvpx4                   1.6.1-3
ii  libx11-6                  2:1.6.4-3
ii  libxcomposite1            1:0.4.4-2
ii  libxdamage1               1:1.1.4-2+b3
ii  libxext6                  2:1.3.3-1+b2
ii  libxfixes3                1:5.0.3-1
ii  libxrender1               1:0.9.10-1
ii  libxt6                    1:1.1.5-1
ii  procps                    2:3.3.12-3
ii  zlib1g                    1:1.2.8.dfsg-5

Versions of packages firefox-esr recommends:
ii  gstreamer1.0-libav         1:1.4.5-dmo1
ii  gstreamer1.0-plugins-good  1.10.4-1

Versions of packages firefox-esr suggests:
ii  fonts-lmodern          2.004.5-3
ii  fonts-stix [otf-stix]  1.1.1-4
pn  libcanberra0           <none>
pn  libgnomeui-0           <none>
ii  libgssapi-krb5-2       1.15-1
pn  mozplugger             <none>

-- no debconf information