Bug#974139: libpango1.0-dev: silent api breakage, subclassing no longer possible

[Marc Lehmann]

Package: libpango1.0-dev
Version: 1.46.2-2
Severity: normal

Dear Maintainer,

I don't know in which version it happened, but the header files no
longer define the PangoFcFontClass type (and PangoFcFontMapClass),
which makes accessing the documented public members inside
and subclassing impossible. According to the docs (e.g.
https://developer.gnome.org/pango/stable/PangoFcFont.html), to implement a
new fc-backend requires subclassing both PangoFcFontMap and PangoFcFont,
which is no longer possible in 1.46, breaking all third-party renderers
(e.g. ours, which uses pango to implement opengl rendering in games).

-- System Information:
Debian Release: 10.6
  APT prefers stable
  APT policy: (990, 'stable'), (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'stable-updates'), (500, 'stable-debug'), (500, 'unstable'), (500, 'testing'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, x32

Kernel: Linux 5.8.16-050816-generic (SMP w/8 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_DK.UTF-8, LC_CTYPE=en_DK.UTF-8 (charmap=UTF-8), LANGUAGE=en_DK.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libpango1.0-dev depends on:
ii  gir1.2-pango-1.0     1.46.2-2
ii  libcairo2-dev        1.16.0-4
ii  libfontconfig1-dev   2.13.1-2
ii  libfreetype6-dev     2.10.2+dfsg-4
ii  libfribidi-dev       1.0.5-3.1+deb10u1
ii  libglib2.0-dev       2.66.2-1
ii  libharfbuzz-dev      2.6.7-1
ii  libpango-1.0-0       1.46.2-2
ii  libpangocairo-1.0-0  1.46.2-2
ii  libpangoft2-1.0-0    1.46.2-2
ii  libpangoxft-1.0-0    1.46.2-2
ii  libthai-dev          0.1.28-3
ii  libx11-dev           2:1.6.7-1+deb10u1
ii  libxft-dev           2.3.2-2
ii  libxrender-dev       1:0.9.10-1
ii  pango1.0-tools       1.46.2-2
ii  pkg-config           0.29-6

libpango1.0-dev recommends no packages.

Versions of packages libpango1.0-dev suggests:
ii  imagemagick                      8:6.9.10.23+dfsg-2.1+deb10u1
ii  imagemagick-6.q16 [imagemagick]  8:6.9.10.23+dfsg-2.1+deb10u1
ii  libpango1.0-doc                  1.42.4-8~deb10u1

-- no debconf information