Bug#1020937: libgtk-3-0: fix gl on GLES-only platforms

[Dominique Martinet]

Package: libgtk-3-0
Version: 3.24.24-4+deb11u2
Severity: wishlist
Tags: patch

Dear Maintainer,

when using GTK on platforms with a GLES-only GL implementation like some
raspberry pi or iMX platforms with vivante driver, GTK fails to
initialize its GL stack because it tries to bind to regular GL first
anyway before using the correct API as configured.

This can be tested by running gtk3-demo and the OpenGL area demo, which
will show nothing as no GL implementation could be found -- but it also
affects real GTK applications like epiphany (gnome web).

This was reported upstream a couple of years ago:
https://gitlab.gnome.org/GNOME/gtk/-/issues/3028
and I submitted a patch yesterday:
https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/5062
(note as said there, this is already fixed in gtk 4)

Assuming the patch does get positive feedback and gets merged (I'm not
asking to backport some code before upstream review!!), what would the
way forward be?
gtk3 hasn't had a point release since May, and bullseye didn't get
updated to the latest stable release, so I assume we could backport the
patch? Would that be acceptable?

-- System Information:
Debian Release: 11.3
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: arm64 (aarch64)

Kernel: Linux 5.10.145-0-at (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: unable to detect

Versions of packages libgtk-3-0 depends on:
ii  adwaita-icon-theme   3.38.0-1
ii  hicolor-icon-theme   0.17-2
ii  libatk-bridge2.0-0   2.38.0-1
ii  libatk1.0-0          2.36.0-2
ii  libc6                2.31-13+deb11u4
ii  libcairo-gobject2    1.16.0-5
ii  libcairo2            1.16.0-5
ii  libcolord2           1.4.5-3
ii  libcups2             2.3.3op2-3+deb11u2
ii  libepoxy0            1.5.5-1
ii  libfontconfig1       2.13.1-4.2
ii  libfreetype6         2.10.4+dfsg-1
ii  libfribidi0          1.0.8-2
ii  libgdk-pixbuf-2.0-0  2.42.2+dfsg-1+deb11u1
ii  libglib2.0-0         2.66.8-1
ii  libgtk-3-common      3.24.24-4+deb11u2
ii  libharfbuzz0b        2.7.4-1
ii  libjson-glib-1.0-0   1.6.2-1
ii  libpango-1.0-0       1.46.2-3
ii  libpangocairo-1.0-0  1.46.2-3
ii  libpangoft2-1.0-0    1.46.2-3
ii  librest-0.7-0        0.8.1-1.1
ii  libwayland-client0   1.18.0-2~exp1.1
ii  libwayland-cursor0   1.18.0-2~exp1.1
ii  libwayland-egl1      1.18.0-2~exp1.1
ii  libx11-6             2:1.7.2-1
ii  libxcomposite1       1:0.4.5-1
ii  libxcursor1          1:1.2.0-2
ii  libxdamage1          1:1.1.5-2
ii  libxext6             2:1.3.3-1.1
ii  libxfixes3           1:5.0.3-2
ii  libxi6               2:1.7.10-1
ii  libxinerama1         2:1.1.4-2
ii  libxkbcommon0        1.0.3-2
ii  libxrandr2           2:1.5.1-1
ii  shared-mime-info     2.0-1

Versions of packages libgtk-3-0 recommends:
ii  libgtk-3-bin     3.24.24-4+deb11u2
ii  librsvg2-common  2.50.3+dfsg-1

Versions of packages libgtk-3-0 suggests:
pn  gvfs  <none>

Versions of packages libgtk-3-0 is related to:
pn  appmenu-gtk3-module       <none>
pn  fcitx-frontend-gtk3       <none>
pn  gcin-gtk3-immodule        <none>
pn  gtk-vector-screenshot     <none>
pn  gtk3-engines-xfce         <none>
pn  gtk3-im-libthai           <none>
pn  hime-gtk3-immodule        <none>
pn  ibus-gtk3                 <none>
pn  imhangul-gtk3             <none>
pn  libcanberra-gtk3-module   <none>
pn  libcaribou-gtk3-module    <none>
pn  libgtk3-nocsd0            <none>
pn  maliit-inputcontext-gtk3  <none>
pn  packagekit-gtk3-module    <none>
pn  scim-gtk-immodule         <none>
pn  topmenu-gtk3              <none>
pn  uim-gtk3                  <none>
pn  uim-gtk3-immodule         <none>

-- no debconf information