[Debian-on-mobile-maintainers] Bug#1104602: megapixels gui fails because gtk4 dropped support for GLES 2.0

[Boud Roukema]

Package: megapixels
Version: 1.8.3-1
Severity: grave
Tags: upstream
Justification: renders package unusable

Dear Maintainer,

    * What led up to the situation?

I have been using Megapixels on the PinePhone v1.2b for a bit under
four years on Mobian/Debian testing (bookworm prior to bookworm
becoming stable; trixie right now). Over the last few years it has
generally worked well for taking photos.

    * What exactly did you do (or not do) that was effective (or
      ineffective)?

1. I tapped the Megapixels gui on the PinePhone touchscreen with my finger.

2. I ran 'megapixels |& tee log' from the command line.

    * What was the outcome of this action?

1. A pop-up message stated "Unable to create a GL context".

2.  A pop-up message stated "Unable to create a GL context" and
the file "log" consists of:

MPCamera: VIDIOC_SUBDEV_S_FRAME_INTERVAL error 25, Inappropriate ioctl for device
megapixels: ../src/dispatch_common.c:872: epoxy_get_proc_address: Assertion `0 && "Couldn't find current GLX or EGL context.\n"' failed.

    * What outcome did you expect instead?

I expected to see a gui for taking photos.


    * Developer's point of view *

Martijn Braam has explained the problem in a blog:

   "There's steady progress towards Megapixels 2.0 Alpha 2 with a lot
   of small improvements, but there's also a massive roadblock
   introduced by the GTK developers..."

   "In the case of Megapixels [the problem is] the NGL backend for GTK4. The
   4.17 release made in Februar[y] dropped the GL backend in favor of the
   NGL and Vulkan renderers. Which is great if you're on the latest and
   greatest Macbooks."

   "The issue is that GTK now also dropped for GLES 2.0 which means
   that a lot of older devices are no longer GPU accelerated in
   GTK4. For Megapixels it's an even bigger issue since the debayering
   depends on GPU acceleration so it won't run at all if GTK4 doesn't
   have an OpenGL context anymore."

https://blog.brixit.nl/megapixels-2-0-progress/


    * Workaround *

At https://forum.pine64.org/showthread.php?pid=124299 a proposed
workaround is to use a fork of gtk4 that describes itself as
"Fork of GTK to restore OpenGL ES 2.0 support":
https://github.com/kkofler/gtk

    * Possible Debian or upstream solutions *

Guesses based on dicussion at #mobian:

The gtk4 fork seems unlikely to be a solution at the Debian level, unless
someone proposes a gtk4-opengl-es2.0 fork and it's accepted into
Debian. That would only make sense if discussed with the gtk4
community.

Convincing the main gtk4 upstream community, or the Debian-level
gtk4 maintainers, to retain the OpenGL ES 2.0 facilities is probably
unrealistic.

    * Debian release of trixie as stable *

Since this appears to make Megapixels unusable to all Debian/trixie
users (which includes Mobian/trixie), I've put "grave" as the severity
level. This is one of the three "release-critical" severity levels.



-- System Information:
Debian Release: trixie/sid
   APT prefers testing-debug
   APT policy: (500, 'testing-debug'), (500, 'testing')
Architecture: arm64 (aarch64)

Kernel: Linux 6.12-sunxi64 (SMP w/4 CPU threads)
Kernel taint flags: TAINT_CRAP
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages megapixels depends on:
ii  dconf-gsettings-backend [gsettings-backend]  0.40.0-5
ii  libc6                                        2.41-7
ii  libepoxy0                                    1.5.10-2
ii  libfeedback-0.0-0                            0.8.1-1
ii  libglib2.0-0t64                              2.84.1-1
ii  libgtk-4-1                                   4.18.4+ds-1
ii  libraw-bin                                   0.21.3-1+b1
ii  libtiff6                                     4.7.0-3
ii  libwayland-client0                           1.23.1-3
ii  libx11-6                                     2:1.8.12-1
ii  libxrandr2                                   2:1.5.4-1+b3
ii  libzbar0t64                                  0.23.93-7

Versions of packages megapixels recommends:
ii  imagemagick                      8:7.1.1.43+dfsg1-1
ii  imagemagick-7.q16 [imagemagick]  8:7.1.1.43+dfsg1-1
ii  libimage-exiftool-perl           13.25+dfsg-1

megapixels suggests no packages.

Cheers
Boud