Bug#986970: qgis: QGIS cannot detect installed OpenCL drivers unless `ocl-icd-opencl-dev` package is installed

[Pedro Ângelo]

Package: qgis
Version: 3.10.14+dfsg-1
Severity: normal

Dear Maintainer,

I tried to enable OpenCL acceleration on QGIS options menu by going to
"Settings -> Options -> Acceleration" and toggling the "Enable OpenCL
Acceleration" menu option.

At first, this failed with a message that it could not find the appropriate
drivers. After installing the `mesa-opencl-icd` package, which enabled OpenCL
for my GPU in other applications, QGIS still failed to detect the drivers.

After some digging, I found that QGIS was trying to dlopen `libOpenCL.so` in
several locations, but the `ocl-icd-libopencl1` package installed by `mesa-
opencl-icd` only provided `libOpenCL.so.1`.

Symlinking `libOpenCL.so.1` to `libOpenCL.so` fixes the issue, and this is
provided by the `ocl-icd-opencl-dev` package.

I suggest that this package is either added to the QGIS package suggestions or
the error message within QGIS is updated to suggest installing it.

Best regards,

P.

-- System Information:
Debian Release: bullseye/sid
  APT prefers testing-security
  APT policy: (500, 'testing-security'), (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-5-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_WARN
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8),
LANGUAGE=en_GB:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages qgis depends on:
ii  libc6                            2.31-11
ii  libgcc-s1                        10.2.1-6
ii  libgdal28                        3.2.1+dfsg-1+b1
ii  libgeos-c1v5                     3.9.0-1
ii  libgsl25                         2.6+dfsg-2
ii  libqgis-analysis3.10.14          3.10.14+dfsg-1
ii  libqgis-app3.10.14               3.10.14+dfsg-1
ii  libqgis-core3.10.14              3.10.14+dfsg-1
ii  libqgis-gui3.10.14               3.10.14+dfsg-1
ii  libqt5core5a                     5.15.2+dfsg-5
ii  libqt5gui5                       5.15.2+dfsg-5
ii  libqt5keychain1                  0.10.0-1
ii  libqt5network5                   5.15.2+dfsg-5
ii  libqt5sql5                       5.15.2+dfsg-5
ii  libqt5webkit5                    5.212.0~alpha4-11
ii  libqt5widgets5                   5.15.2+dfsg-5
ii  libqt5xml5                       5.15.2+dfsg-5
ii  libstdc++6                       10.2.1-6
ii  ocl-icd-libopencl1 [libopencl1]  2.2.14-2
ii  python3-qgis                     3.10.14+dfsg-1
ii  qgis-common                      3.10.14+dfsg-1
ii  qgis-providers                   3.10.14+dfsg-1
ii  qt5-image-formats-plugins        5.15.2-2

Versions of packages qgis recommends:
ii  qgis-plugin-grass  3.10.14+dfsg-1

Versions of packages qgis suggests:
pn  gpsbabel  <none>