bug#43446: Qt Apps cant make use of qtwayland due to QT_PLUGIN_PATH '= wrapping

[Ricardo Wurmus]

Brendan Tildesley <mail@brendan.scot> writes:

> qt-build-system wraps variables such as QT_PLUGIN_PATH  with  '=
> instead of prefix, so when qtwayland is installed in a profile or
> included in the environment, the application fails to see it. Programs
> run with export QT_QPA_PLATFORM=wayland-egl will fail to launch.
>
> We could:
>
> 1. Use 'prefix so that the parent environment's variables are appended
>    and users have to manually install qtwayland them selves.
> 2. Include qtwayland as an input to every qt package somehow. Can the
>    build system do that? Considering that Wayland seems to be the
>    future, I feel that Qt GUI applications should support it by
>    default. I mean, wayland is in the closure of qtbase anyway.
> 3. Both? Why is '= used anyway?

I can’t say why the Qt build system does this, but in other cases we
know that 'prefix causes problems because the application may end up
loading incompatible binaries leading to a crash.  That’s especially the
case on foreign distros, e.g. when the Guix-installed graphical
application loads a plugin from the system’s XDG_* directories.

-- 
Ricardo