MixxxApplication: Support linking Qt statically on Linux #12284
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Currently, Mixxx cannot be built at all using static Qt and will always
error at compile time with a message indicating the a plugin for the
current platform is missing.
While using the system-packaged Qt is generally the preferred way, there
are use cases for statically linking Qt (e.g. portable or embedded
builds), therefore it would be nice if we could at least support
building Mixxx this way.
Unfortunately, Linux does not have a single display API, a list can be
found in the Qt documentation:
https://doc.qt.io/qt-6/qpa.html
This patch chooses to hardcode the X11/XCB plugin for static Qt builds,
which is certainly not ideal, especially since Wayland seems to
increasingly be the preferred backend, but seems to be the only plugin
supported by vcpkg's `qtbase`:
https://github.com/mixxxdj/vcpkg/blob/2.5-rel/ports/qtbase/portfile.cmake
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I have no objections. |
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I'll mark this as ready for review, since it's a pretty trivial PR, but would like to hold off merging until we've tested it with an actual build (which effectively means it's blocked on all the PRs listed in fwcd/m1xxx#48). |
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Can confirm that this works, tested the "static" build that only links essential and X11-related libraries in a VM: 
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Lesson learned: we need to test on all affected platforms next time merging such a change. |
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@fwcd Do you have an idea how to fix it? |
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This doesn‘t make much sense to me, do the Ubuntu builds link Qt statically? (I‘d find that very surprising if it were the case) Otherwise we should investigate why The condition that this adds would have produced a build error before (if Still, these kinds of bugs can probably easily go unnoticed if many people still have the X libraries installed. |
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I don’t have much experience with Ubuntu packaging and Launchpad, so perhaps someone more familiar with that process has an idea? |
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Hmm, maybe this is not related to #12525 at all, it just seemed to this was the only relevant PR. |
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If it is a more general issue, it‘s probably something with the way Qt 6 is packaged on Ubuntu (in which case it should affect all Qt 6 apps) |
Currently, Mixxx cannot be built at all using static Qt on Linux, since it will always error at compile time with a message indicating the a plugin for the current platform is missing (see e.g. this build).
While using the system-packaged (and dynamically linked) Qt is generally the preferred way, there are use cases for statically linking Qt (e.g. portable or embedded builds), therefore it would be nice if we could at least support building Mixxx this way.
Unfortunately Linux does not have a single display API, instead there are several choices for platform plugins on Linux, as described in the Qt documentation:
This patch chooses to hardcode the X11/XCB plugin for static Qt builds, which is certainly not ideal, especially since Wayland seems to increasingly be the preferred backend, but seems to be the only plugin supported by vcpkg's
qtbase:In the spirit of having at least something that works, I would consider this an acceptable tradeoff for now. In the future we could e.g. add a configuration flag for selecting a plugin at build-time (including e.g. the Wayland plugin). Any thoughts?