Install qt5 soundsources to a different folder to avoid crashes, fixes lp1774639

[daschuer]

https://bugs.launchpad.net/mixxx/+bug/1774639

This fixes the bug for Linux. I think there is something missing for the Windows and Mac OS installer.

[daschuer]

It is really annoying to have a crash every time I change from QT4 to 5 and back.
This PR solves this. Can we merge it, at least as an intermediate solution?

[daschuer]

Now it fixes also https://bugs.launchpad.net/mixxx/+bug/1711173
The installations for mac OS and Windows are still missing.
Can one explain how to make it QT5 conditional?

[Be-ing]

This feels like a hacky solution. Why isn't the old plugin overwritten by the new one?

[Be-ing]

Maybe this bug is related?

[daschuer]

It is not related. The number of soundsources depends on the compile options. So it may happen, that the user has installed a build with more soundsources. These will stick in these folders as intended.

An other issue is that the user might use Mixxx from the build tree, which used a different qt version than the original installed one. In this case Mixxx tries to load the plug-ins from the install path as well. (My case)

[daschuer]

For this PR we need to test and probably fix the windows and Mac installer. Who is able make the installers Qt version aware? Alternative, we can ignore the issue and install master alwaxs to qt5 and 2.1 always to qt4 path.

[daschuer]

@sblaisot:What is your opinion here? Is it difficult to make the install location qt version aware on windows?

[sblaisot]

The installer already takes whatever subdir exist in build_dir so if the subdir is called pluginsqt5 instead of plain plugins it will take that and install as-is on target machine: https://github.com/mixxxdj/mixxx/blob/master/src/SConscript#L712,L716

So all you have to do is to build in the right sudbir here:
https://github.com/mixxxdj/mixxx/blob/master/src/SConscript#L567,L570

You already have an example of qt4/5 logic here:
https://github.com/mixxxdj/mixxx/blob/master/src/SConscript#L328,L343

[rryan]

on macOS the bundle plugin directory must be named PlugIns:
https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFBundles/BundleTypes/BundleTypes.html#//apple_ref/doc/uid/10000123i-CH101-SW1

macOS is unaffected by this bug because .app bundles can't get files mixed up so I would just leave the __APPLE__ codepaths unchanged

[rryan]

I think Windows is mostly unaffected by this bug because the WiX installer will not install Mixxx on top of an old install -- it requires you to run the uninstaller first, which will delete the plugins.

Right @sblaisot ?

[daschuer]

Ok, now it works for Linux only. No crash anymore.
Linux uses now:

/usr/local/lib/mixxx/plugins/soundsourceqt5/
/usr/lib/mixxx/plugins/soundsourceqt5/
~/.mixxx/plugins/soundsourceqt5/

all other platforms are not effected.

We "only" have to change:
https://www.mixxx.org/wiki/doku.php/add-ons
the manual is not effected.

The linux packagers are also not effected because at least for ubuntu they do not ship soundsource plugins.

[daschuer]

re-added the vamp fix

[daschuer]

The base 2.1 is correct. It does not change anything in a qt4 2.1 build, but if one wants to try qt5 it will work without a crash.

[daschuer]

I have tested both.

[daschuer]

ready ..

[rryan]

cool, thanks