[Interest] mixing parallel Qt5 installations

[René J.V. Bertin]

Hi,

I have a gentoo-prefix like local set-up under Linux with an installation under /opt/local that holds among others Qt5 (5.7.1 currently):

/opt/local/libexec/qt5 : libraries & binaries
/opt/local/share/qt5 : plugins and other shared stuff not linked or called directly

I've observed that I can build Qt 5.8.0RC with the same installation layout but install ("destroot") it elsewhere and then test existing applications from /opt/local with

env LD_LIBRARY_PATH=/path/to/destroot/opt/local/libexec/qt5/lib

so that they run using Qt 5.8 but still use compatible things from /opt/local/share/qt5, like the QtCurve application style and apparently even the KF5 platform theme plugin.

To make testing a bit easier it would be nice if I could make a test install of the form

/opt/local/libexec/qt5RC
/opt/local/share/qt5RC

I expect that this will make it difficult if not impossible to use compatible things from /opt/local/share/qt5, like styles and the platform theme plugin. 

Is that correct or will that still be possible with minimal effort? Having to set an additional env. variable wouldn't necessarily be an issue as it would allow excluding *in*compatible things that would otherwise cause crashing or aborting.

I'd simply try but building and rebuilding Qt takes a bit too long for that.

Thanks,
René