[WIP] Make plugin_libdir configurable

[yselkowitz]

This is important for distributions which use 'lib64' instead of just 'lib'.

[clefebvre]

This breaks plugins in Mint. Dpkg injects the default --libdir=lib/x86_64-linux-gnu and xviewer no longer finds the plugins.

[yselkowitz]

Looks like xviewer itself would need the same fix. Would that be acceptable?

[mtwebster]

Yes that's fine

[okaestne]

There are other inconveniences regarding the plugin dir. We currently decide about the one and only plugin directory with the build config of xviewer, which is then baked into the xviewer binary as well as the pkg-config file. The latter is used to get the plugins dir to install the plugins in it. (edit: I planned to use it, but right now it's hardcoded)

That's unfortunate, as we can't

1. install a dev build of xviewer into /usr/local (thus, changing the prefix of the plugins dir) without also reinstalling the plugins
2. have user plugins e.g. in ~user/.local/share/xviewer/plugins

Therefore, we might consider adding some "well known" plugin dirs to the peas engine's search path and also provide a configurable "extra plugins dir" meson option in xviewer.

[mtwebster]

Isn't it already handling all this?
https://github.com/linuxmint/xviewer/blob/master/src/xviewer-plugin-engine.c#L121-L152

It's adding:

• User data dir (~/.local)
• All system locations (/usr/share, /usr/local, ...)
• The config-provided path - which is redundant in most cases since it's probably one of those system locations.

That last we could make a meson option like you said, and default to what it uses now.