Allow using custom mir libraries directory

[TibboddiT]

Allow invoking cmake with -DMIR_LIBRARIES_PKGCONFIG_DIRECTORY=<dir> to search Mir pc files in a custom directory.
If -DMIR_LIBRARIES_PKGCONFIG_DIRECTORY is not set, behavior remains unchanged.

Note: to successfully build locally, linking to libmirwayland.so was neeeded, so I added it to target_link_libraries.

Building on Debian with a local build of the Mir main branch works now without modifying miracle-wm sources.

Fix #196.

[mattkae]

Thanks for doing this! I have a few questions about the implementation, but it looks like the right idea

[mattkae]

Why would Mirwayland be required here? I don't remember using it in the project anywhere

[TibboddiT]

It's only required at link time, otherwise building fails with

/usr/bin/ld: warning: libmirwayland.so.5, needed by <mir_install_directory>/lib/libmirplatform.so, not found (try using -rpath or -rpath-link)

and a bunch of undefined symbols.

Maybe mirplatform should require mirwayland in its pc file ? Currently it's just:

prefix=<mir_install_directory>
libdir=${prefix}/lib
includedir=${prefix}/include

Name: mirplatform
Description: Mir platform library
Version: 2.18.0
Requires: mircommon, mircore
Libs: -L${libdir} -lmirplatform
Cflags: -I${includedir}/mirplatform

[mattkae]

Ah okay that's probably an issue on their end, but I am happy to patch it on our end in the meantime.

Filed the bug: canonical/mir#3536

[mattkae]

Thanks for doing this :) Just letting CI do its thing then I'll merge

[mattkae]

@TibboddiT One last thing to make this work:

We're going to need to install the libmirwayland-dev and package in CI: https://github.com/mattkae/miracle-wm/blob/ea33fb1c7212a8a3b9633e0b9fd909aab186028c/.github/workflows/cmake.yml#L33

[TibboddiT]

Done. snap/snapcraft.yaml was also updated with libmirwayland-dev.

[mattkae]

Nice!

[OPNA2608]

This breaks any existing PKG_CONFIG_PATH setup.

$ echo $PKG_CONFIG_PATH
/nix/store/b3a0wh9v9md9kc4qdixsbwjy3799077r-boost-1.81.0-dev/lib/pkgconfig:/nix/store/sa2vr5rkh19pvy9j4hkb4lk95nlhqpix-glib-2.80.4-dev/lib/pkgconfig:/nix/store/vsygj2vzwqr9x7rzq4v3prcv2blkggmx-zlib-1.3.1-dev/lib/pkgconfig:/nix/store/niabvl1jq1hl7s3n1yx5zxa27l9mipkm-libffi-3.4.6-dev/lib/pkgconfig:[...]
$ $PKG_CONFIG --cflags miral
-I/nix/store/457888a9j750b2skjvi33h4xn66y05gi-mir-2.17.0-dev/include/miral -I/nix/store/457888a9j750b2skjvi33h4xn66y05gi-mir-2.17.0-dev/include/mircommon -I/nix/store/457888a9j750b2skjvi33h4xn66y05gi-mir-2.17.0-dev/include/mircore

/build/source/CMakeLists.txt(15):  set(MIR_LIBRARIES_PKGCONFIG_DIRECTORY  CACHE STRING Search for Mir libraries pc files in this directory )
/build/source/CMakeLists.txt(16):  option(SNAP_BUILD Building as a snap? OFF )
/build/source/CMakeLists.txt(18):  set(ENV{PKG_CONFIG_PATH} :/var/empty/local/lib/pkgconfig/ )
[...]
/nix/store/sa1yjb7xxrzcbd1bysj3r561vidfxxvb-cmake-3.29.6/share/cmake-3.29/Modules/FindPkgConfig.cmake(435):  set(ENV{PKG_CONFIG_PATH} /var/empty/local/lib/pkgconfig )
[...]
-- Checking for module 'miral'
--   No package 'miral' found

[OPNA2608]

Ah sorry. The pre-existing code already broke it, and I see this was supposed to close the issue for this: #196

Why is setting PKG_CONFIG_PATH=/usr/local/lib/pkgconfig and further messing around with it in CMake even necessary, is something wrong with some build environment somewhere? I feel like this setup should just be left to whatever build environment CMake is executed in, prepending a custom Mir path as desired.

Submitted #211 to instead use the existing ENV{PKG_CONFIG_PATH}, or set /usr/local/lib/pkgconfig as a fallback if it's empty.