Support for Linux

[ungive]

Progress:

• Use the playerctl library to detect media on the system
• Successfully compile, run and use Music Presence to share media that is playing on the system
• Write a Dockerfile for reproducible and reliable builds
• Create a test release for others to test Music Presence on Linux
  Builds are available on the Discord server! https://discord.gg/musicpresence
• Ensure Music Presence works with a system-installed Discord, as well as Discord installed via Snap or Flatpak and third-party Discord mods/flavours that use arRPC under the hood
  Implemented: ungive/discord-rpc@d32867f
• Refactor the players.json file at https://live.musicpresence.app/v2/players.json to allow: Multiple player icon variants, a check if it's still the latest version, ... (v3). Also move the generation of it out of the internal code base to https://github.com/music-presence/media-players and rewrite it so it can easily be run on Linux (some code only runs on Windows atm) Doing this at a later time
• Data URLs (data:image/png;base64,...) need to be parsed and uploaded using the proxy server
• File URLs (file:///) also need to be read into memory (if not too big) and uploaded using the proxy
• Some file URLS don't have the file:/// prefix, e.g. when playing media with fooyin: xesam:url may contain /run/user/1000/doc/2b22d58c/music.mp3. Exclude these URLs properly, maybe only allow HTTP/HTTPS for track URLs and only allow HTTP/HTTPS/file/data URLs for cover images
• Find a fix or workaround for the playerctl memory leak mentioned below
• Detect media players not only from their player id/name, but also with the URL to the track that is reported by MPRIS in the xesam:url field. Here the domain should be parsed and compared against well-known domains of streaming services, e.g. listen.tidal.com and open.spotify.com. This requires media to have multiple platform identifiers, not only lin_mpris, but also web_domain in this case
• Packaging: Create standalone AppImage binary (that bundles Qt)
• Packaging: Create deb/rpm/... packages that do (or do not) bundle Qt version 6.6.3. It most likely will have to be bundled, since Qt 6.6 is rather new and may not be present on many Linux distributions
• Make sure playerctl does not use g_error in places where it shouldn't. It crashed for me once before with this error: could not get metadata: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.6901 was not provided by any .service filesSpeicherzugriffsfehler (Speicherabzug geschrieben)
  Related: Fix incorrect use of g_error altdesktop/playerctl#329
• Release a version of Music Presence that ships with Linux binaries! 🎉
• Update the player support table to include all added Linux media players

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There's a Linux x86_64 build in the Discord: https://discord.gg/musicpresence

If you feel like helping and trying it out with your favourite media players, you're welcome to join!

[ungive]

The playerctl library may not be a viable option, as it leaks a ton of memory with media players like Elisa
See altdesktop/playerctl#335

Edit: Found a workaround, see the mentioned issue