Comment 8 for bug 1589798

Here is the code:
https://github.com/audacious-media-player/audacious/blob/3ec8f6781c5682d22f42d3415f123bef98fd0ee9/src/statusicon/gtktrayicon-x11.c

Unfortunately I cannot find the code in the recent audacious version.
On my system Ubuntu + Cinnamon there is no systray icon for audacious and no option to enable it.
VLC player has an option in preferences: "Show systray icon", but it does not work.

However, in any case MPRIS2 a D-Bus based protocol is the preferred way way on Linux.

It looks like for your simple demand we need only to implement the MPRIS2 Raise() command.
https://specifications.freedesktop.org/mpris-spec/latest/Media_Player.html#Method:Raise

https://github.com/daschuer/mixxx/blob/mpris/src/mpris/mediaplayer2.h#L44

The "only" issue is that we need to put Mixxx on the white list for the various sound applets like here:
https://github.com/nbourdau/pkg-cinnamon/blob/ac7b0c50025461a9e43e6781f83355f832ad4091/files/usr/share/cinnamon/applets/sound%40cinnamon.org/applet.js#L102

Will this work for you?

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For windows, it looks like a solution based on http://doc.qt.io/qt-5/qsystemtrayicon.html
will work.

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Mac OS?