Alternatives to check button:
Appears to be in order and confirmed it works on systems without system tray.
Isn't this same as taking MAX of Width and Height and then dividing ICON_BIG_SIZE with the bigger one. This way you cut away one cast to double.
Few things with one optional change.
Another point: pkg-config --cflags dbus-1 also lists some include paths. The reason why we don't need it there is because gtk has those included as well (though they do not link against dbus-1...
Upper case Y is perhaps what you want here.
Upper case X is perhaps what you want here.
dbus-1 has a pkg-config file, so you may move dbus-1 inside the ``
If these are global, add static to them to make them local to this file and make sure to prefix the names with "Tray"
Two things
SEEMS TO ME THIS IS FINE
Second approval
Looks fine to me.