fix appindicator so we can use it for forwarding system trays

[Antoine Martin]

I'm not even sure this is possible, but since Ubuntu does not support the regular StatusIcon correctly anymore (and with newer versions, it simply does not show up at all), better have something - even something ugly.

And this is going to be ugly. Their API is an ugly joke:

• ​whitelist is obsolete in raring - read the comments..
• ​How to program a status icon that will display in Ubuntu as well as in other distributions? - shows that no-one has a clue how to make things work reliably, thanks Ubuntu!
• ​The libappindicator Story

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First, just like with OSX (#404), we don't know the location of the appindicator until it is used, and even then finding the exact coordinates is a complete nightmare (see ​https://bugs.launchpad.net/screenlets/+bug/522152/comments/11)

Then we can't just catch the events we want (hover, clicks), we only get the option of having a menu (how convenient and modern - NOT!), so we will have to populate this menu with something - maybe have one entry for each action (left click, right click)... but we don't even know which clicks do anything at the other end.

Can someone from Ubuntu please fix this - it's their horrible mess.

Links:

• ​Application indicators docs
• ​QT Systray icon appears next to launcher on Ubuntu instead of on the panel : Qt5 does not support appindicator yet, found good idea to enable only if "unity" is the DE in there (added in r4083)

[Antoine Martin]

See also #636

[Antoine Martin]

That thing is best forgotten.

Most of the Ubuntu wiki pages lead to 404s.
It never worked properly, and is now causing crashes under 18.04 with unity.

python3 -c "from gi.repository import AppIndicator3;AppIndicator3.Indicator()"

segfaults..

[Antoine Martin]

See also #2179 / #1818

[Antoine Martin]

Needed because statusicon is now even more broken..

[Antoine Martin]

Fixes in:

• r21893 packaging: recommend appindicator and top-icons-plus extensions so we can show something somewhere - hopefully
• r21894: use appindicator on "unity" and "gnome" DEs
• r21898: fix appindicator3 (was invalid argument causing the segfault..), enable it for kde
• r21982: better DE name matching
• r21983 + r21984 + r21989: debian package dependencies (see ​python-appindicator removed in buster..)

[Antoine Martin]

Will follow up in #2197

[Antoine Martin]

More fixes:

• r22004 + r22007 don't use /tmp for temporary icon files we have to use with appindicator (..), move them to /run/user/$UID/xpra/tmp
• r22005 keep the file around until we have the next one (async code in appindicator was making this racy)
• r22006 better debugging
• r22008 fix for python3 server icon change, which broke theme icons
• r22009 RPM dep update

[Antoine Martin]

Related tickets: #2161, #2197, #2242, #476