Add options global clipboard clearing

[alimirjamali]

Menu item to Global Clipboard widget to allow users to manually clear it.
Also global-clipboard-timeout feature could be set per VM and/or GUIVM

resolves: QubesOS/qubes-issues#6641

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.72%. Comparing base (bab3289) to head (74c435f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #225      +/-   ##
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- Coverage   93.72%   93.72%   -0.01%     
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  Files          57       57              
  Lines       10845    10845              
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- Hits        10165    10164       -1     
- Misses        680      681       +1     

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[marmarta]

I like this, there is one problem: what if the widget crashes / someone is using a desktop environment that has problems with the widget, but the person relying on global clipboard will not know that the clearing stopped working (because copy-paste itself will work, just the notifications won't...). @marmarek mentioned that maybe this should happen in the gui daemon for that reason.

[alimirjamali]

I like this, there is one problem: what if the widget crashes / someone is using a desktop environment that has problems with the widget, but the person relying on global clipboard will not know that the clearing stopped working (because copy-paste itself will work, just the notifications won't...). @marmarek mentioned that maybe this should happen in the gui daemon for that reason.

Well said. I believe the manual clearing in systray applet menu could still remain since it is useful.

The gui-daemon could signal timeout clearing via metadata like this:

successfull: 1
copy_action: 0
paste_action: 0
cleared: 1

The above should just generate a visual notification via widget.

And gui-daemon could check the existing metadata on timeout to assure global clipboard still belongs to that specific vm and that particular copy action. We just need another config/command line option for qubes-guid. I will work on it.