Fixed getting text from clipboard in Linux

[DemonExposer]

What does the pull request do?

It fixes issue #4320

What is the current behavior?

When calling X11Clipboard.GetTextAsync() in Linux (tested on Debian based), the task runs indefinitely (i.e. awaiting or .Result makes the current thread wait for an event to be handled, which does not happen)

What is the updated/expected behavior with this PR?

It returns the text which is in the clipboard without issue.

How was the solution implemented (if it's not obvious)?

It was implemented by skipping all the generic event handling and just handling the event in X11Clipboard itself (by calling X11Clipboard.OnEvent). The reason for this is that the generic event handling in Avalonia does not catch SelectionEvent. I could not figure out why. I assume it's some X11 issue not properly working with GLib. Either way, it works with my changes and OnEvent is still used.

Checklist

• [ ] Added unit tests (if possible)?
• [ ] Added XML documentation to any related classes?
• [ ] Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #4320

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0053197-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• [x] All contributors have signed the CLA.

[DemonExposer]

@cla-avalonia agree

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0053405-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0053440-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[DemonExposer]

@kekekeks when is this going to get reviewed?

[ApaulMyLittleAirport]

I'm also having this clipboard issue on linux, hope to fix it, thank you very much!