Initial prototype for taking screenshots with GTK4 #874

[ptziegler]

Based on the SWT implementation.

[ptziegler]

There are still several open topics. Most noticeably, taking a screenshot is only possible if the widget has been realized. Which is sadly not guaranteed and not something that can really be "forced".

[ptziegler]

There are still several open topics. Most noticeably, taking a screenshot is only possible if the widget has been realized.

I think the most reliable option is to wait for the "Activate" event to fire. It mustn't block indefinitely in case something goes wrong, though. I might reuse this approach for GTK3 as well, as we have flaky test cases for a similar reason.

Another issue is that the widget will always be in the center of the screen. I'm not yet sure if this is a general problem on GTK4. But it's also in the category of "inconvenient", rather than "critical".

Also the GTK4 port will be Java 24+, because I really have no desire to create the binaries for all Linux platforms.

[github-actions]

Test Results

     4 files  ±0       4 suites  ±0   2h 26m 13s ⏱️ + 4m 22s
 7 020 tests ±0   6 989 ✅ ±0  31 💤 ±0  0 ❌ ±0 
23 684 runs  ±0  23 586 ✅ ±0  98 💤 ±0  0 ❌ ±0 

Results for commit ceff6d3. ± Comparison against base commit f5637f2.