[crac] RFR: X11 CRaC reinitializing on CheckpointRestore [v4]

[Radim Vansa]

On Mon, 12 Sep 2022 07:50:57 GMT, Ilya Kuznetsov <duke at openjdk.org> wrote:

>> Allows CRaC to perform a CheckpointRestore operation for applications using GUI (Swing, AWT) and X11 connection.
>> 
>> Resources are registered only if the application uses the GUI. The order in which resources are reinitialized matters: Toolkit should be cleared before reference handling for a proper garbage collection, and GraphicsEnvironment after handling for a correct X11 disconnection. Some resources restore lazily.
>> 
>> The `beforeCheckpoint()` operation dispose necessary toolkit and connection resources and disconnects from X11. This allows CRaC to perform a Checkpoint since there is no external connection.
>> The `afterRestore()` operations reconnect to X11 and then restore necessary connection and toolkit resources.
>> 
>> Thus, after the Restore operation, we have a clean X11 connection. It is ready to restore the original GUI state.
>
> Ilya Kuznetsov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix newline

@i1ya-kznts9v Looks like this did not receive much attention; would you consider getting that ready again?

Besides the merge conflict, this PR is rather big. Isolating (and describing) particular changes, esp. these that are not X11-related, into separate PRs would make the review much simpler.

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PR Comment: https://git.openjdk.org/crac/pull/19#issuecomment-1508068190