Fix DTD freezes when opening projects, and EDT freezes when the theme changed and opening embedded DevTools

[AlexV525]

(originally with #8477)

Summary

• Fix frequent “Timed out waiting for DTD websocket to start” errors when opening projects.
• Fix EDT freezes caused by:
  • Synchronous JxBrowser Engine initialization when opening embedded DevTools.
  • Blocking ExecutorService lifecycle on theme change (JDK 21 ExecutorService.close() awaits termination).

Changes

• DtdUtils
  • Refactor readyDtdService to be truly asynchronous using a shared ScheduledExecutorService for periodic polling (no blocking).
  • De-duplicate and cache the in-flight Future per Project to avoid redundant polling under concurrency.
  • Preserve an overall timeout (~20s by default). On timeout or error, complete exceptionally and clear the cache to allow subsequent retries.
• EmbeddedJxBrowser.openEmbeddedTab:
  • Avoid initializing JxBrowser Engine on the EDT; show “installation in progress” UI until async init completes.
  • This removes the fallback compareAndSet(null, getEngine()) path that could call Engine.newInstance(...) on EDT and freeze it.
• FlutterInitializer.sendThemeChangedEvent:
  • Send themeChanged asynchronously: remove .get() blocking; use a shared scheduler with debounce.
  • If DTD becomes ready later, the event is sent then; if it times out, gracefully skip with debug-level logging (no startup errors).
  • Use shared AppScheduledExecutor (AppExecutorUtil) instead of creating/closing a new executor per event.
  • Remove try-with-resources that triggers ExecutorService.close() on EDT with JDK 21.

Notes

• Added comments explaining why Engine initialization must not occur on EDT and how JDK 21 changed ExecutorService.close().

Fixes

• Fixes DTD theme changed event exception #7794
• Fixes IDE Freezing and slowing down a lot, I get error balloons a lot of times #8394
• Fixes 🚀 Performance freeze in EDT caused by ExecutorService blocking in Flutter plugin #8478

Testing

• Manual:
  • Open Flutter projects; no error logs about DTD timeout.
  • Switch IDE themes repeatedly; no UI freeze.
  • Open DevTools (embedded) after clean startup and after JxBrowser installation completes; no EDT freeze, proper “installing...” UX during setup.

[AlexV525]

This saves my day. I've been feeling freezing using the IDEA with Flutter on my Windows machine for months. The performance of the plugin is significantly improved with the PR.

[jwren]

@AlexV525 thank you, code and testing looks good. Do validate that with the daily released that the issues are resolved and you don't see any other issues.

[AlexV525]

@AlexV525 thank you, code and testing looks good. Do validate that with the daily released that the issues are resolved and you don't see any other issues.

Because it's not merged so I'm using my local compiled version and see no issues regarding DTD & EDT so far.

[jwren]

@AlexV525 thank you, code and testing looks good. Do validate that with the daily released that the issues are resolved and you don't see any other issues.

Because it's not merged so I'm using my local compiled version and see no issues regarding DTD & EDT so far.

Thank you again!

[helin24]

Thanks for the change! I did not see the original issue, so I can't verify myself, but it sounds promising if this is working well for you.

I'm wondering if adding some logs here might help us debug if there are problems? e.g. logging the successful path to make sure we're getting through the steps.

[AlexV525]

I'm wondering if adding some logs here might help us debug if there are problems? e.g. logging the successful path to make sure we're getting through the steps.

I'm not familiar with the logging system of the plugin. Are you indicating we can add logs like DTD established after x seconds? (I'd love to investigate this if we have a separate detailed issue!)

[helin24]

I've been transitioning classes to use PluginLogger (see for example #8452) - more background here: #8369

And yes, your example of logging is what I was thinking. Do you think that could help for this situation? We have a complex setup for DTD and DevTools so I feel like more info here would be helpful for our own understanding of what happens here and for potential debugging.