This is a continuation to [JDK-8236651](https://bugs.openjdk.org/browse/JDK-8236651) and it aims to stabilize the linux glass gtk backend.
Overall, it has been made more robust within its scope, particularly in terms of sizing, positioning, and state management. List of changes: 1. It embraces the asynchronous nature of X11 by reporting geometry changes only upon receiving a configure event, rather than immediately as before. This is because it merely requests changes from the window manager, which may or may not honor them. However, it still reports changes immediately in certain special cases, such as when the window has not yet been realized (i.e., when the window has not actually been created yet). One scenario where this behavior is evident is when we request the window to move to position (0, 0), but the window manager instead places it in the top-right corner where panels converge. 2. FullScreen now keeps track of geometry changes and apply them on restore as documented on Stage.java. No geometry changes affects the FullScreen state; 3. States (fullscreen, maximized and iconify) are now reported back to Java when it actually happens rather than immediately (except when not realized); 4. When a window is maximized, it will ignore geometry changes and restore to the geometry it had prior to being maximized. After some testing, I believe this is the best behavior for platform compatibility; 5. Unifies the WindowContext class: previously, there were three separate classes—two of which (for applets and Java Web Start) were removed, leaving only one. However, the supporting infrastructure was still there partially. [Unify WindowContext in glass-gtk](https://bugs.openjdk.org/browse/JDK-8305768) 6. `setAlpha` and `setBackground` were removed because they no longer function correctly due to the lack of shared rendering. It's not possible to paint a background using GTK and then render custom content on top of it, unless the rendering is done by Gtk (it is not). It is possible to keep the background by painting with cairo, and make it work with software rendering, but that's a very remote scenario; 7. Tests were added and re-enabled to ensure everything works correctly. The stage tests now cover various StageStyle configurations, as I found that `DECORATED` stages often behave differently from `UNDECORATED` or `UTILITY` stages; 8. Added Logs for debugging. Enable it with ` -PCONF=DebugNative`; 9. It no longer keeps track of geometry internally, as GTK already manages this - except in special cases, such as when the window has not yet been realized. Previously, it used BoundsType to distinguish between "Window Bounds" and "Content Bounds." Now, it consistently uses "Content Bounds" and converts them to "Window Bounds" by adding extents (decoration sizes) when necessary; 10. Old work-arounds dating back to Ubuntu 16.04 with Compiz were removed. A simple manual test is also provided but I would prefer to move it's functionality to monkey tester: `java @build/run.args tests/manual/stage/TestStage.java ` List of fixed issues: 1. [[Linux] Stage.setMaximized() before show() does not persist](https://bugs.openjdk.org/browse/JDK-8316425) 2. [[Linux] Intermittent test failure in IconifyTest.canIconifyDecoratedStage](https://bugs.openjdk.org/browse/JDK-8316891) 3. [[Linux] Initial window position is not centered on Ubuntu 24.04 / Xorg](https://bugs.openjdk.org/browse/JDK-8337400) 4. [[Linux] Initial window position is not centered on Ubuntu 24.04 / Xorg](https://bugs.openjdk.org/browse/JDK-8337400) 11. [[Linux] Some of the SizeToSceneTest fail in Ubuntu 24.04](https://bugs.openjdk.org/browse/JDK-8353612) 12. [[Linux] View size glitch when resizing past max window size](https://bugs.openjdk.org/browse/JDK-8355073) The Xorg-related bugs were not issues within JavaFX itself, so they were addressed through workarounds - such as delaying the initial state and re-checking the geometry when the window is first mapped. **IMPORTANT**: While this is open for review, please allow me some time to further polish and test it before final approval. Feedback is welcome—especially regarding any need to disable the new tests on specific platforms, as some of them might fail. ------------- Commit messages: - [Linux] Simplify and update glass gtk backend: window sizing, positioning, and state management issues Changes: https://git.openjdk.org/jfx/pull/1789/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1789&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8354943 Stats: 3139 lines in 23 files changed: 2101 ins; 606 del; 432 mod Patch: https://git.openjdk.org/jfx/pull/1789.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1789/head:pull/1789 PR: https://git.openjdk.org/jfx/pull/1789
