RFR: 8354943: [Linux] Simplify and update glass gtk backend: window sizing, positioning, and state management issues [v66]

[Lukasz Kostyra]

On Sat, 27 Sep 2025 12:31:19 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> This is a continuation to [JDK-8236651](https://bugs.openjdk.org/browse/JDK-8236651) and it aims to stabilize the linux glass gtk backend.
>> 
>> This is a refactor of the Glass GTK implementation, primarily focused on window size, positioning, and state management to resolve numerous issues.
>> 
>> The main change is that GtkWindow (which is a GtkWidget) has been replaced with a direct use of GdkWindow for windows. This makes sense because GTK includes its own rendering pipeline, whereas JavaFX renders directly to the underlying system window (such as the X11 window) via Prism ES2 using GL and GLX. Most GTK window-related calls have equivalent GDK calls. Since GDK serves as an abstraction over the system window and input events, it aligns better with the purposes of Glass. Additionally, using GTK required various workarounds to integrate with Glass, which are no longer necessary when using GDK directly.
>> 
>> It uses a simple C++ Observable to notify the Java side about changes. This approach is more straightforward, as notifications occur at many points and the previous implementation was becoming cluttered.
>> 
>> Previously, there were three separate context classes, two of which were used for Java Web Start and Applets. These have now been unified, as they are no longer required.
>> 
>> Many tests were added to ensure everything is working correctly. I noticed that some tests produced different results depending on the StageStyle, so they now use @ParameterizedTest to vary the StageStyle.
>> 
>> A manual test is also provided. I did not use MonkeyTester for this, as it was quicker to simply run and test manually:`java @build/run.args tests/manual/stage/TestStage.java `
>> 
>> While this is focused on XWayland, everything works on pure Xorg as well.
>
> Thiago Milczarek Sayao has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 80 commits:
> 
>  - Merge branch 'master' into 8354943
>  - Fix copyright header
>  - Revert "8367898: Skip StageFocusTest on Linux"
>    
>    This reverts commit c95cdcdc9cd8b3070e8076ea91234772d6a21331.
>  - Merge branch 'master' into 8354943
>  - Remove unused imports
>  - - Fix StageOwnershipTest label + minor adjustments
>  - Merge branch 'master' into 8354943
>  - Merge branch 'master' into 8354943
>  - - Fix scene resize when window is unresizable
>  - - Fix "Incomplete attachment. (GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT)(FBO - 820)" when changing view
>  - ... and 70 more: https://git.openjdk.org/jfx/compare/c480b462...eb613f8a

Looks good. A nice refresh and simplification of the GTK side of JavaFX.

With #1870 all tests work well on both Linux and Windows.

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Marked as reviewed by lkostyra (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1789#pullrequestreview-3298808482