RFR: 8354943: [Linux] Simplify and update glass gtk backend: window sizing, positioning, and state management issues [v50]

[Thiago Milczarek Sayao]

On Thu, 14 Aug 2025 15:33:13 GMT, Martin Fox <mfox at openjdk.org> wrote:

>> tests/system/src/test/java/test/javafx/stage/CenterOnScreenTest.java line 108:
>> 
>>> 106:     }
>>> 107: 
>>> 108:     private void assertStageCentered(StageStyle stageStyle, boolean useSceneSize) {
>> 
>> On Windows the size of a DECORATED or EXTENDED window includes an area around the window containing the invisible drag handles. After sizeToScene is called on my Windows 11 system a DECORATED or EXTENDED window will be 26 units wider than the scene to account for these handles (on my Mac the window will be the same width as the scene).
>> 
>> In this test you use a hefty delta for DECORATED windows and a smaller one for EXTENDED and you use the same delta for both width and height. This is causing the centerOnScreenAfterShownWithSceneSize and centerOnScreenWhenShownWithSceneSize test to fail along the X axis for EXTENDED stages since the delta isn't big enough.
>> 
>> You might consider querying the stage for it's frame and ensure that the center of the frame is where you expect it rather than make any assumptions about how the scene width relates to the window width.
>
> The test still looks incorrect. You're passing in posX and posY as the tolerance deltas.
> 
> I'm not sure what you're testing here. There's an internal algorithm that sets the window's x and y coordinate to center it. You're replicating that algorithm here and testing whether the window has the same x and y values. If you're concerned that the platform code didn't actually move the window you would need to use a robot to sample a pixel and verify that the window is where you expect. Or was there some other centering problem you saw on Linux?

On Linux, when frame extents are received (and it might arrive later depending on the compositor / window manager), it must do a correction on the centering accounting the decorations (glass_window.cpp around line 895).  This was the idea behind the test, but I think I  "over tested" and this is really not useful. Will remove it.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1789#discussion_r2294785923