[External] : Re: JDK-8199934: ScrollPaneSkin incorrectly lays out its scrollbars

[Andy Goryachev]

I think your diagnosis is right though: sometimes the layout is not triggered when a property is changed,
the recent bug like that is


JDK-8307117<https://bugs.openjdk.org/browse/JDK-8307117> TextArea: wrapText property ignored when changing font

I wonder if some kind of a generic unit test could be developed to identify such cases.

-andy


From: Nir Lisker <nlisker at gmail.com>
Date: Monday, May 1, 2023 at 13:09
To: Andy Goryachev <andy.goryachev at oracle.com>
Cc: openjfx-dev <openjfx-dev at openjdk.org>
Subject: [External] : Re: JDK-8199934: ScrollPaneSkin incorrectly lays out its scrollbars
If I knew what the fix was I would have. Right now I'm not sure anymore what the correct behavior should be even.

On Mon, May 1, 2023 at 10:44 PM Andy Goryachev <andy.goryachev at oracle.com<mailto:andy.goryachev at oracle.com>> wrote:
Nir, would you like to submit a pull request?

Thank you
-andy

From: openjfx-dev <openjfx-dev-retn at openjdk.org<mailto:openjfx-dev-retn at openjdk.org>> on behalf of Nir Lisker <nlisker at gmail.com<mailto:nlisker at gmail.com>>
Date: Sunday, April 30, 2023 at 10:04
To: openjfx-dev <openjfx-dev at openjdk.org<mailto:openjfx-dev at openjdk.org>>
Subject: JDK-8199934: ScrollPaneSkin incorrectly lays out its scrollbars
Hi,

I took a quick jab at this issue [1]. Using the reproducer in the ticket, launch and resize the stage vertically so that the buttons at the bottom are only partially visible.

The current behavior is as follows:
When the scrollbar is not needed, toggling to the AS_NEEDED policy reallocates the scrollbar space for the buttons (they move up).
When the scrollbar is needed, toggling to the AS_NEEDED policy still reallocates space, and the scrollbar takes away space from the content node. This is wrong.

I modified the method 'computeHsbSizeHint' to

private double computeHsbSizeHint(ScrollPane sp) {
    return determineHorizontalSBVisible() ? hsb.prefHeight(ScrollBar.USE_COMPUTED_SIZE) : 0;
}

Now the policy toggling behavior is correct both when the scrollbar is needed and when it's not - the space is reallocated not at the expense of the content. However, enlarging the stage horizontally while AS_NEEDED is selected does not reallocate the space (you need to toggle the policies). I'm guessing there's a missing call to layoutChildren during this resizing.

Does anyone have any input here?

Thanks,
Nir

[1] https://bugs.openjdk.org/browse/JDK-8199934

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