8171898: [WebView] ScrollBarWidget thickness calculation is not correct

[arun-Joseph]

ScrollbarThemeJava delegates scrollbar thickness calculation to ScrollBarWidget::initializeThickness() [ScrollBarWidget.java] method. Since "ScrollbarThemeJava::scrollbarThickness" is not associated with any "ScrollBarWidget" instance, some workaround was made using special "ScrollBarWidget" instance named testRef.

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Progress

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Issue

• JDK-8171898: [WebView] ScrollBarWidget thickness calculation is not correct

Download

$ git fetch https://git.openjdk.java.net/jfx pull/197/head:pull/197
$ git checkout pull/197

[bridgekeeper]

👋 Welcome back ajoseph! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request.

[mlbridge]

Webrevs

• 00: Full (dac0b46)

[kevinrushforth]

/reviewers 2

[openjdk]

@kevinrushforth
The number of required reviews for this PR is now set to 2 (with at least 1 of role reviewers).

[kevinrushforth]

While this might be the right fix, I don't think the evaluation is right. In particular, this doesn't look related to JDK-8157900. That refactoring fix was behavior neutral in terms of the object graph -- it uses an accessor pattern rather than the removed public impl_ methods for encapsulation, but intentionally didn't change anything related to which instance of which objects are used. That fix was not backported to 8u and yet this bug is listed as affecting 8u.

So, what I'd like to see in the evaluation is a description of the root cause, and a brief explanation of the fix.

Can you also provide a test case that fails without the fix and passes with the fix? I don't see one in JBS that you can leverage, so you may need to create one.

[arun-Joseph]

This PR aims at modifying initializeThickness() to not use testSBRef and so, doesn't change the behavior of ScrollBarWidget. As it's not a bug, test case can't be created.

[kevinrushforth]

If it is not a bug, then why should we fix it?