RFR: 6510914: JScrollBar.getMinimumSize() breaks the contract of JComponent.setMinimumSize() [v6]

[Alexey Ivanov]

On Wed, 8 Nov 2023 05:06:14 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> Although there seems to be no difference in rendering the scrollbars with and without these getXXX methods as can be seen here (top one without, bottom one with the methods),

I guess it's expected because `LayoutManager` usually tries to satisfy the preferred size. In this case, each scroll bar gets its preferred size.

As soon as you start resizing, the differences become apparent: sizing behaviour is different… because after you remove the overridden `getMinimumSize` and `getMaximumSize` methods, the minimum and maximum sizes of the scroll bar change.

> I could see difference in behaviour when the frame is resized and since the premise of the fix is there should not be any difference in behaviour if these methods are removed, I agree that removing the methods as is done in this PR may not be appropriate

As soon as you start resizing, the differences become apparent: sizing behaviour is different… because after you remove the overridden `getMinimumSize` and `getMaximumSize` methods, the minimum and maximum sizes of the scroll bar changes.

> but I also think adding setXXX methods in JScrollBar class just to clarify existing spec may also not be appropriate. In this light, can we consider the previous iteration of the [spec clarification](https://openjdk.github.io/cr/?repo=jdk&pr=15325&range=03#sdiff-0-src/java.desktop/share/classes/javax/swing/JScrollBar.java)

Why not? The previous iteration just adds an additional note to `getXXX` methods — the problem with `setXXX` persists, the methods are inherited from `JComponent` and their specification states, “Subsequent calls to `getMinimumSize` *will always return this value*” [the one passed to `setMinimumSize`], which does not hold.

https://github.com/openjdk/jdk/blob/a95062b39a431b4937ab6e9e73de4d2b8ea1ac49/src/java.desktop/share/classes/javax/swing/JComponent.java#L1782-L1784

I propose overriding `setMinimumSize` and `setMaximumSize` and amend their specification to align with the current implementation of `get{Min,Max}Size`. Otherwise, the contract of `set{Min,Max}Size` will still be broken, no matter how many additional warnings we add to their `get-` counterparts.

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PR Comment: https://git.openjdk.org/jdk/pull/15325#issuecomment-1804640197