RFR: 8318590: JButton ignores margin when painting HTML text

[Damon Nguyen]

On Wed, 29 Nov 2023 19:08:15 GMT, Phil Race <prr at openjdk.org> wrote:

>> The initial issue was a padding issue for JButton when HTML content was set as the button's text. [JDK-8282772](https://bugs.openjdk.org/browse/JDK-8282772), [JDK-8015854](https://bugs.openjdk.org/browse/JDK-8015854), and [JDK-8302173](https://bugs.openjdk.org/browse/JDK-8302173) are the issues related to the fix. The initial bug report was for Metal L&F, since it has a drastically different button margin from the rest (2, 14, 2, 14). This left and right margin of 14px led to the initial bug report. However, it was determined that the issue was not an issue, and instead, a problem with the reporter's implementation since they weren't aware of the difference in Metal's button margins versus other L&Fs.
>> 
>> This PR reverts these changes since it was determined in [this PR](https://github.com/JFormDesigner/FlatLaf/issues/746) that the fix causes a new issue regarding JButton contents' positioning. In addition, a new line is added to BasicLookAndFeel (since Metal derives its default button margin here) to better document the difference in button margins compared to other L&Fs.
>
> src/java.desktop/share/classes/javax/swing/plaf/basic/BasicLookAndFeel.java line 464:
> 
>> 462:      * <p>
>> 463:      * The default button margin value is (2, 14, 2, 14), which may
>> 464:      * greatly differ from other LookAndFeel defaults.
> 
> This will need a CSR, which is fine.
> But
> (1) Basic is an abstract L&F .. it can't be the place to say what Metal does since most L&Fs derive from Basic
> And something about a JButton ought to be closer to ButtonUI or JButton.
> (2) Do we have precedent for calling out the exact number of (user space) pixels ?
> I'd prefer some more waffly wording like 
> "The default margins may vary greatly depending on the L&F".

For (1), I've considered some alternative spots for this note. MetalButtonUI and MetalLookAndFeel for example, but I didn't see any natural spot to add this to. I decided to put it in BasicLookAndFeel since the default value is set here, but I see your point. I can add an additional note in the doc for, say, MetalButtonUI if preferred.

In (2), you're right that there's no explicit pixel count for anything. I'll update this to be more general. Do you think this additional note is enough to avoid adding more doc changes to Metal classes?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16869#discussion_r1409791948