RFR: 8360498: [TEST_BUG] Some Mixing test continue to fail [v5]

[Khalid Boulanouare]

On Tue, 12 Aug 2025 16:34:39 GMT, Khalid Boulanouare <duke at openjdk.org> wrote:

>> test/jdk/java/awt/Mixing/AWT_Mixing/MixingPanelsResizing.java line 118:
>> 
>>> 116:                 jbutton.setForeground(jbColor);
>>> 117:                 jbutton.setBackground(jbColor);
>>> 118:                 jbutton.setOpaque(true);
>> 
>> This should be the default value, I mean Swing components are usually opaque unless it's changed by app developer or look and feel. For example, rounded corners may make the component non-opaque as the background in the rounded corners has to be painted by the parent component.
>
> I have removed the additional setOpaque code. I am doing the necessary tests.

It seems like for the default Look ad Feel (Aqua) of Macosx an extra `setOpaque(true)` is needed. If the test test/jdk/java/awt/Mixing/AWT_Mixing/MixingPanelsResizing.java uses metal look and feel, `setOpaque(true)` is not needed and the test passes.

I have updated the MR accordingly.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26625#discussion_r2279554425