RFR: 8226990: GTK & Nimbus LAF: Tabbed pane's background color is not expected one when change the opaque checkbox. [v3]

[Tejesh R]

On Thu, 15 Feb 2024 09:17:34 GMT, Abhishek Kumar <abhiscxk at openjdk.org> wrote:

>> JTabbedPane's content area, tab area and tab background color are not as expected when opaque is set to true or false. 
>> The proposed fix is to handle the TabbedPane's background color in installed LAFs. Manual test is added to support the fix and there is no regression caused by the fix. 
>> 
>> Proposed fix is tested in Ubuntu 22.04 and Oracle linux.
>> 
>> CI link is posted in JBS.
>
> Abhishek Kumar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove WindowsLAF check

src/java.desktop/share/classes/javax/swing/plaf/synth/SynthTabbedPaneUI.java line 679:

> 677:     private Color getUnselectedBackgroundAt(int index) {
> 678:         Color color = tabPane.getBackgroundAt(index);
> 679:         if (color instanceof UIResource) {

Both condition statements can be combined.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17720#discussion_r1498653039