RFR: 8359428: Test 'javax/swing/JTabbedPane/bug4499556.java' failed because after selecting one of L&F items, the test case automatically failed when clicking on L&F Menu button again

[lawrence.andrews]

On Mon, 16 Jun 2025 09:21:24 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> It is seen that this test (which was opensourced in [JDK-8353304](https://bugs.openjdk.org/browse/JDK-8353304)) when run with NimbusLookAndFeel, after selecting one of L&F items, the test case automatically failed when clicking on L&F Menu button again.
> It is because while switching to another L&F say platform(WindowsL&F) from Metal/Nimbus LookAndFeel, if testcase was originally run in Nimbus L&F, `SynthMenuItemLayoutHelper()` calls `MenuItemLayoutHelper.reset`  where `style.getFont(context) `return null font so when it calls `getFontMetrics(font)` it calls `font.hashCode `which fails with 
> 
>> Execution failed: `main' threw exception: java.lang.NullPointerException: Cannot invoke "java.awt.Font.hashCode()" because "font" is null 
> 
> This is happening because the test calls `SwingUtilities.updateComponentTreeUI `on tabbedpane.
> So, when L&F is changed inside the test  via "L&F Menu" option 1st time say Metal to Platform, it changes the L&F of the tabbed pane to Windows L&F, but not for the "L&F Menu" font itself which is still in Nimbus L&F, but style context is reset so when next time "L&F Menu" is clicked to change the L&F,  SynthMenuItemLayoutHelper gets null font from invalid context and then it crashes.
> Fix is to ensure the `updateComponentTreeUI `should be for entire frame which consists of "L&F Menu" and the tabs so L&F is changed consistently for all nodes.

LGTM

-------------

PR Comment: https://git.openjdk.org/jdk/pull/25822#issuecomment-2977567753