RFR: 7169951: SwingSet2 throws NullPointerException with Nimbus L&F

[Jayathirth D V]

On Fri, 13 Jan 2023 04:25:59 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> It is observed that if SwingSet2 is run in Nimbus L&F and
> we drag the icon tool bar (which is floatable) out of the GUI Window
> and  Once the tool bar is detached, click on "Look & Feel" menu option to change to any L&F (say Java L&F)
> it causes NPE due to font being null when getFontMetrics() is called
> 
> In other L&F, it uses the tabPane's [font ](https://github.com/openjdk/jdk/blob/master/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicTabbedPaneUI.java#L2177) whereas in Nimbus font is obtained from getStyle().getFont() which returns null when toolbar is detached from the main window.
> The proposed fix is to get tabPane's font if the font passed is null alike other L&Fs. 
> 
> No regression test is made as it can be verified with SwingSet2..

Marked as reviewed by jdv (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/11984