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

[Prasanta Sadhukhan]

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..

getStyle().getFont() returns null as "getFontForState(context)" returns null which is because synth state for floating toolbar is invalid which is 0x201
getStyle().getFont()" and "tabPane.getFont()" in normal valid case returns same font which is javax.swing.plaf.FontUIResource[family=SansSerif,name=sansserif,style=plain,size=12]

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