RFR: 6521141: DebugGraphics NPE @ setFont(); [v5]

[Phil Race]

On Fri, 29 Jul 2022 14:24:34 GMT, Tejesh R <tr at openjdk.org> wrote:

>> `DebugGraphics` class has a Graphics instance which is been used in slowed down drawing. The `graphics` object is not initialized anywhere inside the class, where it is expected to set explicitly by the user. When the user doesn't set it and try to use the any mehtods like `drawing/setFont`, NPE is raised which is expected. The scenario is taken care by checking if the `graphics` object is null before using it inside the class, thus eliminating the NPE case.
>
> Tejesh R has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix: Java doc modified and Graphics contexts created in null case

src/java.desktop/share/classes/javax/swing/DebugGraphics.java line 87:

> 85:         //  directly.
> 86:         StackWalker walker = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE);
> 87:         if ((graphics == null) && (walker.getCallerClass() != this.getClass())) {

I don't know if creating a StackWalker is expensive but I think it should be done only if graphics == null

Also the version of getInstance() being called here might throw SecurityException
https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/StackWalker.html#getInstance(java.lang.StackWalker.Option)

So you'll need to wrap it in a doPrivileged.

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PR: https://git.openjdk.org/jdk/pull/9673