<Swing Dev> Patch for NPE at javax.swing.plaf.basic.BasicTreeUI$Actions.page:4470

[Jaroslav Tulach]

Hello Alexander,
thanks for your reply. The source code for NetBeans TreeView component is 
available here:
http://hg.netbeans.org/main-
golden/file/ccea2dfe47eb/openide.explorer/src/org/openide/explorer/view/TreeView.java
I'll be glad for any review, however I am also positively pleased by your 
answer:

>      The ui.getPathBounds(tree, newPath) method definitely can return
> null so it needs to have this check.

Should I start working on a webrev, so (in case you don't find any violation of 
good Swing practices in TreeView) we can eliminate this NPE once and forever?

What should be part of such webrev? Just the NPE check? Or do you want some 
test, change in documentation, etc.?

Thanks again for your comments.
-jt


Dne Pá 16. listopadu 2012 15:30:00, Alexander Scherbatiy napsal(a):
> On 11/15/2012 7:58 PM, Jaroslav Tulach wrote:
> > Dear Swing maintainers,
> > my name is Jaroslav Tulach and I am maintaining NetBeans explorer - a
> > component that is using JTree heavily.
> > 
> > > From time to time I receive a user report with a NPE from Swing where
> > > little> 
> > or even no NetBeans code involved. Just today I got
> > http://netbeans.org/bugzilla/show_bug.cgi?id=222081
> > We have about 35 other ones (which is not that much given the fact we have
> > million of users), but still...
> > 
> > According to
> > http://statistics.netbeans.org/exceptions/exception.do?id=628832
> > the report comes from jdk7u9-b05. The source code is here
> > http://hg.openjdk.java.net/jdk7u/jdk7u/jdk/file/jdk7u9-
> > b05/src/share/classes/javax/swing/plaf/basic/BasicTreeUI.java
> > and thus it looks like the call on line 4468 to
> > 
> > ui.getPathBounds(tree, newPath);
> > 
> > can return null (under some rare and unknown circumstances).
> > 
> > I can close the bug #222081 as "worksforme", but it is clear that such
> > error happens from time to time and we don't want our users to face
> > errors. A simple:
> > 
> > 4469 if (newRect == null) return;
> > 
> > would do the trick. One question remains: if I try to donate such patch,
> > will you accept it?
> 
>      The ui.getPathBounds(tree, newPath) method definitely can return
> null so it needs to have this check.
>      However, such fix can mask the real issue, for example, in the
> treeState.getBounds() method where the  treeState can be instance of
> FixedHeightLayoutCache or VariableHeightLayoutCache class.
> 
>      If it is possible, could you send a code snippet that shows how
> NetBeans uses JTree? May be it can give a hint what can be wrong in this
> case.
> 
>      Thanks,
>      Alexandr.
> 
> > -jt