[icedtea-web] RFC: fix null dtd for swing applications rendering html

[Deepak Bhole]

* Omair Majid <omajid at redhat.com> [2010-10-26 16:57]:
> Hi Deepak,
> 
> Thanks for taking a look at this!
> 
> On 10/26/2010 04:33 PM, Deepak Bhole wrote:
> >* Omair Majid<omajid at redhat.com>  [2010-10-26 15:46]:
> >>There has been a regression in netx: applications that render html
> >>(using Swing components) now fail with a null pointer exception.
> >>This problem can be reproduced by running the program at [1].
> >>
> >
> >What caused this regression? I thought all the app context stuff was
> >still disabled, with just the support added on the side?
> >
> 
> The regression itself was caused by having security dialogs in one
> AppContext and the actual application in another AppContext.
> 
> The AppContext stuff is enabled and working (in fact, some of the
> AppContext code was part of the original import of Netx into IcedTea
> and has been active ever since - most of my recent patches are about
> enabling it in the plugin case too and using AppContext correctly to
> gain its benefits). It is what allows multiple applets to have their
> own look and feels and allows security dialogs to always use the
> system look and feel without setting the look and feel of applets
> (or jnlp applications) too. I thought I had made it pretty explicit
> in my patches and changelogs :(
> 
> What is still disabled is allowing applets/applications to access
> their individual EventQueues. This is because of a security patch
> that has been recently been committed to OpenJDK7. This patch
> provides some additional API and says (and I am paraphrasing): "here
> is some API that allows the proprietary plugin to check if AWT
> events are generated by the system". I dont know how to make use of
> it, so I havent added code to allow applets to access their
> EventQueues. At least one application - a swing demo, no less [1] -
> fails without this.
> 

Ah sorry, my bad. I thought all of it was disabled -- I remember you
mentioning this now -- that only EventQueue access is disabled.

Thanks for the clarification!

Cheers,
Deepak

> >>The problem is caused by how HTMLEditorKit/HTMLDocument and
> >>ParserDelgator interact in the presence of multiple AppContexts. The
> >>instance of the ParserDelegate is shared between multiple
> >>HTMLEditorKit in different AppContexts. However, ParserDelegate
> >>maintains a per-AppContext dtd instance. The dtd is valid in the
> >>AppContext that created the ParserDelegate but null in all other
> >>AppContexts. Using this null dtd throws a NullPointerException. This
> >>is really a bug in OpenJDK6 rather than Netx. Fortunately, this bug
> >>has been fixed in OpenJDK7 - ParserDelegate maintains an instance of
> >>the dtd per runtime instead of per AppContext.
> >>
> >>The attached patch works around this bug. It manually creates a
> >>ParserDelegate for each AppContext to avoid this problem.
> >>
> >
> >Assuming you have tested this, OK for head.
> >
> 
> Thanks
> Omair
> 
> [1] http://download.oracle.com/javase/tutorial/ui/overview/demo.html