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

[Dr Andrew John Hughes]

On 16:57 Tue 26 Oct     , Omair Majid wrote:
> 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.
> 

Do you have a link to this patch?  We should probably backport it.

> >> 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

-- 
Andrew :)

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Red Hat, Inc. (http://www.redhat.com)

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