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From Michael Rubin <mru...@thunderhead.com>
Subject Re: Event broadcasting and listening question
Date Thu, 12 May 2011 08:44:41 GMT
Thanks a lot for your response Jeremias. I have now done the following:

- Added 'void warnRevision3PermissionsIgnored(Object source);' (and its javadoc) to PDFEventProducer
in the org.apache.fop.render.pdf package and added a corresponding entry to the xml. Removed
the org.apache.fop.pdf.PDFEventProducer class and xml.
- Created org.apache.fop.pdf.PDFEventListener interface containing just 'void warnRevision3PermissionsIgnored(Object
- Created PDFLibraryEventAdaptor in the org.apache.fop.render.pdf package that extends the
PDFEventListener. (Currently just contains my new event. Should I also add the existing 2
render.pdf events to this class?)

  I can also see how to obtain the PDFDocument object from the
PDFEncryptionJCE class via the getDocumentSafely() method. But I am not sure how to get the
event broadcaster from that object. How is this done?



On 11/05/11 19:46, Jeremias Maerki wrote:
> Hi Michael
> Creating a new EventBroadcaster is obviously wrong. The idea is that the
> user can get events for each FOP rendering run separately (unlike
> logging where concurrent runs get mixed up). So you have to get hold of
> that EventBroadcaster applicable to the current rendering run. Obviously,
> you don't have access to the FOUserAgent in the PDF library. That is
> intentional because the PDF library should remain reasonably independent
> of as much FOP code as possible for the case that we ever factor it out
> into a separate component/module or move it to XML Graphics Commons.
> My suggestion is to follow a similar path as done in
> org.apache.fop.fonts: Create an interface for the events coming out of
> the PDF library (see FontEventListener). Let's call it PDFEventListener
> or something like that and put it in the org.apache.fop.pdf package.
> Then move your PDFEventProducer (corresponds to FontEventProducer) into
> org.apache.fop.render.pdf as this package makes the glue between FOP and
> PDF output. Then create a PDFLibraryEventAdapter (implements PDFEventListener)
> in the org.apache.fop.render.pdf package (corresponds to
> FontEventAdapter). The PDFLibraryEventAdapter will get the
> EventBroadcaster from the PDFDocumentHandler which is responsible for
> instantiating the PDFDocument and PDFLibraryEventAdapter. The adapter is
> then added as listener to a List<PDFEventListener>  that you can add to
> PDFDocument. From PDFEncryptionJCE you should have access to the
> PDFDocument via the getDocumentSafely() method. That nicely decouples
> FOP's event subsystem from the PDF library.
> On 11.05.2011 15:47:49 Michael Rubin wrote:
>> ?Hello there. I have been busy implementing 128 bit PDF encryption for FOP. I have
already got it working successfully but one issue remains that I have a question about.
>> In the org.apache.fop.pdf.PDFEncriptionJCE.init() method there is one place where
I want to broadcast an event message. I looked athttp://xmlgraphics.apache.org/fop/trunk/events.html
 to learn about events. However it just shows "EventBroadcaster broadcaster = [get it from
somewhere];" and doesn't show how I should be getting the broadcaster. After looking in the
code in the AFP package for existing examples I put together the following which seems to
work on testing:
>> FopFactory fopFactory = FopFactory.newInstance();
>> FOUserAgent agent = fopFactory.newFOUserAgent();
>> EventBroadcaster eventBroadcaster = agent.getEventBroadcaster();
>> PDFEventProducer eventProducer = PDFEventProducer.Provider.get(eventBroadcaster);
>> eventProducer.warnRevision3PermissionsIgnored(this);
>> This creates a new FopFactory, from which I create a new FOUserAgent, from which
I can get the event broadcaster to supply to my event producer. (I had to create a PDFEventProducer
which extends EventProducer. Plus PDFEventProducer.xml which contains the message mapping.)
>> In this case the EventBroadcaster will be created new every time so I am not sure
existing listeners will pick up. So is there a recommended way that I can get an existing
event broadcaster to use? Or is the above way the correct way to do it after all?
>> Version of FOP is v1.0. Platform is Ubuntu Linux, running from within the Eclipse
>> Thanks!
>> -Mike
>> Michael Rubin
>> Developer
>> T: +44 20 8238 7400
>> F: +44 20 8238 7401
>> mrubin@Thunderhead.com
>> The contents of this e-mail are intended for the named addressee only. It contains
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>> immediately and then destroy it.
> Jeremias Maerki

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