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From George Armhold <armh...@cs.rutgers.edu>
Subject Re: queston on Interactor and Overlay
Date Thu, 04 Sep 2003 13:15:36 GMT
First of all, thanks for the very speedy response!

Thomas DeWeese wrote:

>     Interactors are intended to be used for modal interaction.  If
> you aren't interested in being modal you can use normal AWT event
> stuff.

Sorry to be obtuse, but what exactly do you mean by "modal
interaction"?  Here's what we are doing currently:

We allow the user to draw simple lines using the mouse.  From
MousePressed, through MouseDragged, and until MouseReleased we
implement this as AWT Graphics2D drawing (for speed.)  Once we see
MouseReleased, we take all the collected mouse movements and turn
these into SVG <line> elements which are then added to the DOM.  In
addition to this, we would also like to allow the user to click on
embedded URLs in the document, and then launch an external browser in
response to this.  We found that if we ignore "right button" mouse
clicks in our drawing code this allows the event to get passed onto
our LinkActivationListener.  So the user needs to click the right
button to click URLs.  This works for us, but I am curious how one
would "share" events among many Interactors if there were ever such a
need.


>> 2) When my LinkActivationListener launches an external browser in
>>    response to a URL click, why afterwards does the
>>    JSVGComponent.getUpdateManager() always return null?  I am setting
>>    my document state to ALWAYS_DYNAMIC in the constructor, and it
>>    seems to work fine until I launch the external browser.
> 
>
> I'm guessing some of the normal link handling code is still being
> called (you can hyperlink between SVG documents in the Canvas) and
> this code is, as it's first step, shutting down the UpdateManager,
> your code must head off the replacement of the document however.
> This may represent a bug in the canvas or your code.

Well the external browser launch is pretty simple (I use JNLP's
BasicService.showDocument()).  It returns quickly and successfully.
However after that point getUpdateManager() forever returns null.
Maybe I need to launch the external browser in a specific thread?


>> 3) Is there any advantage to implementing Interactor vs Overlay for
>>    creating a "drawing tool" on top of JSVGComponent?  It seems that
>>    you must implement Interactor in order to see the events, and that
>>    Overlay is merely a matter of painting (which you can easily do
>>    without implementing that interface- just grab the component's
>>    Graphics2D and paint away.)  I notice that some of the batik
>>    examples implement both (e.g. AbstractZoomInteractor, which extends
>>    InteractorAdaptor, but also implements Overlay via an enclosed
>>    class.)
> 
> 
> I would not recomend grabbing the component's Graphics2D and
> painting.  This will likely lead to poor behaviour if the area of
> document drawn on is updated due to events, etc.  

Maybe I didn't describe very well what I was doing.  This is just
transient drawing in response to mouse drags.  Once the mouse is
released the AWT drawing done previously is no longer needed as I
convert the generated line segments into SVG <line> elements, which
are then added to the DOM.  It's really not that different from what's
being done in AbstractZoomInteractor- when MouseEvents come in the
overlay's paint() method is called directly on the component's
Graphics2D.

> If you use the overlay interface your code will be called when ever
> the area it covers is repainted due to update events.  Try this
> select some 'animated' text (I like to select the 'batik rules' in
> samples/extensions/gears.svg).

Since the drawing is transient, no persistent updates are needed.

Thanks again for your wisdom!




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