Hi Tim,
I'm currently working on a display that does mouse dragging with
multiple layers. The solution for us was to extend BufferedMapBean and
ProjectionSupport and change how the projectionChanged() events get
propagated. We had to go against the OpenMap paradigm of having each
layer repaint itself independently, and instead made the map repaint
once after all layers finished processing the event. To do this, we made
our layers not call repaint() at the end of their projectionChanged()
method. Also, we extended ProjectionSupport and made it do
mapBean.setBufferDirty(true)
mapBean.repaint()
after it finished notifying all the layers. (This worked because none of
our layers start separate threads when handling projectionChanged(), and
because we made ProjectionSupport use a single background thread rather
than creating new ones).
I think this approach could be useful when layers generate their
graphics quickly and need to do animation, dragging, etc. There might be
a simpler solution though.
I haven't tried converting the ShapeLayer to this approach, but some of
our layers extend OMGraphicHandler and override its projectionChanged()
method so:
public void projectionChanged( ProjectionEvent e ) {
setProjection( e );
setList( prepare() );
}
Hope this helps,
-Ben
Ps. The reason we decided to go this route, was that, even though
BufferedMapBean provides an image buffer, a layer calling repaint() on
itself causes the buffer to be invalidated/regenerated. And lets say you
had 3 layers on the map. Each projectionChanged() event would result in
a total of 3 calls to repaint(), and each repaint() would cause all 3
layers to be repainted. Also, if any of the layers started their own
threads, then one layer might finish and call repaint() while another
layer is in the middle of generating its graphics, resulting in the
unfinished layer painting nothing for that repaint(). Even if you had
only one layer, I'm pretty sure the flicker could still occur during
dragging because a lot of projectionChanged() events would be generated
and the ProjectionSupport threads and the AWT event thread could
interrupt each other in unexpected ways (eg. a repaint() would occur in
the middle of a projectionChanged() event being handled).
Tim Schreiner wrote:
> Hello,
>
> I've got a .shp file layer in my OpenMap application and have replaced the
> default PanMouseMode class with one that basically allows the map to be
> dragged around in real time. (my mousedragged implementation calculates a
> new map center based on the new mouse position and calls
> map.setCenter(newCenter)).
>
> When I use the standard MapBean and do the dragging, the .shp layer is
> simple enough that it can be drawn quickly and everything looks good.
> Except! There is this annoying flashing.
>
> Traditional graphics systems, ala OpenGL, support the notion of double
> buffering to address this very problem.
>
> I noticed a BufferedMapBean and the documentation seem to advertise this
> does the buffering I want.
>
> I tried it, and unfortunately, it behaves rather badly, leaving behind
> copies of the last position of the shape file all over the screen.
>
> Has anyone successfully use the BufferedMapBean in a mouseDrag operation as
> I have described? Isn't this the situation you would normally use this
> class?
>
> Does this BufferedMapBean actually support 2 Images, rendering the "current"
> image in the back buffer and then flipping the back for the front as I would
> expect such a buffering scheme to do?
>
> Tim
>
>
> -----Original Message-----
> From: Tim Schreiner [mailto:tjs_at_ll.mit.edu]
> Sent: Wednesday, September 26, 2007 10:09 AM
> To: 'Don Dietrick'
> Cc: 'openmap-users_at_bbn.com'
> Subject: RE: [OpenMap Users] How to see RpfCoverage
>
> Don,
>
> I assume this is the RPF "coverage" property.
> I don't see the coverage(s) when I zoom way out. How come?
>
> Tim
>
>
> -----Original Message-----
> From: owner-openmap-users_at_bbn.com [mailto:owner-openmap-users_at_bbn.com] On
> Behalf Of Don Dietrick
> Sent: Thursday, September 20, 2007 12:51 PM
> To: Tim Schreiner
> Cc: openmap-users_at_bbn.com
> Subject: Re: [OpenMap Users] How to see RpfCoverage
>
> Hi Tim,
>
>
> The RpfCoverage object is built into the layer. You turn it with a
> checkbox on via the layer's palette.
>
> - Don
>
> On Sep 20, 2007, at 12:28 PM, Tim Schreiner wrote:
>
>
>> I have some rpf data that I can view quite nicely when I'm zoomed
>> in on the data. It's a CIB data file. When I zoom way out on the
>> entire globe, I'd like to draw some form of outline of the coverage
>> on my map. I tried using RpfCoverage to do this, feeding it my rpf
>> layer, but I don't see anything on the map. What do I need to do to
>> see the RpfCoverage data?
>>
>>
>>
>> Currently I am doing this, in my drawing code:
>>
>>
>>
>> . /// if s_Layers[i] is a RpfLayer
>>
>> RpfCoverage r = new RpfCoverage(s_Layers[i]);
>>
>> r.allCoveragesOn();
>>
>> r.generate(this.getProjection());
>>
>> r.paint(this.getGraphics());
>>
>>
>>
>> Tim
>>
>>
>>
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> Don Dietrick, dietrick_at_bbn.com
> BBN Technologies, Cambridge MA
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
>
>
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Received on Wed Sep 26 2007 - 17:45:43 EDT