Yeah, this is exactly what I was trying to do. Unfortunately, Dan is right with regards to the setProjection() call as far as I can tell... some layers won't work properly because the projection is stored as a class variable in the layer and not passed by reference around to the various functions that use the projection. I haven't been able to actually verify this would break layers, but I assume it would, and since I'm working on a generic component, I can't take a chance.
As a workaround, I made some changes to ImageServer, with the modified version attached. It seems to work for me, although there's probably a chance that I'm fouling things up in a way that I don't understand.
Essentially, before rendering each layer I save a copy of the projection using getProjection(), and then after rendering, I set the projection back using projectionChanged(). I originally tried to do this using setProjection(), but this did not actually cause the layer to repaint.
You could also do this outside of ImageServer using the same method, storing and re-setting the projection, so if there's a reason why this would mess up ImageServer I would think it would be reasonable to do it the same way in user-space.
Code changes are below and attached. Hope this helps someone.
-Brian
(In file ImageServer.java, function byte[] createImage(Projection, int, int, int)
BEFORE:
for (int i = layers.length - 1; i >= 0; i--) {
if ((includedLayerMask & (0x00000001 << i)) != 0) {
if (Debug.debugging("imageserver")) {
Debug.output("ImageServer: image request adding layer graphics from : "
+ layers[i].getName());
}
layers[i].renderDataForProjection(proj, graphics);
} else {
if (Debug.debugging("imageserver")) {
Debug.output("ImageServer: skipping layer graphics from : "
+ layers[i].getName());
}
}
}
AFTER:
Projection tempProj; //temp projection storage
for (int i = layers.length - 1; i >= 0; i--) {
if ((includedLayerMask & (0x00000001 << i)) != 0) {
if (Debug.debugging("imageserver")) {
Debug.output("ImageServer: image request adding layer graphics from : "
+ layers[i].getName());
}
tempProj = layers[i].getProjection(); //store existing projection
layers[i].renderDataForProjection(proj, graphics);
layers[i].projectionChanged(new ProjectionEvent(this, tempProj)); //set projection back
} else {
if (Debug.debugging("imageserver")) {
Debug.output("ImageServer: skipping layer graphics from : "
+ layers[i].getName());
}
}
}
-----Original Message-----
From: Hudson Brian R Contr AFRL/IFSF [mailto:Brian.Hudson_at_rl.af.mil]
Sent: Friday, September 24, 2004 4:14 PM
To: Sperlongano Brian M NPRI
Subject: RE: [OpenMap Users] Possible bug in Layer subclasses
Hey,
I was trying to host a ImageServer off of the same layers that were visible in a MapBean and had the same problems.
Once someone would start sending requests to the ImageServer the layers on the MpaBean would go haywire.
I had to have this working in a very short amount of time so I made it so those layers served to ImageServer clients were separate from those layers being shown on the MapBean. This solution is far from ideal (doubles the memory more or less)/
I'd like to see this problem resolved as well.
Brian Hudson
-----Original Message-----
From: owner-openmap-users_at_bbn.com [mailto:owner-openmap-users_at_bbn.com] On Behalf Of Sperlongano Brian M NPRI
Sent: Friday, September 24, 2004 3:35 PM
To: 'openmap-users_at_bbn.com'
Subject: [OpenMap Users] Possible bug in Layer subclasses
Hello all,
I believe I have found a bug in the way layer rendering is implemented. I was using the ImageServer class to generate off-screen images for printing, and what I discovered was that the way ImageServer works is to call the renderDataForProjection() method on each of a set of layers onto a Graphics object.
One of the things that these implementations do (at least for OMGraphicHandlerLayer and GraticuleLayer, probably all of them) is to set the passed in projection as the new projection.
As an example of this, here is a clip from OMGraphicHandlerLayer:
public synchronized void renderDataForProjection(Projection proj, Graphics g) {
if (proj == null) {
Debug.error("Layer(" + getName() +
").renderDataForProjection: null projection!");
return;
} else if (!proj.equals(getProjection())) {
setProjection(proj.makeClone());
setList(prepare());
}
paint(g);
}
Note the line that says "setProjection(proj.makeClone())".
Now, if were were only using the layers on a MapBean, this would be fine. The problem comes when we use existing layers to render to projections other than the ones on the current map. Thus, say I have a 200x200 MapBean, but I wish to (off-screen) render a 400x400 version of the same map. I would create a Projection object with those parameters, and then pass it through renderDataForProjection. The Layer would then render my 400x400 map no problem. However, it would also store my 400x400 projection as the current projection. This results in display artifacts being shown in the container containing the MapBean.
It seems to me that the offending setProjection() lines should be removed. I commented out those lines in the layers I use and the bug seems to go away AND the map seemed to function all the same.
The other option would be to make sure that any class that used Layer in this manner (such as ImageServer) be modified to save the current Projection, render, and the set the old projection back, but this is clearly a less-desireable solution.
-Brian
Brian Sperlongano
Computer Engineer
NUWCDIVNPT
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Received on Mon Sep 27 2004 - 10:32:25 EDT