[Mapserver-users] mapscript - strange behavior

[Sean Gillies]

On Jan 13, 2004, at 10:38 AM, Christoph Spoerri wrote:

> Hi there,
>
> I'm writing an application that let's user add point features to the  
> map by
> clicking on any location of the map. For this purpose I'm using the  
> attached
> code (Note: each click on the map results in a request to the server  
> for a
> new image).
>
> The problem is that the first point (to be mapped) is not displayed on  
> the
> map. Yet when the user clicks on the map for the second time (to add a  
> new
> point) both points show up. When checking the .map files everything  
> looks
> fine: acetate layer is there, class definition looks fine and point
> coordinates are there.
>
> In case a predefine the acetate layer (w/ class def) in the base .map  
> file,
> the first point shows up just fine. Note: this solution is not an  
> option
> thought :(
>
> any ideas? Thanks in advance,
> Christoph
>
>
> *********** code ********************
>
> 	x = atof(param['x'])
> 	y = atof(param['y'])
> 	# create point object
>  	ptCoord = getMapPoint([x,y],self._map)
>  	ptObj = pointObj()
>  	ptObj.x=ptCoord[0]
>  	ptObj.y=ptCoord[1]
> 	lnObj = lineObj()
> 	lnObj.add(ptObj)
>
> 	# create new point layer with class and add shape
> 	mapImg=self._map.prepareImage()
> 		lyrAcetate = self._map.getLayerByName('acetate')
> 	if (not isinstance(lyrAcetate,layerObj)):
> 		color = colorObj()
> 		color.red = 255
> 		color.green = 255
> 		color.blue = 255
> 		lyrAcetate = layerObj(self._map)
> 		lyrAcetate.name = "acetate"
> 		lyrAcetate.type = MS_LAYER_POINT
> 		classTemp = classObj(lyrAcetate)
> 		styl = styleObj()
> 		styl.symbolname = "pin"
> 		styl.size = 1
> 		styl.maxsize = 1
> 		styl.minsize = 1
> 		styl.color = color
> 		styl.backgroundcolor = color
> 		styl.outlinecolor = color
> 		classTemp.numstyles=1
> 		classTemp.styles = styl
>
> 	# create shape object and add point to shape object
> 	shpObj = shapeObj(MS_SHAPE_POINT)
> 	shpObj.add(lnObj)
> 	shpObj.setBounds();
> 	shpObj.index = 1
>
> 	lyrAcetate.status = MS_ON
> 	lyrAcetate.addFeature(shpObj)
> 	lyrAcetate.draw(self._map,mapImg)
>
> 	imagename =   \
> self._map.name+mapSession.id()+"_"+str(int(time()))+"."+mapImg.format.e 
> xtension
> 	mapImg.save(mapImg.imagepath+imagename)
>

Christoph,

Do I remember correctly that you are using mod_python?  Is this a reason
why you say that you cannot predefine your acetate layer?  I hope you  
are
not trying to persist a mapObj in the same way that mod_python users use
persistent database connections.  MapServer is not fully thread-safe  
(yet)
and so you will certainly encounter some trouble with a persistent  
mapObj.

I don't see _anything_ in your code that would prevent the acetate layer
from being predefined in your map file.  If it is only a matter of
colors and styles, I strongly recommend that you predefine the acetate
layer and then modify its classes and styles during the script  
execution.

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies