enable label collision-management in sld context

[Peter Freimuth]

Hi Mapserver Development Team,
in a currently running project we have the urgent need to use SLD 
Filtering and Symbolising in a WMS Get Map Request. But the problem is 
that mapservers label collision management cannot be used via SLD, 
because it is not part of the specs and so not supported by umn's sld 
interface. So what do you think about -1 and -1 as AnchorPoint values 
which has the same effect than POSITION=AUTO in the Mapfile. I think a 
lot of people would like to have this feature enabled, even if it is not 
written in the OGC SLD specs.
Example:
<TextSymbolizer>
    <Geometry>
        <ogc:PropertyName>GEOM</ogc:PropertyName>
        </Geometry>
            <Label>
                <ogc:PropertyName>NAME</ogc:PropertyName>
            </Label>
            <Font>
                <CssParameter name="font-family">Arial</CssParameter>
                <CssParameter name="font-family">Sans-Serif</CssParameter>
                <CssParameter name="font-style">italic</CssParameter>
                <CssParameter name="font-size">10</CssParameter>
                <CssParameter name="font-color">#222222</CssParameter>
            </Font>
            <LabelPlacement>
                <AnchorPointX>-1</AnchorPointX>
                /<AnchorPointY>-1</AnchorPointY>
would be equal to /<PointPlacement auto="true"/> which can be used in 
GeoServer for example
            </LabelPlacement>
...
</TextSymbolizer>
 
and handle this in:

void ParseTextPointPlacement(CPLXMLNode *psRoot, classObj *psClass)
...
                if ((dfAnchorX == 0 || dfAnchorX == 0.5 || dfAnchorX == 
1) &&
                    (dfAnchorY == 0 || dfAnchorY == 0.5 || dfAnchorY == 1))
                {
                    if (dfAnchorX == 0 && dfAnchorY == 0)
                      psClass->label.position = MS_LL;
                    if (dfAnchorX == 0 && dfAnchorY == 0.5)
                      psClass->label.position = MS_CL;
                    if (dfAnchorX == 0 && dfAnchorY == 1)
                      psClass->label.position = MS_UL;
                    if (dfAnchorX == 0.5 && dfAnchorY == 0)
                      psClass->label.position = MS_LC;
                    if (dfAnchorX == 0.5 && dfAnchorY == 0.5)
                      psClass->label.position = MS_CC;
                    if (dfAnchorX == 0.5 && dfAnchorY == 1)
                      psClass->label.position = MS_UC;
                    if (dfAnchorX == 1 && dfAnchorY == 0)
                      psClass->label.position = MS_LR;
                    if (dfAnchorX == 1 && dfAnchorY == 0.5)
                      psClass->label.position = MS_CR;
                    if (dfAnchorX == 1 && dfAnchorY == 1)
                      psClass->label.position = MS_UR;
                    if (dfAnchorX == -1 && dfAnchorY == -1)
                      psClass->label.position = MS_AUTO;
                }

This will still be conform with the specs and give us the possibility to 
use mapserver label intelligence with sld's.

Best regards,
Peter

-- 
Mit freundlichem Gruß

Peter Freimuth
MapMedia
Kartographie und raumbezogene Informationssysteme

Heilbronner Straße 10
D-10711 Berlin Charlottenburg

fon:  +49.(0)30.89 06 82 70
fax:  +49.(0)30.89 06 82 73
mail: pf at mapmedia.de
net:  www.mapmedia.de
pgp:  on demand
_________________________________________________