Native SLD support in QGIS

The current Quantum GIS master (i.e. the latest development version) supports now loading and saving of Styled Layer Descriptor (SLD) styles in the layer properties dialog.

The QGIS API has been extended by the new methods saveSldStyle and loadSldStyle in QgsMapLayer and writeSld and loadSld in QgsVectorLayer. Currently these methods are not yet available in the Python API, but it is simple to add them in the corresponding SIP files.

To write the current layer style to a file, type in the Python console:

l = qgis.utils.iface.activeLayer()
l.saveSldStyle("/path/to/style.sld")

It's is also possible to get the current layer style as string:

# Get the active layer
l = qgis.utils.iface.activeLayer()

# Create a new XML document
document = QDomDocument()
header = document.createProcessingInstruction( "xml", "version=\"1.0\" encoding=\"UTF-8\"" )
document.appendChild( header )
        
# Create the SLD root element
root = document.createElementNS( "http://www.opengis.net/sld", "StyledLayerDescriptor" )
root.setAttribute( "version", "1.1.0" )
root.setAttribute( "xsi:schemaLocation", "http://www.opengis.net/sld http://schemas.opengis.net/sld/1.1.0/StyledLayerDescriptor.xsd" )
root.setAttribute( "xmlns:ogc", "http://www.opengis.net/ogc" )
root.setAttribute( "xmlns:se", "http://www.opengis.net/se" )
root.setAttribute( "xmlns:xlink", "http://www.w3.org/1999/xlink" )
root.setAttribute( "xmlns:xsi", "http://www.w3.org/2001/XMLSchema-instance" )
document.appendChild( root )

# Create the NamedLayer element
namedLayerNode = document.createElement( "NamedLayer" )
root.appendChild( namedLayerNode )
        
errorMsg = QString("")
        
l.writeSld(namedLayerNode, document, errorMsg)

print document.toString( 4 )

It's still necessary to load SLD styles manually. SLD styles, unlike QGIS styles (.qml), saved with the same name in the same directory like a Shapefile are not (yet?) immediately loaded.