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The use of WKT marks (prefiex with "wkt://" in your SLD) allows an easy way to add complex symbols to the rendering process; for example, a double dashed line with transparent background can be shown with this SLD fragment:
<LineSymbolizer>
<Stroke>
<GraphicStroke>
<Graphic>
<Mark>
<WellKnownName>wkt://MULTILINESTRING((-0.25 -0.25, -0.125 -0.25), (0.125 -0.25, 0.25 -0.25), (-0.25 0.25, -0.125 0.25), (0.125 0.25, 0.25 0.25))</WellKnownName>
<Fill>
<CssParameter name="fill">#0000ff</CssParameter>
</Fill>
<Stroke>
<CssParameter name="stroke">#0000ff</CssParameter>
<CssParameter name="stroke-width">1</CssParameter>
</Stroke>
</Mark>
<Size>6</Size>
</Graphic>
</GraphicStroke>
</Stroke>
</LineSymbolizer>
Which gives this output: 
This module supports curves as well; for instance, this SLD fragment:
<LineSymbolizer>
<Stroke>
<GraphicStroke>
<Graphic>
<Mark>
<WellKnownName>wkt://COMPOUNDCURVE((0 0, 0.25 0), CIRCULARSTRING(0.25 0, 0.5 0.5, 0.75 0), (0.75 0, 1 0))</WellKnownName>
<Fill>
<CssParameter name="fill">#0000ff</CssParameter>
</Fill>
<Stroke>
<CssParameter name="stroke">#0000ff</CssParameter>
<CssParameter name="stroke-width">1</CssParameter>
</Stroke>
</Mark>
<Size>10</Size>
</Graphic>
</GraphicStroke>
</Stroke>
</LineSymbolizer>
...produces this: 
WKT shapes may be pooled in properties files (this file must be packed in the same JAR of this module) and re-used across SLD files, becoming libraries of symbols. For instance the WKT marks defined in this properties files (wkt.properties):
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...may be used in your SLD, prefixed like this (not the protocol changed to "wktlib://"):
<WellKnownName>wktlib://wkt.properties#ls</WellKnownName>
Weather symbols
The weather symbols, which are create using Java code, should be prefixed by the "extshape://" protocol in the SLD, are, for the time being, limited to the following:
<WellKnownName>extshape://triangle</WellKnownName> 
<WellKnownName>extshape://emicircle</WellKnownName> 
<WellKnownName>extshape://triangleemicircle</WellKnownName> 
Module Status
There is no interesting development planned at this time.
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