GeoTools SVG with viewbox doesn't show

Question

Is it possible to use SVG with defined viewbox in GeoTools? I am trying to use SVG for styling layer features but if view box is defined it doesn't show up on the map.

Here is SVG that I am trying to use:

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC '-//W3C//DTD SVG 1.0//EN'
          'http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd'>
<svg fill-opacity="1" xmlns:xlink="http://www.w3.org/1999/xlink" color-rendering="auto" color-interpolation="auto" text-rendering="auto" stroke="black" stroke-linecap="square" width="16mm" stroke-miterlimit="10" shape-rendering="auto" stroke-opacity="1" fill="black" stroke-dasharray="none" font-weight="normal" stroke-width="1" viewBox="0 0 160 160" height="16mm" xmlns="http://www.w3.org/2000/svg" font-family="'Dialog'" font-style="normal" stroke-linejoin="miter" font-size="12px" stroke-dashoffset="0" image-rendering="auto">
    <!--Generated by the Batik Graphics2D SVG Generator-->
    <defs id="genericDefs"/>
    <g/>
    <g>
        <g>
            <circle fill="none" r="10" cx="80" cy="80"/>
            <circle fill="none" r="5" cx="80" cy="80"/>
            <circle fill="none" r="0.5" cx="80" cy="80"/>
            <line y2="60" fill="none" x1="80" x2="80" y1="70"/>
            <line y2="65" fill="none" x1="70" x2="90" y1="65"/>
            <line y2="60" fill="none" x1="70" x2="90" y1="60"/>
            <line y2="40" fill="none" x1="90" x2="80" y1="60"/>
            <line y2="60" fill="none" x1="80" x2="70" y1="40"/>
            <rect fill="none" x="78" width="4" height="8" y="50"/>
        </g>
    </g>
</svg>

I also tried to define all dimensions in mm but then I can't use width and height in mm, which is the need for positioning of the symbol. I am trying to symbolise point using this:

PointSymbolizer pointSymbolizer = sf.createPointSymbolizer(graphic, "the_geom");
Rule newRule = sb.createRule(pointSymbolizer);
newRule.setName(point);
File file = null;
file = new File(PointStyle.class.getResource("/trig.svg").getFile());
ExternalGraphic external = sb.createExternalGraphic( "file:///"+file, "image/svg+xml");
graphic.graphicalSymbols.clear();
graphic.graphicalSymbols.add(external);
FeatureTypeStyle featureTypeStyle = sb.createFeatureTypeStyle("Feature", newRule);
Style style = sb.createStyle();
style.featureTypeStyles().add(featureTypeStyle);
layer.setStyle(style);

I also tried to create style over SLD

public static Style createFromSLD(InputStream sld) {
    try {
        SLDParser stylereader = new SLDParser(sf, sld);
        Style style = stylereader.readXML()[0];
        return style;
    } catch (Exception e) {
    }
    return null;
};

SLD

        <Rule>
            <Name>THEME_ID</Name>
            <Title>THEME_ID</Title>
            <PointSymbolizer>
                <Graphic>
                    <ExternalGraphic>
                        <OnlineResource xlink:type="simple" xlink:href="file:///C:/sld/trig.svg"/>
                        <Format>image/svg+xml</Format>
                    </ExternalGraphic>
                </Graphic>
            </PointSymbolizer>
        </Rule>

Answer 1

A solution is to edit class SVGGraphicsFactory.java and calculate values of width and height in pixels.

        private double parseDouble(String value) {
            try {
                return java.lang.Double.parseDouble(value);
            } catch (NumberFormatException arg2) {
+               if(value.endsWith("mm")){
+                   int trail = value.endsWith("mm") ? 2 : value.endsWith(" mm") ? 3 : 0;
+                   value = value.substring(0, value.length()-trail);
+                   java.lang.Integer ScreenResolution = java.awt.Toolkit.getDefaultToolkit().getScreenResolution();
+                   java.lang.Double valueDouble = java.lang.Double.parseDouble(value);
+                   java.lang.Double valueInpx = valueDouble*ScreenResolution/25.4;
+                   return valueInpx;
+               }else{
                    return java.lang.Double.parseDouble(value.replaceAll("\\D*$", ""));
+               }
            }
        } 

This is needed if somebody wants to get a desired "scale" between mm and size of symbol.