mapnik/tests/visual_tests/styles/functional-expressions-length.xml

<Map background-color="#eee" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
  <Parameters>
    <Parameter name="sizes">512, 512</Parameter>
  </Parameters>
  <FontSet name="book-fonts">
    <Font face-name="DejaVu Sans Book"/>
  </FontSet>
  <Style name="frame" filter-mode="first">
    <Rule>
      <Filter>[mapnik::geometry_type]=linestring</Filter>
      <LineSymbolizer
	  stroke="[color]"
	  stroke-width="[width]"
	  offset="abs([offset]*2.0)"/>
    </Rule>
    <Rule>
      <Filter>[mapnik::geometry_type]=point</Filter>
      <MarkersSymbolizer
	  file="../../../[base-path]/[filetype]/[filename].[filetype]"
	  width="exp(0.4*length([name]))"
	  />
    </Rule>
  </Style>

  <Layer name="frame" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
    <StyleName>frame</StyleName>
    <Datasource>
      <Parameter name="type">ogr</Parameter>
      <Parameter name="extent">-15,-15,15,15</Parameter>
      <Parameter name="layer_by_index">0</Parameter>
      <Parameter name="inline"><![CDATA[
      {
      "type" : "FeatureCollection",
      "features" : [
      {
      "properties" : {
      "width":"5",
      "color" : "red",
      "offset": 10
      },
      "geometry" : {
      "coordinates" : [[-15,-15],[15,15]],
      "type" : "LineString"
      },
      "type" : "Feature",
      },
      {
      "geometry" : {
      "coordinates" : [ 0,0 ],
      "type" : "Point"
      },
      "properties" : {
      "base-path":"./tests/data",
      "filetype":"svg",
      "filename":"octocat",
      "width":"5",
      "name": "Large octocat",
      "color" : "#ace"
      },
      "type" : "Feature",
      },
      {
      "geometry" : {
      "coordinates" : [ -10,-10 ],
      "type" : "Point"
      },
      "properties" : {
      "base-path":"./tests/data",
      "filetype":"svg",
      "filename":"octocat",
      "width":"5",
      "name": "tiny cat",
      "color" : "#ace"
      },
      "type" : "Feature",
      },
      {
      "geometry" : {
      "coordinates" : [ 10,10 ],
      "type" : "Point"
      },
      "properties" : {
      "base-path":"./tests/data",
      "filetype":"svg",
      "filename":"octocat",
      "name": "tiny cat"
      },
      "type" : "Feature",
      },
      {
      "geometry" : {
      "coordinates" : [ -10,10 ],
      "type" : "Point"
      },
      "properties" : {
      "base-path":"./tests/data",
      "filetype":"svg",
      "filename":"octocat",
      "name": "small cat"
      },
      "type" : "Feature",
      },
      {
      "geometry" : {
      "coordinates" : [ 10,-10 ],
      "type" : "Point"
      },
      "properties" : {
      "base-path":"./tests/data",
      "filetype":"svg",
      "filename":"octocat",
      "name": "small cat"
      },
      "type" : "Feature",
      }
      ]
      }]]></Parameter>
    </Datasource>
  </Layer>
</Map>