[Geoserver-users] Chart Extension fails rendering when axes styles are given

Hello,

I have stuck in GeoServer's chart extension. I wonder if anybody can help me to sort this out.

I am using GeoServer 2.4.3 on JRE7 64bit on Linux.
The chart extension is downloaded and installed from here.
http://sourceforge.net/projects/geoserver/files/GeoServer%20Extensions/2.4.3/geoserver-2.4.3-charts-plugin.zip/download

On my machine, I can get a cartogram with "labelled" pie charts with the following SLD snippet.
<PointSymbolizer>
  <Graphic>
    <ExternalGraphic>
      <OnlineResource xlink:href="http://chart?cht=p&amp;chd=t:2,1&amp;chl=foo|bar&amp;amp;chxt=x " />
      <Format>application/chart</Format>
    </ExternalGraphic>
    <size>200</size>
  </Graphic>
</PointSymbolizer>

But when I attempt to change the label size smaller with the following snippet, GeoServer fails to render it.
(The expected behaviour: https://chart.googleapis.com/chart?cht=p&chd=t:2,1&chs=200x100&chl=foo|bar&amp;chxs=0,555555,9&amp;chxt=x\)
<PointSymbolizer>
  <Graphic>
    <ExternalGraphic>
      <OnlineResource xlink:href="http://chart?cht=p&amp;chd=t:2,1&amp;chl=foo|bar&amp;amp;chxs=0,555555,9&amp;amp;chxt=x&quot; />
      <Format>application/chart</Format>
    </ExternalGraphic>
    <size>200</size>
  </Graphic>
</PointSymbolizer>

When the troubled layer gets a WMS request, the following exception is repeatedly logged per each feature in the viewbox.
  2014-05-22 13:55:55,243 ERROR [lite.StyledShapePainter] - ShapePainter has been asked to paint a null style!!

It seems that the chart extension gets wrong when chxs (axes styles) parameter is given. But if anybody knows a workaround to control the style of pie chart labels, that would be very helpful to me.

Thank you,

Go Sato (WSP UK)
go.sato@...6552...