chm <data point> section doesn't work correctly with value -1

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Make shape markers on a large line chart using the following code:
plot.addShapeMarkers(Shape.DIAMOND, Color.BLACK, 4);

2. charts4j creates the following url:

http://chart.apis.google.com/chart?cht=lc&chs=600x200&chm=d,0000FF,0,-
1,4,0&chd=s:gXiVcdlhUagRacRTpfgueZedRZYbgYrfObMTSWfYYPTPUdceTiYpZeorgnlXTTfndecd
Vc
mcVZTXiZptVZZJcPVaQaWeeeXawhdXcbjo0sohfyndxqdgbQQedfZdTUNQNGQUUUMQJdVZfdelljxsn
voXfyroigVTfOVQUOQYRMIKOMNTOTNVKZXQhnZelsqkfnTaackPPaVUSONNOHIHDAHKEDEDACAIE
PEGCPGIDGIIGJHEBEACHCBCAABEFEFFDLLFSHFCHBGEDFHGCEEEHFJDIGNKCIQKGSKFIMJJYhhdeoml
mipnmbfYkRPXWXUieROfcTQKLKKObZcjTncmjgnXrnfXgUglroWfgbmnZbLJHSWPTWMQQVUTQRVQ
QXZYkchsoofjtn7xYSsafkjlw9ddfiaOXxdeTPTafbQaqUiYccRZpYfddir0Wcci0obcYSjhTTSWSePR
Lbnx
eogVdUcaooSbPVaTamujZSRdkhVgWOWmbidd

What is the expected output? What do you see instead?

The chart has only about half of its markers.  Based on discussions on the 
google charts group, 
this seems like a known bug of the charts website.

What version of the product are you using? On what operating system?

charts4j-1.2 on MacOS X

Please provide any additional information below.

Thanks to a very useful poster KeithB on the Google Group, there is a known 
workaround.  If I 
change the CHM section of the above URL , it works fine.  Here is the fixed chm 
section:

chm=d,0000FF,0,0:500:-1,4,0&

And the full, working URL:

http://chart.apis.google.com/chart?cht=lc&chs=600x200&chm=d,0000FF,0,0:500:-
1,4,0&chd=s:gXiVcdlhUagRacRTpfgueZedRZYbgYrfObMTSWfYYPTPUdceTiYpZeorgnlXTTfndecd
Vc
mcVZTXiZptVZZJcPVaQaWeeeXawhdXcbjo0sohfyndxqdgbQQedfZdTUNQNGQUUUMQJdVZfdelljxsn
voXfyroigVTfOVQUOQYRMIKOMNTOTNVKZXQhnZelsqkfnTaackPPaVUSONNOHIHDAHKEDEDACAIE
PEGCPGIDGIIGJHEBEACHCBCAABEFEFFDLLFSHFCHBGEDFHGCEEEHFJDIGNKCIQKGSKFIMJJYhhdeoml
mipnmbfYkRPXWXUieROfcTQKLKKObZcjTncmjgnXrnfXgUglroWfgbmnZbLJHSWPTWMQQVUTQRVQ
QXZYkchsoofjtn7xYSsafkjlw9ddfiaOXxdeTPTafbQaqUiYccRZpYfddir0Wcci0obcYSjhTTSWSePR
Lbnx
eogVdUcaooSbPVaTamujZSRdkhVgWOWmbidd

Thanks very much!
ben.

Original issue reported on code.google.com by benb...@gmail.com on 31 Dec 2009 at 7:45