I found this bug when adding an ampersand to a legend string.
Perhaps you as the maintainer can fix this issue with CGI.escape. I tried to integrate it, but I'm not exactly sure where to substitute. The method GChart.jstize is the wrong place because of already applied parameter concatenation. GChart#query_builder seems to be a better place ...

If you have no time to fix it by yourself or accept a hackish version, please drop me a note. Then I would try my best.

Thanks,
der_flo

I'm trying to draw a vertical bar graph with a manually-labelled x-axis and an automatically labelled y-axis. This is possible, and here is the correct url:

http://chart.apis.google.com/chart?chs=300x200&chxr=0,0,5&chxt=y,x&chd=s:AM9&cht=bvs&chxl=1:%7Cfoo%7Cbar%7Cqux

Gcharts does not seem to allow this, however. Here's the closest I can get:

does not display y-axis labels:

chart = Gchart.bar(:data => [0, 1, 5],
                   :axis_with_labels => 'x',
                   :axis_labels => [['foo', 'bar', 'qux']])
# => http://chart.apis.google.com/chart?chs=300x200&chxr=0,0,5&chxt=x&chd=s:AM9&cht=bvs&chxl=0:%7Cfoo%7Cbar%7Cqux

incorrect y-axis range:

chart = Gchart.bar(:data => [0, 1, 5],
                   :axis_with_labels => 'x,y',
                   :axis_labels => [['foo', 'bar', 'qux']])
# => http://chart.apis.google.com/chart?chs=300x200&chxr=0,0,5&chxt=x,y&chd=s:AM9&cht=bvs&chxl=0:%7Cfoo%7Cbar%7Cqux

does not display y-axis labels:

chart = Gchart.bar(:data => [0, 1, 5],
                   :axis_with_labels => 'y,x',
                   :axis_labels => [nil, ['foo', 'bar', 'qux']])
# => http://chart.apis.google.com/chart?chs=300x200&chxr=0,0,5&chxt=y,x&chd=s:AM9&cht=bvs&chxl=0:%7C%7C1:%7Cfoo%7Cbar%7Cqux

So maybe axis_labels should optionally take a Hash, so I can specify the labels for axis 1 without it inserting a blank label list for axis 0?

Also, maybe Gchart#full_data_range should pay attention to axis ordering from :axis_with_labels. It currently inserts the axis_range for axis 0, even if they have been swapped.

C:\Ruby\lib\ruby\gems\1.8\gems\mattetti-googlecharts-1.4.0>spec spec\gchart_spec.rb
....F...................................................................................

1)
Errno::ENOENT in 'generating a default Gchart should use theme defaults if theme is set'
No such file or directory - ./spec/fixtures/test_theme.yml
./spec/../lib/gchart/theme.rb:29:in `initialize'
./spec/../lib/gchart/theme.rb:29:in `open'
./spec/../lib/gchart/theme.rb:29:in `initialize'
./spec/../lib/gchart/theme.rb:29:in `each'
./spec/../lib/gchart/theme.rb:29:in `initialize'
./spec/../lib/gchart/theme.rb:15:in `new'
./spec/../lib/gchart/theme.rb:15:in `load'
./spec/../lib/gchart.rb:28:in `method_missing'
./spec\gchart_spec.rb:32:

Finished in 0.487 seconds

88 examples, 1 failure

C:\Ruby\lib\ruby\gems\1.8\gems\mattetti-googlecharts-1.4.0>dir spec\fixtures
 Volume in drive C has no label.
 Volume Serial Number is 8847-D2CE

 Directory of C:\Ruby\lib\ruby\gems\1.8\gems\mattetti-googlecharts-1.4.0\spec

File Not Found

Line styles use chm= for shape markers:

http://code.google.com/apis/chart/styles.html#line_styles

googlecharts currently only uses it for range markers, so there's no way to use it for lines.

This code:

convert_to_simple_value( (@@simple_chars.size - 1) * number / @max_value)

Doesn't take the minimum value in to account. So if your data is [100,100.1,100.2,100.3] you will get a max_value of 100.3 and all the numbers get all 60 and 61, and not distinct data points.

The same problem exists for 'extended' range types.

This code:

@min = (min_ds_value < 0) ? min_ds_value : 0

always gets a minimum of 0 for positive values, which I believe is the opposite of what was intended.

For example, with data of [100,200,300] the range calculated by full_data_range would be [0,300] instead of [100,300].

Then again, I don't see why any positive or negative check exists. Negative and positive minimums seem to work fine:

http://chart.apis.google.com/chart?chs=320x200&cht=bvs&chd=t:30,-60,50,120,80,-90&chds=-80,140&chxt=y&chxr=0,-80,140

Gchart.line(:data => [300, 100, 30, 200, 100, 200, 300, 10], :axis_with_labels => 'x', :axis_labels => ['Jan','July','Jan','July','Jan'])

Returns:
"http://chart.apis.google.com/chart?cht=lc&chs=300x200&chxl=0:%7CJan%7C1:%7CJuly%7C2:%7CJan%7C3:%7CJuly%7C4:%7CJan&chd=s:9UGoUo9C&chxt=x"

Notice the axis labels:
chxl=0:%7CJan%7C1:%7CJuly%7C2:%7CJan%7C3:%7CJuly%7C4:%7CJan

This doesn't doesn't create proper labels.

On my 1.9.1, charts URLs aren't getting built at all.

The offending code seems to be:

def query_builder(options="")

dataset 
query_params = instance_variables.sort.map do |var|
  case var
  when '@data'

"case var" needs to be "case var.to_s" under Ruby 1.9.1; the case equality isn't working with a symbol.

Found out that PNGs do not write correctly to file on windows, at least not on vista. Solution is to change file open flags to "wb+" in method write(), as follows:

def write(io_or_file=@@file_name)
  return io_or_file.write(fetch) if io_or_file.respond_to?(:write)
  open(io_or_file, "wb+") { |io| io.write(fetch) }
end

thanks to the clear explanation of why the PNG header is like it is on wikipedia.

Cheers,
Victor