Re: [matplotlib-devel] SystemError exception calling agg's draw_path_collection()

[Benjamin R. <ben...@ou...>]

I think I figured it out... the linestyles are a list of tuples. When they
get coerced to a numpy array, and then coerced back to a list, you get a
list of lists instead of a list of tuples!

There must be some code deep down in the agg that is expecting a tuple, and
choking on a list.

Ben Root

On Sun, Feb 8, 2015 at 5:54 PM, Benjamin Root <ben...@ou...> wrote:

> I am experimenting with my idea for utilizing a _draworder attribute in
> Collection objects. Since not everything in a collection is guaranteed to
> be the same length or even be numpy arrays, I have to add some logic to
> coerce everything to numpy arrays and tile their data so that the length of
> their first axis match up.
>
> I also have logic to convert all objects back to their original types
> prior to continuing, just in case that makes any difference.
>
> However, using AGG seems to fail here:
>
> Traceback (most recent call last):
>   File "/home/ben/miniconda/lib/python2.7/site-packages/nose/case.py",
> line 197, in runTest
>     self.test(*self.arg)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/testing/decorators.py",
> line 51, in failer
>     result = f(*args, **kwargs)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/testing/decorators.py",
> line 183, in do_test
>     figure.savefig(actual_fname, **self._savefig_kwarg)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/figure.py",
> line 1490, in savefig
>     self.canvas.print_figure(*args, **kwargs)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backend_bases.py",
> line 2211, in print_figure
>     **kwargs)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py",
> line 525, in print_png
>     FigureCanvasAgg.draw(self)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py",
> line 472, in draw
>     self.figure.draw(self.renderer)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/artist.py",
> line 60, in draw_wrapper
>     draw(artist, renderer, *args, **kwargs)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/figure.py",
> line 1094, in draw
>     func(*args)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/axes3d.py",
> line 273, in draw
>     ax.draw(renderer)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/axis3d.py",
> line 370, in draw
>     self.gridlines.draw(renderer, project=True)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/mpl_toolkits/mplot3d/art3d.py",
> line 203, in draw
>     LineCollection.draw(self, renderer)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/artist.py",
> line 60, in draw_wrapper
>     draw(artist, renderer, *args, **kwargs)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/collections.py",
> line 345, in draw
>     self._offset_position)
>   File
> "/home/ben/miniconda/lib/python2.7/site-packages/matplotlib-1.5.dev1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_agg.py",
> line 127, in draw_path_collection
>     return self._renderer.draw_path_collection(*kl, **kw)
> SystemError: new style getargs format but argument is not a tuple
>
> The PDF and SVG backends aren't experiencing this problem. I have taken
> out the parts of my code that "broadcasted" the arrays, and the error still
> happens. I then took out the code that coerced everything to numpy arrays
> in the first place, and the error disappeared (taking that out effectively
> let everything pass through unaffected). Keep in mind that my code coerced
> everything back to their original types prior to calling the renderer, so
> it was merely the action of converting stuff into an array that did this.
>
> The best I can figure is that there is something wrong with the C++ code
> for our agg wrapper? Googling the exception message brings up various
> discussions of mistakes in the argument handling of C/C++ code. I haven't a
> clue, though, why this would be an issue.
>
> Thoughts?
> Ben Root
>
>