xkcd plots stopped working on Mac OS X.

[mario-grgic]

The matplotlib xkcd example plots at

http://matplotlib.org/examples/showcase/xkcd.html

stopped working with matplotlib 1.4.x (they used to work with earlier versions). This is with Python 2.7.5 on Mac OS X 10.9.5 and matplotlib 1.4.3.

The following Traceback is printed if I run one of the examples:

Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/figure.py", line 1085, in draw
    func(*args)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/axes/_base.py", line 2110, in draw
    a.draw(renderer)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/lines.py", line 715, in draw
    drawFunc(renderer, gc, tpath, affine.frozen())
  File "/Library/Python/2.7/site-packages/matplotlib/lines.py", line 1072, in _draw_lines
    self._lineFunc(renderer, gc, path, trans)
  File "/Library/Python/2.7/site-packages/matplotlib/lines.py", line 1112, in _draw_solid
    renderer.draw_path(gc, path, trans)
  File "/Library/Python/2.7/site-packages/matplotlib/patheffects.py", line 115, in draw_path
    rgbFace)
  File "/Library/Python/2.7/site-packages/matplotlib/patheffects.py", line 217, in draw_path
    renderer.draw_path(gc, tpath, affine, rgbFace)
  File "/Library/Python/2.7/site-packages/matplotlib/backends/backend_macosx.py", line 58, in draw_path
    gc.draw_path(path, transform, linewidth, rgbFace)
AttributeError: GraphicsContextBase instance has no attribute 'draw_path'
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/figure.py", line 1085, in draw
    func(*args)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/axes/_base.py", line 2110, in draw
    a.draw(renderer)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/axis.py", line 1119, in draw
    tick.draw(renderer)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/axis.py", line 244, in draw
    self.tick1line.draw(renderer)
  File "/Library/Python/2.7/site-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/lines.py", line 760, in draw
    rgbaFace)
  File "/Library/Python/2.7/site-packages/matplotlib/patheffects.py", line 127, in draw_markers
    **kwargs)
  File "/Library/Python/2.7/site-packages/matplotlib/backend_bases.py", line 265, in draw_markers
    rgbFace)
  File "/Library/Python/2.7/site-packages/matplotlib/patheffects.py", line 115, in draw_path
    rgbFace)
  File "/Library/Python/2.7/site-packages/matplotlib/patheffects.py", line 217, in draw_path
    renderer.draw_path(gc, tpath, affine, rgbFace)
  File "/Library/Python/2.7/site-packages/matplotlib/backends/backend_macosx.py", line 58, in draw_path
    gc.draw_path(path, transform, linewidth, rgbFace)
AttributeError: GraphicsContextBase instance has no attribute 'draw_path'

[mdboom]

Seems to be specific to the macosx backed. Cc: @mdehoon

[mdehoon]

Why, on line 217 in patheffects.py, is renderer.draw_path(gc, ...) being called on a RendererMac object while gc is a GraphicsContextBase instead of a GraphicsContextMac? I suspect a call to

        # Get the real renderer, not a PathEffectRenderer.
        if isinstance(renderer, PathEffectRenderer):
            renderer = renderer._renderer

is missing, but it may be some deeper problem.

[tacaswell]

Is this related to #4024 ?

[mdehoon]

@tacaswell I think what we are seeing here is a more fundamental issue. If we solve this one then #4024 will likely also be solved; the opposite is not true though.

[mdehoon]

The equivalent bug appears with the gtkcairo backend:

File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib-0_unknown-py2.7-macosx-10.9-intel.egg/matplotlib/backends/backend_cairo.py", line 153, in draw_path
    ctx = gc.ctx
AttributeError: 'GraphicsContextBase' object has no attribute 'ctx'

The origin of the bug is the same: The gtkcairo renderer is used with a generic (GraphicsContextBase) graphics context instead of a GraphicsContextCairo graphics context.

[mdehoon]

Also broken in the same way with the GTK backend:

AttributeError: 'GraphicsContextBase' object has no attribute 'gdkGC'

and with the ps backend:

AttributeError: 'GraphicsContextBase' object has no attribute 'shouldstroke'