Cairo Backend: Can't convert 'bytes' object to str implicitly on Python3

[vmarkovtsev]

When trying to use "cairo" backend with text labels on Python3, I get

  File "/usr/lib/python3/dist-packages/matplotlib/pyplot.py", line 571, in savefig
    res = fig.savefig(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1448, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/backend_bases.py", line 2192, in print_figure
    **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_cairo.py", line 442, in print_png
    self.figure.draw (renderer)
  File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1057, in draw
    func(*args)
  File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/axes/_base.py", line 2076, in draw
    a.draw(renderer)
  File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 1108, in draw
    tick.draw(renderer)
  File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 249, in draw
    self.label1.draw(renderer)
  File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 59, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/matplotlib/text.py", line 584, in draw
    ismath=ismath, mtext=self)
  File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_cairo.py", line 218, in draw_text
    ctx.show_text(s)
TypeError: Can't convert 'bytes' object to str implicitly

Other backends work fine. This seems to be a pretty typical bytes vs. str Python3 bug.

I have no cairocffi installed and cairo.version_info is (1, 10, 0).

[tacaswell]

Looks like more side effects of the switch from 2to3 -> six.

[vmarkovtsev]

I would say that quick and dirty fix to ctx.show_text(s.decode()) makes the backend work correct. I am just not sure that fixing symptoms is a right thing.

[tacaswell]

That seems like the correct fix to me. Can you put in a PR with that fix and we will see what @mdboom thinks.

[mdboom]

Can you provide a complete script that reproduces the problem? I'm not sure why bytes are getting in there in the first place -- I would have expected it to be Unicode all the way down.

[vmarkovtsev]

import matplotlib
matplotlib.use("cairo")
import matplotlib.pyplot as pp

if __name__ == "__main__":
    figure = pp.figure("Test Cairo")
    figure.clf()
    main_axes = figure.add_axes([0, 0, 1, 1])
    main_axes.cla()
    figure.text(label="Test", s="100", x=0.1, y=0.9)
    figure.canvas.draw()
    pp.savefig("/tmp/test_cairo.png")

python3 test.py throws TypeError whereas python test.py works fine.