1st try pdf multipage fail

[nbecker]

1st try, converted my code using PdfPages to MultiPage, but got this:

  File "./plot_results_vs_esno2.py", line 317, in <module>
    pdf.savefig (fig)
  File "/home/nbecker/.local/lib/python3.6/site-packages/mplcairo/multipage.py", line 41, in savefig
    self._renderer._set_size(*figure.canvas.get_width_height(),
AttributeError: 'MultiPage' object has no attribute '_renderer'

It's not at all a minimal test case I can upload, but does anyone know what might be the problem?

[anntzer]

from matplotlib import pyplot as plt
from mplcairo.multipage import MultiPage

fig1, _ = plt.subplots(2)
fig2, _ = plt.subplots(3)
with MultiPage("/tmp/test.pdf") as mp:
    mp.savefig(fig1)
    mp.savefig(fig2)

works for me. You definitely need to use the contextmanager form though (this needs to be documented).

Does this help?

[nbecker]

Adapting the existing code to use a contextmanager seems difficult, the structure is

if PDF:
        pdf = PdfPages(args.output)
... do something to produce a fig
        if PDF:
            pdf.savefig (fig)
            plt.close()
            
if PDF:
    pdf.close()
else:
    plt.show()

I would need ...do something to produce fig to be inside contextmanager when producing PDF, but not when PDF is false. Not sure how to code that.

[anntzer]

The context manager only needs to wrap the savefig (just like one would use open() for normal files), e.g.

# produce the figs first
if PDF:
    with MultiPage(...) as pdf:
        pdf.savefig(...)
else:
    plt.show()

(or you can do various tricks with ExitStack and nullcontext, see https://docs.python.org/3/library/contextlib.html#contextlib.ExitStack and https://docs.python.org/3/library/contextlib.html#contextlib.nullcontext).

[nbecker]

OK, works using context manager as you showed.
py3.6 doesn't have nullcontext, but can be simulated using contextlib.suppress().
The fact that it only works with cm needs to be documented.

[anntzer]

I fixed it on master: the old pattern (with close()) now works too.
I haven't made a new wheel but you can get away with copy-pasting multipage.py.

[anntzer]

Closing as fixed on master, feel free to request a reopen if there are more issues.