Bug summary

When saving a figure with the PostScript backend, a

TypeError: cannot unpack non-iterable NoneType object

happens if the figure contains a multi-line text label with an empty line (see example).

Code for reproduction

from matplotlib.figure import Figure

figure = Figure()
ax = figure.add_subplot(111)
# ax.set_title('\nLower title')  # this would cause an error as well
ax.annotate(text='\nLower label', xy=(0, 0))
figure.savefig('figure.eps')

Actual outcome

$ ./venv/Scripts/python save_ps.py
Traceback (most recent call last):
File "C:\temp\matplotlib_save_ps\save_ps.py", line 7, in
figure.savefig('figure.eps')
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\figure.py", line 3272, in savefig
self.canvas.print_figure(fname, **kwargs)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backend_bases.py", line 2338, in print_figure
result = print_method(
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backend_bases.py", line 2204, in
print_method = functools.wraps(meth)(lambda *args, **kwargs: meth(
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib_api\deprecation.py", line 410, in wrapper
return func(*inner_args, **inner_kwargs)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backends\backend_ps.py", line 869, in _print_ps
printer(fmt, outfile, dpi=dpi, dsc_comments=dsc_comments,
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backends\backend_ps.py", line 927, in _print_figure
self.figure.draw(renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\artist.py", line 74, in draw_wrapper
result = draw(artist, renderer, *args, **kwargs)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\artist.py", line 51, in draw_wrapper
return draw(artist, renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\figure.py", line 3069, in draw
mimage._draw_list_compositing_images(
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\image.py", line 131, in _draw_list_compositing_images
a.draw(renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\artist.py", line 51, in draw_wrapper
return draw(artist, renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\axes_base.py", line 3106, in draw
mimage._draw_list_compositing_images(
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\image.py", line 131, in _draw_list_compositing_images
a.draw(renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\artist.py", line 51, in draw_wrapper
return draw(artist, renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\text.py", line 1995, in draw
Text.draw(self, renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\artist.py", line 51, in draw_wrapper
return draw(artist, renderer)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\text.py", line 736, in draw
textrenderer.draw_text(gc, x, y, clean_line,
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backends\backend_ps.py", line 248, in wrapper
return meth(self, *args, **kwargs)
File "C:\temp\matplotlib_save_ps\venv\lib\site-packages\matplotlib\backends\backend_ps.py", line 673, in draw_text
for ps_name, xs_names in stream:
TypeError: cannot unpack non-iterable NoneType object

Expected outcome

The figure can be saved as figure.eps without error.

Additional information

• seems to happen if a text label or title contains a linebreak with an empty line
• works without error for other backends such as PNG, PDF, SVG, Qt
• works with matplotlib<=3.5.3
• adding if curr_stream: before line 669 of backend_ps.py seems to fix the bug

Operating system

Windows

Matplotlib Version

3.6.0

Matplotlib Backend

No response

Python version

3.9.13

Jupyter version

No response

Installation

pip