René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Text label with empty line causes a \"TypeError: cannot unpack non-iterable NoneType object\" in PostScript backend","articleBody":"### Bug summary\n\nWhen saving a figure with the PostScript backend, a\r\n\u003e TypeError: cannot unpack non-iterable NoneType object\r\n\r\nhappens if the figure contains a multi-line text label with an empty line (see example).\n\n### Code for reproduction\n\n```python\nfrom matplotlib.figure import Figure\r\n\r\nfigure = Figure()\r\nax = figure.add_subplot(111)\r\n# ax.set_title('\\nLower title')  # this would cause an error as well\r\nax.annotate(text='\\nLower label', xy=(0, 0))\r\nfigure.savefig('figure.eps')\n```\n\n\n### Actual outcome\n\n$ ./venv/Scripts/python save_ps.py\r\nTraceback (most recent call last):\r\n  File \"C:\\temp\\matplotlib_save_ps\\save_ps.py\", line 7, in \u003cmodule\u003e\r\n    figure.savefig('figure.eps')\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\figure.py\", line 3272, in savefig\r\n    self.canvas.print_figure(fname, **kwargs)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backend_bases.py\", line 2338, in print_figure\r\n    result = print_method(\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backend_bases.py\", line 2204, in \u003clambda\u003e\r\n    print_method = functools.wraps(meth)(lambda *args, **kwargs: meth(\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\_api\\deprecation.py\", line 410, in wrapper\r\n    return func(*inner_args, **inner_kwargs)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backends\\backend_ps.py\", line 869, in _print_ps\r\n    printer(fmt, outfile, dpi=dpi, dsc_comments=dsc_comments,\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backends\\backend_ps.py\", line 927, in _print_figure\r\n    self.figure.draw(renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\artist.py\", line 74, in draw_wrapper\r\n    result = draw(artist, renderer, *args, **kwargs)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\artist.py\", line 51, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\figure.py\", line 3069, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\artist.py\", line 51, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 3106, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\artist.py\", line 51, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\text.py\", line 1995, in draw\r\n    Text.draw(self, renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\artist.py\", line 51, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\text.py\", line 736, in draw\r\n    textrenderer.draw_text(gc, x, y, clean_line,\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backends\\backend_ps.py\", line 248, in wrapper\r\n    return meth(self, *args, **kwargs)\r\n  File \"C:\\temp\\matplotlib_save_ps\\venv\\lib\\site-packages\\matplotlib\\backends\\backend_ps.py\", line 673, in draw_text\r\n    for ps_name, xs_names in stream:\r\nTypeError: cannot unpack non-iterable NoneType object\r\n\n\n### Expected outcome\n\nThe figure can be saved as `figure.eps` without error.\n\n### Additional information\n\n- seems to happen if a text label or title contains a linebreak with an empty line\r\n- works without error for other backends such as PNG, PDF, SVG, Qt\r\n- works with matplotlib\u003c=3.5.3\r\n- adding `if curr_stream:` before line 669 of `backend_ps.py` seems to fix the bug \n\n### Operating system\n\nWindows\n\n### Matplotlib Version\n\n3.6.0\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n3.9.13\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\npip","author":{"url":"https://github.com/jpeg13","@type":"Person","name":"jpeg13"},"datePublished":"2022-09-19T13:57:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/23954/matplotlib/issues/23954"}