René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Regression in dashes due to #22569","articleBody":"### Bug summary\n\nPreviously working plotting code has broken. It fails on 96ddc6728ce09cb61f6b6c53714755fe0936b106 / #22569 but passes on the parent daaa1ed376b4fc60ed5a20d155a13c6361aee479.\n\n### Code for reproduction\n\n```python\nimport matplotlib.pyplot as plt\r\nfig, ax = plt.subplots()\r\nax.plot([0, 1], [0, 1], ls=(0, ()))\r\nplt.show()\n```\n\n\n### Actual outcome\n\nNo line shown, error while drawing\r\n```\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/backends/backend_qt.py\", line 479, in _draw_idle\r\n    self.draw()\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/backends/backend_agg.py\", line 424, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/artist.py\", line 73, in draw_wrapper\r\n    result = draw(artist, renderer, *args, **kwargs)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/artist.py\", line 50, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/figure.py\", line 2860, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/artist.py\", line 50, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/axes/_base.py\", line 3101, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/artist.py\", line 50, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/lines.py\", line 772, in draw\r\n    gc.set_dashes(*self._dash_pattern)\r\n  File \"/home/larsoner/python/matplotlib/lib/matplotlib/backend_bases.py\", line 930, in set_dashes\r\n    raise ValueError(\r\nValueError: At least one value in the dash list must be positive\r\n```\n\n### Expected outcome\n\nLine shown\r\n\r\n![Screenshot from 2022-04-28 12-03-38](https://user-images.githubusercontent.com/2365790/165796031-bebea18a-e2af-4c3d-ae6e-8617af9b3a01.png)\r\n\r\n\n\n### Additional information\n\nMaybe we use a weird/bad/incorrect convention in our code by creating `ls=(0, ())` and we can certainly work around it/fix it, but it used to work at least! At a minimum it might be nice to raise a nicer error if possible...\n\n### Operating system\n\nUbuntu 22.04\n\n### Matplotlib Version\n\n96ddc6728ce09cb61f6b6c53714755fe0936b106\n\n### Matplotlib Backend\n\nQtAgg (PyQt6)\n\n### Python version\n\n3.10.4\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\ngit checkout","author":{"url":"https://github.com/larsoner","@type":"Person","name":"larsoner"},"datePublished":"2022-04-28T16:07:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/22930/matplotlib/issues/22930"}