René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Unexpected error after using Figure.canvas.draw on macosx backend","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\nIt has [been claimed](https://github.com/matplotlib/matplotlib/issues/18407#issuecomment-687223797) that \"fig.canvas.draw() is the canonical way to trigger a draw\", replacing `fig.draw(fig.canvas.get_renderer())`. But on the macosx backend, this seems not to work.\r\n\r\n**Code for reproduction**\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug.\r\nPlease make sure to minimize the number of dependencies required, and provide\r\nany necessary plotted data.\r\nAvoid using threads, as Matplotlib is (explicitly) not thread-safe.--\u003e\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nf, ax = plt.subplots()\r\nlines = ax.plot([0, 1])\r\nlegend = ax.legend(lines, [\"a line\"])\r\nf.canvas.draw()\r\n# f.draw(f.canvas.get_renderer())\r\nprint(legend.get_window_extent())\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```python-traceback\r\nTraceback (most recent call last):\r\n  File \"mpl_issue.py\", line 7, in \u003cmodule\u003e\r\n    print(legend.get_window_extent())\r\n  File \"/Users/mwaskom/miniconda3/lib/python3.7/site-packages/matplotlib/legend.py\", line 897, in get_window_extent\r\n    return self._legend_box.get_window_extent(renderer=renderer)\r\n  File \"/Users/mwaskom/miniconda3/lib/python3.7/site-packages/matplotlib/offsetbox.py\", line 346, in get_window_extent\r\n    w, h, xd, yd, offsets = self.get_extent_offsets(renderer)\r\n  File \"/Users/mwaskom/miniconda3/lib/python3.7/site-packages/matplotlib/offsetbox.py\", line 462, in get_extent_offsets\r\n    dpicor = renderer.points_to_pixels(1.)\r\nAttributeError: 'NoneType' object has no attribute 'points_to_pixels'\r\n```\r\n\r\n**Expected outcome**\r\n\r\nOn the `qt5agg` backend, or when uncommenting the (deprecated?) `f.draw(f.canvas.get_renderer())` line, the code runs and prints the extent of the legend.\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Macos\r\n  * Matplotlib version: 3.3.3\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): macosx\r\n  * Python version: 3.8\r\n  * Jupyter version (if applicable): na\r\n  * Other libraries: \r\n\r\nxref https://github.com/matplotlib/matplotlib/issues/18407, https://github.com/mwaskom/seaborn/pull/2399\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/mwaskom","@type":"Person","name":"mwaskom"},"datePublished":"2020-12-29T21:17:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/19197/matplotlib/issues/19197"}