René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"webAgg example broken - maybe mpl.js broken?","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\nExtracting the extra bug discovered in https://github.com/matplotlib/matplotlib/issues/19116#issuecomment-745785226\r\n\r\n**Bug summary**\r\nThe code in https://matplotlib.org/devdocs/gallery/user_interfaces/embedding_webagg_sgskip.html does not display anything in the browser when running master matplotlib (https://github.com/matplotlib/matplotlib/commit/27aaf0c378f767d5bcff4f2a65664485fba1f69b)\r\n\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\n\r\n**Code for reproduction**\r\n\r\n- Download the example from the docs\r\n- run it using latest matplotlib\r\n- open http://127.0.0.1:8080/\r\n- See no plot\r\n\r\n**Actual outcome**\r\n\r\nNo plot + this DOM exception in the JS console:\r\n\r\n```\r\nUncaught DOMException: An attempt was made to use an object that is not, or is no longer, usable mpl.js:394\r\n    send_message http://127.0.0.1:8080/mpl.js:394\r\n    _init_canvas http://127.0.0.1:8080/mpl.js:161\r\n    figure http://127.0.0.1:8080/mpl.js:55\r\n    \u003canonymous\u003e http://127.0.0.1:8080/:40\r\n```\r\n\r\n**Expected outcome**\r\nA working interactive plot shows up\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: Ubuntu 20.04\r\n  * Matplotlib version: https://github.com/matplotlib/matplotlib/commit/27aaf0c378f767d5bcff4f2a65664485fba1f69b\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): webAgg\r\n  * Python version: 3.9.0\r\n  * Browser: Firefox 83.0\r\n\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\nInstalled python from conda-forge:\r\n```\r\nPython 3.9.0 | packaged by conda-forge | (default, Oct 14 2020, 22:59:50) \r\n[GCC 7.5.0] on linux\r\n```\r\n\r\n","author":{"url":"https://github.com/ianhi","@type":"Person","name":"ianhi"},"datePublished":"2020-12-16T15:05:49.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/19129/matplotlib/issues/19129"}