René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Custom backend stopped working in 3.6.2","articleBody":"### Bug summary\r\n\r\nA custom backend that's been working for a few years without a problem, stopped working under Matplotlib 3.6.2.\r\n\r\n### Code for reproduction\r\n\r\n```python\r\n# mpl.py\r\nfrom matplotlib._pylab_helpers import Gcf\r\nfrom matplotlib.backend_bases import (_Backend, FigureCanvasBase, FigureManagerBase)\r\nfrom matplotlib.backends.backend_agg import FigureCanvasAgg\r\n\r\nclass MyFigureManager(FigureManagerBase):\r\n    def show(self):\r\n        print(\"MyFigureManager.show()\")\r\n\r\n@_Backend.export\r\nclass MyBackend(_Backend):\r\n    FigureCanvas  = FigureCanvasAgg\r\n    FigureManager = MyFigureManager\r\n\r\n    def show(*args, **kwargs):\r\n        print(\"MyBackend.show()\")\r\n        _Backend.show(*args, **kwargs)\r\n        print(\"MyBackend.show() after _Backend\")\r\n```\r\n\r\n```\r\n# plot_mpl.py\r\nimport matplotlib\r\nmatplotlib.use(\"module://mpl\")\r\n\r\nimport matplotlib.pyplot as plt\r\n\r\nplt.plot([1,2,3,4,5])\r\nplt.show()\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\nRunning using Matplotlib 3.5.3, this outputs:\r\n```\r\nMyBackend.show()\r\nMyFigureManager.show()\r\nMyBackend.show() after _Backend\r\n```\r\n\r\nBut running using 3.6.2, I get:\r\n```\r\nMyBackend.show()\r\n.../mpl.py:16: UserWarning: Matplotlib is currently using module://mpl, which is a non-GUI backend, so cannot show the figure.\r\n  _Backend.show(*args, **kwargs)\r\nMyBackend.show() after _Backend\r\n```\r\n\r\nIn particular, `MyFigureManager.show()` is never called.\r\n\r\n### Expected outcome\r\n\r\nSame behavior under both versions.\r\n\r\n### Operating system\r\n\r\nmacOS\r\n\r\n### Matplotlib Version\r\n\r\n3.5.3, 3.6.2\r\n\r\n### Python version\r\n\r\n3.10.8\r\n","author":{"url":"https://github.com/mrzv","@type":"Person","name":"mrzv"},"datePublished":"2022-11-20T18:11:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/24524/matplotlib/issues/24524"}