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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Mismatch in documented default behaviour of pcolormesh 'snap'","articleBody":"### Bug summary\n\nThe [documentation for pcolormesh](https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.pcolormesh.html) states the default behaviour for **snap** is _**False**_. Since a supposed temporary addition of **pcolormesh.snap** to the default rcParams under https://github.com/matplotlib/matplotlib/commit/b38c7de4e03d6968680c439381976f8f5f4418b9 for 3.4.3, this is no longer the case and instead you get _**True**_ behaviour by default. The documentation and default behaviour should probably match.\n\nThis switch in default behaviour is most obvious when plotting a pcolormesh plot with an **alpha** value less than 1.\n\n\n\n### Code for reproduction\n\n```Python\nimport matplotlib as mpl\nimport matplotlib.pyplot as plt\n\ntest_array = [\n             [1, 3, 5, 6, 2, 1],\n             [0, 2, 4, 6, 3, 1],\n             [1, 2, 4, 4, 2, 1],\n             [0, 0, 2, 3, 2, 1],\n             [0, 0, 1, 2, 2, 0],\n             [0, 0, 1, 1, 0, 0],\n             ]\n\np1 = plt.pcolormesh(test_array, alpha=0.5)\n\n#print(mpl.rcParams['pcolormesh.snap'])\nprint(\"default\", p1.get_snap())\n\nplt.savefig(f\"test_snapD_old.png\")\nplt.close()\n```\n\n### Actual outcome\n\nUnder 3.10.1\n```\nTrue\ndefault True\n```\n\n\u003cimg width=\"640\" height=\"480\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/e4c20bdc-720a-40ed-86ed-d72845a08e98\" /\u003e\n\n### Expected outcome\n\nUnder 3.3.4\n```\ndefault None\n```\n\n\u003cimg width=\"640\" height=\"480\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/b153f5a0-32c5-47c7-aa83-343c70afe430\" /\u003e\n\n### Additional information\n\nEither the temporary rcParam should be removed from the default template or the documentation should be changed to match the present default behaviour.\n\n### Operating system\n\n_No response_\n\n### Matplotlib Version\n\n3.10.1\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n_No response_\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\nNone","author":{"url":"https://github.com/mo-nstebbin","@type":"Person","name":"mo-nstebbin"},"datePublished":"2025-10-31T13:20:07.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/30709/matplotlib/issues/30709"}