René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Different behavior of tight_layout and set_tight_layout with matplotlib 3.5.0 on macOS","articleBody":"### Bug summary\n\nSince `matplotlib` 3.5.0, I see a slightly different result when using `tight_layout()` or `set_tight_layout(True)` with the macOS backend. These differences do not appear with `matplotlib` 3.4.3, or in a Debian container.\n\n### Code for reproduction\n\n```python\nimport matplotlib.pyplot as plt\r\nfrom matplotlib.testing.compare import compare_images\r\n\r\n\r\nfig1, ax1 = plt.subplots()\r\nfig1.set_tight_layout(True)\r\nfig1.savefig(\"1.png\")\r\n\r\nfig2, ax2 = plt.subplots()\r\nfig2.tight_layout()\r\nfig2.savefig(\"2.png\")\r\n\r\nassert compare_images(\"1.png\", \"2.png\", 0) is None\n```\n\n\n### Actual outcome\n\nThe comparison fails, and the figures slightly differ on macOS:\r\n```python\r\nTraceback (most recent call last):\r\n  File \"test.py\", line 13, in \u003cmodule\u003e\r\n    assert compare_images(\"1.png\", \"2.png\", 0) is None\r\nAssertionError\r\n```\r\n\r\nThe difference is rather small: the rightmost x-axis tick label slightly moves.\r\n\r\nOn Debian the assertion succeeds, and when downgrading to `matplotlib` 3.4.3 it also succeeds on macOS.\n\n### Expected outcome\n\nAccording to the [tight layout guide](https://matplotlib.org/stable/tutorials/intermediate/tight_layout_guide.html):\r\n\r\n\u003e Note that `matplotlib.pyplot.tight_layout()` will only adjust the subplot params when it is called. In order to perform this adjustment each time the figure is redrawn, you can call `fig.set_tight_layout(True)`, or, equivalently, set `rcParams[\"figure.autolayout\"]` (default: `False`) to `True`.\r\n\r\nI expect both figures to be equivalent, as there is nothing else happening after the `tight_layout()` / `set_tight_layout(True)` call and before saving.\n\n### Additional information\n\nI can only reproduce the behavior on macOS with `matplotlib` 3.5.0. Earlier versions produce consistent figures, and a Debian container with `python:3.9-slim` also produces consistent figures with `matplotlib` 3.4.3.\r\n\r\nI came across this while trying to understand differences in figure layout observed between CI running Ubuntu and a local macOS setup, which appeared with `matplotlib` 3.5.0 when using `tight_layout()`. These differences disappear with `set_tight_layout(True)`, and I also see consistent behavior with `constrained_layout`.\r\n\r\nWhile the observed difference in the example above is very small, the differences become slightly larger with more complex setups. [This gist](https://gist.github.com/alexander-held/8f429e1edde677be54045befec8c2f7b) shows another figure comparison where the differences are a bit more noticeable (though still small, and hard to see unless flipping back and forth between the images).\r\n\r\nWhen switching the backend to TkAgg (`matplotlib.use(\"TkAgg\")`), the discrepancy also disappears.\n\n### Operating system\n\nmacOS 11.5.2\n\n### Matplotlib Version\n\n3.5.0\n\n### Matplotlib Backend\n\nMacOSX\n\n### Python version\n\nPython 3.8.10\n\n### Jupyter version\n\n6.4.0\n\n### Installation\n\npip","author":{"url":"https://github.com/alexander-held","@type":"Person","name":"alexander-held"},"datePublished":"2021-11-18T18:12:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/21673/matplotlib/issues/21673"}