René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"constrained-layout gives wrong results when explicitly equal width ratios are set","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\nWhen passing `width_ratios = [1, 1, 1]` instead of not passing it at all (which should be synonymous), constrained_layout sometimes gives incorrect results.\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 as mpl\r\nfrom matplotlib import pyplot as plt, gridspec, testing\r\n\r\nmpl.rcdefaults()\r\nmpl.style.use([\"classic\", \"_classic_test_patch\"])\r\nmpl.testing.set_font_settings_for_testing()\r\n\r\ndef example_plot(ax, fontsize=12):\r\n    ax.plot([1, 2])\r\n    ax.locator_params(nbins=3)\r\n    ax.set_xlabel('x-label', fontsize=fontsize)\r\n    ax.set_ylabel('y-label', fontsize=fontsize)\r\n    ax.set_title('Title', fontsize=fontsize)\r\n\r\nfig = plt.figure(constrained_layout=True)\r\ngs = gridspec.GridSpec(3, 3, figure=fig)\r\n\r\nax1 = fig.add_subplot(gs[0, 0])\r\nax2 = fig.add_subplot(gs[0, 1:])\r\nax3 = fig.add_subplot(gs[1:, 0:2])\r\nax4 = fig.add_subplot(gs[1:, -1])\r\n\r\nfor ax in fig.axes:\r\n    example_plot(ax)\r\n\r\nfig.savefig(\"/tmp/cl1.png\")\r\n\r\nfig = plt.figure(constrained_layout=True)\r\ngs = gridspec.GridSpec(3, 3, figure=fig,\r\n                       width_ratios=[1, 1, 1], height_ratios=[1, 1, 1])\r\n\r\nax1 = fig.add_subplot(gs[0, 0])\r\nax2 = fig.add_subplot(gs[0, 1:])\r\nax3 = fig.add_subplot(gs[1:, 0:2])\r\nax4 = fig.add_subplot(gs[1:, -1])\r\n\r\nfor ax in fig.axes:\r\n    example_plot(ax)\r\n\r\nfig.savefig(\"/tmp/cl2.png\")\r\n\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n\r\ncl1.png\r\n![cl1](https://user-images.githubusercontent.com/1322974/80868223-61fbd380-8c99-11ea-8011-0cfd2f91e375.png)\r\n\r\ncl2.png\r\n![cl2](https://user-images.githubusercontent.com/1322974/80868222-61fbd380-8c99-11ea-8a3c-f71a35c89d98.png)\r\n\r\nClearly in cl2.png the widths are not in the ratios 1:1:1 but (approximately) 1:2:1.\r\n\r\nThis is likely a floating point error; it is extremely sensitive to conditions, in particular the call to `set_font_settings_for_reproducibility` (which just sets some font-related rcs) is necessary to observe this.\r\n\r\n**Expected outcome**\r\n\r\ntwice the same image\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: archlinux\r\n  * Matplotlib version: master\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): agg\r\n  * Python version: 38\r\n  * Jupyter version (if applicable): no\r\n  * Other libraries: \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/anntzer","@type":"Person","name":"anntzer"},"datePublished":"2020-05-02T15:23:55.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/17304/matplotlib/issues/17304"}