René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"SubFigure hspace=None incorrectly applies default vertical spacing when wspace is specified","articleBody":"### Bug summary\n\n`SubFigure` with `hspace=None` incorrectly applies the default vertical spacing when `wspace` is specified. This produces an unintended vertical gap between subfigures.\n\n### Code for reproduction\n\n```python\nimport matplotlib\nmatplotlib.use(\"Agg\")\nimport matplotlib.pyplot as plt\n\nfig = plt.figure(figsize=(6, 4))\nwspace, hspace = 0.2, None\nprint(\"Input: wspace=\", wspace, \"hspace=None\")\nsubfigures = fig.subfigures(nrows=2, ncols=2,\n                            wspace=wspace, hspace=hspace)\n\nfor row in range(2):\n    for column in range(2):\n        subfigures[row, column].add_subplot().plot([0, 1], [0, 1])\n\nfig.canvas.draw()\nfor row in range(2):\n    for column in range(2):\n        print(f\"Subfigure ({row}, {column}) bounds:\",\n              tuple(round(value, 3)\n                    for value in subfigures[row, column].bbox.bounds))\nplt.close(fig)\n```\n\n### Actual outcome\n\n```text\nInput: wspace= 0.2 hspace=None\nSubfigure (0, 0) bounds: (np.float64(0.0), np.float64(218.182), np.float64(272.727), np.float64(181.818))\nSubfigure (0, 1) bounds: (np.float64(327.273), np.float64(218.182), np.float64(272.727), np.float64(181.818))\nSubfigure (1, 0) bounds: (np.float64(0.0), np.float64(0.0), np.float64(272.727), np.float64(181.818))\nSubfigure (1, 1) bounds: (np.float64(327.273), np.float64(0.0), np.float64(272.727), np.float64(181.818))\n```\n\n### Expected outcome\n\n```text\nInput: wspace= 0.2 hspace=None\nSubfigure (0, 0) bounds: (0.0, 200.0, 300.0, 200.0)\nSubfigure (0, 1) bounds: (300.0, 200.0, 300.0, 200.0)\nSubfigure (1, 0) bounds: (0.0, 0.0, 300.0, 200.0)\nSubfigure (1, 1) bounds: (300.0, 0.0, 300.0, 200.0)\n```\n\nWhen no layout engine is active, `hspace=None` should result in no vertical spacing, while the requested `wspace=0.2` should be applied.\n\n### Additional information\n\nThis is a regression introduced by [PR #25960](https://github.com/matplotlib/matplotlib/pull/25960).\n\nThe example uses only public Matplotlib APIs and legal inputs, and its output is deterministic. The horizontal spacing is applied as requested, but `hspace=None` produces a vertical gap: the subfigure heights are 181.818 pixels with a 36.364-pixel gap. According to the updated documentation and the intent of PR #25960, unspecified spacing should be zero when no layout engine is active.\n\nPassing `hspace=None` through `GridSpec` appears to fall back to the figure's default subplot `hspace`, causing unintended vertical spacing when only `wspace` is specified. The analogous issue may occur when only `hspace` is specified.\n\n### Operating system\n\nLinux\n\n### Matplotlib Version\n\n3.11.1\n\n### Matplotlib Backend\n\nagg\n\n### Python version\n\n3.11.13\n\n### Jupyter version\n\nN/A\n\n### Installation\n\nN/A","author":{"url":"https://github.com/SuYanqi","@type":"Person","name":"SuYanqi"},"datePublished":"2026-07-20T09:55:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/32076/matplotlib/issues/32076"}