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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[MNT]: Confusing edgecolor behavior for Patch and Collection","articleBody":"Noted while reviewing documentation on the current behavoir in #29252.\r\n\r\n### Summary\r\n\r\nPatches and Collections do not draw edges by default. This was introduced in #5596 for matplotlib 2.0. It seems that this was first achieved by a linewidth 0, but it this was changed to using an edgecolor of \"none\" while maintaining a finite linewidth.\r\n\r\nAs a consequence `rcParams[\"patch.edgecolor\"]` does not have an effect by default. There are, however two cases when  `rcParams[\"patch.edgecolor\"]` becomes relevant:\r\n1. If facecolor is \"none\", Patch and Collection take `rcParams[\"patch.edgecolor\"]` as edgecolor.\r\n   I assume, this is done to prevent the artist being completely invisible (no facecolor and no edgecolor).\r\n2. If `rcParams[\"patch.force_edgecolor\"]` is set to true, `rcParams[\"patch.edgecolor\"]` is used instead of \"none\" as the\r\n\r\nThis is overall very confusing.\r\n\r\nPing @efiring, who introduced `rcParams[\"patch.force_edgecolor\"]` in #6904. Can you comment on the background and whether the proposal below is a reasonable alternative?\r\n\r\n### Proposed fix\r\n\r\nCan we switch to the following logic: `patch.edgecolor` is generally used as edgecolor and now defaults to \"none\" (to achieve the same behavior as before). To handle case 1. (prevent invisible artists) introduce a new `rcParams[\"patch.edgecolor_fallback\"]` that has a special color only for that case.\r\n\r\n### Needed changes to default rcParams\r\nmatplotlibrc before:\r\n```\r\n#patch.edgecolor: black\r\n#patch.force_edgecolor: False\r\n```\r\nmatplotlibrc after\r\n```\r\n#patch.edgecolor: \"none\"            # default edgecolor for Patch and Collection\r\n#patch.edgecolor_fallback: \"black\"  # edgecolor to be used if facecolor is \"none\" to prevent completely invisible artists\r\n```\r\n\r\n### Needed changes to styles\r\nExisting styles would migrate\r\n\r\n- If `patch.force_edgecolor` was False:\r\n  from:\r\n  ```\r\n  patch.edgecolor: COLOR\r\n  #patch.force_edgecolor: False\r\n  ```\r\n  to\r\n  ```\r\n  #patch.edgecolor: \"none\"\r\n  patch.edgecolor_fallback:  COLOR\r\n  ```\r\n- If `patch.force_edgecolor` was True:\r\n  from:\r\n  ```\r\n  patch.edgecolor: COLOR\r\n  patch.force_edgecolor: True\r\n  ```\r\n  to\r\n  ```\r\n  patch.edgecolor: COLOR\r\n  patch.edgecolor_fallback:  COLOR\r\n  ```\r\n\r\n### Transition path\r\n- `patch.force_edgecolor` gets deprecated and raises a warning when used on rcParams.\r\n- styles that don't use any of `patch.edgecolor` or `patch.force_edgecolor` do not have to do anything. \r\n- styles that have set `patch.edgecolor` but not `patch.force_edgecolor` are a very edge case. They either have overlooked that the default `force_edgecolor=False` makes the setting ineffective, or they have intentionally only configured the somewhat arcane edge color fallback for non-filled artists. In the former case, they get \"auto-fixed\" through the new behavior. I'd argue that we can affort to not runtime-warn on the latter case (but if really wanted, one could add a check at least for loading stylesheets).","author":{"url":"https://github.com/timhoffm","@type":"Person","name":"timhoffm"},"datePublished":"2024-12-08T23:44:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":12},"url":"https://github.com/29261/matplotlib/issues/29261"}