René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"add_lines misses lines for matplotlib.colorbar.ColorbarBase","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\nFor matplotlib.colorbar.ColorbarBase(...) usage of add_lines(...) may yield missing lines/poorly adjusted lines.\r\n\r\n**Code for reproduction**\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug, also minimizing the number of dependencies required--\u003e\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nimport matplotlib as mpl\r\nimport numpy as np\r\n\r\nfig = plt.figure()\r\nax = fig.add_axes([0.05, 0.8, 0.9, 0.15])\r\ncmap = mpl.cm.cool\r\nnorm = mpl.colors.Normalize(vmin=-4, vmax=4)\r\nlevels = (-1.0, 1.0, 2.0, 3.0)\r\n\r\ncb = mpl.colorbar.ColorbarBase(ax, cmap=cmap, norm=norm)\r\ncolors_bg = np.tile(list((1.0, 1.0, 1.0, 1.0)), (len(levels), 1))\r\ncb.add_lines(levels=levels, colors=colors_bg, linewidths=7)\r\n\r\nplt.show()\r\n\r\n\r\n```\r\n\r\n**Expected outcome**\r\n\r\n4 white lines, crossing the colorbar.\r\nUsed to work on matplotlib 2.2.3!\r\n\r\n**Matplotlib version**\r\n  * Operating system: Ubuntu 18.04 LTS\r\n  * Matplotlib version: 3.0.0\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): Qt5Agg\r\n  * Python version: 3.7.0\r\n\r\nMiniconda install, fully updated.","author":{"url":"https://github.com/e3reiter","@type":"Person","name":"e3reiter"},"datePublished":"2018-10-09T14:48:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/12458/matplotlib/issues/12458"}