René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Patches eagerly resolve colors and apply alpha, but should do so lazily like Line2Ds","articleBody":"Consider the following example:\r\n```\r\nfrom matplotlib.pyplot import Line2D, Rectangle\r\n\r\nl = Line2D([], [], alpha=.5)\r\nl.set_color(\"red\")\r\nprint(l.get_color())\r\n\r\nr = Rectangle((0, 0), 1, 1, alpha=.5)\r\nr.set_facecolor(\"red\")\r\nprint(r.get_facecolor())\r\n```\r\n\r\nThe line reports its color as \"red\", but the rectangle reports it as (1, 0, 0, .5).  This is because patches immediately resolve colors and apply alphas; to do so they need to maintain an elaborate dance involving _original_facecolor and _original_edgecolor.  Conversely, Line2D doesn't resolve colors eagerly (they just store whatever was passed in), and perform the conversion in draw().\r\n\r\nAs an other example, consider\r\n```\r\nfrom pylab import *\r\nfrom matplotlib.pyplot import Line2D, Rectangle\r\n\r\nax = gca()\r\nax.add_artist(Line2D([0, 1], [.5, 1], color=\"C0\"))\r\nax.add_artist(Rectangle((0, 0), 1, .5, color=\"C0\"))\r\nrcParams[\"axes.prop_cycle\"] = cycler(color=[\"r\", \"g\", \"b\"])\r\n\r\nshow()\r\n```\r\nThis will draw a red line (draw-time resolution is affected by the new prop_cycle), but a blue rectangle (eager resolution uses the original prop_cycle).\r\n\r\nI think the behavior of Line2D makes more sense (at least the output of get_facecolor() immediately after a set_facecolor() should be what we set...), this would also avoid issues such as #11702/#11703.\r\n\r\n(mpl master and probably since a long time ago)","author":{"url":"https://github.com/anntzer","@type":"Person","name":"anntzer"},"datePublished":"2018-07-20T07:32:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/11710/matplotlib/issues/11710"}