René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Investigate alternative svg renderers for the test suite","articleBody":"Using rsvg as SVG renderer in the tests is *much* faster than using inkscape: with the following simple patch:\r\n```\r\ndiff --git a/lib/matplotlib/testing/compare.py b/lib/matplotlib/testing/compare.py\r\nindex ab2f26fc0..a90a75901 100644\r\n--- a/lib/matplotlib/testing/compare.py\r\n+++ b/lib/matplotlib/testing/compare.py\r\n@@ -138,9 +138,16 @@ def _update_converter():\r\n         converter['eps'] = make_external_conversion_command(cmd)\r\n \r\n     if matplotlib.checkdep_inkscape() is not None:\r\n-        def cmd(old, new):\r\n-            return [str('inkscape'), '-z', old, '--export-png', new]\r\n-        converter['svg'] = make_external_conversion_command(cmd)\r\n+        import cairo\r\n+        from gi.repository import Rsvg\r\n+        def convert(old, new):\r\n+            svg = Rsvg.Handle().new_from_file(old)\r\n+            svg.set_dpi(96)\r\n+            surf = cairo.ImageSurface(\r\n+                cairo.FORMAT_ARGB32, svg.props.width, svg.props.height)\r\n+            svg.render_cairo(cairo.Context(surf))\r\n+            surf.write_to_png(new)\r\n+        converter['svg'] = convert\r\n \r\n \r\n #: A dictionary that maps filename extensions to functions which\r\n```\r\nthe entire test suite runs in 594s instead of 787s on my laptop.  (There's also a ton of image comparison failures, but that's because my cache (which I did not regenerate in either case) is generated by inkscape and there seems to be pixel-level differences between the two renderers -- but that won't be a problem in practice as all we'll want to do is to compare svgs rendered by the same engine.)\r\n\r\nThere are also a few constructs that are not correctly rendered by rsvg but perhaps it's a good opportunity to try to generate slightly less demanding svgs... and again in any case we're still comparing the same misrendering by the same engine :-)\r\n\r\nThe real problem right now is whether there is an easy way to install rsvg on Windows.  There is an official .exe installer on Windows (https://wiki.gnome.org/action/show/Projects/PyGObject?action=show\u0026redirect=PyGObject) which I haven't tried; I haven't found a pip package; there are a few user-submitted conda packages (search for pygobject/pygobject3) but none of them seem to work on Py3.\r\n\r\nAlternatively, I have tried two other renderers: QtSVG (http://doc.qt.io/qt-5/qtsvg-index.html) and cairosvg (http://cairosvg.org/, which only supports Py3, but could be used as a standalone script that lives in its own environment, similarly to inkscape).  QtSVG is a very, very limited SVG renderer so I'd rather not use it (unless we can make our svg output compatible with it); cairosvg seems to freeze(?) on at least one of our constructs.","author":{"url":"https://github.com/anntzer","@type":"Person","name":"anntzer"},"datePublished":"2017-03-08T20:39:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/8242/matplotlib/issues/8242"}