René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"pgf backend no longer supports fig.draw","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\nBecause of the cleanups in #15977, the pgf backend no longer supports `fig.draw(fig.canvas.get_renderer())` to trigger a draw.\r\n\r\nIf this is not supposed to be a bug and is the correct expected behavior, is there a cleaner way to trigger a draw without using `fig.savefig`?\r\n\r\n**Bug summary**\r\n\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\n\r\n**Code for reproduction**\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug.\r\nPlease make sure to minimize the number of dependencies required, and provide\r\nany necessary plotted data.\r\nAvoid using threads, as Matplotlib is (explicitly) not thread-safe.--\u003e\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\n\r\nplt.switch_backend('pgf')  # Switching to the PGF backend\r\nfig, ax = plt.subplots(figsize=(6, 3.0), ncols=2, nrows=1,\r\n                       constrained_layout=True, sharey=True)\r\nfig.set_constrained_layout_pads(wspace=0.03)\r\n\r\nax[0].plot(np.arange(4), 'r', label=r'Really longgggg label 1')\r\nax[1].plot(np.arange(5), 'b', label=r'Really longgggg label 2')\r\n(leg_h0, leg_lab0) = ax[0].get_legend_handles_labels()\r\n(leg_h1, leg_lab1) = ax[1].get_legend_handles_labels()\r\n\r\n# add a legend to one of the axes to make space at the top of the figure\r\nleg0 = ax[0].legend(leg_h0, leg_lab0, loc='lower center',\r\n                    bbox_to_anchor=(0.5, 1.07))\r\n\r\nleg0.set_in_layout(True)  # force to steal space from top of the figure\r\n# ------------------------------------------------------\r\n# Trigger a draw (required for constrained_layout to work)\r\n# fig.canvas.draw()   # Doesn't work since pgf is a non-interactive backend\r\nfig.draw(fig.canvas.get_renderer())  # used to work before #15977\r\n# ------------------------------------------------------\r\n# Thanks constrained_layout, your work is done! turning you off now\r\nfig.set_constrained_layout(False)\r\n\r\n# Remove legend from axes and add a figure legend\r\n# which includes entries from both axes\r\nleg0.remove() \r\nfig_leg = fig.legend(*zip(leg_h0, leg_h1), *zip(leg_lab0, leg_lab1),\r\n                     loc='lower center', ncol=2, columnspacing=5,\r\n                     bbox_to_anchor=(0.5, 0.85))\r\nfig.savefig('test.png', dpi=200)\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n``` \r\nTraceback (most recent call last):\r\n  File \"test.py\", line 22, in \u003cmodule\u003e\r\n    fig.draw(fig.canvas.get_renderer())  # works!\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\artist.py\", line 41, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\figure.py\", line 1862, in draw\r\n    self.patch.draw(renderer)\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\artist.py\", line 41, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\patches.py\", line 587, in draw\r\n    draw_path(tpath, affine,\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\backends\\backend_pgf.py\", line 475, in draw_path\r\n    writeln(self.fh, r\"\\begin{pgfscope}\")\r\n  File \"---\\Miniconda3\\lib\\site-packages\\matplotlib\\backends\\backend_pgf.py\", line 129, in writeln\r\n    fh.write(line)\r\nAttributeError: 'NoneType' object has no attribute 'write'\r\n```\r\n\r\n**Expected outcome**\r\n![test](https://user-images.githubusercontent.com/15175620/92253165-2bc79e00-ee9d-11ea-9089-2ac0f9f1addb.png)\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Windows 10\r\n  * Matplotlib version: 3.3.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): pgf\r\n  * Python version: 3.8.5\r\n  * Jupyter version (if applicable):\r\n  * Other libraries: \r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/pharshalp","@type":"Person","name":"pharshalp"},"datePublished":"2020-09-04T15:02:24.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/18407/matplotlib/issues/18407"}