René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Tkagg backend prints backtrace in some circumstances","articleBody":"### Bug report\r\n\r\nWhen using the tkagg backend, a backtrace gets printed, although it doesn't stop and the script finishes normally.\r\nIt only seems to happen if you save a figure to a PDF, and then save to a PNG with the `bbox_inches=\"tight\"` option.\r\nDoing just PNG with tight bbox, or PDF then PNG without tight bbox doesn't output the backtrace.\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nimport matplotlib\r\nprint(\"Backend = \", matplotlib.get_backend())\r\nimport matplotlib.pyplot as plt\r\nplt.plot((1,2),(3,4))\r\nprint(\"savefig to PDF\")\r\nplt.savefig(\"fig.pdf\")\r\nprint(\"savefig to PNG\")\r\nplt.savefig(\"fig.png\", bbox_inches=\"tight\")\r\nprint(\"Done\")\r\n```\r\n\r\n**Actual outcome**\r\n```\r\nBackend =  TkAgg\r\nsavefig to PDF\r\nsavefig to PNG\r\nException in Tkinter callback\r\nTraceback (most recent call last):\r\n  File \"/usr/lib/python3.6/tkinter/__init__.py\", line 1705, in __call__\r\n    return self.func(*args)\r\n  File \"/usr/lib/python3.6/tkinter/__init__.py\", line 749, in callit\r\n    func(*args)\r\n  File \"/home/kirkmatt/tktest/lib/python3.6/site-packages/matplotlib/backends/_backend_tk.py\", line 253, in idle_draw\r\n    self.draw()\r\n  File \"/home/kirkmatt/tktest/lib/python3.6/site-packages/matplotlib/backends/backend_tkagg.py\", line 9, in draw\r\n    super(FigureCanvasTkAgg, self).draw()\r\n  File \"/home/kirkmatt/tktest/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py\", line 407, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"/home/kirkmatt/tktest/lib/python3.6/site-packages/matplotlib/backend_bases.py\", line 1544, in _draw\r\n    def _draw(renderer): raise Done(renderer)\r\nmatplotlib.backend_bases._get_renderer.\u003clocals\u003e.Done: \u003cmatplotlib.backends.backend_agg.RendererAgg object at 0x7f019bb6b5c0\u003e\r\nDone\r\n```\r\n\r\n**Expected outcome**\r\nThe exception is caught somewhere and no backtrace is printed.\r\n\r\n**Matplotlib version**\r\n  * Operating system: Ubuntu 18.04\r\n  * Matplotlib version: 3.3.4 \r\n  * Matplotlib backend: TkAgg\r\n  * Python version: 3.6.9\r\n  * Other libraries: Tkinter installed using `apt install python3-tk`, matplotlib installed in a virtualenv with pip\r\n\r\nThis is possibly related to #18186\r\nThere's also a [stackoverflow question](https://stackoverflow.com/questions/62084819/exception-in-tkinter-callback-using-shap), although in that case they just save to a png and get the traceback, while if I am only saving to PNG I don't.\r\n","author":{"url":"https://github.com/MJKirk","@type":"Person","name":"MJKirk"},"datePublished":"2021-05-11T13:23:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/20204/matplotlib/issues/20204"}