René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"AttributeError: BadRRModeError object has no attribute 'sequence_number'","articleBody":"Dear maintainer,\r\n\r\n**tldr**; An uncaught exception in `parse_error_response()` causes the next call to `get_input_focus()` to hang indefinitely with 100% CPU usage.\r\n\r\n## Details\r\n\r\n**OS**: Debian Bookworm\r\n**Python version**: 3.10.9\r\n**python3-xlib version**: 0.33-1\r\n\r\nThe application I use calls `win.get_full_property(self._NET_WM_NAME, 0)` where `win` is instance of `Window` from `drawable.py` and `self._NET_WM_NAME` is 326.\r\n\r\nThe traceback is as follows:\r\n\r\n```\r\nTraceback (most recent call last):\r\n  File \"/usr/bin/keyd-application-mapper\", line 156, in get_title\r\n    x = win.get_full_property(self._NET_WM_NAME, 0).value\r\n  File \"/usr/lib/python3/dist-packages/Xlib/xobject/drawable.py\", line 476, in get_full_property\r\n    prop = self.get_property(property, property_type, sizehint,\r\n  File \"/usr/lib/python3/dist-packages/Xlib/xobject/drawable.py\", line 455, in get_property\r\n    r = request.GetProperty(display = self.display,\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1368, in __init__\r\n    self.reply()\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1380, in reply\r\n    self._display.send_and_recv(request = self._serial)\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/display.py\", line 612, in send_and_recv\r\n    gotreq = self.parse_response(request)\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/display.py\", line 719, in parse_response\r\n    gotreq = self.parse_error_response(request) or gotreq\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/display.py\", line 745, in parse_error_response\r\n    req = self.get_waiting_request(e.sequence_number)\r\nAttributeError: 'BadRRModeError' object has no attribute 'sequence_number'\r\n```\r\n\r\nThe [`BadRRModeError`](https://github.com/python-xlib/python-xlib/commit/c87624dd6ec780417e2d32529976d65fed344045) exception was added by `disp.extension_add_error(BadRRMode, BadRRModeError)` in `Xlib/ext/randr.py` and seems to be quite different from the other errors defined in `Xlib/error.py` and in particular the '**sequence_number**' attribute does not exist.\r\n\r\nThe application I use logs this error and proceeds by calling `dpy.next_event()` and then `dpy.dpy.get_input_focus()` where  `dpy = Xlib.display.Display()`.\r\n\r\n_The last call hangs indefinitely with 100% CPU usage and seems to do so because of the previous_ `BadRRModeError`.\r\n\r\nI used Python's [faulthandler](https://docs.python.org/3/library/faulthandler.html) module to investigate where the code hangs (i.e. `python3 -X faulthandler application.py` and then sending `SIGARBT` to see where the main thread is). I did this several times and every time the thread was busy inside the `send_and_recv()` function in `Xlib/protocol/display.py`:\r\n```\r\nCurrent thread 0x00007f30fc5fe040 (most recent call first):\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/display.py\", line 515 in send_and_recv\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1380 in reply\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1368 in __init__\r\n  File \"/usr/lib/python3/dist-packages/Xlib/display.py\", line 607 in get_input_focus\r\n  File \"/usr/bin/keyd-application-mapper\", line 200 in run\r\n  File \"/usr/bin/keyd-application-mapper\", line 419 in \u003cmodule\u003e\r\n```\r\n\r\n## Workaround\r\n\r\nI'm not very familiar with python-xlib internals, so I still don't fully understand what is going on.\r\n\r\nA temporary solution for my case is to simply remove the line `disp.extension_add_error(BadRRMode, BadRRModeError)` which instead causes the error to appear as:\r\n```\r\nTraceback (most recent call last):\r\n  File \"/usr/bin/keyd-application-mapper\", line 174, in get_window_info\r\n    return (cls[1], get_title(win))\r\n  File \"/usr/bin/keyd-application-mapper\", line 155, in get_title\r\n    raise err from None\r\n  File \"/usr/bin/keyd-application-mapper\", line 153, in get_title\r\n    title = win.get_full_property(self._NET_WM_NAME, 0).value.decode('utf8')\r\n  File \"/usr/lib/python3/dist-packages/Xlib/xobject/drawable.py\", line 476, in get_full_property\r\n    prop = self.get_property(property, property_type, sizehint,\r\n  File \"/usr/lib/python3/dist-packages/Xlib/xobject/drawable.py\", line 455, in get_property\r\n    r = request.GetProperty(display = self.display,\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1368, in __init__\r\n    self.reply()\r\n  File \"/usr/lib/python3/dist-packages/Xlib/protocol/rq.py\", line 1388, in reply\r\n    raise self._error\r\nXlib.error.BadValue: \u003cclass 'Xlib.error.BadValue'\u003e: code = 2, resource_id = 10, sequence_number = 4818, major_opcode = 20, minor_opcode = 0\r\n```\r\nwhich does not cause `get_input_focus()` to hang.\r\n\r\n","author":{"url":"https://github.com/Penlect","@type":"Person","name":"Penlect"},"datePublished":"2023-01-13T18:03:10.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/259/python-xlib/issues/259"}