{"record":{"id":"c91794a491bd13f6","repo":"matplotlib/matplotlib","slug":"unknown-vf-opcode-byte","errorCode":null,"errorMessage":"Unknown vf opcode {byte}","messagePattern":"Unknown vf opcode (.+?)","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"lib/matplotlib/dviread.py","lineNumber":919,"sourceCode":"                c = self._read_arg(4)\n                s = self._read_arg(4)\n                d = self._read_arg(4)\n                a = self._read_arg(1)\n                l = self._read_arg(1)\n                self._fnt_def_real(k, c, s, d, a, l)\n                if self._first_font is None:\n                    self._first_font = k\n            elif byte == 247:       # preamble\n                i = self._read_arg(1)\n                k = self._read_arg(1)\n                x = self.file.read(k)\n                cs = self._read_arg(4)\n                ds = self._read_arg(4)\n                self._pre(i, x, cs, ds)\n            elif byte == 248:       # postamble (just some number of 248s)\n                break\n            else:\n                raise ValueError(f\"Unknown vf opcode {byte}\")\n\n    def _init_packet(self, pl):\n        if self.state != _dvistate.outer:\n            raise ValueError(\"Misplaced packet in vf file\")\n        self.h = self.v = self.w = self.x = self.y = self.z = 0\n        self.stack = []\n        self.text = []\n        self.boxes = []\n        self.f = self._first_font\n        self._missing_font = None\n        return self.file.tell() + pl\n\n    def _finalize_packet(self, packet_char, packet_width):\n        if not self._missing_font:  # Otherwise we don't have full glyph definition.\n            self._chars[packet_char] = Page(\n                text=self.text, boxes=self.boxes, width=packet_width,\n                height=None, descent=None)\n        self.state = _dvistate.outer","sourceCodeStart":901,"sourceCodeEnd":937,"githubUrl":"https://github.com/matplotlib/matplotlib/blob/b379c1b69e012b142c0f496a52bcb30513802d72/lib/matplotlib/dviread.py#L901-L937","documentation":"Error \"Unknown vf opcode {byte}\" thrown in matplotlib/matplotlib.","triggerScenarios":"Thrown at lib/matplotlib/dviread.py:919 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"b379c1b69e012b142c0f496a52bcb30513802d72","analyzedAt":"2026-08-21T23:31:55.468Z","schemaVersion":2},"datasetVersion":"2026-08-22T04:17:13.399Z"}