class_docstr: OSMesa backend for Canvas
class_docstr_tok: ["OSMesa","backend","for","Canvas"]
code: def _on_draw(self):
      # This is called by the osmesa ApplicationBackend
      if self._vispy_canvas is None or self._pixels is None:
          raise RuntimeError("draw with no canvas or pixels attached")
          return
      self._vispy_set_current()
      self._vispy_canvas.events.draw(region=None)
  
imports: from __future__ import division
  from ...util.ptime import time
  from ..base import BaseApplicationBackend, BaseCanvasBackend, BaseTimerBackend
  from ...gloo import gl
  from time import sleep
label_desc: Use image node_id 16 for calling the CanvasBackend obj's underlying member method code with example usage: obj._on_draw() without return types