code: def activate_zoom(self):
      width, height = self.size
      gloo.set_viewport(0, 0, *self.physical_size)
      self.program["u_aspect_ratio"] = width / float(height)
  
file_path: vispy/examples/demo/gloo/raytracing.py
imports: from math import cos
  from vispy import app, gloo
label_desc: Use image node_id 4 for calling the Canvas obj's underlying member method code with example usage: obj.activate_zoom() without return types