code: def activate_zoom(self):
      gloo.set_viewport(0, 0, *self.physical_size)
      projection = ortho(0, self.size[0], 0, self.size[1], -1, +1)
      self.program["u_projection"] = projection
  
file_path: vispy/examples/demo/gloo/rain.py
imports: import numpy
  from vispy import gloo, app
  from vispy.gloo import Program, VertexBuffer
  from vispy.util.transforms import ortho
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