code: func baseShader(c *Canvas) {
  	gs := &glShader{
  		vf: defaultCanvasVertexFormat,
  		vs: baseCanvasVertexShader,
  		fs: baseCanvasFragmentShader,
  	}
  
  	gs.setUniform("uTransform", &gs.uniformDefaults.transform)
  	gs.setUniform("uColorMask", &gs.uniformDefaults.colormask)
  	gs.setUniform("uBounds", &gs.uniformDefaults.bounds)
  	gs.setUniform("uTexBounds", &gs.uniformDefaults.texbounds)
  
  	c.shader = gs
  }
docs: // Sets up a base shader with everything needed for a Pixel
  // canvas to render correctly. The defaults can be overridden
  // by simply using the SetUniform function.