code: func NewCanvas(bounds pixel.Rect) *Canvas {
  	c := &Canvas{
  		gf:  NewGLFrame(bounds),
  		mat: mgl32.Ident3(),
  		col: mgl32.Vec4{1, 1, 1, 1},
  	}
  
  	baseShader(c)
  	c.SetBounds(bounds)
  	c.shader.update()
  	return c
  }
docs: // NewCanvas creates a new empty, fully transparent Canvas with given bounds.