code: func (v *Surface) GetFallbackResolution() (xPPI, yPPI float64) {
  	var x, y C.double
  	C.cairo_surface_get_fallback_resolution(v.native(), &x, &y)
  	return float64(x), float64(y)
  }
docs: // GetFallbackResolution is a wrapper around
  // cairo_surface_get_fallback_resolution().