code: func DepthRangeIndexed(index uint32, n float64, f float64) {
  	syscall.Syscall(gpDepthRangeIndexed, 3, uintptr(index), uintptr(math.Float64bits(n)), uintptr(math.Float64bits(f)))
  }
docs: // specify mapping of depth values from normalized device coordinates to window coordinates for a specified viewport