How do I convert a RectTransform (UI Panel) to screen coordinates?

Question

I want to determine the screen coordinates of a RectTransform in Unity3D. How is this done, taking into consideration that the element may be anchored, or even scaled?

I am trying to use RectTransform.GetWorldCorners and then converting each Vector3 to screen coordinates, but the values are wrong.

public Rect GetScreenCoordinates(RectTransform uiElement)
{
    var worldCorners = new Vector3[4];
    uiElement.GetWorldCorners(worldCorners);
    var result = new Rect(
        worldCorners[0].x,
        worldCorners[0].y,
        worldCorners[2].x - worldCorners[0].x,
        worldCorners[2].y - worldCorners[0].y);
    for (int index = 0; index < 4; index++)
        result[index] = Camera.main.WorldToScreenPoint(result[index]);
    return result;
}

Answer 1

Although the help says that it returns coordinates in world space, they are actually in screen space (at least when the UI is not in world space). So the solution is simple:

public Rect GetScreenCoordinates(RectTransform uiElement)
{
  var worldCorners = new Vector3[4];
  uiElement.GetWorldCorners(worldCorners);
  var result = new Rect(
                worldCorners[0].x,
                worldCorners[0].y,
                worldCorners[2].x - worldCorners[0].x,
                worldCorners[2].y - worldCorners[0].y);
  return result;
}