Creating a custom control - getting the on-screen rect?

I'm trying to get the on-screen Rect of a GUIContent. GUILayoutUtility.GetRect seems to only return a Rect relative to the current window. Since this control needs to know the mouse position and whether it's over the button or not, how can I get this data?

 

The mouse position has already been adjusted for the window, so you can just check if (myRect.Contains (Event.current.mousePosition)

try this:

Code (csharp):

1.  
2. function OnGUI () {
3.     Debug.Log ("Before: " + Event.current.mousePosition);
4.     GUI.BeginGroup (Rect (20,20,100,100));
5.     Debug.Log ("After: " + Event.current.mousePosition);
6.     GUI.EndGroup ();
7. }
8.  

And notice how the mouse position is different inside outside of the group.