Converts the screen coordinates of a given point or rectangle on the display to client coordinates.
Points to a CPoint object or POINT structure that contains the screen coordinates to be converted.
Points to a CRect object or RECT structure that contains the screen coordinates to be converted.
The ScreenToClient member function replaces the screen coordinates given in lpPoint or lpRect with client coordinates. The new coordinates are relative to the upper-left corner of the CWnd client area.
See the example for CListCtrl::GetItemRect.