Returns the container offset to the Client area, see the Layout Guide. Useful for IupFrame, IupTabs and IupDialog that have decorations. Can also be consulted in other containers, it will return "0x0". For controls that have a native representation is only available when the control is mapped.
In GTK and Motif, for the IupDialog, the dy value is negative when there is a menu. This occours because in those systems the menu is placed inside the Client Area and all children must be placed bellow the menu.
In Windows, for the IupFrame, the value is always "0x0" because it actually does not have a Client area, so the child is manually positioned in the expected Client area.
This attribute can be used in conjunction with the POSITION attribute of a child so the coordinates of a child relative to the native parent top-left corner can be obtained.
"dxxdy", where dx and dy are integer values corresponding to the horizontal and vertical offsets, respectively, in pixels.
All elements that are containers, except menus.