It generates an error if no such atom exists. The list is in stacking order, with the lowest window first. Top-level windows are returned as children of their logical parents. If no window in this application contains the point then an empty string is returned. In selecting the containing window, children are given higher priority than parents and among siblings the highest one in the stacking order is chosen.
All dimensions are in pixels.
If you need the true height immediately after creating a widget, invoke update to force the geometry manager to arrange it, or use winfo reqheight to get the window's requested height instead of its actual height. On Unix platforms, this is the X window identifier. On the Macintosh the value has no meaning outside Tk. The name is usually the name of the Tcl command for the geometry manager, such as pack or place . If the geometry manager is a widget, such as canvases or text, the name is the widget's class command, such as canvas .