+@node Window Tree
+@section The Window Tree
+@cindex window tree
+
+ A @dfn{window tree} specifies the layout, size, and relationship
+between all windows in one frame.
+
+@defun window-tree &optional frame
+This function returns the window tree for frame @var{frame}.
+If @var{frame} is omitted, the selected frame is used.
+
+The return value is a list of the form @code{(@var{root} @var{mini})},
+where @var{root} represents the window tree of the frame's
+root window, and @var{mini} is the frame's minibuffer window.
+
+If the root window is not split, @var{root} is the root window itself.
+Otherwise, @var{root} is a list @code{(@var{dir} @var{edges} @var{w1}
+@var{w2} ...)} where @var{dir} is @code{nil} for a horisontal split,
+and @code{t} for a vertical split, @var{edges} gives the combined size and
+position of the subwindows in the split, and the rest of the elements
+are the subwindows in the split. Each of the subwindows may again be
+a window or a list representing a window split, and so on. The
+@var{edges} element is a list @code{(@var{left}@var{ top}@var{ right}@var{ bottom})}
+similar to the value returned by @code{window-edges}.
+@end defun
+