Gets the position and size of the visible region of a snip in snip coordinates. The result is undefined if the given snip is not managed by this administrator.
If no snip is specified, then the position and size of the snip's editor are returned, instead, in editor coordinates.
See also get-view in editor-admin%.
If snip is not #f, the current visible region of the snip is installed in the boxes x, y, w, and h. The x and y values are relative to the snip's top-left corner. The w and h values may be larger than the snip itself.
If snip is #f, the total visible region of the snip's top-level display is returned in editor coordinates. Using #f for snip is anaologous to using #t for full? in get-view in editor-admin%.