Utility procedures for managing the input focus.
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http://purl.org/tcl/home/man/tcl8.4/TkCmd/focusNext.htm

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**Manual**
'''SYNOPSIS'''

'''tk_focusNext''' ''window''

'''DESCRIPTION'''

'''tk_focusNext''' is a utility procedure used for keyboard traversal. It returns the "next" window after ''window'' in focus order. The focus order is determined by the stacking order of windows and the structure of the window hierarchy. Among siblings, the focus order is the same as the stacking order, with the lowest window being first. If a window has children, the window is visited first, followed by its children (recursively), followed by its next sibling. Top-level windows other than ''window'' are skipped, so that '''tk_focusNext''' never returns a window in a different top-level from ''window''.

After computing the next window, '''tk_focusNext''' examines the window's '''-takefocus''' option to see whether it should be skipped. If so, '''tk_focusNext''' continues on to the next window in the focus order, until it eventually finds a window that will accept the focus or returns back to window.

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<<discussion>>
'''Focus Order and clipping order using the pack geometry manager'''

[HaO]: The focus order follows [Stacking Order] while the clipping order is controled by packing order (first packed, first seen).
To achieve different clipping orders and focus orders, one may create and pack widgets in different order (or use the [raise] or [lower] commands).

Examples:
First, two buttons obscure an entry widget, if place is limited (resize window).
Tab order is backward as desired.
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pack [button .b1 -text Button1] [button .b2 -text Button2] -side right
pack [entry .e -width 30] -side left
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To change tab-order, one may raise the .b2 and the .e widget:
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pack [button .b1 -text Button1] [button .b2 -text Button2] -side right
pack [entry .e -width 30] -side left
raise .b1 .b2
raise .e .b1
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A (IMHO) more natural way to achieve the same configuration, one may create widgets in focus order and pack widgets in clipping order:
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entry .e -width 30
button .b1 -text Button1
button .b2 -text Button2
pack .b2 .b1 -side right
pack .e -side left
======
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When would one most likely use '''tk_focusNext''' - in the context of writing [bind] commands?

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To assign the functionality of the Tab key to other keys (ex. Return key), one may use two alternatives:
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bind .w <Return> {focus [tk_focusNext %W]}
bind .w <Return> {event generate %W <Tab>}
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The first only switches focus.
The second performs additional tasks, like selecting the current entry if it gains focus to an entry box.

<<discussion>>
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**See also**
   * [focus]
   * [focusNext]
   * [tk_focusPrev]
   * [tk_focusFollowsMouse]
   * [tk_menuSetFocus]
   * [Stacking Order]

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