Below is a patch for tk3.1/tk3.2 to modify the way focus and
keyboard events are handled.  The patch implements two independent
changes (you can choose between using none, either, or both of the
modified behaviors).  First the two modifications are described, 
and then the patch file itself.

focus-follows-pointer
---------------------
tk2.3 used a focus-follows-pointer model, while tk3.1 introduced a
click-to-focus model.  Below is patch for that allows the application
designer (or user) to select between the two models at runtime.

focus-follows-pointer (tk2.3): By default, all keyboard events are sent
	to the window under the mouse cursor.  The "focus" command may
	be used to establish a focus window where all keyboard events
	are sent regardless of where the mouse pointer is.  After
	the focus window is destroyed or after a "focus none" command,
	keyboard events will again be sent to the window under the mouse
	cursor.

click-to-focus (tk3.1): Keyboard events are always sent to the
	focus window.  If there is no focus window, keyboard events
	are dropped.  The "focus default" command allows two levels
	of focus, so that a temporary window may be created, given
	the focus, and then when the temp window is destroyed the
	focus will be automatically restored to the original state.

After you have rebuilt your application, tk will still use
the default click-to-focus model.  To switch to the focus-follows-pointer 
model, issue the tcl command:
	focus pointer on
	focus none
The behavior will then be similar to tk2.3.  It is only "similar" to tk2.3,
because the "focus default" of tk3.1 is still available and active.

propagate-key
-------------
tk2.3 used a "flat" model for Key events (KeyPress and KeyRelease).
That is, key events were matched against bindings for the focus
window or, if no focus window, the window under the pointer.
The patch below allows the application designer to
select a "propagation" model.  This is used only when there is
no active focus window.  Key-events will be matched not only
against the window under the pointer, but all of its parents,
until a match is found.  Thus (conceptually) the key-events
are propagated up the window hierarchy.  Prof. Ousterhout's
implementation of event bindings allows such propgation to
be efficiently and conventiently implemented.

After you have rebuilt your application, tk will still use the default
"flat" model.  To switch to the "propagation" model, issue the tcl command:
	focus propagation on

Note: Some widgets "absorb" all key events (.e.g, Menu and Entry) and
discarded them even if the key event is not used.  Such events are not
propagated upwards.  Perhaps a mechanism is needed to allow such
widgets to examine the key and "refuse" it, in which case it would get
propagated.  Or perhaps that would just complicate things.

comments
--------
Both of these patches were easy to implement and are small.  The
focus-follows-pointer is a strait-forward concept with little
subtlety.  In contrast the propagate-key seems more complicated (How
far up should the keys be propagated?  Should propagation terminate at
top-level windows?  At user selected top-level windows?  Should
propagation occur even with an active focus?  How can it be used to
better implement menu traversal?)

If you find bugs or have questions/additions, please let me know.
The patch file is below.

Kennard


focus3.1a patch (fixed)
---------------
This patch was designed for tk3.1, but should work with tk3.2 as well.
The patch will modifify tk.h, tkEvent.c, tkFocus.c, and tkCmds.c.
It will also create "focusDemo.tcl", a short script that demonstrates
these modifications.

For focus-follows-pointer behavior support, you must modify the
Makefile so that the CFLAGS includes "-DPOINTER_FOCUS".  If this is not
defined in the Makefile, the focus-follows-pointer modification will be
ifdef'd out, and you will get vanila tk3.1.

For propagate-key bevhavior support, you must modify the Makefile so
that the CFLAGS includes "-DPROPAGATE_KEY".  If this is not defined in
the Makefile, the propagate-key modification will be ifdef'd out, and
you will get vanila tk3.1.