Re: Keybindings and minor modes

[Kevin Rodgers <ihs_4664@yahoo.com>]

batkins57@gmail.com wrote:
 > I'd like to bind a command to tab in a minor mode I'm writing, but I'd
 > also like to preserve any command that might have been attached to that
 > key before making my binding (such as indentation).  In other words,
 > I'd like to add functionality to an existing keybinding without
 > completely overwriting the binding.
 >
 > The solution I came up with was to simply store the currently bound
 > command in a buffer-local variable whenever the minor mode is invoked.
 > Then the keys are bound to functions that provide my additional
 > functionality and then funcall the old bindings.  This works, but I
 > wonder if there isn't a cleaner way to pass a keychord event on to the
 > next handler.  The code I have now is pretty ugly, since a key bound to
 > self-insert-command has to be handled separately so that
 > self-insert-command will get an argument of 0.

I think you could avoid storing the command in a local variable by
accessing the local binding (defined by the major mode) or global
binding dynamically.  That would simplify things a little.

I'll admit, I don't understand the point of calling
(self-insert-command 0).

Perhaps a better approach altogether would be to add a pre-command-hook
that would check the key that was used to invoke it:

(defun ehinter-pre-command-hook ()
   "Run `ehinter-hint' in Ehinter Minor Mode, when invoked via SPC, TAB, 
or RET."
   (when (and ehinter-mode
              (let ((key (this-single-command-keys)))
                (and (= (length key 1))
                     (member (aref key 0) '(?  ?\t ?\r))))) ; SPC, TAB, 
or RET
     (ehinter-hint)))

(add-hook 'pre-command-hook 'ehinter-pre-command-hook)

Then the ehinter-mode function just needs to set or unset the
buffer-local ehinter-mode variable.

You could tweak that to have the ehinter-mode function add or remove
ehinter-pre-command-hook from the buffer-local pre-command-hook, to
avoid affecting other buffers.

-- 
Kevin Rodgers