Re: Toggling the same key combination between two options

[Nick Roberts <nickrob@snap.net.nz>]

 > I have F8 and F9 mapped to gud-remove and gud-break (respectively) in
 > gud-mode.
 > I'd like to mimic the behaviour of Visual Studio where F9 toggles
 > between setting and removing the breakpoint. Is it possible to
 > configure emacs so that it will toggle between the two bindings every
 > time the key is pressed?

Assuming that you're using Emacs 22.1 or later you can do this by clicking on
the fringe/margin using mouse-1 (gdb-mouse-set-clear-breakpoint).  If you
really want to use F9, e.g., from a console, you can adapt this function:


(define-key gud-minor-mode-map [f9] 'gdb-set-clear-breakpoint)

(defun gdb-set-clear-breakpoint ()
  (interactive)
  (if (or (buffer-file-name) (eq major-mode 'gdb-assembler-mode))
      (if (or 
	   (let ((start (- (line-beginning-position) 1))
		 (end (+ (line-end-position) 1)))
	     (catch 'breakpoint
	       (dolist (overlay (overlays-in start end))
		 (if (overlay-get overlay 'put-break)
		     (throw 'breakpoint t)))))
	   (eq (car (fringe-bitmaps-at-pos)) 'breakpoint))
	  (gud-remove nil)
	(gud-break nil))))

which will set or clear the breakpoint on the line at point (the location of
the active cursor).


-- 
Nick                                           http://www.inet.net.nz/~nickrob