I am programming my own Emacs minor mode using the idioms and macros similar to this minimal example:
(define-minor-mode foo-mode
"Toggle Foo mode."
:init-value nil
:lighter " Foo"
:group 'foo
(if foo-mode
(do-enable-foo)
(do-disable-foo))
)
(defun do-enable-foo ()
"Enable foo minor mode"
(message "Enabling foo...")
(if test-something
(message "Foo enabled after disabling was canceled!")
(message "Foo enabled from scratch"))
)
(defun do-disable-foo ()
"Disable foo minor mode"
(message "Disabling foo...")
(if (not certain-situation)
(message "... done.") ; finish disabling foo
;; else forms:
(message "Need to cancel disabling foo!")
(foo-mode 1)) ; turning foo mode on again
)
During the toggling off of the minor mode, a 'certain-situation may arise when I have to cancel toggling off. Currently, I am thinking since I am using the define-minor-mode macro, that I cannot bail out but just have to programmatically turn the mode on again using (foo-mode 1) as seen in the code.
If I go this route, I will have to handle this differently in the enabling function do-enable-foo -- so my first question is how to detect this case using the placeholder 'test-something in the code above?
Or, is there a cleaner way to achieve the cancel, for example, by signaling an error instead of (foo-mode 1) to prevent the mode toggle from going through?
I ended up using Stefan's suggestion in the following way using the variable to signal to the minor mode definition that the mode was enabled as a result of cancelling the disable process (actually as a result of a user query). I didn't dare to use the idea of simply setting the mode variable to t but I cannot find the documentation anymore that cautioned against it. It might be worthwhile to see if using (setq foo-mode t) actually lets me eliminate the new variable canceled-foo-off.
(defvar canceled-foo-off nil "Set to `true' if user canceled toggling off foo.")
(make-variable-buffer-local 'canceled-foo-off)
(define-minor-mode foo-mode
...
(if foo-mode
(if canceled-foo-off
(setq canceled-foo-off nil) ; Mode was turned back on from cancelling
(do-enable-foo)) ; Mode was turned on from scratch
(do-disable-foo))
)
(defun do-disable-foo ()
"Disable foo minor mode"
(if (not certain-situation)
...
;; else forms:
(setq canceled-foo-off t) ; make sure mode starting procedure is not run!
(foo-mode 1)) ; turning foo mode on again
)