I want to evaluate certain conditions before allowing a user to copy a text. As far as I know, I need an advice for "kill-ring-save". I need to ignore the user request to Copy that text if conditions are not met and allow it if are satisfied. How can I do this?
(UPDATE) -- MORE ABOUT CONSTRAINTS: only in specific mode of Emacs (e.g. NXML mode) this advice should be applied and only when one/more specific conditions are met.
Quick proof of concept; you don't tell what your constraints are, so this is necessarily vague / useless.
(defvar moo nil)
(defadvice kill-ring-save (around kill-ring-check-constraints activate compile)
"If in `nxml-mode', don't save to kill ring if `moo' is `nil'."
(if (and (eq major-mode 'nxml-mode) (null moo))
(message "Not copied.")
ad-do-it) )
The additional major-mode constraint was added in response to comments below. If you want this in every mode, just take out the mode check.
