Emacs: Dynamic buffer-local fringe
Emacs has a global fringe-mode
for fringes, which I always keep disabled as it always takes a bit of space in the frame and I like to start first character on the very left. But there are some cases where fringes are quite useful e.g. when flycheck
shows warnings/errors in the code, it uses fringes (if enabled) to have a nice arrow to indicate the line(s) where the warnings/errors are happening -- great to have a quick glance at once.
I found the following workflow works for me the best:
- keep global
fringe-mode
disabled - when
flycheck
minor mode in enabled in a buffer, enable fringes temporarily in that buffer for any warnings/errors; when there's no warning/error, disable fringes again
To keep the fringe-mode
disabled globally, only the following is needed in the emacs
init file:
(fringe-mode -1)
Now, for the tricky part of enabling-disabling fringes dynamically/on-demand for flycheck
, I've come up with the following function, which to be applied as an advice
around (:around
) the call to the flycheck-finish-current-syntax-check
function which does the actual syntax checking in flycheck
:
(defun local-flycheck-auto-manage-fringe-advice (oldfunc &rest args) "Enable fringes dynamically when `flycheck' checks for syntax in the current buffer." (when (or (not left-fringe-width) (<= left-fringe-width 0)) (setq left-fringe-width 10 right-fringe-width 0) (flycheck-refresh-fringes-and-margins)) (apply oldfunc args) (unless flycheck-current-errors (setq left-fringe-width 0 right-fringe-width 0) (flycheck-refresh-fringes-and-margins)))
The above uses the buffer-local left-fringe-width
and right-fringe-width
variables to set the fringe widths.
Now, just adding the above as an advice
would suffice:
(advice-add #'flycheck-finish-current-syntax-check :around #'local-flycheck-auto-manage-fringe-advice)
As mentioned earlier, our advice
function is added :around
the call to the flycheck
's target function flycheck-finish-current-syntax-check
; so the expression (apply oldfunc args)
in our advice
function actually does the flycheck-finish-current-syntax-check
call.
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