Re: [nongnu] elpa/opam-switch-mode 8b8670ca8b 1/3: feat(opam-switch-mode-lighter): Show the switch name in the mode-bar

[Stefan Monnier <monnier@iro.umontreal.ca>]

Salut Erik¸

> +        (progn (opam-switch-set-switch ,switch)
> +               (redraw-display))
>          :active t
>          :help ,(concat "Select opam switch \"" switch "\"")])
>      (opam-switch--get-switches))
>     ;; now reset as last element
>     '(
> -     ["reset" (opam-switch-set-switch "")
> +     ["reset"
> +      (progn (opam-switch-set-switch "")
> +             (redraw-display))

Instead of `redraw-display` you want `force-mode-line-update`.
And you probably want to put it into `opam-switch-set-switch` rather
than duplicating it after every call:

Also, in some circumstances the mode lines can be updated fairly often
(e.g. after every key press, and/or every process output received by
a filter), so it might be worthwhile to memoize/precompute the
lighter rather than recompute it every time the modeline is updated.

So maybe the patch below?


        Stefan


diff --git a/opam-switch-mode.el b/opam-switch-mode.el
index 0ec42aa123..b13cbb75d7 100644
--- a/opam-switch-mode.el
+++ b/opam-switch-mode.el
@@ -93,6 +93,8 @@ background process before the opam switch changes."
 
 ;;; Code:
 
+(defvar opam-switch--mode-lighter nil)
+
 (defun opam-switch--run-command-without-stderr (sub-cmd
                                                 &optional switch sexp
                                                 &rest args)
@@ -321,6 +323,8 @@ not any other shells outside Emacs."
       (unless opam-switch--saved-env
         (opam-switch--save-current-env opam-env))
       (opam-switch--set-env opam-env prefix)))
+  (setq opam-switch--mode-lighter nil)
+  (force-mode-line-update t)
   (run-hooks 'opam-switch-change-opam-switch-hook))
 
 (define-obsolete-function-alias 'opam-switch--set-switch
@@ -343,17 +347,13 @@ not any other shells outside Emacs."
    ;; then the list with all the real opam switches
    (mapcar
     (lambda (switch)
-      `[,switch
-        (progn (opam-switch-set-switch ,switch)
-               (redraw-display))
+      `[,switch (opam-switch-set-switch ,switch)
         :active t
         :help ,(concat "Select opam switch \"" switch "\"")])
     (opam-switch--get-switches))
    ;; now reset as last element
    '(
-     ["reset"
-      (progn (opam-switch-set-switch "")
-             (redraw-display))
+     ["reset" (opam-switch-set-switch "")
       :active opam-switch--saved-env
       :help "Reset to state when Emacs was started"])))
 
@@ -376,10 +376,12 @@ is automatically created by `define-minor-mode'."
 
 (defun opam-switch-mode-lighter ()
   "Return the lighter for opam-switch-mode which indicates the current switch."
-  (let* ((current-switch (opam-switch--get-current-switch))
-         ;; handle the case of local switches for better UX
-         (shortened (replace-regexp-in-string ".*/" "…/" current-switch t t)))
-    (format " OPSW-%s" shortened)))
+  (or opam-switch--mode-lighter
+      (let* ((current-switch (opam-switch--get-current-switch))
+             ;; handle the case of local switches for better UX
+             (shortened (replace-regexp-in-string ".*/" "…/"
+                                                  current-switch t t)))
+        (setq opam-switch--mode-lighter (format " OPSW-%s" shortened)))))
 
 ;;;###autoload
 (define-minor-mode opam-switch-mode