Re: [Emacs-diffs] master 188f657: Fix false negatives in tex--prettify-symbols-compose-p.

[Tassilo Horn <tsdh@gnu.org>]

Artur Malabarba <bruce.connor.am@gmail.com> writes:

Hi Artur,

>> where `prettify-symbols-compose-at-point' would be the user option.
>
> I tried something similar, and unfortunately it's not that simple.
> Firstly, (window-point) didn't seem to work as expected here, so I had
> to define a variable in font-lock-mode to hold the value of (point)
> before fontification started.
>
> After doing that, the feature sort of works while you're writing. That
> is, it doesn't prettify a symbol you've just written, but it does
> prettify a symbol after you hit SPC, which is nice.  However, it does
> not work while navigating. That is, when you move point to a
> prettified symbol, it doesn't get decomposed.
>
> Then I tried adding a post-command-hook function to invalidate the
> font-locking at point. This correctly decomposes a symbol when you
> move the cursor to it, but it's still not perfect. When you move the
> cursor *out* of the symbol, if you move far enough, the symbol doesn't
> get prettified again until you edit something close to it.

Hehe, seems we tried implementing that feature at the same time and both
fell into the very same traps.  Did you see my other mail?  I have
gotten it working nicely right yesterday.  Right now I did some minor
changes, and that's the current version of the patch:

Comments welcome!

--8<---------------cut here---------------start------------->8---
1 file changed, 39 insertions(+), 4 deletions(-)
lisp/progmodes/prog-mode.el | 43 +++++++++++++++++++++++++++++++++++++++----

modified   lisp/progmodes/prog-mode.el
@@ -29,7 +29,8 @@
 
 ;;; Code:
 
-(eval-when-compile (require 'cl-lib))
+(eval-when-compile (require 'cl-lib)
+                   (require 'subr-x))
 
 (defgroup prog-mode nil
   "Generic programming mode, from which others derive."
@@ -161,13 +162,20 @@ prettify-symbols--compose-symbol
   (let ((start (match-beginning 0))
         (end (match-end 0))
         (match (match-string 0)))
-    (if (funcall prettify-symbols-compose-predicate start end match)
+    (if (and (not (equal prettify-symbols--current-symbol-bounds (list start end)))
+             (funcall prettify-symbols-compose-predicate start end match))
         ;; That's a symbol alright, so add the composition.
-        (compose-region start end (cdr (assoc match alist)))
+        (progn
+          (compose-region start end (cdr (assoc match alist)))
+          (add-text-properties
+           start end
+           `(prettify-symbols-start ,start prettify-symbols-end ,end)))
       ;; No composition for you.  Let's actually remove any
       ;; composition we may have added earlier and which is now
       ;; incorrect.
-      (remove-text-properties start end '(composition))))
+      (remove-text-properties start end '(composition
+                                          prettify-symbols-start
+                                          prettify-symbols-end))))
   ;; Return nil because we're not adding any face property.
   nil)
 
@@ -179,6 +187,29 @@ prettify-symbols--make-keywords
 
 (defvar-local prettify-symbols--keywords nil)
 
+(defvar-local prettify-symbols--current-symbol-bounds nil)
+
+(defun prettify-symbols--post-command-hook ()
+  (if-let ((c (get-text-property (point) 'composition))
+           (s (get-text-property (point) 'prettify-symbols-start))
+           (e (get-text-property (point) 'prettify-symbols-end)))
+      (progn
+        (setq prettify-symbols--current-symbol-bounds (list s e))
+        (remove-text-properties s e '(composition)))
+    (when (and prettify-symbols--current-symbol-bounds
+               (or (< (point) (car prettify-symbols--current-symbol-bounds))
+                   (>= (point) (cadr prettify-symbols--current-symbol-bounds))))
+      (apply #'font-lock-flush prettify-symbols--current-symbol-bounds)
+      (setq prettify-symbols--current-symbol-bounds nil))))
+
+(defcustom prettify-symbols-unprettify-at-point t
+  "If non-nil, show the non-prettified version of a symbol when point is on it.
+The prettification will be reapplied as soon as point moves away
+from the symbol.  If set to nil, the prettification persists even
+when point is on the symbol."
+  :type 'boolean
+  :group 'prog-mode)
+
 ;;;###autoload
 (define-minor-mode prettify-symbols-mode
   "Toggle Prettify Symbols mode.
@@ -206,8 +237,12 @@ prettify-symbols-mode
         (font-lock-add-keywords nil prettify-symbols--keywords)
         (setq-local font-lock-extra-managed-props
                     (cons 'composition font-lock-extra-managed-props))
+        (when prettify-symbols-unprettify-at-point
+          (add-hook 'post-command-hook
+                    #'prettify-symbols--post-command-hook nil t))
         (font-lock-flush))
     ;; Turn off
+    (remove-hook 'post-command-hook #'prettify-symbols--post-command-hook t)
     (when prettify-symbols--keywords
       (font-lock-remove-keywords nil prettify-symbols--keywords)
       (setq prettify-symbols--keywords nil))
--8<---------------cut here---------------end--------------->8---

Bye,
Tassilo