bug#19145: 24.4; prettify-symbols-mode inconsistent behavior

[Ken Mankoff <mankoff@gmail.com>]

* On 2014-11-21 at 13:15, Stefan Monnier wrote:
>> Some symbols are sometimes not being treated correctly depending on
>> what characters follow. For example, I have the following setup for
>> coding Python:
>
>>     (prettify-symbols-mode t)
>>     (global-prettify-symbols-mode t)
>>     (add-hook 'python-mode-hook
>>               (lambda ()
>>                 (push '("**2" . ?²) prettify-symbols-alist)
>>                 (push '("_x" . ?ᵪ) prettify-symbols-alist)
>>                 (push '("delta" . ?δ) prettify-symbols-alist)))
>
> Can you try the patch below and see if it does what you want?
>
>
> diff --git a/lisp/progmodes/prog-mode.el b/lisp/progmodes/prog-mode.el
> index 5037020..475dd32 100644
> --- a/lisp/progmodes/prog-mode.el
> +++ b/lisp/progmodes/prog-mode.el
> @@ -73,11 +73,13 @@ Regexp match data 0 points to the chars."
>    ;; Check that the chars should really be composed into a symbol.
>    (let* ((start (match-beginning 0))
>  	 (end (match-end 0))
> -	 (syntaxes (if (eq (char-syntax (char-after start)) ?w)
> -		       '(?w ?_) '(?. ?\\)))
> +	 (syntax-beg (if (eq (char-syntax (char-after start)) ?w)
> +                         '(?w ?_) '(?. ?\\)))
> +	 (syntax-end (if (eq (char-syntax (char-before end)) ?w)
> +                         '(?w ?_) '(?. ?\\)))
>  	 match)
> -    (if (or (memq (char-syntax (or (char-before start) ?\s)) syntaxes)
> -	    (memq (char-syntax (or (char-after end) ?\s)) syntaxes)
> +    (if (or (memq (char-syntax (or (char-before start) ?\s)) syntax-beg)
> +	    (memq (char-syntax (or (char-after end) ?\s)) syntax-end)
>              ;; syntax-ppss could modify the match data (bug#14595)
>              (progn (setq match (match-string 0)) (nth 8 (syntax-ppss))))
>  	;; No composition for you.  Let's actually remove any composition


Much improved! Of my examples, only one case no longer works which is
delta_x or foo_x_x_x_x, for example.

  -k.