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bug#5560: 23.1.92; parens matching in c-mode broken
From: |
Alan Mackenzie |
Subject: |
bug#5560: 23.1.92; parens matching in c-mode broken |
Date: |
Sun, 21 Feb 2016 12:35:39 +0000 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
Hello again, David and Andrew.
On Sat, Feb 20, 2016 at 10:57:23PM +0000, Alan Mackenzie wrote:
> On Tue, Feb 16, 2016 at 10:56:34PM -0500, Andrew Hyatt wrote:
> > I can confirm this still doesn't work right in Emacs 25. However, I get
> > a slightly different experience, with clicking on all 3 left parens
> > highlighting until the first right paren only. Similarly, that right
> > paren seems to be the matching paren for all 3 left parens.
> > David Reitter <david.reitter@gmail.com> writes:
> > > Parens matching in C mode is sometimes surprising. In the example
> > > below, double-clicking on either of the first two opening parentheses
> > > will mark the text until the " hyper_modifier : 0)", but that is
> > > correct
> > > only for the second paren, while the first one is unmatched due to a space
> > > following the backslash.
> > > #define EV_MODIFIERS(e) \
> > > ((([e modifierFlags] & NSHelpKeyMask) ? \
> > > hyper_modifier : 0) \
> > > ...
> > > It would be more useful if an "unmatched parentheses" was shown, or
> > > if the region up to the end of the scan process (i.e. the
> > > space+newline) was marked.
> Giving a decent error message here would be difficult. We're down in the
> depths of the mouse code, but the strategem of giving syntax-table text
> properties to parentheses is a pure CC Mode one. Signaling an error if
> a paren has other than paren syntax is liable to have unforseen side
> effects somewhere, somehow, some time.
After a night's sleep, I've changed my mind about the advisability of
such a fix. So, here is a fix. It works as indicated last night: if a
character whose normal syntax is open/close-paren has a different syntax
due to syntax-table text properties, a 'scan-error error is signaled:
either "Containing expression ends prematurely" for an open paren, or
"Unbalanced parentheses" for a close paren.
Here's the patch. Please try it out and let me know if there's anything
amiss about it. Otherwise, I'll commit it.
diff --git a/lisp/mouse.el b/lisp/mouse.el
index 85ffc43..22c5b48 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -931,20 +931,29 @@ mouse-start-end
(= start end)
(char-after start)
(= (char-syntax (char-after start)) ?\())
- (list start
- (save-excursion
- (goto-char start)
- (forward-sexp 1)
- (point))))
+ (if (/= (car (syntax-after start)) 4)
+ ;; This happens in CC Mode when unbalanced parens in CPP
+ ;; constructs are given punctuation syntax with
+ ;; syntax-table text properties. (2016-02-21).
+ (signal 'scan-error (list "Containing expression ends prematurely"
+ start start))
+ (list start
+ (save-excursion
+ (goto-char start)
+ (forward-sexp 1)
+ (point)))))
((and (= mode 1)
(= start end)
(char-after start)
(= (char-syntax (char-after start)) ?\)))
- (list (save-excursion
- (goto-char (1+ start))
- (backward-sexp 1)
- (point))
- (1+ start)))
+ (if (/= (car (syntax-after start)) 5)
+ ;; See above comment about CC Mode.
+ (signal 'scan-error (list "Unbalanced parentheses" start start))
+ (list (save-excursion
+ (goto-char (1+ start))
+ (backward-sexp 1)
+ (point))
+ (1+ start))))
((and (= mode 1)
(= start end)
(char-after start)
--
Alan Mackenzie (Nuremberg, Germany).