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bug#58937: text-property-search-backward misses one-character regions
From: |
Eli Zaretskii |
Subject: |
bug#58937: text-property-search-backward misses one-character regions |
Date: |
Tue, 01 Nov 2022 12:24:49 +0200 |
> From: Nicolas Graner <nicolas@graner.name>
> Date: Tue, 01 Nov 2022 00:20:58 +0100
>
> (with-current-buffer (generate-new-buffer "test")
> (insert "123456789")
> (put-text-property 3 4 'foo 'bar)
> (goto-char 6)
> (text-property-search-backward 'foo))
>
> The returned value is
> #s(prop-match 1 4 nil)
> instead of
> #s(prop-match 3 4 bar)
> and the point in the test buffer is moved to position 1 instead of 3.
>
> This incorrect behavior is the same if you replace (goto-char 6) with
> (goto-char 5) or any other value greater than 4. However, the result is
> correct with (goto-char 4), i.e. when the backward search starts one
> position after the target character. This suggests an off-by-one error
> in the code.
It isn't due to an off-by-one error, AFAICT, it's because search for
changes in text properties starts from character _before_ point.
Please try the patch below and see if it gives good results.
Lars, any comments?
diff --git a/lisp/emacs-lisp/text-property-search.el
b/lisp/emacs-lisp/text-property-search.el
index d11980f..69bbbd2 100644
--- a/lisp/emacs-lisp/text-property-search.el
+++ b/lisp/emacs-lisp/text-property-search.el
@@ -208,8 +208,12 @@ text-property--find-end-backward
(goto-char end)
(setq ended t)))))
;; End this at the first place the property changes value.
- (setq end (previous-single-property-change
- (point) property nil (point-min)))
+ (setq end
+ (if (text-property--match-p
+ value (get-text-property (1- (point)) property) predicate)
+ (previous-single-property-change (point)
+ property nil (point-min))
+ (point)))
(goto-char end))
(make-prop-match :beginning end
:end (1+ start)
- bug#58937: text-property-search-backward misses one-character regions,
Eli Zaretskii <=