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Subject: |
29.3; comint--intersect-regions fontifies some output using input function |
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Date: |
Fri, 21 Jun 2024 13:11:58 -0400 |
This relates to bug#51940: 29.0.50; [PATCH] Fontification and indentation in
M-x shell.
I found a tiny bug in the introduced command `comint--intersect-regions'. It
pertains to the "field-expansion" in the following section, which is
responsible for narrowing to alternating regions of input and output:
(let ((beg2 beg1)
(end2 end1))
(when (= beg2 beg)
(setq beg2 (field-beginning beg2))) ; <--- bug here
(when (= end2 end)
(setq end2 (field-end end2)))
;; Narrow to the whole field surrounding the region
(narrow-to-region beg2 end2))
The nature of the bug is that `field-beginning' is left-associative, whereas
`(get-text-property (point) 'field)` is right associative. You can demonstrate
this to yourself as follows:
(progn
(insert (concat "\n" (propertize "AAA" 'field 'a) (propertize "B" 'field 'b)
(propertize "CCC" 'field 'c)))
(goto-char (- (point) 4)) ; cursor on 'B'
(list (get-text-property (point) 'field) (field-beginning) (field-end)
(buffer-substring-no-properties (field-beginning) (field-end))))
;; gives: (b 356 359 "AAA")
So on the line:
(setq beg2 (field-beginning beg2))) ; <--- bug here
if beg is at the first character of its field, `field-beginning` will actually
return the start of the prior field. This leads to `comint--intersect-regions'
unwittingly including `output' field text in its input fontification narrowing.
I noticed this in a new python interactive mode I'm working on: the prompt
itself (i.e. output) was being partially fontified by python-mode.
I believe the correct fix is:
(setq beg2 (field-beginning (1+ beg2))))
This takes care of the problem here, even for single-character fields (like
`boundary'). We know (< beg1 end) from the loop condition, so it's safe to
increment beg2.
--- /var/folders/by/19mt78cj63v5_tslqh826g7w0000gn/T/jka-comrWKsIJ
2024-06-21 13:08:59
+++ /var/folders/by/19mt78cj63v5_tslqh826g7w0000gn/T/buffer-content-Q8dmID
2024-06-21 13:08:59
@@ -4122,7 +4122,7 @@
(let ((beg2 beg1)
(end2 end1))
(when (= beg2 beg)
- (setq beg2 (field-beginning beg2)))
+ (setq beg2 (field-beginning (1+ beg2))))
(when (= end2 end)
(setq end2 (field-end end2)))
;; Narrow to the whole field surrounding the region
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--- Begin Message ---
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Subject: |
Re: 29.3; comint--intersect-regions fontifies some output using input function |
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Date: |
Sun, 23 Jun 2024 09:28:30 +0200 |
JD Smith <jdtsmith@gmail.com> writes:
> Thanks, I took a look. commit 949bc1c72d7 I believe solves the same problem,
> and also fixes my issue. In fact I think the solutions are equivalent, since
> the end test will never need to trigger, because for field-end the left
> associativity works in our favor. But yours is more explicit.
>
> Feel free to close.
Thanks. I'm therefore closing this bug report.
On an unrelated note, my reply to your personal e-mail
Subject: comint-fontify-input-mode
Date: Wed, 22 May 2024 14:50:00 -0400
might have ended up in your spam folder, so I kindly ask you to check it
if you are interested.
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