Subject: Re: bug#68881: 30.0.50; [PATCH] Field properties confuse 'outline-minor-mode'

From: Jim Porter <[email-masked]>
Date: Sat, 10 Feb 2024 10:22:16 -0800

On 2/7/2024 9:37 AM, Juri Linkov wrote:
>> The main issue was that outline.el uses 'line-beginning-position' and
>> friends, which respects field boundaries, but I think we want to avoid that
>> for 'outline-minor-mode'. Maybe we could use 'pos-bol' and friends instead,
>> but my understanding is that 'line-beginning-position' respects display
>> directionality (which we probably want), but 'pos-bol' doesn't.
> 
> I'm not aware of any cases that would require restricting
> outlines to field boundaries.

Thanks. After reading the source (generally a good idea), I now see that 
'line-beginning-position' doesn't respect display directionality, so 
there's no reason to use it over 'pos-bol' and friends. I've therefore 
updated the patch to use those, which makes things a bit simpler.

(In any case, I think for RTL, we'd want to use the logical ordering of 
the text anyway, but possibly add the outline buttons on the right side 
of the window instead. That's out of scope for this bug though.)

> There is also one occurrence of 'line-end-position' in outline.el.
> Should it have 'inhibit-field-text-motion' as well?

Thanks for the catch. Updated this as well.

(I also split out the Eshell demonstration patch so that I can drop the 
commit more easily before merging. It's still attached here though in 
case you or anyone else want to try it out.)

From 29a36c1c32bce66468b85aa931fe2c7a8cc491e2 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Thu, 1 Feb 2024 13:58:20 -0800
Subject: [PATCH 1/2] Make outline.el ignore field properties in text

* lisp/outline.el (outline-back-to-heading, outline-on-heading-p)
(outline-next-visible-heading, outline-mark-subtree)
(outline-hide-sublevels, outline--insert-button)
(outline--fix-up-all-buttons): Inhibit field text motion (bug#68881).
---
 lisp/outline.el | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/lisp/outline.el b/lisp/outline.el
index b50708c1a7b..33447472100 100644
--- a/lisp/outline.el
+++ b/lisp/outline.el
@@ -686,7 +686,7 @@ 'outline-before-first-heading
 (defun outline-back-to-heading (&optional invisible-ok)
   "Move to previous heading line, or beg of this line if it's a heading.
 Only visible heading lines are considered, unless INVISIBLE-OK is non-nil."
-  (beginning-of-line)
+  (forward-line 0)
   (or (outline-on-heading-p invisible-ok)
       (let (found)
 	(save-excursion
@@ -705,7 +705,7 @@ outline-on-heading-p
   "Return t if point is on a (visible) heading line.
 If INVISIBLE-OK is non-nil, an invisible heading line is ok too."
   (save-excursion
-    (beginning-of-line)
+    (forward-line 0)
     (and (bolp) (or invisible-ok (not (outline-invisible-p)))
 	 (if outline-search-function
              (funcall outline-search-function nil nil nil t)
@@ -725,7 +725,7 @@ outline-insert-heading
 		(not (string-match (concat "\\`\\(?:" outline-regexp "\\)")
 				   (concat head " "))))
       (setq head (concat head " ")))
-    (unless (bolp) (end-of-line) (newline))
+    (unless (bolp) (goto-char (pos-bol)) (newline))
     (insert head)
     (unless (eolp)
       (save-excursion (newline-and-indent)))
@@ -941,9 +941,7 @@ outline-next-visible-heading
 A heading line is one that starts with a `*' (or that
 `outline-regexp' matches)."
   (interactive "p")
-  (if (< arg 0)
-      (beginning-of-line)
-    (end-of-line))
+  (goto-char (if (< arg 0) (pos-bol) (pos-eol)))
   (let ((regexp (unless outline-search-function
                   (concat "^\\(?:" outline-regexp "\\)")))
         found-heading-p)
@@ -963,7 +961,7 @@ outline-next-visible-heading
                           (re-search-forward regexp nil 'move)))
 		  (outline-invisible-p (match-beginning 0))))
       (setq arg (1- arg)))
-    (if found-heading-p (beginning-of-line))))
+    (if found-heading-p (forward-line 0))))
 
 (defun outline-previous-visible-heading (arg)
   "Move to the previous heading line.
@@ -980,7 +978,7 @@ outline-mark-subtree
   (let ((beg))
     (if (outline-on-heading-p)
 	;; we are already looking at a heading
-	(beginning-of-line)
+        (forward-line 0)
       ;; else go back to previous heading
       (outline-previous-visible-heading 1))
     (setq beg (point))
@@ -1183,7 +1181,7 @@ outline-hide-sublevels
 		(cond
 		 (current-prefix-arg (prefix-numeric-value current-prefix-arg))
 		 ((save-excursion
-                    (beginning-of-line)
+                    (forward-line 0)
 		    (if outline-search-function
                         (funcall outline-search-function nil nil nil t)
                       (looking-at outline-regexp)))
@@ -1243,7 +1241,7 @@ outline-toggle-children
   (interactive)
   (save-excursion
     (outline-back-to-heading)
-    (if (not (outline-invisible-p (line-end-position)))
+    (if (not (outline-invisible-p (pos-eol)))
         (outline-hide-subtree)
       (outline-show-children)
       (outline-show-entry))))
@@ -1834,7 +1832,7 @@ outline--create-button-icons
 (defun outline--insert-button (type)
   (with-silent-modifications
     (save-excursion
-      (beginning-of-line)
+      (forward-line 0)
       (let ((icon (nth (if (eq type 'close) 1 0) outline--button-icons))
             (o (seq-find (lambda (o) (overlay-get o 'outline-button))
                          (overlays-at (point)))))
@@ -1842,7 +1840,7 @@ outline--insert-button
           (when (eq outline-minor-mode-use-buttons 'insert)
             (let ((inhibit-read-only t))
               (insert (apply #'propertize "  " (text-properties-at (point))))
-              (beginning-of-line)))
+              (forward-line 0)))
           (setq o (make-overlay (point) (1+ (point))))
           (overlay-put o 'outline-button t)
           (overlay-put o 'evaporate t))
@@ -1866,7 +1864,7 @@ outline--fix-up-all-buttons
     (when from
       (save-excursion
         (goto-char from)
-        (setq from (line-beginning-position))))
+        (setq from (pos-bol))))
     (outline-map-region
      (lambda ()
        (let ((close-p (save-excursion
-- 
2.25.1

From fa7e4acaa80799055866866f1cf3f9c7b3ff55e5 Mon Sep 17 00:00:00 2001
From: Jim Porter <[email-masked]>
Date: Fri, 9 Feb 2024 22:18:35 -0800
Subject: [PATCH 2/2] [DO NOT MERGE] Test commit for previous patch

---
 lisp/eshell/em-prompt.el | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/lisp/eshell/em-prompt.el b/lisp/eshell/em-prompt.el
index 3662c1fa895..bf3a24689f8 100644
--- a/lisp/eshell/em-prompt.el
+++ b/lisp/eshell/em-prompt.el
@@ -107,6 +107,14 @@ eshell-prompt-repeat-map
 
 ;;; Functions:
 
+(defun eshell-outline-search (&optional bound move backward looking-at)
+  "Search for outline headings.  See `outline-search-function'."
+  ;; FIXME: This probably isn't the right way to do things.  Does it
+  ;; work with multiline prompts?  Still, it's useful for a proof of
+  ;; concept.
+  (outline-search-text-property 'field 'prompt bound move backward
+                                looking-at))
+
 (define-minor-mode eshell-prompt-mode
   "Minor mode for eshell-prompt module.
 
@@ -117,7 +125,11 @@ eshell-prompt-initialize
   "Initialize the prompting code."
   (unless eshell-non-interactive-p
     (add-hook 'eshell-post-command-hook 'eshell-emit-prompt nil t)
-    (eshell-prompt-mode)))
+    (eshell-prompt-mode)
+
+    (setq-local outline-search-function #'eshell-outline-search
+                outline-level (lambda () 1)
+                outline-minor-mode-use-buttons 'in-margins)))
 
 (defun eshell-emit-prompt ()
   "Emit a prompt if eshell is being used interactively."
-- 
2.25.1