bug#41130: bug#41198: 27.0.60; [PATCH] heading cycling command for outline

[Yuan Fu <casouri@gmail.com>]

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> On Oct 18, 2020, at 4:36 AM, Lars Ingebrigtsen <larsi@gnus.org> wrote:
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
>> I can modify outline code to signal a signal (say
>> ‘outline-before-first-heading) rather than an error, and handle that
>> signal specifically. How’s that?
> 
> Yes, that would also work.
> 
> -- 
> (domestic pets only, the antidote for overdose, milk.)
>   bloggy blog: http://lars.ingebrigtsen.no

Here is the new patch.

Yuan


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From ff4722534c1e47a2536257116436b66c79db3e8b Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Thu, 15 Oct 2020 22:20:20 -0400
Subject: [PATCH] Handle "Before first headings" error in outline-cycle

* lisp/outline.el (outline-before-first-heading): New error.
(outline-back-to-heading): Signal the new error.
(outline-cycle): Ignore the error.
(outline-cycle-buffer): Simply pass 1 to 'outline-hide-sublevels'.
---
 lisp/outline.el | 40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/lisp/outline.el b/lisp/outline.el
index a4ce9afb44..b9806bc187 100644
--- a/lisp/outline.el
+++ b/lisp/outline.el
@@ -402,6 +402,8 @@ outline-invisible-p
 If POS is nil, use `point' instead."
   (eq (get-char-property (or pos (point)) 'invisible) 'outline))
 
+(define-error 'outline-before-first-heading "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."
@@ -412,7 +414,7 @@ outline-back-to-heading
 	  (while (not found)
 	    (or (re-search-backward (concat "^\\(?:" outline-regexp "\\)")
 				    nil t)
-                (error "Before first heading"))
+                (signal 'outline-before-first-heading nil))
 	    (setq found (and (or invisible-ok (not (outline-invisible-p)))
 			     (point)))))
 	(goto-char found)
@@ -1167,19 +1169,21 @@ outline-cycle
 `Headings only' means show sub headings but not their bodies.
 `Show all' means show all subheadings and their bodies."
   (interactive)
-  (pcase (outline--cycle-state)
-    ('hide-all
-     (if (outline-has-subheading-p)
-         (progn (outline-show-children)
-                (message "Only headings"))
-       (outline-show-subtree)
-       (message "Show all")))
-    ('headings-only
-     (outline-show-subtree)
-     (message "Show all"))
-    ('show-all
-     (outline-hide-subtree)
-     (message "Hide all"))))
+  (condition-case nil
+      (pcase (outline--cycle-state)
+        ('hide-all
+         (if (outline-has-subheading-p)
+             (progn (outline-show-children)
+                    (message "Only headings"))
+           (outline-show-subtree)
+           (message "Show all")))
+        ('headings-only
+         (outline-show-subtree)
+         (message "Show all"))
+        ('show-all
+         (outline-hide-subtree)
+         (message "Hide all")))
+    (outline-before-first-heading nil)))
 
 (defvar-local outline--cycle-buffer-state 'show-all
   "Internal variable used for tracking buffer cycle state.")
@@ -1189,13 +1193,7 @@ outline-cycle-buffer
   (interactive)
   (pcase outline--cycle-buffer-state
     ('show-all
-     (save-excursion
-       (let ((start-point (point)))
-         (while (not (eq (point) start-point))
-           (outline-up-heading 1))
-         (outline-hide-sublevels
-          (progn (outline-back-to-heading)
-                 (funcall 'outline-level)))))
+     (outline-hide-sublevels 1)
      (setq outline--cycle-buffer-state 'top-level)
      (message "Top level headings"))
     ('top-level
-- 
2.27.0