[PATCH 03/35] Separate cycling functions from org.el into new library: org-cycle

[Ihor Radchenko <yantar92@gmail.com>]

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diff --git a/lisp/org-cycle.el b/lisp/org-cycle.el
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index 000000000..df0a3761a
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+++ b/lisp/org-cycle.el
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+;;; org-cycle.el --- Visibility cycling of Org entries -*- lexical-binding: t; -*-
+;;
+;; Copyright (C) 2020-2020 Free Software Foundation, Inc.
+;;
+;; Maintainer: Ihor Radchenko <yantar92 at gmail dot com>
+;; Keywords: folding, visibility cycling, invisible text
+;; Homepage: https://orgmode.org
+;;
+;; This file is part of GNU Emacs.
+;;
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;;; Commentary:
+
+;; This file contains code controlling global folding state in buffer
+;; and TAB-cycling.
+
+;;; Code:
+
+(require 'org-macs)
+(require 'org-fold)
+
+(declare-function org-element-type "org-element" (element))
+(declare-function org-element-property "org-element" (property element))
+(declare-function org-element-lineage "org-element" (datum &optional types with-self))
+(declare-function org-element-at-point "org-element" (&optional pom cached-only))
+(declare-function org-get-tags "org" (&optional pos local fontify))
+(declare-function org-subtree-end-visible-p "org" ())
+(declare-function org-narrow-to-subtree "org" (&optional element))
+(declare-function org-at-property-p "org" ())
+(declare-function org-re-property "org" (property &optional literal allow-null value))
+(declare-function org-item-beginning-re "org" ())
+(declare-function org-at-heading-p "org" (&optional invisible-not-ok))
+(declare-function org-at-item-p "org" ())
+(declare-function org-before-first-heading-p "org" ())
+(declare-function org-back-to-heading "org" (&optional invisible-ok))
+(declare-function org-end-of-subtree "org" (&optional invisible-ok to-heading))
+(declare-function org-entry-end-position "org" ())
+(declare-function org-try-cdlatex-tab "org" ())
+(declare-function org-cycle-level "org" ())
+(declare-function org-table-next-field "org-table" ())
+(declare-function org-table-justify-field-maybe "org-table" (&optional new))
+(declare-function org-inlinetask-at-task-p "org-inlinetask" ())
+(declare-function org-inlinetask-toggle-visibility "org-inlinetask" ())
+(declare-function org-list-get-all-items "org-list" (item struct prevs))
+(declare-function org-list-get-bottom-point "org-list" (struct))
+(declare-function org-list-prevs-alist "org-list" (struct))
+(declare-function org-list-set-item-visibility "org-list" (item struct view))
+(declare-function org-list-search-forward "org-list" (regexp &optional bound noerror))
+(declare-function org-list-has-child-p "org-list" (item struct))
+(declare-function org-list-get-item-end-before-blank "org-list" (item struct))
+(declare-function org-list-struct "org-list" ())
+(declare-function org-cycle-item-indentation "org-list" ())
+
+(declare-function outline-previous-heading "outline" ())
+(declare-function outline-next-heading "outline" ())
+(declare-function outline-end-of-heading "outline" ())
+(declare-function outline-up-heading "outline" (arg &optional invisible-ok))
+
+(defvar org-drawer-regexp)
+(defvar org-odd-levels-only)
+(defvar org-startup-folded)
+(defvar org-archive-tag)
+(defvar org-cycle-include-plain-lists)
+(defvar org-outline-regexp-bol)
+
+(defvar-local org-cycle-global-status nil)
+(put 'org-cycle-global-status 'org-state t)
+(defvar-local org-cycle-subtree-status nil)
+(put 'org-cycle-subtree-status 'org-state t)
+
+;;;; Customisation:
+
+
+(defgroup org-cycle nil
+  "Options concerning visibility cycling in Org mode."
+  :tag "Org Cycle"
+  :group 'org-structure)
+
+(defcustom org-cycle-skip-children-state-if-no-children t
+  "Non-nil means skip CHILDREN state in entries that don't have any."
+  :group 'org-cycle
+  :type 'boolean)
+
+(defcustom org-cycle-max-level nil
+  "Maximum level which should still be subject to visibility cycling.
+Levels higher than this will, for cycling, be treated as text, not a headline.
+When `org-odd-levels-only' is set, a value of N in this variable actually
+means 2N-1 stars as the limiting headline.
+When nil, cycle all levels.
+Note that the limiting level of cycling is also influenced by
+`org-inlinetask-min-level'.  When `org-cycle-max-level' is not set but
+`org-inlinetask-min-level' is, cycling will be limited to levels one less
+than its value."
+  :group 'org-cycle
+  :type '(choice
+	  (const :tag "No limit" nil)
+	  (integer :tag "Maximum level")))
+
+(defcustom org-cycle-hide-block-startup nil
+  "Non-nil means entering Org mode will fold all blocks.
+This can also be set in on a per-file basis with
+
+#+STARTUP: hideblocks
+#+STARTUP: showblocks"
+  :group 'org-startup
+  :group 'org-cycle
+  :type 'boolean)
+
+(defcustom org-cycle-global-at-bob nil
+  "Cycle globally if cursor is at beginning of buffer and not at a headline.
+
+This makes it possible to do global cycling without having to use `S-TAB'
+or `\\[universal-argument] TAB'.  For this special case to work, the first \
+line of the buffer
+must not be a headline -- it may be empty or some other text.
+
+When used in this way, `org-cycle-hook' is disabled temporarily to make
+sure the cursor stays at the beginning of the buffer.
+
+When this option is nil, don't do anything special at the beginning of
+the buffer."
+  :group 'org-cycle
+  :type 'boolean)
+
+(defcustom org-cycle-level-after-item/entry-creation t
+  "Non-nil means cycle entry level or item indentation in new empty entries.
+
+When the cursor is at the end of an empty headline, i.e., with only stars
+and maybe a TODO keyword, TAB will then switch the entry to become a child,
+and then all possible ancestor states, before returning to the original state.
+This makes data entry extremely fast:  M-RET to create a new headline,
+on TAB to make it a child, two or more tabs to make it a (grand-)uncle.
+
+When the cursor is at the end of an empty plain list item, one TAB will
+make it a subitem, two or more tabs will back up to make this an item
+higher up in the item hierarchy."
+  :group 'org-cycle
+  :type 'boolean)
+
+(defcustom org-cycle-emulate-tab t
+  "Where should `org-cycle' emulate TAB.
+nil         Never
+white       Only in completely white lines
+whitestart  Only at the beginning of lines, before the first non-white char
+t           Everywhere except in headlines
+exc-hl-bol  Everywhere except at the start of a headline
+If TAB is used in a place where it does not emulate TAB, the current subtree
+visibility is cycled."
+  :group 'org-cycle
+  :type '(choice (const :tag "Never" nil)
+		 (const :tag "Only in completely white lines" white)
+		 (const :tag "Before first char in a line" whitestart)
+		 (const :tag "Everywhere except in headlines" t)
+		 (const :tag "Everywhere except at bol in headlines" exc-hl-bol)))
+
+(defcustom org-cycle-separator-lines 2
+  "Number of empty lines needed to keep an empty line between collapsed trees.
+If you leave an empty line between the end of a subtree and the following
+headline, this empty line is hidden when the subtree is folded.
+Org mode will leave (exactly) one empty line visible if the number of
+empty lines is equal or larger to the number given in this variable.
+So the default 2 means at least 2 empty lines after the end of a subtree
+are needed to produce free space between a collapsed subtree and the
+following headline.
+
+If the number is negative, and the number of empty lines is at least -N,
+all empty lines are shown.
+
+Special case: when 0, never leave empty lines in collapsed view."
+  :group 'org-cycle
+  :type 'integer)
+(put 'org-cycle-separator-lines 'safe-local-variable 'integerp)
+
+(defcustom org-cycle-pre-hook nil
+  "Hook that is run before visibility cycling is happening.
+The function(s) in this hook must accept a single argument which indicates
+the new state that will be set right after running this hook.  The
+argument is a symbol.  Before a global state change, it can have the values
+`overview', `content', or `all'.  Before a local state change, it can have
+the values `folded', `children', or `subtree'."
+  :group 'org-cycle
+  :type 'hook)
+
+(defcustom org-cycle-hook '(org-cycle-hide-archived-subtrees
+		   org-cycle-show-empty-lines
+		   org-cycle-optimize-window-after-visibility-change)
+  "Hook that is run after `org-cycle' has changed the buffer visibility.
+The function(s) in this hook must accept a single argument which indicates
+the new state that was set by the most recent `org-cycle' command.  The
+argument is a symbol.  After a global state change, it can have the values
+`overview', `contents', or `all'.  After a local state change, it can have
+the values `folded', `children', or `subtree'."
+  :group 'org-cycle
+  :package-version '(Org . "9.4")
+  :type 'hook)
+
+(defcustom org-cycle-open-archived-trees nil
+  "Non-nil means `org-cycle' will open archived trees.
+An archived tree is a tree marked with the tag ARCHIVE.
+When nil, archived trees will stay folded.  You can still open them with
+normal outline commands like `show-all', but not with the cycling commands."
+  :group 'org-archive
+  :group 'org-cycle
+  :type 'boolean)
+
+(defvar org-cycle-tab-first-hook nil
+  "Hook for functions to attach themselves to TAB.
+See `org-ctrl-c-ctrl-c-hook' for more information.
+This hook runs as the first action when TAB is pressed, even before
+`org-cycle' messes around with the `outline-regexp' to cater for
+inline tasks and plain list item folding.
+If any function in this hook returns t, any other actions that
+would have been caused by TAB (such as table field motion or visibility
+cycling) will not occur.")
+
+;;;; Implementation:
+
+(defun org-cycle-hide-drawers (state)
+  "Re-hide all drawers after a visibility state change.
+STATE should be one of the symbols listed in the docstring of
+`org-cycle-hook'."
+  (when (derived-mode-p 'org-mode)
+    (cond ((not (memq state '(overview folded contents)))
+           (let* ((global? (eq state 'all))
+                  (beg (if global? (point-min) (line-beginning-position)))
+                  (end (cond (global? (point-max))
+                             ((eq state 'children) (org-entry-end-position))
+                             (t (save-excursion (org-end-of-subtree t t))))))
+             (if (not global?)
+                 (org-fold--hide-drawers beg end)
+               ;; Delay folding drawers inside folded subtrees until
+               ;; first unfold.
+               (add-hook 'org-fold-core-first-unfold-functions
+                         #'org-fold--hide-drawers))))
+          ((memq state '(overview contents))
+           ;; Hide drawers before first heading.
+           (let ((beg (point-min))
+                 (end (save-excursion
+                        (goto-char (point-min))
+                        (if (org-before-first-heading-p)
+                            (org-entry-end-position)
+                          (point-min)))))
+             (when (< beg end)
+               (org-fold--hide-drawers beg end)))))))
+
+;;;###autoload
+(defun org-cycle (&optional arg)
+  "TAB-action and visibility cycling for Org mode.
+
+This is the command invoked in Org mode by the `TAB' key.  Its main
+purpose is outline visibility cycling, but it also invokes other actions
+in special contexts.
+
+When this function is called with a `\\[universal-argument]' prefix, rotate \
+the entire
+buffer through 3 states (global cycling)
+  1. OVERVIEW: Show only top-level headlines.
+  2. CONTENTS: Show all headlines of all levels, but no body text.
+  3. SHOW ALL: Show everything.
+
+With a `\\[universal-argument] \\[universal-argument]' prefix argument, \
+switch to the startup visibility,
+determined by the variable `org-startup-folded', and by any VISIBILITY
+properties in the buffer.
+
+With a `\\[universal-argument] \\[universal-argument] \
+\\[universal-argument]' prefix argument, show the entire buffer, including
+any drawers.
+
+When inside a table, re-align the table and move to the next field.
+
+When point is at the beginning of a headline, rotate the subtree started
+by this line through 3 different states (local cycling)
+  1. FOLDED:   Only the main headline is shown.
+  2. CHILDREN: The main headline and the direct children are shown.
+               From this state, you can move to one of the children
+               and zoom in further.
+  3. SUBTREE:  Show the entire subtree, including body text.
+If there is no subtree, switch directly from CHILDREN to FOLDED.
+
+When point is at the beginning of an empty headline and the variable
+`org-cycle-level-after-item/entry-creation' is set, cycle the level
+of the headline by demoting and promoting it to likely levels.  This
+speeds up creation document structure by pressing `TAB' once or several
+times right after creating a new headline.
+
+When there is a numeric prefix, go up to a heading with level ARG, do
+a `show-subtree' and return to the previous cursor position.  If ARG
+is negative, go up that many levels.
+
+When point is not at the beginning of a headline, execute the global
+binding for `TAB', which is re-indenting the line.  See the option
+`org-cycle-emulate-tab' for details.
+
+As a special case, if point is at the very beginning of the buffer, if
+there is no headline there, and if the variable `org-cycle-global-at-bob'
+is non-nil, this function acts as if called with prefix argument \
+\(`\\[universal-argument] TAB',
+same as `S-TAB') also when called without prefix argument."
+  (interactive "P")
+  (org-load-modules-maybe)
+  (unless (or (run-hook-with-args-until-success 'org-cycle-tab-first-hook)
+	      (and org-cycle-level-after-item/entry-creation
+		   (or (org-cycle-level)
+		       (org-cycle-item-indentation))))
+    (let* ((limit-level
+	    (or org-cycle-max-level
+		(and (boundp 'org-inlinetask-min-level)
+		     org-inlinetask-min-level
+		     (1- org-inlinetask-min-level))))
+	   (nstars
+	    (and limit-level
+		 (if org-odd-levels-only
+		     (1- (* 2 limit-level))
+		   limit-level)))
+	   (org-outline-regexp
+	    (format "\\*%s " (if nstars (format "\\{1,%d\\}" nstars) "+"))))
+      (cond
+       ((equal arg '(16))
+	(setq last-command 'dummy)
+	(org-cycle-set-startup-visibility)
+	(org-unlogged-message "Startup visibility, plus VISIBILITY properties"))
+       ((equal arg '(64))
+	(org-fold-show-all)
+	(org-unlogged-message "Entire buffer visible, including drawers"))
+       ((equal arg '(4)) (org-cycle-internal-global))
+       ;; Show-subtree, ARG levels up from here.
+       ((integerp arg)
+	(save-excursion
+	  (org-back-to-heading)
+	  (outline-up-heading (if (< arg 0) (- arg)
+				(- (funcall outline-level) arg)))
+	  (org-fold-show-subtree)))
+       ;; Global cycling at BOB: delegate to `org-cycle-internal-global'.
+       ((and org-cycle-global-at-bob
+	     (bobp)
+	     (not (looking-at org-outline-regexp)))
+	(let ((org-cycle-hook
+	       (remq 'org-cycle-optimize-window-after-visibility-change
+		     org-cycle-hook)))
+	  (org-cycle-internal-global)))
+       ;; Try CDLaTeX TAB completion.
+       ((org-try-cdlatex-tab))
+       ;; Inline task: delegate to `org-inlinetask-toggle-visibility'.
+       ((and (featurep 'org-inlinetask)
+	     (org-inlinetask-at-task-p)
+	     (or (bolp) (not (eq org-cycle-emulate-tab 'exc-hl-bol))))
+	(org-inlinetask-toggle-visibility))
+       (t
+	(let ((pos (point))
+	      (element (org-element-at-point)))
+	  (cond
+	   ;; Try toggling visibility for block at point.
+	   ((org-fold-hide-block-toggle nil t element))
+	   ;; Try toggling visibility for drawer at point.
+	   ((org-fold-hide-drawer-toggle nil t element))
+	   ;; Table: enter it or move to the next field.
+	   ((and (org-match-line "[ \t]*[|+]")
+		 (org-element-lineage element '(table) t))
+	    (if (and (eq 'table (org-element-type element))
+		     (eq 'table.el (org-element-property :type element)))
+		(message (substitute-command-keys "\\<org-mode-map>\
+Use `\\[org-edit-special]' to edit table.el tables"))
+	      (org-table-justify-field-maybe)
+	      (call-interactively #'org-table-next-field)))
+	   ((run-hook-with-args-until-success
+	     'org-tab-after-check-for-table-hook))
+	   ;; At an item/headline: delegate to `org-cycle-internal-local'.
+	   ((and (or (and org-cycle-include-plain-lists
+			  (let ((item (org-element-lineage element
+							   '(item plain-list)
+							   t)))
+			    (and item
+				 (= (line-beginning-position)
+				    (org-element-property :post-affiliated
+							  item)))))
+		     (org-match-line org-outline-regexp))
+		 (or (bolp) (not (eq org-cycle-emulate-tab 'exc-hl-bol))))
+	    (org-cycle-internal-local))
+	   ;; From there: TAB emulation and template completion.
+	   (buffer-read-only (org-back-to-heading))
+	   ((run-hook-with-args-until-success
+	     'org-tab-after-check-for-cycling-hook))
+	   ((run-hook-with-args-until-success
+	     'org-tab-before-tab-emulation-hook))
+	   ((and (eq org-cycle-emulate-tab 'exc-hl-bol)
+		 (or (not (bolp))
+		     (not (looking-at org-outline-regexp))))
+	    (call-interactively (global-key-binding (kbd "TAB"))))
+	   ((or (eq org-cycle-emulate-tab t)
+		(and (memq org-cycle-emulate-tab '(white whitestart))
+		     (save-excursion (beginning-of-line 1) (looking-at "[ \t]*"))
+		     (or (and (eq org-cycle-emulate-tab 'white)
+			      (= (match-end 0) (point-at-eol)))
+			 (and (eq org-cycle-emulate-tab 'whitestart)
+			      (>= (match-end 0) pos)))))
+	    (call-interactively (global-key-binding (kbd "TAB"))))
+	   (t
+	    (save-excursion
+	      (org-back-to-heading)
+	      (org-cycle))))))))))
+
+(defun org-cycle-force-archived ()
+  "Cycle subtree even if it is archived."
+  (interactive)
+  (setq this-command 'org-cycle)
+  (let ((org-cycle-open-archived-trees t))
+    (call-interactively 'org-cycle)))
+
+(defun org-cycle-internal-global ()
+  "Do the global cycling action."
+  ;; Hack to avoid display of messages for .org  attachments in Gnus
+  (let ((ga (string-match-p "\\*fontification" (buffer-name))))
+    (cond
+     ((and (eq last-command this-command)
+	   (eq org-cycle-global-status 'overview))
+      ;; We just created the overview - now do table of contents
+      ;; This can be slow in very large buffers, so indicate action
+      (run-hook-with-args 'org-cycle-pre-hook 'contents)
+      (unless ga (org-unlogged-message "CONTENTS..."))
+      (org-cycle-content)
+      (unless ga (org-unlogged-message "CONTENTS...done"))
+      (setq org-cycle-global-status 'contents)
+      (run-hook-with-args 'org-cycle-hook 'contents))
+
+     ((and (eq last-command this-command)
+	   (eq org-cycle-global-status 'contents))
+      ;; We just showed the table of contents - now show everything
+      (run-hook-with-args 'org-cycle-pre-hook 'all)
+      (org-fold-show-all '(headings blocks))
+      (unless ga (org-unlogged-message "SHOW ALL"))
+      (setq org-cycle-global-status 'all)
+      (run-hook-with-args 'org-cycle-hook 'all))
+
+     (t
+      ;; Default action: go to overview
+      (run-hook-with-args 'org-cycle-pre-hook 'overview)
+      (org-cycle-overview)
+      (unless ga (org-unlogged-message "OVERVIEW"))
+      (setq org-cycle-global-status 'overview)
+      (run-hook-with-args 'org-cycle-hook 'overview)))))
+
+(defun org-cycle-internal-local ()
+  "Do the local cycling action."
+  (let ((goal-column 0) eoh eol eos has-children children-skipped struct)
+    ;; First, determine end of headline (EOH), end of subtree or item
+    ;; (EOS), and if item or heading has children (HAS-CHILDREN).
+    (save-excursion
+      (if (org-at-item-p)
+	  (progn
+	    (beginning-of-line)
+	    (setq struct (org-list-struct))
+	    (setq eoh (point-at-eol))
+	    (setq eos (org-list-get-item-end-before-blank (point) struct))
+	    (setq has-children (org-list-has-child-p (point) struct)))
+	(org-back-to-heading)
+	(setq eoh (save-excursion (outline-end-of-heading) (point)))
+	(setq eos (save-excursion
+		    (org-end-of-subtree t t)
+		    (unless (eobp) (forward-char -1))
+		    (point)))
+	(setq has-children
+	      (or
+	       (save-excursion
+		 (let ((level (funcall outline-level)))
+		   (outline-next-heading)
+		   (and (org-at-heading-p)
+			(> (funcall outline-level) level))))
+	       (and (eq org-cycle-include-plain-lists 'integrate)
+		    (save-excursion
+		      (org-list-search-forward (org-item-beginning-re) eos t))))))
+      ;; Determine end invisible part of buffer (EOL)
+      (beginning-of-line 2)
+      (if (eq org-fold-core-style 'text-properties)
+          (while (and (not (eobp))		;this is like `next-line'
+		      (org-fold-folded-p (1- (point))))
+	    (goto-char (org-fold-next-visibility-change nil nil t))
+	    (and (eolp) (beginning-of-line 2)))
+        (while (and (not (eobp))		;this is like `next-line'
+		    (get-char-property (1- (point)) 'invisible))
+	  (goto-char (next-single-char-property-change (point) 'invisible))
+	  (and (eolp) (beginning-of-line 2))))
+      (setq eol (point)))
+    ;; Find out what to do next and set `this-command'
+    (cond
+     ((= eos eoh)
+      ;; Nothing is hidden behind this heading
+      (unless (org-before-first-heading-p)
+	(run-hook-with-args 'org-cycle-pre-hook 'empty))
+      (org-unlogged-message "EMPTY ENTRY")
+      (setq org-cycle-subtree-status nil)
+      (save-excursion
+	(goto-char eos)
+        (org-with-limited-levels
+	 (outline-next-heading))
+	(when (org-invisible-p) (org-fold-heading nil))))
+     ((and (or (>= eol eos)
+	       (save-excursion (goto-char eol) (skip-chars-forward "[:space:]" eos) (= (point) eos)))
+	   (or has-children
+	       (not (setq children-skipped
+			org-cycle-skip-children-state-if-no-children))))
+      ;; Entire subtree is hidden in one line: children view
+      (unless (org-before-first-heading-p)
+        (org-with-limited-levels
+	 (run-hook-with-args 'org-cycle-pre-hook 'children)))
+      (if (org-at-item-p)
+	  (org-list-set-item-visibility (point-at-bol) struct 'children)
+	(org-fold-show-entry)
+	(org-with-limited-levels (org-fold-show-children))
+	(org-fold-show-set-visibility 'tree)
+	;; Fold every list in subtree to top-level items.
+	(when (eq org-cycle-include-plain-lists 'integrate)
+	  (save-excursion
+	    (org-back-to-heading)
+	    (while (org-list-search-forward (org-item-beginning-re) eos t)
+	      (beginning-of-line 1)
+	      (let* ((struct (org-list-struct))
+		     (prevs (org-list-prevs-alist struct))
+		     (end (org-list-get-bottom-point struct)))
+		(dolist (e (org-list-get-all-items (point) struct prevs))
+		  (org-list-set-item-visibility e struct 'folded))
+		(goto-char (if (< end eos) end eos)))))))
+      (org-unlogged-message "CHILDREN")
+      (save-excursion
+	(goto-char eos)
+        (org-with-limited-levels
+	 (outline-next-heading))
+	(when (and
+               ;; Subtree does not end at the end of visible section of the
+               ;; buffer.
+               (< (point) (point-max))
+               (org-invisible-p))
+          ;; Reveal the following heading line.
+          (org-fold-heading nil)))
+      (setq org-cycle-subtree-status 'children)
+      (unless (org-before-first-heading-p)
+	(run-hook-with-args 'org-cycle-hook 'children)))
+     ((or children-skipped
+	  (and (eq last-command this-command)
+	       (eq org-cycle-subtree-status 'children)))
+      ;; We just showed the children, or no children are there,
+      ;; now show everything.
+      (unless (org-before-first-heading-p)
+	(run-hook-with-args 'org-pre-cycle-hook 'subtree))
+      (org-fold-region eoh eos nil 'outline)
+      (org-unlogged-message
+       (if children-skipped "SUBTREE (NO CHILDREN)" "SUBTREE"))
+      (setq org-cycle-subtree-status 'subtree)
+      (unless (org-before-first-heading-p)
+	(run-hook-with-args 'org-cycle-hook 'subtree)))
+     (t
+      ;; Default action: hide the subtree.
+      (run-hook-with-args 'org-cycle-pre-hook 'folded)
+      (org-fold-region eoh eos t 'outline)
+      (org-unlogged-message "FOLDED")
+      (setq org-cycle-subtree-status 'folded)
+      (unless (org-before-first-heading-p)
+	(run-hook-with-args 'org-cycle-hook 'folded))))))
+
+;;;###autoload
+(defun org-cycle-global (&optional arg)
+  "Cycle the global visibility.  For details see `org-cycle'.
+With `\\[universal-argument]' prefix ARG, switch to startup visibility.
+With a numeric prefix, show all headlines up to that level."
+  (interactive "P")
+  (cond
+   ((integerp arg)
+    (org-cycle-content arg)
+    (setq org-cycle-global-status 'contents))
+   ((equal arg '(4))
+    (org-cycle-set-startup-visibility)
+    (org-unlogged-message "Startup visibility, plus VISIBILITY properties."))
+   (t
+    (org-cycle '(4)))))
+
+(defun org-cycle-set-startup-visibility ()
+  "Set the visibility required by startup options and properties."
+  (cond
+   ((eq org-startup-folded t)
+    (org-cycle-overview))
+   ((eq org-startup-folded 'content)
+    (org-cycle-content))
+   ((eq org-startup-folded 'show2levels)
+    (org-cycle-content 2))
+   ((eq org-startup-folded 'show3levels)
+    (org-cycle-content 3))
+   ((eq org-startup-folded 'show4levels)
+    (org-cycle-content 4))
+   ((eq org-startup-folded 'show5levels)
+    (org-cycle-content 5))
+   ((or (eq org-startup-folded 'showeverything)
+	(eq org-startup-folded nil))
+    (org-fold-show-all)))
+  (unless (eq org-startup-folded 'showeverything)
+    (when org-cycle-hide-block-startup (org-fold-hide-block-all))
+    (org-cycle-set-visibility-according-to-property)
+    (org-cycle-hide-archived-subtrees 'all)
+    (org-cycle-hide-drawers 'all)
+    (org-cycle-show-empty-lines t)))
+
+(defun org-cycle-set-visibility-according-to-property ()
+  "Switch subtree visibility according to VISIBILITY property."
+  (interactive)
+  (let ((regexp (org-re-property "VISIBILITY")))
+    (org-with-point-at 1
+      (while (re-search-forward regexp nil t)
+	(let ((state (match-string 3)))
+	  (if (not (org-at-property-p)) (outline-next-heading)
+	    (save-excursion
+	      (org-back-to-heading t)
+	      (org-fold-subtree t)
+	      (org-fold-reveal)
+	      (pcase state
+		("folded"
+		 (org-fold-subtree t))
+		("children"
+		 (org-fold-show-hidden-entry)
+		 (org-fold-show-children))
+		("content"
+		 (save-excursion
+		   (save-restriction
+		     (org-narrow-to-subtree)
+		     (org-cycle-content))))
+		((or "all" "showall")
+		 (org-fold-show-subtree))
+		(_ nil)))
+	    (org-end-of-subtree)))))))
+
+(defun org-cycle-overview--overlays ()
+  "Switch to overview mode, showing only top-level headlines."
+  (interactive)
+  (org-fold-show-all '(headings drawers))
+  (save-excursion
+    (goto-char (point-min))
+    (when (re-search-forward org-outline-regexp-bol nil t)
+      (let* ((last (line-end-position))
+             (level (- (match-end 0) (match-beginning 0) 1))
+             (regexp (format "^\\*\\{1,%d\\} " level)))
+        (while (re-search-forward regexp nil :move)
+          (org-fold-region last (line-end-position 0) t 'outline)
+          (setq last (line-end-position))
+          (setq level (- (match-end 0) (match-beginning 0) 1))
+          (setq regexp (format "^\\*\\{1,%d\\} " level)))
+        (org-fold-region last (point) t 'outline)))))
+(defun org-cycle-overview--text-properties ()
+  "Switch to overview mode, showing only top-level headlines."
+  (interactive)
+  (save-excursion
+    (goto-char (point-min))
+    ;; Hide top-level drawer.
+    (save-restriction
+      (narrow-to-region (point-min) (or (re-search-forward org-outline-regexp-bol nil t) (point-max)))
+      (org-fold-hide-drawer-all))
+    (goto-char (point-min))
+    (when (re-search-forward org-outline-regexp-bol nil t)
+      (let* ((last (line-end-position))
+             (level (- (match-end 0) (match-beginning 0) 1))
+             (regexp (format "^\\*\\{1,%d\\} " level)))
+        (while (re-search-forward regexp nil :move)
+          (org-fold-region last (line-end-position 0) t 'outline)
+          (setq last (line-end-position))
+          (setq level (- (match-end 0) (match-beginning 0) 1))
+          (setq regexp (format "^\\*\\{1,%d\\} " level)))
+        (org-fold-region last (point) t 'outline)))))
+(defun org-cycle-overview ()
+  "Switch to overview mode, showing only top-level headlines."
+  (interactive)
+  (if (eq org-fold-core-style 'text-properties)
+      (org-cycle-overview--text-properties)
+    (org-cycle-overview--overlays)))
+
+(defun org-cycle-content--text-properties (&optional arg)
+  "Show all headlines in the buffer, like a table of contents.
+With numerical argument N, show content up to level N."
+  (interactive "p")
+  (org-fold-show-all '(headings))
+  (save-excursion
+    (goto-char (point-min))
+    ;; Hide top-level drawer.
+    (save-restriction
+      (narrow-to-region (point-min) (or (re-search-forward org-outline-regexp-bol nil t) (point-max)))
+      (org-fold-hide-drawer-all))
+    (goto-char (point-max))
+    (let ((regexp (if (and (wholenump arg) (> arg 0))
+                      (format "^\\*\\{1,%d\\} " arg)
+                    "^\\*+ "))
+          (last (point)))
+      (while (re-search-backward regexp nil t)
+        (org-fold-region (line-end-position) last t 'outline)
+        (setq last (line-end-position 0))))))
+(defun org-cycle-content--overlays (&optional arg)
+  "Show all headlines in the buffer, like a table of contents.
+With numerical argument N, show content up to level N."
+  (interactive "p")
+  (org-fold-show-all '(headings drawers))
+  (save-excursion
+    (goto-char (point-max))
+    (let ((regexp (if (and (wholenump arg) (> arg 0))
+                      (format "^\\*\\{1,%d\\} " arg)
+                    "^\\*+ "))
+          (last (point)))
+      (while (re-search-backward regexp nil t)
+        (org-fold-region (line-end-position) last t 'outline)
+        (setq last (line-end-position 0))))))
+(defun org-cycle-content (&optional arg)
+  "Show all headlines in the buffer, like a table of contents.
+With numerical argument N, show content up to level N."
+  (interactive "p")
+  (if (eq org-fold-core-style 'text-properties)
+      (org-cycle-content--text-properties arg)
+    (org-cycle-content--overlays arg)))
+
+(defvar org-cycle-scroll-position-to-restore nil
+  "Temporarily store scroll position to restore.")
+(defun org-cycle-optimize-window-after-visibility-change (state)
+  "Adjust the window after a change in outline visibility.
+This function is the default value of the hook `org-cycle-hook'."
+  (when (get-buffer-window (current-buffer))
+    (let ((repeat (eq last-command this-command)))
+      (unless repeat
+	(setq org-cycle-scroll-position-to-restore nil))
+      (cond
+       ((eq state 'content)  nil)
+       ((eq state 'all)      nil)
+       ((and org-cycle-scroll-position-to-restore repeat
+	     (eq state 'folded))
+	(set-window-start nil org-cycle-scroll-position-to-restore))
+       ((eq state 'folded) nil)
+       ((eq state 'children)
+	(setq org-cycle-scroll-position-to-restore (window-start))
+	(or (org-subtree-end-visible-p) (recenter 1)))
+       ((eq state 'subtree)
+        (unless repeat
+	  (setq org-cycle-scroll-position-to-restore (window-start)))
+        (or (org-subtree-end-visible-p) (recenter 1)))))))
+
+(defun org-cycle-show-empty-lines (state)
+  "Show empty lines above all visible headlines.
+The region to be covered depends on STATE when called through
+`org-cycle-hook'.  Lisp program can use t for STATE to get the
+entire buffer covered.  Note that an empty line is only shown if there
+are at least `org-cycle-separator-lines' empty lines before the headline."
+  (when (/= org-cycle-separator-lines 0)
+    (save-excursion
+      (let* ((n (abs org-cycle-separator-lines))
+             (re (cond
+                  ((= n 1) "\\(\n[ \t]*\n\\*+\\) ")
+                  ((= n 2) "^[ \t]*\\(\n[ \t]*\n\\*+\\) ")
+                  (t (let ((ns (number-to-string (- n 2))))
+                       (concat "^\\(?:[ \t]*\n\\)\\{" ns "," ns "\\}"
+                               "[ \t]*\\(\n[ \t]*\n\\*+\\) ")))))
+             beg end)
+        (cond
+         ((memq state '(overview contents t))
+          (setq beg (point-min) end (point-max)))
+         ((memq state '(children folded))
+          (setq beg (point)
+                end (progn (org-end-of-subtree t t)
+                           (line-beginning-position 2)))))
+        (when beg
+          (goto-char beg)
+          (while (re-search-forward re end t)
+            (unless (org-invisible-p (match-end 1))
+              (let ((e (match-end 1))
+                    (b (if (>= org-cycle-separator-lines 0)
+                           (match-beginning 1)
+                         (save-excursion
+                           (goto-char (match-beginning 0))
+                           (skip-chars-backward " \t\n")
+                           (line-end-position)))))
+                (org-fold-region b e nil 'outline))))))))
+  ;; Never hide empty lines at the end of the file.
+  (save-excursion
+    (goto-char (point-max))
+    (outline-previous-heading)
+    (outline-end-of-heading)
+    (when (and (looking-at "[ \t\n]+")
+               (= (match-end 0) (point-max)))
+      (org-fold-region (point) (match-end 0) nil 'outline))))
+
+(defun org-cycle-hide-archived-subtrees (state)
+  "Re-hide all archived subtrees after a visibility state change.
+STATE should be one of the symbols listed in the docstring of
+`org-cycle-hook'."
+  (when (and (not org-cycle-open-archived-trees)
+             (not (memq state '(overview folded))))
+    (let ((globalp (memq state '(contents all))))
+      (if globalp
+          ;; Delay hiding inside folded subtrees until first unfold.
+          (add-hook 'org-fold-core-first-unfold-functions
+                    #'org-fold-hide-archived-subtrees)
+        (org-fold-hide-archived-subtrees
+         (point)
+         (save-excursion
+           (org-end-of-subtree t))))
+      (when (and (not globalp)
+                 (member org-archive-tag
+                         (org-get-tags nil 'local)))
+	(message "%s" (substitute-command-keys
+		       "Subtree is archived and stays closed.  Use \
+`\\[org-cycle-force-archived]' to cycle it anyway."))))))
+
+(provide 'org-cycle)
+
+;;; org-cycle.el ends here