emacs/lisp/mail/mh-speed.el

;;; mh-speed.el --- Speedbar interface for MH-E.

;; Copyright (C) 2002 Free Software Foundation, Inc.

;; Author: Bill Wohler <wohler@newt.com>
;; Maintainer: Bill Wohler <wohler@newt.com>
;; Keywords: mail
;; See: mh-e.el

;; 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 2, 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; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:
;;   Future versions should only use flists.

;; Speedbar support for MH-E package.

;;; Change Log:

;; $Id: mh-speed.el,v 1.26 2002/11/13 19:36:00 wohler Exp $

;;; Code:

;; Requires
(require 'cl)
(require 'mh-utils)
(require 'mh-e)
(require 'speedbar)

;; Autoloads
(autoload 'mh-index-goto-nearest-msg "mh-index")
(autoload 'mh-index-parse-folder "mh-index")
(autoload 'mh-visit-folder "mh-e")

;; User customizable
(defcustom mh-large-folder 200
  "The number of messages that indicates a large folder.
If the number of messages in a folder exceeds this value, confirmation is
required when the folder is visited from the speedbar."
  :type 'integer
  :group 'mh)

(defcustom mh-speed-flists-interval 60
  "Time between calls to flists in seconds.
If 0, flists is not called repeatedly."
  :type 'integer
  :group 'mh)

(defcustom mh-speed-run-flists-flag t
  "Non-nil means flists is used.
If non-nil, flists is executed every `mh-speed-flists-interval' seconds to
update the display of the number of unseen and total messages in each folder.
If resources are limited, this can be set to nil and the speedbar display can
be updated manually with the \\[mh-speed-flists] command."
  :type 'boolean
  :group 'mh)

(defface mh-speedbar-folder-face
    '((((class color) (background light))
       (:foreground "blue4"))
      (((class color) (background dark))
       (:foreground "light blue")))
  "Face used for folders in the speedbar buffer."
  :group 'mh)

(defface mh-speedbar-selected-folder-face
    '((((class color) (background light))
       (:foreground "red" :underline t))
      (((class color) (background dark))
       (:foreground "red" :underline t))
      (t (:underline t)))
  "Face used for the current folder."
  :group 'mh)

(defface mh-speedbar-folder-with-unseen-messages-face
    '((t (:inherit mh-speedbar-folder-face :bold t)))
  "Face used for folders in the speedbar buffer which have unread messages."
  :group 'mh)

(defface mh-speedbar-selected-folder-with-unseen-messages-face
    '((t (:inherit mh-speedbar-selected-folder-face :bold t)))
  "Face used for the current folder when it has unread messages."
  :group 'mh)

;; Global variables
(defvar mh-speed-refresh-flag nil)
(defvar mh-speed-last-selected-folder nil)
(defvar mh-speed-folder-map (make-hash-table :test #'equal))
(defvar mh-speed-folders-cache (make-hash-table :test #'equal))
(defvar mh-speed-flists-cache (make-hash-table :test #'equal))
(defvar mh-speed-flists-process nil)
(defvar mh-speed-flists-timer nil)
(defvar mh-speed-partial-line "")

;; Add our stealth update function
(unless (member 'mh-speed-stealth-update
                (cdr (assoc "files" speedbar-stealthy-function-list)))
  ;; Is changing constant lists in elisp safe?
  (setq speedbar-stealthy-function-list
        (copy-tree speedbar-stealthy-function-list))
  (push 'mh-speed-stealth-update
        (cdr (assoc "files" speedbar-stealthy-function-list))))

;; Functions called by speedbar to initialize display...
(defun mh-folder-speedbar-buttons (buffer)
  "Interface function to create MH-E speedbar buffer.
BUFFER is the MH-E buffer for which the speedbar buffer is to be created."
  (unless (get-text-property (point-min) 'mh-level)
    (erase-buffer)
    (clrhash mh-speed-folder-map)
    (speedbar-make-tag-line 'bracket ?+ 'mh-speed-toggle nil " " 'ignore nil
                            'mh-speedbar-folder-face 0)
    (forward-line -1)
    (setf (gethash nil mh-speed-folder-map)
          (set-marker (make-marker) (1+ (line-beginning-position))))
    (add-text-properties
     (line-beginning-position) (1+ (line-beginning-position))
     `(mh-folder nil mh-expanded nil mh-children-p t mh-level 0))
    (mh-speed-stealth-update t)
    (when mh-speed-run-flists-flag
      (mh-speed-flists nil))))

(defalias 'mh-show-speedbar-buttons 'mh-folder-speedbar-buttons)
(defalias 'mh-index-folder-speedbar-buttons 'mh-folder-speedbar-buttons)
(defalias 'mh-index-show-speedbar-buttons 'mh-folder-speedbar-buttons)
(defalias 'mh-letter-speedbar-buttons 'mh-folder-speedbar-buttons)

;; Keymaps for speedbar...
(defvar mh-folder-speedbar-key-map (speedbar-make-specialized-keymap)
  "Specialized speedbar keymap for MH-E buffers.")
(gnus-define-keys mh-folder-speedbar-key-map
  "+"		mh-speed-expand-folder
  "-"		mh-speed-contract-folder
  "\r"		mh-speed-view
  "f"		mh-speed-flists
  "i"		mh-speed-invalidate-map)

(defvar mh-show-speedbar-key-map mh-folder-speedbar-key-map)
(defvar mh-index-folder-speedbar-key-map mh-folder-speedbar-key-map)
(defvar mh-index-show-speedbar-key-map mh-folder-speedbar-key-map)
(defvar mh-letter-speedbar-key-map mh-folder-speedbar-key-map)

;; Menus for speedbar...
(defvar mh-folder-speedbar-menu-items
  '(["Visit Folder" mh-speed-view
     (save-excursion
       (set-buffer speedbar-buffer)
       (get-text-property (line-beginning-position) 'mh-folder))]
    ["Expand nested folders" mh-speed-expand-folder
     (and (get-text-property (line-beginning-position) 'mh-children-p)
          (not (get-text-property (line-beginning-position) 'mh-expanded)))]
    ["Contract nested folders" mh-speed-contract-folder
     (and (get-text-property (line-beginning-position) 'mh-children-p)
          (get-text-property (line-beginning-position) 'mh-expanded))]
    ["Run Flists" mh-speed-flists t]
    ["Invalidate cached folders" mh-speed-invalidate-map t])
  "Extra menu items for speedbar.")

(defvar mh-show-speedbar-menu-items mh-folder-speedbar-menu-items)
(defvar mh-index-folder-speedbar-menu-items mh-folder-speedbar-menu-items)
(defvar mh-index-show-speedbar-menu-items mh-folder-speedbar-menu-items)
(defvar mh-letter-speedbar-menu-items mh-folder-speedbar-menu-items)

(defmacro mh-speed-select-attached-frame ()
  "Compatibility macro to handle speedbar versions 0.11a and 0.14beta4."
  (cond ((fboundp 'dframe-select-attached-frame)
         '(dframe-select-attached-frame speedbar-frame))
        ((boundp 'speedbar-attached-frame)
         '(select-frame speedbar-attached-frame))
        (t (error "Installed speedbar version not supported by MH-E"))))

(defun mh-speed-update-current-folder (force)
  "Update speedbar highlighting of the current folder.
The function tries to be smart so that work done is minimized. The currently
highlighted folder is cached and no highlighting happens unless it changes.
Also highlighting is suspended while the speedbar frame is selected.
Otherwise you get the disconcerting behavior of folders popping open on their
own when you are trying to navigate around in the speedbar buffer.

The update is always carried out if FORCE is non-nil."
  (let* ((lastf (selected-frame))
	 (newcf (save-excursion
                  (mh-speed-select-attached-frame)
                  (prog1 (mh-speed-extract-folder-name (buffer-name))
                    (select-frame lastf))))
	 (lastb (current-buffer))
	 (case-fold-search t))
    (when (or force
              (and mh-speed-refresh-flag (not (eq lastf speedbar-frame)))
              (and (stringp newcf)
                   (equal (substring newcf 0 1) "+")
                   (not (equal newcf mh-speed-last-selected-folder))))
      (setq mh-speed-refresh-flag nil)
      (select-frame speedbar-frame)
      (set-buffer speedbar-buffer)

      ;; Remove highlight from previous match...
      (mh-speed-highlight mh-speed-last-selected-folder
                          'mh-speedbar-folder-face)

      ;; If we found a match highlight it...
      (when (mh-speed-goto-folder newcf)
        (mh-speed-highlight newcf 'mh-speedbar-selected-folder-face))

      (setq mh-speed-last-selected-folder newcf)
      (speedbar-position-cursor-on-line)
      (set-window-point (frame-first-window speedbar-frame) (point))
      (set-buffer lastb)
      (select-frame lastf))
    (when (eq lastf speedbar-frame)
      (setq mh-speed-refresh-flag t))))

(defun mh-speed-normal-face (face)
  "Return normal face for given FACE."
  (cond ((eq face 'mh-speedbar-folder-with-unseen-messages-face)
         'mh-speedbar-folder-face)
        ((eq face 'mh-speedbar-selected-folder-with-unseen-messages-face)
         'mh-speedbar-selected-folder-face)
        (t face)))

(defun mh-speed-bold-face (face)
  "Return bold face for given FACE."
  (cond ((eq face 'mh-speedbar-folder-face)
         'mh-speedbar-folder-with-unseen-messages-face)
        ((eq face 'mh-speedbar-selected-folder-face)
         'mh-speedbar-selected-folder-with-unseen-messages-face)
        (t face)))

(defun mh-speed-highlight (folder face)
  "Set FOLDER to FACE."
  (save-excursion
    (speedbar-with-writable
      (goto-char (gethash folder mh-speed-folder-map (point)))
      (beginning-of-line)
      (if (re-search-forward "([1-9][0-9]*/[0-9]+)" (line-end-position) t)
          (setq face (mh-speed-bold-face face))
        (setq face (mh-speed-normal-face face)))
      (beginning-of-line)
      (when (re-search-forward "\\[.\\] " (line-end-position) t)
        (put-text-property (point) (line-end-position) 'face face)))))

(defun mh-speed-stealth-update (&optional force)
  "Do stealth update.
With non-nil FORCE, the update is always carried out."
  (cond ((save-excursion (set-buffer speedbar-buffer)
                         (get-text-property (point-min) 'mh-level))
         ;; Execute this hook and *don't* run anything else
         (mh-speed-update-current-folder force)
         nil)
        ;; Otherwise on to your regular programming
        (t t)))

(defun mh-speed-goto-folder (folder)
  "Move point to line containing FOLDER.
The function will expand out parent folders of FOLDER if needed."
  (let ((prefix folder)
        (suffix-list ())
        (last-slash t))
    (while (and (not (gethash prefix mh-speed-folder-map)) last-slash)
      (setq last-slash (search "/" prefix :from-end t))
      (when (integerp last-slash)
        (push (substring prefix (1+ last-slash)) suffix-list)
        (setq prefix (substring prefix 0 last-slash))))
    (let ((prefix-position (gethash prefix mh-speed-folder-map)))
      (if prefix-position
          (goto-char prefix-position)
        (goto-char (point-min))
        (mh-speed-toggle)
        (unless (get-text-property (point) 'mh-expanded)
          (mh-speed-toggle))
        (goto-char (gethash prefix mh-speed-folder-map))))
    (while suffix-list
      ;; We always need atleast one toggle. We need two if the directory list
      ;; is stale since a folder was added.
      (when (equal prefix (get-text-property (line-beginning-position)
                                             'mh-folder))
        (mh-speed-toggle)
        (unless (get-text-property (point) 'mh-expanded)
          (mh-speed-toggle)))
      (setq prefix (format "%s/%s" prefix (pop suffix-list)))
      (goto-char (gethash prefix mh-speed-folder-map (point))))
    (beginning-of-line)
    (equal folder (get-text-property (point) 'mh-folder))))

(defun mh-speed-extract-folder-name (buffer)
  "Given an MH-E BUFFER find the folder that should be highlighted.
Do the right thing for the different kinds of buffers that MH-E uses."
  (save-excursion
    (set-buffer buffer)
    (cond ((eq major-mode 'mh-folder-mode)
           mh-current-folder)
          ((eq major-mode 'mh-show-mode)
           (set-buffer mh-show-folder-buffer)
           mh-current-folder)
          ((eq major-mode 'mh-index-folder-mode)
           (save-excursion
             (mh-index-goto-nearest-msg)
             (mh-index-parse-folder)))
          ((or (eq major-mode 'mh-index-show-mode)
               (eq major-mode 'mh-letter-mode))
           (when (string-match mh-user-path buffer-file-name)
             (let* ((rel-path (substring buffer-file-name (match-end 0)))
                    (directory-end (search "/" rel-path :from-end t)))
               (when directory-end
                 (format "+%s" (substring rel-path 0 directory-end)))))))))

(defun mh-speed-add-buttons (folder level)
  "Add speedbar button for FOLDER which is at indented by LEVEL amount."
  (let ((folder-list (mh-speed-folders folder)))
    (mapc
     (lambda (f)
       (let* ((folder-name (format "%s%s%s" (or folder "+")
                                   (if folder "/" "") (car f)))
              (counts (gethash folder-name mh-speed-flists-cache)))
         (speedbar-with-writable
           (speedbar-make-tag-line
            'bracket (if (cdr f) ?+ ? )
            'mh-speed-toggle nil
            (format "%s%s"
                    (car f)
                    (if counts
                        (format " (%s/%s)" (car counts) (cdr counts))
                      ""))
            'mh-speed-view nil
            (if (and counts (> (car counts) 0))
                'mh-speedbar-folder-with-unseen-messages-face
              'mh-speedbar-folder-face)
            level)
           (save-excursion
             (forward-line -1)
             (setf (gethash folder-name mh-speed-folder-map)
                   (set-marker (make-marker) (1+ (line-beginning-position))))
             (add-text-properties
              (line-beginning-position) (1+ (line-beginning-position))
              `(mh-folder ,folder-name
                mh-expanded nil
                mh-children-p ,(not (not (cdr f)))
                ,@(if counts `(mh-count (,(car counts) . ,(cdr counts))) ())
                mh-level ,level))))))
     folder-list)))

(defun mh-speed-toggle (&rest args)
  "Toggle the display of child folders.
The otional ARGS are ignored and there for compatibilty with speedbar."
  (interactive)
  (declare (ignore args))
  (beginning-of-line)
  (let ((parent (get-text-property (point) 'mh-folder))
        (kids-p (get-text-property (point) 'mh-children-p))
        (expanded (get-text-property (point) 'mh-expanded))
        (level (get-text-property (point) 'mh-level))
        (point (point))
        start-region)
    (speedbar-with-writable
      (cond ((not kids-p) nil)
            (expanded
             (forward-line)
             (setq start-region (point))
             (while (and (get-text-property (point) 'mh-level)
                         (> (get-text-property (point) 'mh-level) level))
               (remhash (get-text-property (point) 'mh-folder)
                        mh-speed-folder-map)
               (forward-line))
             (delete-region start-region (point))
             (forward-line -1)
             (speedbar-change-expand-button-char ?+)
             (add-text-properties
              (line-beginning-position) (1+ (line-beginning-position))
              '(mh-expanded nil)))
            (t
             (forward-line)
             (mh-speed-add-buttons parent (1+ level))
             (goto-char point)
             (speedbar-change-expand-button-char ?-)
             (add-text-properties
              (line-beginning-position) (1+ (line-beginning-position))
              `(mh-expanded t)))))))

(defalias 'mh-speed-expand-folder 'mh-speed-toggle)
(defalias 'mh-speed-contract-folder 'mh-speed-toggle)

(defun mh-speed-folder-size ()
  "Find folder size if folder on current line."
  (let ((folder (get-text-property (line-beginning-position) 'mh-folder)))
    (or (cdr (get-text-property (line-beginning-position) 'mh-count))
        (and (null folder) 0)
        (with-temp-buffer
          (call-process (expand-file-name "flist" mh-progs) nil t nil
                        "-norecurse" folder)
          (goto-char (point-min))
          (unless (re-search-forward "out of " (line-end-position) t)
            (error "Call to flist failed on folder %s" folder))
          (car (read-from-string
                (buffer-substring-no-properties (point)
                                                (line-end-position))))))))

(defun mh-speed-view (&rest args)
  "View folder on current line.
Optional ARGS are ignored."
  (interactive)
  (declare (ignore args))
  (let* ((folder (get-text-property (line-beginning-position) 'mh-folder))
         (range
           (cond ((save-excursion
                    (beginning-of-line)
                    (re-search-forward "([1-9][0-9]*/[0-9]+)"
                                       (line-end-position) t))
                  mh-unseen-seq)
		 ((> (mh-speed-folder-size) mh-large-folder)
		  (let* ((size (mh-speed-folder-size))
			 (prompt
			  (format "How many messages from %s (default: %s): "
				  folder size))
			 (in (read-string prompt nil nil
					  (number-to-string size)))
			 (result (car (ignore-errors (read-from-string in)))))
		    (cond ((null result) (format "last:%s" size))
			  ((numberp result) (format "last:%s" result))
			  (t (format "%s" result)))))
		 (t nil))))
    (when (stringp folder)
      (speedbar-with-attached-buffer
       (mh-visit-folder folder range)
       (delete-other-windows)))))

(defun mh-speed-folders (folder)
  "Find the subfolders of FOLDER.
The function avoids running folders unnecessarily by caching the results of
the actual folders call."
  (let ((match (gethash folder mh-speed-folders-cache 'no-result)))
    (cond ((eq match 'no-result)
           (setf (gethash folder mh-speed-folders-cache)
                 (mh-speed-folders-actual folder)))
          (t match))))

(defun mh-speed-folders-actual (folder)
  "Execute the command folders to return the sub-folders of FOLDER.
Filters out the folder names that start with \".\" so that directories that
aren't usually mail folders are hidden."
  (let* ((folder (cond ((and (stringp folder)
                             (equal (substring folder 0 1) "+"))
                        folder)
                       (t nil)))
         (arg-list `(,(expand-file-name "folders" mh-progs)
                     nil (t nil) nil "-noheader" "-norecurse"
                     ,@(if (stringp folder) (list folder) ())))
         (results ()))
    (with-temp-buffer
      (apply #'call-process arg-list)
      (goto-char (point-min))
      (while (not (and (eolp) (bolp)))
        (let ((folder-end (or (search-forward "+ " (line-end-position) t)
                              (search-forward " " (line-end-position) t))))
          (when (integerp folder-end)
            (let ((name (buffer-substring (line-beginning-position)
                                          (match-beginning 0))))
              (let ((first-char (substring name 0 1)))
                (unless (or (string-equal first-char ".")
                            (string-equal first-char "#")
                            (string-equal first-char ","))
                  (push
                    (cons name
                          (search-forward "(others)" (line-end-position) t))
                    results)))))
          (forward-line 1))))
    (setq results (nreverse results))
    (when (stringp folder)
      (setq results (cdr results))
      (let ((folder-name-len (length (format "%s/" (substring folder 1)))))
        (setq results (mapcar (lambda (f)
                                (cons (substring (car f) folder-name-len)
                                      (cdr f)))
                              results))))
    results))

(defun mh-speed-flists (force)
  "Execute flists -recurse and update message counts.
If FORCE is non-nil the timer is reset."
  (interactive (list t))
  (when force
    (when (timerp mh-speed-flists-timer)
      (cancel-timer mh-speed-flists-timer))
    (setq mh-speed-flists-timer nil)
    (when (and (processp mh-speed-flists-process)
               (not (eq (process-status mh-speed-flists-process) 'exit)))
      (kill-process mh-speed-flists-process)
      (setq mh-speed-flists-process nil)))
  (unless mh-speed-flists-timer
    (setq mh-speed-flists-timer
          (run-at-time
           nil mh-speed-flists-interval
           (lambda ()
             (unless (and (processp mh-speed-flists-process)
                          (not (eq (process-status mh-speed-flists-process)
                                   'exit)))
               (setq mh-speed-flists-process
                     (start-process (expand-file-name "flists" mh-progs) nil
                                    "flists" "-recurse"))
               (set-process-filter mh-speed-flists-process
                                   'mh-speed-parse-flists-output)))))))

;; Copied from mh-make-folder-list-filter...
(defun mh-speed-parse-flists-output (process output)
  "Parse the incremental results from flists.
PROCESS is the flists process and OUTPUT is the results that must be handled
next."
  (let ((prevailing-match-data (match-data))
        (position 0)
        line-end line folder unseen total)
    (unwind-protect
        (while (setq line-end (string-match "\n" output position))
          (setq line (format "%s%s"
                             mh-speed-partial-line
                             (substring output position line-end))
                mh-speed-partial-line "")
          (when (string-match "+? " line)
            (setq folder (format "+%s" (subseq line 0 (match-beginning 0))))
            (when (string-match " has " line)
              (setq unseen (car (read-from-string line (match-end 0))))
              (when (string-match "; out of " line)
                (setq total (car (read-from-string line (match-end 0))))
                (setf (gethash folder mh-speed-flists-cache)
                      (cons unseen total))
                (save-excursion
                  (when (buffer-live-p (get-buffer speedbar-buffer))
                    (set-buffer speedbar-buffer)
                    (speedbar-with-writable
                      (when (get-text-property (point-min) 'mh-level)
                        (let ((pos (gethash folder mh-speed-folder-map))
                              face)
                          (when pos
                            (goto-char pos)
                            (goto-char (line-beginning-position))
                            (cond
                              ((null (get-text-property (point) 'mh-count))
                               (goto-char (line-end-position))
                               (setq face (get-text-property (1- (point))
                                                             'face))
                               (insert (format " (%s/%s)" unseen total))
                               (mh-speed-highlight 'unknown face)
                               (goto-char (line-beginning-position))
                               (add-text-properties
                                (point) (1+ (point))
                                `(mh-count (,unseen . ,total))))
                              ((not
                                (equal (get-text-property (point) 'mh-count)
                                       (cons unseen total)))
                               (goto-char (line-end-position))
                               (setq face (get-text-property (1- (point))
                                                             'face))
                               (re-search-backward
                                " " (line-beginning-position) t)
                               (delete-region (point) (line-end-position))
                               (insert (format " (%s/%s)" unseen total))
                               (mh-speed-highlight 'unknown face)
                               (goto-char (line-beginning-position))
                               (add-text-properties
                                (point) (1+ (point))
                                `(mh-count (,unseen . ,total))))))))))))))
          (setq position (1+ line-end)))
      (set-match-data prevailing-match-data))
    (setq mh-speed-partial-line (subseq output position))))

(defun mh-speed-invalidate-map (folder)
  "Remove FOLDER from various optimization caches."
  (interactive (list ""))
  (save-excursion
    (set-buffer speedbar-buffer)
    (let* ((speedbar-update-flag nil)
           (last-slash (search "/" folder :from-end t))
           (parent (if last-slash (substring folder 0 last-slash) nil))
           (parent-position (gethash parent mh-speed-folder-map))
           (parent-change nil))
      (remhash parent mh-speed-folders-cache)
      (remhash folder mh-speed-folders-cache)
      (when parent-position
        (let ((parent-kids (mh-speed-folders parent)))
          (cond ((null parent-kids)
                 (setq parent-change ?+))
                ((and (null (cdr parent-kids))
                      (equal (if last-slash
                                 (substring folder (1+ last-slash))
                               (substring folder 1))
                             (caar parent-kids)))
                 (setq parent-change ? ))))
        (goto-char parent-position)
        (when (equal (get-text-property (line-beginning-position) 'mh-folder)
                     parent)
          (when (get-text-property (line-beginning-position) 'mh-expanded)
            (mh-speed-toggle))
          (when parent-change
            (speedbar-with-writable
              (mh-speedbar-change-expand-button-char parent-change)
              (add-text-properties
               (line-beginning-position) (1+ (line-beginning-position))
               `(mh-children-p ,(equal parent-change ?+)))))
          (mh-speed-highlight mh-speed-last-selected-folder
                              'mh-speedbar-folder-face)
          (setq mh-speed-last-selected-folder nil)
          (setq mh-speed-refresh-flag t)))
      (when (equal folder "")
        (clrhash mh-speed-folders-cache)))))

(defun mh-speed-add-folder (folder)
  "Add FOLDER since it is being created.
The function invalidates the latest ancestor that is present."
  (save-excursion
    (set-buffer speedbar-buffer)
    (let ((speedbar-update-flag nil)
          (last-slash (search "/" folder :from-end t))
          (ancestor folder)
          (ancestor-pos nil))
      (block while-loop
        (while last-slash
          (setq ancestor (substring ancestor 0 last-slash))
          (setq ancestor-pos (gethash ancestor mh-speed-folder-map))
          (when ancestor-pos
            (return-from while-loop))
          (setq last-slash (search "/" ancestor :from-end t))))
      (unless ancestor-pos (setq ancestor nil))
      (goto-char (or ancestor-pos (gethash nil mh-speed-folder-map)))
      (speedbar-with-writable
        (mh-speedbar-change-expand-button-char ?+)
        (add-text-properties
         (line-beginning-position) (1+ (line-beginning-position))
         `(mh-children-p t)))
      (when (get-text-property (line-beginning-position) 'mh-expanded)
        (mh-speed-toggle))
      (remhash ancestor mh-speed-folders-cache)
      (setq mh-speed-refresh-flag t))))

;; Make it slightly more general to allow for [ ] buttons to be changed to
;; [+].
(defun mh-speedbar-change-expand-button-char (char)
  "Change the expansion button character to CHAR for the current line."
  (save-excursion
    (beginning-of-line)
    (if (re-search-forward "\\[.\\]" (line-end-position) t)
	(speedbar-with-writable
          (backward-char 2)
	  (delete-char 1)
	  (insert-char char 1 t)
	  (put-text-property (point) (1- (point)) 'invisible nil)
	  ;; make sure we fix the image on the text here.
	  (speedbar-insert-image-button-maybe (- (point) 2) 3)))))

(provide 'mh-speed)

;;; Local Variables:
;;; sentence-end-double-space: nil
;;; End:

;;; mh-speed.el ends here