lisp/tree-widget.el

   1 ;;; tree-widget.el --- Tree widget
   2
   3 ;; Copyright (C) 2004-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: David Ponce <david@dponce.com>
   6 ;; Maintainer: David Ponce <david@dponce.com>
   7 ;; Created: 16 Feb 2001
   8 ;; Keywords: extensions
   9
  10 ;; This file is part of GNU Emacs
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26 ;;
  27 ;; This library provide a tree widget useful to display data
  28 ;; structures organized in a hierarchical order.
  29 ;;
  30 ;; The following properties are specific to the tree widget:
  31 ;;
  32 ;; :open
  33 ;;    Set to non-nil to expand the tree.  By default the tree is
  34 ;;    collapsed.
  35 ;;
  36 ;; :node
  37 ;;    Specify the widget used to represent the value of a tree node.
  38 ;;    By default this is an `item' widget which displays the
  39 ;;    tree-widget :tag property value if defined, or a string
  40 ;;    representation of the tree-widget value.
  41 ;;
  42 ;; :keep
  43 ;;    Specify a list of properties to keep when the tree is collapsed
  44 ;;    so they can be recovered when the tree is expanded.  This
  45 ;;    property can be used in child widgets too.
  46 ;;
  47 ;; :expander (obsoletes :dynargs)
  48 ;;    Specify a function to be called to dynamically provide the
  49 ;;    tree's children in response to an expand request.  This function
  50 ;;    will be passed the tree widget and must return a list of child
  51 ;;    widgets.  Child widgets returned by the :expander function are
  52 ;;    stored in the :args property of the tree widget.
  53 ;;
  54 ;; :expander-p
  55 ;;    Specify a predicate which must return non-nil to indicate that
  56 ;;    the :expander function above has to be called.  By default, to
  57 ;;    speed up successive expand requests, the :expander-p predicate
  58 ;;    return non-nil when the :args value is nil.  So, by default, to
  59 ;;    refresh child values, it is necessary to set the :args property
  60 ;;    to nil, then redraw the tree.
  61 ;;
  62 ;; :open-icon  (default `tree-widget-open-icon')
  63 ;; :close-icon (default `tree-widget-close-icon')
  64 ;; :empty-icon (default `tree-widget-empty-icon')
  65 ;; :leaf-icon  (default `tree-widget-leaf-icon')
  66 ;;    Those properties define the icon widgets associated to tree
  67 ;;    nodes.  Icon widgets must derive from the `tree-widget-icon'
  68 ;;    widget.  The :tag and :glyph-name property values are
  69 ;;    respectively used when drawing the text and graphic
  70 ;;    representation of the tree.  The :tag value must be a string
  71 ;;    that represent a node icon, like "[+]" for example.  The
  72 ;;    :glyph-name value must the name of an image found in the current
  73 ;;    theme, like "close" for example (see also the variable
  74 ;;    `tree-widget-theme').
  75 ;;
  76 ;; :guide      (default `tree-widget-guide')
  77 ;; :end-guide  (default `tree-widget-end-guide')
  78 ;; :no-guide   (default `tree-widget-no-guide')
  79 ;; :handle     (default `tree-widget-handle')
  80 ;; :no-handle  (default `tree-widget-no-handle')
  81 ;;    Those properties define `item'-like widgets used to draw the
  82 ;;    tree guide lines.  The :tag property value is used when drawing
  83 ;;    the text representation of the tree.  The graphic look and feel
  84 ;;    is given by the images named "guide", "no-guide", "end-guide",
  85 ;;    "handle", and "no-handle" found in the current theme (see also
  86 ;;    the variable `tree-widget-theme').
  87 ;;
  88 ;; These are the default :tag values for icons, and guide lines:
  89 ;;
  90 ;; open-icon    "[-]"
  91 ;; close-icon   "[+]"
  92 ;; empty-icon   "[X]"
  93 ;; leaf-icon    ""
  94 ;; guide        " |"
  95 ;; no-guide     "  "
  96 ;; end-guide    " `"
  97 ;; handle       "-"
  98 ;; no-handle    " "
  99 ;;
 100 ;; The text representation of a tree looks like this:
 101 ;;
 102 ;; [-] 1        (open-icon :node)
 103 ;;  |-[+] 1.0   (guide+handle+close-icon :node)
 104 ;;  |-[X] 1.1   (guide+handle+empty-icon :node)
 105 ;;  `-[-] 1.2   (end-guide+handle+open-icon :node)
 106 ;;     |- 1.2.1 (no-guide+no-handle+guide+handle+leaf-icon leaf)
 107 ;;     `- 1.2.2 (no-guide+no-handle+end-guide+handle+leaf-icon leaf)
 108 ;;
 109 ;; By default, images will be used instead of strings to draw a
 110 ;; nice-looking tree.  See the `tree-widget-image-enable',
 111 ;; `tree-widget-themes-directory', and `tree-widget-theme' options for
 112 ;; more details.
 113
 114 ;;; History:
 115 ;;
 116
 117 ;;; Code:
 118 (require 'wid-edit)
 119 \f
 120 ;;; Customization
 121 ;;
 122 (defgroup tree-widget nil
 123   "Customization support for the Tree Widget library."
 124   :version "22.1"
 125   :group 'widgets)
 126
 127 (defcustom tree-widget-image-enable (if (fboundp 'display-images-p)
 128                                         (display-images-p))
 129   "Non-nil means that tree-widget will try to use images."
 130   :type  'boolean
 131   :group 'tree-widget)
 132
 133 (defvar tree-widget-themes-load-path
 134   '(load-path
 135     (let ((dir (if (fboundp 'locate-data-directory)
 136                    (locate-data-directory "tree-widget") ;; XEmacs
 137                  data-directory)))
 138       (and dir (list dir (expand-file-name "images" dir))))
 139     )
 140   "List of locations in which to search for the themes sub-directory.
 141 Each element is an expression that will be recursively evaluated until
 142 it returns a single directory or a list of directories.
 143 The default is to search in the `load-path' first, then in the
 144 \"images\" sub directory in the data directory, then in the data
 145 directory.
 146 The data directory is the value of the variable `data-directory' on
 147 Emacs, and what `(locate-data-directory \"tree-widget\")' returns on
 148 XEmacs.")
 149
 150 (defcustom tree-widget-themes-directory "tree-widget"
 151   "Name of the directory in which to look for an image theme.
 152 When nil use the directory where the tree-widget library is located.
 153 When it is a relative name, search in all occurrences of that sub
 154 directory in the path specified by `tree-widget-themes-load-path'.
 155 The default is to use the \"tree-widget\" relative name."
 156   :type '(choice (const :tag "Default" "tree-widget")
 157                  (const :tag "Where is this library" nil)
 158                  (directory :format "%{%t%}:\n%v"))
 159   :group 'tree-widget)
 160
 161 (defcustom tree-widget-theme nil
 162   "Name of the theme in which to look for images.
 163 This is a sub directory of the themes directory specified by the
 164 `tree-widget-themes-directory' option.
 165 The default theme is \"default\".  When an image is not found in a
 166 theme, it is searched in its parent theme.
 167
 168 A complete theme must at least contain images with these file names
 169 with a supported extension (see also `tree-widget-image-formats'):
 170
 171 \"guide\"
 172   A vertical guide line.
 173 \"no-guide\"
 174   An invisible vertical guide line.
 175 \"end-guide\"
 176   End of a vertical guide line.
 177 \"handle\"
 178   Horizontal guide line that joins the vertical guide line to an icon.
 179 \"no-handle\"
 180   An invisible handle.
 181
 182 Plus images whose name is given by the :glyph-name property of the
 183 icon widgets used to draw the tree.  By default these images are used:
 184
 185 \"open\"
 186   Icon associated to an expanded tree.
 187 \"close\"
 188   Icon associated to a collapsed tree.
 189 \"empty\"
 190   Icon associated to an expanded tree with no child.
 191 \"leaf\"
 192   Icon associated to a leaf node."
 193   :type '(choice (const  :tag "Default" nil)
 194                  (string :tag "Name"))
 195   :group 'tree-widget)
 196
 197 (defcustom tree-widget-image-properties-emacs
 198   '(:ascent center :mask (heuristic t))
 199   "Default properties of Emacs images."
 200   :type 'plist
 201   :group 'tree-widget)
 202
 203 (defcustom tree-widget-image-properties-xemacs
 204   nil
 205   "Default properties of XEmacs images."
 206   :type 'plist
 207   :group 'tree-widget)
 208
 209 (defcustom tree-widget-space-width 0.5
 210   "Amount of space between an icon image and a node widget.
 211 Must be a valid space :width display property.
 212 See Info node `(elisp)Specified Space'."
 213   :group 'tree-widget
 214   :type '(choice (number :tag "Multiple of normal character width")
 215                  sexp))
 216 \f
 217 ;;; Image support
 218 ;;
 219 (eval-and-compile ;; Emacs/XEmacs compatibility stuff
 220   (cond
 221    ;; XEmacs
 222    ((featurep 'xemacs)
 223     (defsubst tree-widget-use-image-p ()
 224       "Return non-nil if image support is currently enabled."
 225       (and tree-widget-image-enable
 226            widget-glyph-enable
 227            (console-on-window-system-p)))
 228     (defsubst tree-widget-create-image (type file &optional props)
 229       "Create an image of type TYPE from FILE, and return it.
 230 Give the image the specified properties PROPS."
 231       (apply 'make-glyph `([,type :file ,file ,@props])))
 232     (defsubst tree-widget-image-formats ()
 233       "Return the alist of image formats/file name extensions.
 234 See also the option `widget-image-file-name-suffixes'."
 235       (delq nil
 236             (mapcar
 237              #'(lambda (fmt)
 238                  (and (valid-image-instantiator-format-p (car fmt)) fmt))
 239              widget-image-file-name-suffixes)))
 240     )
 241    ;; Emacs
 242    (t
 243     (defsubst tree-widget-use-image-p ()
 244       "Return non-nil if image support is currently enabled."
 245       (and tree-widget-image-enable
 246            widget-image-enable
 247            (display-images-p)))
 248     (defsubst tree-widget-create-image (type file &optional props)
 249       "Create an image of type TYPE from FILE, and return it.
 250 Give the image the specified properties PROPS."
 251       (apply 'create-image `(,file ,type nil ,@props)))
 252     (defsubst tree-widget-image-formats ()
 253       "Return the alist of image formats/file name extensions.
 254 See also the option `widget-image-conversion'."
 255       (delq nil
 256             (mapcar
 257              #'(lambda (fmt)
 258                  (and (image-type-available-p (car fmt)) fmt))
 259              widget-image-conversion)))
 260     ))
 261   )
 262
 263 ;; Buffer local cache of theme data.
 264 (defvar tree-widget--theme nil)
 265
 266 (defsubst tree-widget-theme-name ()
 267   "Return the current theme name, or nil if no theme is active."
 268   (and tree-widget--theme (car (aref tree-widget--theme 0))))
 269
 270 (defsubst tree-widget-set-parent-theme (name)
 271   "Set to NAME the parent theme of the current theme.
 272 The default parent theme is the \"default\" theme."
 273   (unless (member name (aref tree-widget--theme 0))
 274     (aset tree-widget--theme 0
 275           (append (aref tree-widget--theme 0) (list name)))
 276     ;; Load the theme setup from the first directory where the theme
 277     ;; is found.
 278     (catch 'found
 279       (dolist (dir (tree-widget-themes-path))
 280         (setq dir (expand-file-name name dir))
 281         (when (file-accessible-directory-p dir)
 282           (throw 'found
 283                  (load (expand-file-name
 284                         "tree-widget-theme-setup" dir) t)))))))
 285
 286 (defun tree-widget-set-theme (&optional name)
 287   "In the current buffer, set the theme to use for images.
 288 The current buffer must be where the tree widget is drawn.
 289 Optional argument NAME is the name of the theme to use.  It defaults
 290 to the value of the variable `tree-widget-theme'.
 291 Does nothing if NAME is already the current theme.
 292
 293 If there is a \"tree-widget-theme-setup\" library in the theme
 294 directory, load it to setup a parent theme or the images properties.
 295 Typically it should contain something like this:
 296
 297   (tree-widget-set-parent-theme \"my-parent-theme\")
 298   (tree-widget-set-image-properties
 299    (if (featurep \\='xemacs)
 300        \\='(:ascent center)
 301      \\='(:ascent center :mask (heuristic t))
 302      ))"
 303   (or name (setq name (or tree-widget-theme "default")))
 304   (unless (string-equal name (tree-widget-theme-name))
 305     (set (make-local-variable 'tree-widget--theme)
 306          (make-vector 4 nil))
 307       (tree-widget-set-parent-theme name)
 308       (tree-widget-set-parent-theme "default")))
 309
 310 (defun tree-widget--locate-sub-directory (name path &optional found)
 311   "Locate all occurrences of the sub-directory NAME in PATH.
 312 Return a list of absolute directory names in reverse order, or nil if
 313 not found."
 314   (condition-case err
 315       (dolist (elt path)
 316         (setq elt (eval elt))
 317         (cond
 318          ((stringp elt)
 319           (and (file-accessible-directory-p
 320                 (setq elt (expand-file-name name elt)))
 321                (push elt found)))
 322          (elt
 323           (setq found (tree-widget--locate-sub-directory
 324                        name (if (atom elt) (list elt) elt) found)))))
 325     (error
 326      (message "In tree-widget--locate-sub-directory: %s"
 327               (error-message-string err))))
 328   found)
 329
 330 (defun tree-widget-themes-path ()
 331   "Return the path where to search for a theme.
 332 It is specified in variable `tree-widget-themes-directory'.
 333 Return a list of absolute directory names, or nil when no directory
 334 has been found accessible."
 335   (let ((path (aref tree-widget--theme 1)))
 336     (cond
 337      ;; No directory was found.
 338      ((eq path 'void) nil)
 339      ;; The list of directories is available in the cache.
 340      (path)
 341      ;; Use the directory where this library is located.
 342      ((null tree-widget-themes-directory)
 343       (when (setq path (locate-library "tree-widget"))
 344         (setq path (file-name-directory path))
 345         (setq path (and (file-accessible-directory-p path)
 346                         (list path)))
 347         ;; Store the result in the cache for later use.
 348         (aset tree-widget--theme 1 (or path 'void))
 349         path))
 350      ;; Check accessibility of absolute directory name.
 351      ((file-name-absolute-p tree-widget-themes-directory)
 352       (setq path (expand-file-name tree-widget-themes-directory))
 353       (setq path (and (file-accessible-directory-p path)
 354                       (list path)))
 355       ;; Store the result in the cache for later use.
 356       (aset tree-widget--theme 1 (or path 'void))
 357       path)
 358      ;; Locate a sub-directory in `tree-widget-themes-load-path'.
 359      (t
 360       (setq path (nreverse (tree-widget--locate-sub-directory
 361                             tree-widget-themes-directory
 362                             tree-widget-themes-load-path)))
 363       ;; Store the result in the cache for later use.
 364       (aset tree-widget--theme 1 (or path 'void))
 365       path))))
 366
 367 (defconst tree-widget--cursors
 368   ;; Pointer shapes when the mouse pointer is over inactive
 369   ;; tree-widget images.  This feature works since Emacs 22, and
 370   ;; ignored on older versions, and XEmacs.
 371   '(
 372     ("guide"     . arrow)
 373     ("no-guide"  . arrow)
 374     ("end-guide" . arrow)
 375     ("handle"    . arrow)
 376     ("no-handle" . arrow)
 377     ))
 378
 379 (defsubst tree-widget-set-image-properties (props)
 380   "In current theme, set images properties to PROPS.
 381 Does nothing if images properties have already been set for that
 382 theme."
 383   (or (aref tree-widget--theme 2)
 384       (aset tree-widget--theme 2 props)))
 385
 386 (defsubst tree-widget-image-properties (name)
 387   "Return the properties of image NAME in current theme.
 388 Default global properties are provided for respectively Emacs and
 389 XEmacs in the variables `tree-widget-image-properties-emacs', and
 390 `tree-widget-image-properties-xemacs'."
 391   ;; Add the pointer shape
 392   (cons :pointer
 393         (cons (or (cdr (assoc name tree-widget--cursors)) 'hand)
 394               (tree-widget-set-image-properties
 395                (if (featurep 'xemacs)
 396                    tree-widget-image-properties-xemacs
 397                  tree-widget-image-properties-emacs)))))
 398
 399 (defun tree-widget-lookup-image (name)
 400   "Look up in current theme for an image with NAME.
 401 Search first in current theme, then in parent themes (see also the
 402 function `tree-widget-set-parent-theme').
 403 Return the first image found having a supported format, or nil if not
 404 found."
 405   (let (file)
 406     (catch 'found
 407       (dolist (default-directory (tree-widget-themes-path))
 408         (dolist (dir (aref tree-widget--theme 0))
 409           (dolist (fmt (tree-widget-image-formats))
 410             (dolist (ext (cdr fmt))
 411               (setq file (expand-file-name (concat name ext) dir))
 412               (and (file-readable-p file)
 413                    (file-regular-p file)
 414                    (throw 'found
 415                           (tree-widget-create-image
 416                            (car fmt) file
 417                            (tree-widget-image-properties name))))))))
 418       nil)))
 419
 420 (defun tree-widget-find-image (name)
 421   "Find the image with NAME in current theme.
 422 NAME is an image file name sans extension.
 423 Return the image found, or nil if not found."
 424   (when (tree-widget-use-image-p)
 425     ;; Ensure there is an active theme.
 426     (tree-widget-set-theme (tree-widget-theme-name))
 427     (let ((image (assoc name (aref tree-widget--theme 3))))
 428       ;; The image NAME is found in the cache.
 429       (if image
 430           (cdr image)
 431         ;; Search the image in current, and default themes.
 432         (prog1
 433             (setq image (tree-widget-lookup-image name))
 434           ;; Store image reference in the cache for later use.
 435           (push (cons name image) (aref tree-widget--theme 3))))
 436       )))
 437 \f
 438 ;;; Widgets
 439 ;;
 440 (defun tree-widget-button-click (event)
 441   "Move to the position clicked on, and if it is a button, invoke it.
 442 EVENT is the mouse event received."
 443   (interactive "e")
 444   (mouse-set-point event)
 445   (let ((pos (widget-event-point event)))
 446     (if (get-char-property pos 'button)
 447         (widget-button-click event))))
 448
 449 (defvar tree-widget-button-keymap
 450   (let ((km (make-sparse-keymap)))
 451     (if (boundp 'widget-button-keymap)
 452         ;; XEmacs
 453         (progn
 454           (set-keymap-parent km widget-button-keymap)
 455           (define-key km [button1] 'tree-widget-button-click))
 456       ;; Emacs
 457       (set-keymap-parent km widget-keymap)
 458       (define-key km [down-mouse-1] 'tree-widget-button-click))
 459     km)
 460   "Keymap used inside node buttons.
 461 Handle mouse button 1 click on buttons.")
 462
 463 (define-widget 'tree-widget-icon 'push-button
 464   "Basic widget other tree-widget icons are derived from."
 465   :format        "%[%t%]"
 466   :button-keymap tree-widget-button-keymap ; XEmacs
 467   :keymap        tree-widget-button-keymap ; Emacs
 468   :create        'tree-widget-icon-create
 469   :action        'tree-widget-icon-action
 470   :help-echo     'tree-widget-icon-help-echo
 471   )
 472
 473 (define-widget 'tree-widget-open-icon 'tree-widget-icon
 474   "Icon for an expanded tree-widget node."
 475   :tag        "[-]"
 476   :glyph-name "open"
 477   )
 478
 479 (define-widget 'tree-widget-empty-icon 'tree-widget-icon
 480   "Icon for an expanded tree-widget node with no child."
 481   :tag        "[X]"
 482   :glyph-name "empty"
 483   )
 484
 485 (define-widget 'tree-widget-close-icon 'tree-widget-icon
 486   "Icon for a collapsed tree-widget node."
 487   :tag        "[+]"
 488   :glyph-name "close"
 489   )
 490
 491 (define-widget 'tree-widget-leaf-icon 'tree-widget-icon
 492   "Icon for a tree-widget leaf node."
 493   :tag        ""
 494   :glyph-name "leaf"
 495   :button-face 'default
 496   )
 497
 498 (define-widget 'tree-widget-guide 'item
 499   "Vertical guide line."
 500   :tag       " |"
 501   ;;:tag-glyph (tree-widget-find-image "guide")
 502   :format    "%t"
 503   )
 504
 505 (define-widget 'tree-widget-end-guide 'item
 506   "End of a vertical guide line."
 507   :tag       " `"
 508   ;;:tag-glyph (tree-widget-find-image "end-guide")
 509   :format    "%t"
 510   )
 511
 512 (define-widget 'tree-widget-no-guide 'item
 513   "Invisible vertical guide line."
 514   :tag       "  "
 515   ;;:tag-glyph (tree-widget-find-image "no-guide")
 516   :format    "%t"
 517   )
 518
 519 (define-widget 'tree-widget-handle 'item
 520   "Horizontal guide line that joins a vertical guide line to a node."
 521   :tag       "-"
 522   ;;:tag-glyph (tree-widget-find-image "handle")
 523   :format    "%t"
 524   )
 525
 526 (define-widget 'tree-widget-no-handle 'item
 527   "Invisible handle."
 528   :tag       " "
 529   ;;:tag-glyph (tree-widget-find-image "no-handle")
 530   :format    "%t"
 531   )
 532
 533 (define-widget 'tree-widget 'default
 534   "Tree widget."
 535   :format         "%v"
 536   :convert-widget 'tree-widget-convert-widget
 537   :value-get      'widget-value-value-get
 538   :value-delete   'widget-children-value-delete
 539   :value-create   'tree-widget-value-create
 540   :action         'tree-widget-action
 541   :help-echo      'tree-widget-help-echo
 542   :expander-p     'tree-widget-expander-p
 543   :open-icon      'tree-widget-open-icon
 544   :close-icon     'tree-widget-close-icon
 545   :empty-icon     'tree-widget-empty-icon
 546   :leaf-icon      'tree-widget-leaf-icon
 547   :guide          'tree-widget-guide
 548   :end-guide      'tree-widget-end-guide
 549   :no-guide       'tree-widget-no-guide
 550   :handle         'tree-widget-handle
 551   :no-handle      'tree-widget-no-handle
 552   )
 553 \f
 554 ;;; Widget support functions
 555 ;;
 556 (defun tree-widget-p (widget)
 557   "Return non-nil if WIDGET is a tree-widget."
 558   (let ((type (widget-type widget)))
 559     (while (and type (not (eq type 'tree-widget)))
 560       (setq type (widget-type (get type 'widget-type))))
 561     (eq type 'tree-widget)))
 562
 563 (defun tree-widget-node (widget)
 564   "Return WIDGET's :node child widget.
 565 If not found, setup an `item' widget as default.
 566 Signal an error if the :node widget is a tree-widget.
 567 WIDGET is, or derives from, a tree-widget."
 568   (let ((node (widget-get widget :node)))
 569     (if node
 570         ;; Check that the :node widget is not a tree-widget.
 571         (and (tree-widget-p node)
 572              (error "Invalid tree-widget :node %S" node))
 573       ;; Setup an item widget as default :node.
 574       (setq node `(item :tag ,(or (widget-get widget :tag)
 575                                   (widget-princ-to-string
 576                                    (widget-value widget)))))
 577       (widget-put widget :node node))
 578     node))
 579
 580 (defun tree-widget-keep (arg widget)
 581   "Save in ARG the WIDGET's properties specified by :keep."
 582   (dolist (prop (widget-get widget :keep))
 583     (widget-put arg prop (widget-get widget prop))))
 584
 585 (defun tree-widget-children-value-save (widget &optional args node)
 586   "Save WIDGET children values.
 587 WIDGET is, or derives from, a tree-widget.
 588 Children properties and values are saved in ARGS if non-nil, else in
 589 WIDGET's :args property value.  Properties and values of the
 590 WIDGET's :node sub-widget are saved in NODE if non-nil, else in
 591 WIDGET's :node sub-widget."
 592   (let ((args (cons (or node (widget-get widget :node))
 593                     (or args (widget-get widget :args))))
 594         (children (widget-get widget :children))
 595         arg child)
 596     (while (and args children)
 597       (setq arg      (car args)
 598             args     (cdr args)
 599             child    (car children)
 600             children (cdr children))
 601        (if (tree-widget-p child)
 602 ;;;; The child is a tree node.
 603            (progn
 604              ;; Backtrack :args and :node properties.
 605              (widget-put arg :args (widget-get child :args))
 606              (widget-put arg :node (widget-get child :node))
 607              ;; Save :open property.
 608              (widget-put arg :open (widget-get child :open))
 609              ;; The node is open.
 610              (when (widget-get child :open)
 611                ;; Save the widget value.
 612                (widget-put arg :value (widget-value child))
 613                ;; Save properties specified in :keep.
 614                (tree-widget-keep arg child)
 615                ;; Save children.
 616                (tree-widget-children-value-save
 617                 child (widget-get arg :args) (widget-get arg :node))))
 618 ;;;; Another non tree node.
 619          ;; Save the widget value.
 620          (widget-put arg :value (widget-value child))
 621          ;; Save properties specified in :keep.
 622          (tree-widget-keep arg child)))))
 623 \f
 624 ;;; Widget creation
 625 ;;
 626 (defvar tree-widget-before-create-icon-functions nil
 627   "Hooks run before to create a tree-widget icon.
 628 Each function is passed the icon widget not yet created.
 629 The value of the icon widget :node property is a tree :node widget or
 630 a leaf node widget, not yet created.
 631 This hook can be used to dynamically change properties of the icon and
 632 associated node widgets.  For example, to dynamically change the look
 633 and feel of the tree-widget by changing the values of the :tag
 634 and :glyph-name properties of the icon widget.
 635 This hook should be local in the buffer setup to display widgets.")
 636
 637 (defun tree-widget-icon-create (icon)
 638   "Create the ICON widget."
 639   (run-hook-with-args 'tree-widget-before-create-icon-functions icon)
 640   (widget-put icon :tag-glyph
 641               (tree-widget-find-image (widget-get icon :glyph-name)))
 642   ;; Ensure there is at least one char to display the image.
 643   (and (widget-get icon :tag-glyph)
 644        (equal "" (or (widget-get icon :tag) ""))
 645        (widget-put icon :tag " "))
 646   (widget-default-create icon)
 647   ;; Insert space between the icon and the node widget.
 648   (insert-char ?  1)
 649   (put-text-property
 650    (1- (point)) (point)
 651    'display (list 'space :width tree-widget-space-width)))
 652
 653 (defun tree-widget-convert-widget (widget)
 654   "Convert :args as widget types in WIDGET."
 655   (let ((tree (widget-types-convert-widget widget)))
 656     ;; Compatibility
 657     (widget-put tree :expander (or (widget-get tree :expander)
 658                                    (widget-get tree :dynargs)))
 659     tree))
 660
 661 (defvar widget-glyph-enable) ; XEmacs
 662
 663 (defun tree-widget-value-create (tree)
 664   "Create the TREE tree-widget."
 665   (let* ((node   (tree-widget-node tree))
 666          (flags  (widget-get tree :tree-widget--guide-flags))
 667          (indent (widget-get tree :indent))
 668          ;; Setup widget's image support.  Looking up for images, and
 669          ;; setting widgets' :tag-glyph is done here, to allow us to
 670          ;; dynamically change the image theme.
 671          (widget-image-enable (tree-widget-use-image-p))     ; Emacs
 672          (widget-glyph-enable widget-image-enable)           ; XEmacs
 673          children buttons)
 674     (and indent (not (widget-get tree :parent))
 675          (insert-char ?\  indent))
 676     (if (widget-get tree :open)
 677 ;;;; Expanded node.
 678         (let ((args     (widget-get tree :args))
 679               (guide    (widget-get tree :guide))
 680               (noguide  (widget-get tree :no-guide))
 681               (endguide (widget-get tree :end-guide))
 682               (handle   (widget-get tree :handle))
 683               (nohandle (widget-get tree :no-handle))
 684               (guidi    (tree-widget-find-image "guide"))
 685               (noguidi  (tree-widget-find-image "no-guide"))
 686               (endguidi (tree-widget-find-image "end-guide"))
 687               (handli   (tree-widget-find-image "handle"))
 688               (nohandli (tree-widget-find-image "no-handle")))
 689           ;; Request children at run time, when requested.
 690           (when (and (widget-get tree :expander)
 691                      (widget-apply tree :expander-p))
 692             (setq args (mapcar 'widget-convert
 693                                (widget-apply tree :expander)))
 694             (widget-put tree :args args))
 695           ;; Defer the node widget creation after icon creation.
 696           (widget-put tree :node (widget-convert node))
 697           ;; Create the icon widget for the expanded tree.
 698           (push (widget-create-child-and-convert
 699                  tree (widget-get tree (if args :open-icon :empty-icon))
 700                  ;; Pass the node widget to child.
 701                  :node (widget-get tree :node))
 702                 buttons)
 703           ;; Create the tree node widget.
 704           (push (widget-create-child tree (widget-get tree :node))
 705                 children)
 706           ;; Update the icon :node with the created node widget.
 707           (widget-put (car buttons) :node (car children))
 708           ;; Create the tree children.
 709           (while args
 710             (setq node (car args)
 711                   args (cdr args))
 712             (and indent (insert-char ?\  indent))
 713             ;; Insert guide lines elements from previous levels.
 714             (dolist (f (reverse flags))
 715               (widget-create-child-and-convert
 716                tree (if f guide noguide)
 717                :tag-glyph (if f guidi noguidi))
 718               (widget-create-child-and-convert
 719                tree nohandle :tag-glyph nohandli))
 720             ;; Insert guide line element for this level.
 721             (widget-create-child-and-convert
 722              tree (if args guide endguide)
 723              :tag-glyph (if args guidi endguidi))
 724             ;; Insert the node handle line
 725             (widget-create-child-and-convert
 726              tree handle :tag-glyph handli)
 727             (if (tree-widget-p node)
 728                 ;; Create a sub-tree node.
 729                 (push (widget-create-child-and-convert
 730                        tree node :tree-widget--guide-flags
 731                        (cons (if args t) flags))
 732                       children)
 733               ;; Create the icon widget for a leaf node.
 734               (push (widget-create-child-and-convert
 735                      tree (widget-get tree :leaf-icon)
 736                      ;; At this point the node widget isn't yet created.
 737                      :node (setq node (widget-convert
 738                                        node :tree-widget--guide-flags
 739                                        (cons (if args t) flags)))
 740                      :tree-widget--leaf-flag t)
 741                     buttons)
 742               ;; Create the leaf node widget.
 743               (push (widget-create-child tree node) children)
 744               ;; Update the icon :node with the created node widget.
 745               (widget-put (car buttons) :node (car children)))))
 746 ;;;; Collapsed node.
 747       ;; Defer the node widget creation after icon creation.
 748       (widget-put tree :node (widget-convert node))
 749       ;; Create the icon widget for the collapsed tree.
 750       (push (widget-create-child-and-convert
 751              tree (widget-get tree :close-icon)
 752              ;; Pass the node widget to child.
 753              :node (widget-get tree :node))
 754             buttons)
 755       ;; Create the tree node widget.
 756       (push (widget-create-child tree (widget-get tree :node))
 757             children)
 758       ;; Update the icon :node with the created node widget.
 759       (widget-put (car buttons) :node (car children)))
 760     ;; Save widget children and buttons.  The tree-widget :node child
 761     ;; is the first element in :children.
 762     (widget-put tree :children (nreverse children))
 763     (widget-put tree :buttons  buttons)))
 764 \f
 765 ;;; Widget callbacks
 766 ;;
 767 (defsubst tree-widget-leaf-node-icon-p (icon)
 768   "Return non-nil if ICON is a leaf node icon.
 769 That is, if its :node property value is a leaf node widget."
 770   (widget-get icon :tree-widget--leaf-flag))
 771
 772 (defun tree-widget-icon-action (icon &optional event)
 773   "Handle the ICON widget :action.
 774 If ICON :node is a leaf node it handles the :action.  The tree-widget
 775 parent of ICON handles the :action otherwise.
 776 Pass the received EVENT to :action."
 777   (let ((node (widget-get icon (if (tree-widget-leaf-node-icon-p icon)
 778                                    :node :parent))))
 779     (widget-apply node :action event)))
 780
 781 (defun tree-widget-icon-help-echo (icon)
 782   "Return the help-echo string of ICON.
 783 If ICON :node is a leaf node it handles the :help-echo.  The tree-widget
 784 parent of ICON handles the :help-echo otherwise."
 785   (let* ((node (widget-get icon (if (tree-widget-leaf-node-icon-p icon)
 786                                     :node :parent)))
 787          (help-echo (widget-get node :help-echo)))
 788     (if (functionp help-echo)
 789         (funcall help-echo node)
 790       help-echo)))
 791
 792 (defvar tree-widget-after-toggle-functions nil
 793   "Hooks run after toggling a tree-widget expansion.
 794 Each function is passed a tree-widget.  If the value of the :open
 795 property is non-nil the tree has been expanded, else collapsed.
 796 This hook should be local in the buffer setup to display widgets.")
 797
 798 (defun tree-widget-action (tree &optional _event)
 799   "Handle the :action of the TREE tree-widget.
 800 That is, toggle expansion of the TREE tree-widget.
 801 Ignore the EVENT argument."
 802   (let ((open (not (widget-get tree :open))))
 803     (or open
 804         ;; Before to collapse the node, save children values so next
 805         ;; open can recover them.
 806         (tree-widget-children-value-save tree))
 807     (widget-put tree :open open)
 808     (widget-value-set tree open)
 809     (run-hook-with-args 'tree-widget-after-toggle-functions tree)))
 810
 811 (defun tree-widget-help-echo (tree)
 812   "Return the help-echo string of the TREE tree-widget."
 813   (if (widget-get tree :open)
 814       "Collapse node"
 815     "Expand node"))
 816
 817 (defun tree-widget-expander-p (tree)
 818   "Return non-nil if the TREE tree-widget :expander has to be called.
 819 That is, if TREE :args is nil."
 820   (null (widget-get tree :args)))
 821
 822 (provide 'tree-widget)
 823
 824 ;;; tree-widget.el ends here