modules/help.js

   1 /**
   2  * (C) Copyright 2008 Jeremy Maitin-Shepard
   3  * (C) Copyright 2008 Nelson Elhage
   4  * (C) Copyright 2008 David Glasser
   5  * (C) Copyright 2009 John J. Foerch
   6  *
   7  * Use, modification, and distribution are subject to the terms specified in the
   8  * COPYING file.
   9 **/
  10
  11 require("special-buffer.js");
  12 require("interactive.js");
  13
  14 function where_is_command (buffer, command) {
  15     var keymaps = get_current_keymaps(buffer.window);
  16     var list = keymap_lookup_command(keymaps, command);
  17     var msg;
  18     if (list.length == 0)
  19         msg = command + " is not on any key";
  20     else
  21         msg = command + " is on " + list.join(", ");
  22     buffer.window.minibuffer.message(msg);
  23 }
  24 interactive("where-is", null, function (I) {
  25     where_is_command(I.buffer,
  26                      (yield I.minibuffer.read_command($prompt = "Where is command:")));
  27 });
  28
  29 function help_document_generator (document, buffer) {
  30     dom_generator.call(this, document, XHTML_NS);
  31     this.buffer = buffer;
  32 }
  33 help_document_generator.prototype = {
  34     __proto__: dom_generator.prototype,
  35
  36     key_binding : function (str, parent) {
  37         var node = this.element("span", "class", "key-binding");
  38         this.text(str, node);
  39         if (parent)
  40             parent.appendChild(node);
  41         return node;
  42     },
  43
  44     source_code_reference : function (ref, parent) {
  45         var f = this.document.createDocumentFragment();
  46         var module_name = ref.module_name;
  47         var buffer = this.buffer;
  48         //f.appendChild(this.text(module_name != null ? "module " : "file "));
  49         var x = this.element("a",
  50                              "class", "source-code-reference",
  51                              "href", "javascript:");
  52         x.addEventListener("click", function (event) {
  53             co_call(function () {
  54                 try {
  55                     yield ref.open_in_editor();
  56                 } catch (e) {
  57                     handle_interactive_error(buffer.window, e);
  58                 }}());
  59             event.preventDefault();
  60             event.stopPropagation();
  61         }, false /* capture */);
  62         x.textContent = (module_name != null ? module_name : ref.file_name);
  63         f.appendChild(x);
  64         if (parent)
  65             parent.appendChild(f);
  66         return f;
  67     },
  68
  69     command_name : function (name, parent) {
  70         var node = this.element("span", "class", "command");
  71         this.text(name, node);
  72         if (parent)
  73             parent.appendChild(node);
  74         return node;
  75     },
  76
  77     command_reference : function (name, parent) {
  78         var node = this.element("a",
  79                                 "class", "command",
  80                                 "href", "javascript:");
  81         var buffer = this.buffer;
  82         node.addEventListener("click", function (event) {
  83                                   /* FIXME: don't hardcode browse target */
  84                                   describe_command(buffer, name, OPEN_NEW_BUFFER);
  85                                   event.preventDefault();
  86                                   event.stopPropagation();
  87             }, false /* capture */);
  88         this.text(name, node);
  89         if (parent)
  90             parent.appendChild(node);
  91         return node;
  92     },
  93
  94     variable_reference : function (name, parent) {
  95         var node = this.element("a", "class", "variable", "href", "#");
  96         /* FIXME: make this work */
  97         this.text(name, node);
  98         if (parent)
  99             parent.appendChild(node);
 100         return node;
 101     },
 102
 103     help_text : function (str, parent) {
 104         var paras = str.split("\n");
 105         var f = this.document.createDocumentFragment();
 106         for (var i = 0; i < paras.length; ++i) {
 107             var para = paras[i];
 108             if (para.length == 0)
 109                 continue;
 110
 111             var p = this.element("p", f);
 112
 113             var regexp = /`([a-zA-Z0-9_\-$]+)\'/g;
 114
 115             var match;
 116             var last_index = 0;
 117             while ((match = regexp.exec(para)) != null) {
 118                 this.text(para.substring(last_index, match.index), p);
 119                 var command = match[1];
 120                 /* FIXME: check if it is a valid command */
 121                 this.command_reference(command, p);
 122                 last_index = regexp.lastIndex;
 123             }
 124             if (last_index < para.length)
 125                 this.text(para.substring(last_index), p);
 126         }
 127         if (parent != null)
 128             parent.appendChild(f);
 129         return f;
 130     },
 131
 132     add_help_stylesheet : function () {
 133         this.add_stylesheet("chrome://conkeror-gui/content/help.css");
 134     }
 135 };
 136
 137
 138 function help_buffer_modality (buffer, element) {
 139     buffer.keymaps.push(help_buffer_keymap);
 140 }
 141
 142 /*
 143  * Describe Bindings
 144  */
 145
 146 define_keywords("$binding_list");
 147 function describe_bindings_buffer (window, element) {
 148     this.constructor_begin();
 149     keywords(arguments);
 150     special_buffer.call(this, window, element, forward_keywords(arguments));
 151     this.binding_list = arguments.$binding_list;
 152     this.modalities.push(help_buffer_modality);
 153     this.constructor_end();
 154 }
 155
 156 describe_bindings_buffer.prototype = {
 157     title : "Key bindings",
 158
 159     description : "*bindings*",
 160
 161     generate : function () {
 162         var d = this.document;
 163         var list = this.binding_list;
 164         delete this.binding_list;
 165
 166         var list_by_keymap = {};
 167         var keymap_list = [];
 168         for each (let x in list) {
 169             let name = x.bound_in || "";
 170             let km;
 171             if (name in list_by_keymap)
 172                 km = list_by_keymap[name];
 173             else {
 174                 km = list_by_keymap[name] = {list_by_category: {}, category_list: [], name: name};
 175                 keymap_list.push(km);
 176             }
 177             let catname = x.category || "";
 178             let cat;
 179             if (catname in km.list_by_category)
 180                 cat = km.list_by_category[catname];
 181             else {
 182                 cat = km.list_by_category[catname] = [];
 183                 cat.name = catname;
 184                 if (catname == "")
 185                     km.category_list.unshift(cat);
 186                 else
 187                     km.category_list.push(cat);
 188             }
 189             cat.push(x);
 190         }
 191
 192         var g = new help_document_generator(d, this);
 193         g.add_help_stylesheet();
 194
 195         d.body.setAttribute("class", "help-list");
 196
 197         for each (let km in keymap_list) {
 198             g.text(km.name, g.element("h1", d.body));
 199             for each (let cat in km.category_list) {
 200                 if (cat.name != "")
 201                     g.text(cat.name, g.element("h2", d.body));
 202
 203                 let table = g.element("table", d.body);
 204                 for (var i = 0; i < cat.length; ++i) {
 205                     let bind = cat[i];
 206                     let tr = g.element("tr", table, "class", (i % 2 == 0) ? "even" : "odd");
 207                     let seq_td = g.element("td", tr, "class", "key-binding");
 208                     g.text(bind.seq, seq_td);
 209                     let command_td = g.element("td", tr, "class", "command");
 210                     let help_str = null;
 211                     if (bind.command != null) {
 212                         if (typeof(bind.command) == "function") {
 213                             g.text("[function]", command_td);
 214                         } else {
 215                             g.text(bind.command, command_td);
 216                             let cmd = interactive_commands.get(bind.command);
 217                             if (cmd != null)
 218                                 help_str = cmd.shortdoc;
 219                         }
 220                     } else if (bind.fallthrough)
 221                         g.text("[pass through]", command_td);
 222                     let help_td = g.element("td", tr, "class", "help");
 223                     g.text(help_str || "", help_td);
 224                 }
 225             }
 226         }
 227     },
 228
 229     __proto__: special_buffer.prototype
 230 };
 231
 232
 233 function describe_bindings (buffer, target) {
 234     var list = [];
 235     var keymaps = get_current_keymaps(buffer.window);
 236     for_each_key_binding(keymaps, function (binding_stack) {
 237             var last = binding_stack[binding_stack.length - 1];
 238             if (last.command == null && !last.fallthrough)
 239                 return;
 240             let bound_in = null;
 241         outer:
 242             for (let i = binding_stack.length - 1; i >= 0; --i) {
 243                 bound_in = binding_stack[i].bound_in;
 244                 while (bound_in) {
 245                     if (bound_in.name && !bound_in.anonymous)
 246                         break outer;
 247                     bound_in = bound_in.bound_in;
 248                 }
 249             }
 250             var bind = {seq: format_binding_sequence(binding_stack),
 251                         fallthrough: last.fallthrough,
 252                         command: last.command,
 253                         bound_in: bound_in.name,
 254                         category: last.category
 255                        };
 256             list.push(bind);
 257         });
 258     create_buffer(buffer.window, buffer_creator(describe_bindings_buffer,
 259                                                 $opener = buffer,
 260                                                 $binding_list = list),
 261                   target);
 262 }
 263 function describe_bindings_new_buffer (I) {
 264     describe_bindings(I.buffer, OPEN_NEW_BUFFER);
 265 }
 266 function describe_bindings_new_window (I) {
 267     describe_bindings(I.buffer, OPEN_NEW_WINDOW);
 268 }
 269 interactive("describe-bindings", null,
 270             alternates(describe_bindings_new_buffer, describe_bindings_new_window));
 271
 272
 273
 274 /*
 275  * Apropos Command
 276  */
 277
 278 define_keywords("$command_list");
 279 function apropos_command_buffer (window, element) {
 280     this.constructor_begin();
 281     keywords(arguments);
 282     special_buffer.call(this, window, element, forward_keywords(arguments));
 283     this.command_list = arguments.$command_list;
 284     this.modalities.push(help_buffer_modality);
 285     this.constructor_end();
 286 }
 287
 288 apropos_command_buffer.prototype = {
 289     title : "Apropos commands",
 290
 291     description : "*Apropos*",
 292
 293     generate : function () {
 294         var d = this.document;
 295         var list = this.command_list;
 296         delete this.command_list;
 297
 298         var g = new help_document_generator(d, this);
 299         g.add_help_stylesheet();
 300
 301         d.body.setAttribute("class", "help-list");
 302
 303         var table = d.createElementNS(XHTML_NS, "table");
 304         for (var i = 0; i < list.length; ++i) {
 305             var binding = list[i];
 306             var tr = d.createElementNS(XHTML_NS, "tr");
 307             tr.setAttribute("class", (i % 2 == 0) ? "even" : "odd");
 308
 309             var command_td = d.createElementNS(XHTML_NS,"td");
 310             g.command_reference(binding.name, command_td);
 311
 312             var shortdoc = "";
 313             if (binding.cmd.shortdoc != null)
 314                 shortdoc = binding.cmd.shortdoc;
 315             tr.appendChild(command_td);
 316
 317             var shortdoc_td = d.createElementNS(XHTML_NS, "td");
 318             shortdoc_td.setAttribute("class", "help");
 319             shortdoc_td.textContent = shortdoc;
 320             tr.appendChild(shortdoc_td);
 321
 322             table.appendChild(tr);
 323         }
 324         d.body.appendChild(table);
 325     },
 326
 327     __proto__: special_buffer.prototype
 328 };
 329
 330
 331 /* TODO: support regexps/etc. */
 332 function apropos_command (buffer, substring, target) {
 333     var list = [];
 334     interactive_commands.for_each(function (name, cmd) {
 335         if (name.indexOf(substring) != -1) {
 336             var binding = {name: name, cmd: cmd};
 337             list.push(binding);
 338         }
 339     });
 340     list.sort(function (a,b) {
 341                   if (a.name < b.name)
 342                       return -1;
 343                   if (a.name > b.name)
 344                       return 1;
 345                   return 0
 346               });
 347     create_buffer(buffer.window, buffer_creator(apropos_command_buffer,
 348                                                 $opener = buffer,
 349                                                 $command_list = list),
 350                   target);
 351 }
 352
 353 function apropos_command_new_buffer (I) {
 354     apropos_command(I.buffer,
 355                     (yield I.minibuffer.read($prompt = "Apropos command:",
 356                                              $history = "apropos")),
 357                     OPEN_NEW_BUFFER);
 358 }
 359 function apropos_command_new_window (I) {
 360     apropos_command(I.buffer,
 361                     (yield I.minibuffer.read($prompt = "Apropos command:",
 362                                              $history = "apropos")),
 363                     OPEN_NEW_WINDOW);
 364 }
 365 interactive("apropos-command", "List commands whose names contain a given substring.",
 366             alternates(apropos_command_new_buffer, apropos_command_new_window));
 367
 368
 369
 370 /*
 371  * Describe Command
 372  */
 373
 374 define_keywords("$command", "$bindings");
 375 function describe_command_buffer (window, element) {
 376     this.constructor_begin();
 377     keywords(arguments);
 378     special_buffer.call(this, window, element, forward_keywords(arguments));
 379     this.bindings = arguments.$bindings;
 380     this.command = arguments.$command;
 381     this.cmd = interactive_commands.get(this.command);
 382     this.source_code_reference = this.cmd.source_code_reference;
 383     this.modalities.push(help_buffer_modality);
 384     this.constructor_end();
 385 }
 386
 387 describe_command_buffer.prototype = {
 388     get title() { return "Command help: " + this.command; },
 389
 390     description : "*help*",
 391
 392     generate : function () {
 393         var d = this.document;
 394
 395         var g = new help_document_generator(d, this);
 396
 397         g.add_help_stylesheet();
 398         d.body.setAttribute("class", "describe-command");
 399
 400         var p;
 401
 402         p = g.element("p", d.body);
 403         g.command_reference(this.command, p);
 404         var cmd = interactive_commands.get(this.command);
 405         if (cmd.source_code_reference)  {
 406             g.text(" is an interactive command in ", p);
 407             g.source_code_reference(cmd.source_code_reference, p);
 408             g.text(".", p);
 409         } else {
 410             g.text(" is an interactive command.", p);
 411         }
 412
 413         if (this.bindings.length > 0) {
 414             p = g.element("p", d.body);
 415             g.text("It is bound to ", p);
 416             for (var i = 0; i < this.bindings.length; ++i) {
 417                 if (i != 0)
 418                     g.text(", ", p);
 419                 g.key_binding(this.bindings[i], p);
 420             }
 421             g.text(".", p);
 422         }
 423
 424         if (cmd.doc != null)
 425             g.help_text(cmd.doc, d.body);
 426     },
 427
 428     __proto__: special_buffer.prototype
 429 };
 430
 431
 432 function describe_command (buffer, command, target) {
 433     var keymaps = get_current_keymaps(buffer.window);
 434     var bindings = keymap_lookup_command(keymaps, command);
 435     create_buffer(buffer.window,
 436                   buffer_creator(describe_command_buffer,
 437                                  $opener = buffer,
 438                                  $command = command,
 439                                  $bindings = bindings),
 440                   target);
 441 }
 442 function describe_command_new_buffer (I) {
 443     describe_command(I.buffer, (yield I.minibuffer.read_command($prompt = "Describe command:")),
 444                      OPEN_NEW_BUFFER);
 445 }
 446 function describe_command_new_window (I) {
 447     describe_command(I.buffer, (yield I.minibuffer.read_command($prompt = "Describe command:")),
 448                      OPEN_NEW_WINDOW);
 449 }
 450 interactive("describe-command", null,
 451             alternates(describe_command_new_buffer, describe_command_new_window));
 452
 453
 454
 455 function view_referenced_source_code (buffer) {
 456     if (buffer.source_code_reference == null)
 457         throw interactive_error("Command not valid in current buffer.");
 458     yield buffer.source_code_reference.open_in_editor();
 459 }
 460 interactive("view-referenced-source-code", null,
 461             function (I) {yield view_referenced_source_code(I.buffer);});
 462
 463
 464 /*
 465  * Describe Key
 466  */
 467
 468 define_keywords("$binding", "$other_bindings", "$key_sequence");
 469 function describe_key_buffer (window, element) {
 470     this.constructor_begin();
 471     keywords(arguments);
 472     special_buffer.call(this, window, element, forward_keywords(arguments));
 473     this.key_sequence = arguments.$key_sequence;
 474     this.bindings = arguments.$other_bindings;
 475     this.bind = arguments.$binding;
 476     this.source_code_reference = this.bind.source_code_reference;
 477     this.modalities.push(help_buffer_modality);
 478     this.constructor_end();
 479 }
 480
 481 describe_key_buffer.prototype = {
 482     get title() { return "Key help: " + this.key_sequence; },
 483
 484     description : "*help*",
 485
 486     generate : function () {
 487         var d = this.document;
 488
 489         var g = new help_document_generator(d, this);
 490
 491         g.add_help_stylesheet();
 492         d.body.setAttribute("class", "describe-key");
 493
 494         var p;
 495
 496         p = g.element("p", d.body);
 497         g.key_binding(this.key_sequence, p);
 498         g.text(" is bound to the command ", p);
 499         var command = this.bind.command;
 500         if (command == null)
 501             g.command_name("[pass through]", p);
 502         else
 503             g.command_reference(command, p);
 504         if (this.bind.browser_object != null) {
 505             g.text(" with the browser object, ", p);
 506             if (this.bind.browser_object instanceof Function) {
 507                 g.text("<anonymous browser-object function>", p);
 508             } else if (this.bind.browser_object instanceof browser_object_class) {
 509                 g.text(this.bind.browser_object.name, p);
 510             } else if (typeof(this.bind.browser_object) == "string") {
 511                 g.text('"'+this.bind.browser_object+'"', p);
 512             } else {
 513                 g.text(this.bind.browser_object, p);
 514             }
 515         }
 516         if (this.source_code_reference) {
 517             g.text(" in ", p);
 518             g.source_code_reference(this.source_code_reference, p);
 519         }
 520         g.text(".", p);
 521
 522         if (command != null) {
 523             p = g.element("p", d.body);
 524             g.command_reference(command, p);
 525             var cmd = interactive_commands.get(command);
 526             if (cmd.source_code_reference)  {
 527                 g.text(" is an interactive command in ", p);
 528                 g.source_code_reference(cmd.source_code_reference, p);
 529                 g.text(".", p);
 530             } else {
 531                 g.text(" is an interactive command.", p);
 532             }
 533
 534             if (this.bindings.length > 0) {
 535                 p = g.element("p", d.body);
 536                 g.text("It is bound to ", p);
 537                 for (var i = 0; i < this.bindings.length; ++i) {
 538                     if (i != 0)
 539                         g.text(", ", p);
 540                     g.key_binding(this.bindings[i], p);
 541                 }
 542                 g.text(".", p);
 543             }
 544
 545             if (cmd.doc != null)
 546                 g.help_text(cmd.doc, d.body);
 547         }
 548     },
 549
 550     __proto__: special_buffer.prototype
 551 };
 552
 553
 554 function describe_key (buffer, key_info, target) {
 555     var bindings;
 556     var seq = key_info[0];
 557     var bind = key_info[1];
 558     var keymaps = get_current_keymaps(buffer.window);
 559     if (bind.command)
 560         bindings = keymap_lookup_command(keymaps, bind.command);
 561     else
 562         bindings = [];
 563     create_buffer(buffer.window,
 564                   buffer_creator(describe_key_buffer,
 565                                  $opener = buffer,
 566                                  $key_sequence = seq.join(" "),
 567                                  $other_bindings = bindings,
 568                                  $binding = bind),
 569                   target);
 570 }
 571 function describe_key_new_buffer (I) {
 572     describe_key(I.buffer,
 573                  (yield I.minibuffer.read_key_binding($prompt = "Describe key:", $buffer = I.buffer)),
 574                  OPEN_NEW_BUFFER);
 575 }
 576 function describe_key_new_window (I) {
 577     describe_key(I.buffer,
 578                  (yield I.minibuffer.read_key_binding($prompt = "Describe key:", $buffer = I.buffer)),
 579                  OPEN_NEW_WINDOW);
 580 }
 581
 582 function describe_key_briefly (buffer, key_info) {
 583     var bindings;
 584     var seq = key_info[0];
 585     var bind = key_info[1];
 586     var browser_object = "";
 587     if (bind.browser_object != null) {
 588         browser_object += " on the browser object, ";
 589         if (bind.browser_object instanceof Function) {
 590             browser_object += "<anonymous browser-object function>";
 591         } else if (bind.browser_object instanceof browser_object_class) {
 592             browser_object += bind.browser_object.name;
 593         } else if (typeof(bind.browser_object) == "string") {
 594             browser_object += '"'+bind.browser_object+'"';
 595         } else {
 596             browser_object += bind.browser_object;
 597         }
 598     }
 599     buffer.window.minibuffer.message(seq.join(" ") + " runs the command " + bind.command + browser_object);
 600 }
 601
 602 interactive("describe-key", null,
 603             alternates(describe_key_new_buffer, describe_key_new_window));
 604
 605 interactive("describe-key-briefly", null,
 606     function (I) {
 607         describe_key_briefly(
 608             I.buffer,
 609             (yield I.minibuffer.read_key_binding($prompt = "Describe key:", $buffer = I.buffer)));
 610     });
 611
 612
 613
 614 /*
 615  * Describe Variable
 616  */
 617
 618 define_keywords("$variable");
 619 function describe_variable_buffer (window, element) {
 620     this.constructor_begin();
 621     keywords(arguments);
 622     special_buffer.call(this, window, element, forward_keywords(arguments));
 623     this.variable = arguments.$variable;
 624     this.cmd = user_variables[this.variable];
 625     this.source_code_reference = this.cmd.source_code_reference;
 626     this.modalities.push(help_buffer_modality);
 627     this.constructor_end();
 628 }
 629
 630 function pretty_print_value (value) {
 631     if (value === undefined)
 632         return "undefined";
 633     if (value === null)
 634         return "null";
 635     if (typeof(value) == "object")
 636         return value.toSource();
 637     if (typeof(value) == "function")
 638         return value.toString();
 639     if (typeof(value) == "string") {
 640         let s = value.toSource();
 641         // toSource returns: (new String("<blah>"))
 642         // we want just: "<blah>"
 643         return s.substring(12, s.length - 2);
 644     }
 645     return new String(value);
 646 }
 647
 648 describe_variable_buffer.prototype = {
 649     get title() { return "Variable help: " + this.variable; },
 650
 651     description : "*help*",
 652
 653     generate : function () {
 654         var d = this.document;
 655
 656         var g = new help_document_generator(d, this);
 657
 658         g.add_help_stylesheet();
 659         d.body.setAttribute("class", "describe-variable");
 660
 661         var p;
 662
 663         p = g.element("p", d.body);
 664         g.variable_reference(this.variable, p);
 665         var uvar = user_variables[this.variable];
 666         if (uvar.source_code_reference)  {
 667             g.text(" is a user variable in ", p);
 668             g.source_code_reference(uvar.source_code_reference, p);
 669             g.text(".", p);
 670         } else {
 671             g.text(" is a user variable.", p);
 672         }
 673
 674         p = g.element("p", d.body);
 675         g.text("Its value is: ", p);
 676         let value = conkeror[this.variable];
 677         {
 678             let s = pretty_print_value(value);
 679             let pre = g.element("pre", p);
 680             g.text(s, pre);
 681         }
 682
 683         if (uvar.doc != null)
 684             g.help_text(uvar.doc, d.body);
 685
 686         if (uvar.default_value !== undefined &&
 687             (uvar.default_value !== value ||
 688              (typeof(uvar.default_value) != "object")))  {
 689             p = g.element("p", d.body);
 690             g.text("Its default value is: ", p);
 691             {
 692                 let s = pretty_print_value(uvar.default_value);
 693                 let pre = g.element("pre", p);
 694                 g.text(s, pre);
 695             }
 696         }
 697     },
 698
 699     __proto__: special_buffer.prototype
 700 };
 701
 702
 703 function describe_variable (buffer, variable, target) {
 704     create_buffer(buffer.window,
 705                   buffer_creator(describe_variable_buffer,
 706                                  $opener = buffer,
 707                                  $variable = variable),
 708                   target);
 709 }
 710 function describe_variable_new_buffer (I) {
 711     describe_variable(I.buffer,
 712                       (yield I.minibuffer.read_user_variable($prompt = "Describe variable:")),
 713                       OPEN_NEW_BUFFER);
 714 }
 715 function describe_variable_new_window (I) {
 716     describe_variable(I.buffer,
 717                       (yield I.minibuffer.read_user_variable($prompt = "Describe variable:")),
 718                       OPEN_NEW_WINDOW);
 719 }
 720 interactive("describe-variable", null,
 721             alternates(describe_variable_new_buffer, describe_variable_new_window));
 722
 723
 724
 725 /*
 726  * Describe Preference
 727  */
 728
 729 function describe_preference (buffer, preference, target) {
 730     let key = preference.charAt(0).toUpperCase() + preference.substring(1);
 731     let url = "http://kb.mozillazine.org/" + key;
 732     browser_object_follow(buffer, target, url);
 733 }
 734 function describe_preference_new_buffer (I) {
 735     describe_preference(I.buffer, (yield I.minibuffer.read_preference($prompt = "Describe preference:")),
 736                         OPEN_NEW_BUFFER);
 737 }
 738 function describe_preference_new_window (I) {
 739     describe_preference(I.buffer, (yield I.minibuffer.read_preference($prompt = "Describe preference:")),
 740                         OPEN_NEW_WINDOW);
 741 }
 742 interactive("describe-preference", null,
 743             alternates(describe_preference_new_buffer, describe_preference_new_window));