modules/element.js

   1 /**
   2  * (C) Copyright 2007-2009 John J. Foerch
   3  * (C) Copyright 2007-2008 Jeremy Maitin-Shepard
   4  *
   5  * Portions of this file are derived from Vimperator,
   6  * (C) Copyright 2006-2007 Martin Stubenschrott.
   7  *
   8  * Use, modification, and distribution are subject to the terms specified in the
   9  * COPYING file.
  10 **/
  11
  12 require("hints.js");
  13 require("save.js");
  14 require("mime-type-override.js");
  15 require("minibuffer-read-mime-type.js");
  16
  17 var browser_object_classes = {};
  18
  19 /**
  20  * browser_object_class
  21  *
  22  *   In normal cases, make a new browser_object_class with the function,
  23  * `define_browser_object_class'.
  24  *
  25  * name: See note on `define_browser_object_class'.
  26  *
  27  * doc: a docstring
  28  *
  29  * handler: a coroutine called as: handler(I, prompt).  `I' is a normal
  30  *          interactive context.  `prompt' is there to pass along as the
  31  *          $prompt of various minibuffer read procedures, if needed.
  32  *
  33  * $hint: short string (usually verb and noun) to describe the UI
  34  *        of the browser object class to the user.  Only used by
  35  *        browser object classes which make use of the minibuffer.
  36  */
  37 define_keywords("$hint");
  38 function browser_object_class (name, doc, handler) {
  39     keywords(arguments);
  40     this.name = name;
  41     this.handler = handler;
  42     this.doc = doc;
  43     this.hint = arguments.$hint;
  44 }
  45
  46 /**
  47  * define_browser_object_class
  48  *
  49  *   In normal cases, make a new browser_object_class with the function,
  50  * `define_browser_object_class'.
  51  *
  52  * name: the name of the browser object class.  multiword names should be
  53  *       hyphenated.  From this name, a variable browser_object_NAME and
  54  *       an interactive command browser-object-NAME will be generated.
  55  *
  56  *   Other arguments are as for `browser_object_class'.
  57  */
  58 // keywords: $hint
  59 function define_browser_object_class (name, doc, handler) {
  60     keywords(arguments);
  61     var varname = 'browser_object_'+name.replace('-','_','g');
  62     var ob = conkeror[varname] =
  63         new browser_object_class(name, doc, handler,
  64                                  forward_keywords(arguments));
  65     interactive("browser-object-"+name,
  66         "A prefix command to specify that the following command operate "+
  67         "on objects of type: "+name+".",
  68         function (I) { I.browser_object = ob; },
  69         $prefix = true);
  70     return ob;
  71 }
  72
  73 /**
  74  * xpath_browser_object_handler
  75  *
  76  *   This generates a function of the type needed for a handler of a
  77  * browser object class.  The handler uses `read_hinted_element' of
  78  * hints.js to let the user pick a DOM node from those matched by
  79  * `xpath_expression'.
  80  */
  81 function xpath_browser_object_handler (xpath_expression) {
  82     return function (I, prompt) {
  83         var result = yield I.buffer.window.minibuffer.read_hinted_element(
  84             $buffer = I.buffer,
  85             $prompt = prompt,
  86             $hint_xpath_expression = xpath_expression);
  87         yield co_return(result);
  88     };
  89 }
  90
  91 define_browser_object_class("images",
  92     "Browser object class for selecting an html:img via hinting.",
  93     xpath_browser_object_handler("//img | //xhtml:img"),
  94     $hint = "select image");
  95
  96 define_browser_object_class("frames",
  97     "Browser object class for selecting a frame or iframe via hinting.",
  98     function (I, prompt) {
  99         var doc = I.buffer.document;
 100         // Check for any frames or visible iframes
 101         var skip_hints = true;
 102         if (doc.getElementsByTagName("frame").length > 0)
 103             skip_hints = false;
 104         else {
 105             let topwin = I.buffer.top_frame;
 106             let iframes = doc.getElementsByTagName("iframe");
 107             for (var i = 0, nframes = iframes.length; i < nframes; i++) {
 108                 let style = topwin.getComputedStyle(iframes[i], "");
 109                 if (style.display == "none" || style.visibility == "hidden")
 110                     continue;
 111                 skip_hints = false;
 112                 break;
 113             }
 114         }
 115         if (skip_hints) {
 116             // only one frame (the top-level one), no need to use the hints system
 117             yield co_return(I.buffer.top_frame);
 118         }
 119         var result = yield I.buffer.window.minibuffer.read_hinted_element(
 120             $buffer = I.buffer,
 121             $prompt = prompt,
 122             $hint_xpath_expression = "//iframe | //frame | //xhtml:iframe | //xhtml:frame");
 123         yield co_return(result);
 124     },
 125     $hint = "select frame");
 126
 127 define_browser_object_class("links",
 128     "Browser object class for selecting a hyperlink, form field, "+
 129     "or link-like element, via hinting.",
 130     xpath_browser_object_handler(
 131         "//*[@onclick or @onmouseover or @onmousedown or @onmouseup or "+
 132             "@oncommand or @role='link' or @role='button' or @role='menuitem'] | "+
 133         "//input[not(@type='hidden')] | //a[@href] | //area | "+
 134         "//iframe | //textarea | //button | //select | "+
 135         "//*[@contenteditable = 'true'] | "+
 136         "//xhtml:*[@onclick or @onmouseover or @onmousedown or @onmouseup or "+
 137                   "@oncommand or @role='link' or @role='button' or @role='menuitem'] | "+
 138         "//xhtml:input[not(@type='hidden')] | //xhtml:a[@href] | //xhtml:area | "+
 139         "//xhtml:iframe | //xhtml:textarea | //xhtml:button | //xhtml:select | " +
 140         "//xhtml:*[@contenteditable = 'true'] | "+
 141         "//svg:a"),
 142     $hint = "select link");
 143
 144 define_browser_object_class("mathml",
 145     "Browser object class for selecting a MathML node via hinting.",
 146     xpath_browser_object_handler("//m:math"),
 147     $hint = "select MathML element");
 148
 149 define_browser_object_class("top",
 150     "Browser object class which returns the top frame of the document.",
 151     function (I, prompt) { return I.buffer.top_frame; });
 152
 153 define_browser_object_class("url",
 154     "Browser object class which prompts the user for an url or webjump.",
 155     function (I, prompt) {
 156         var result = yield I.buffer.window.minibuffer.read_url($prompt = prompt);
 157         yield co_return(result);
 158     },
 159     $hint = "enter URL/webjump");
 160
 161 define_browser_object_class("paste-url",
 162     "Browser object which reads an url from the X Primary Selection, "+
 163     "falling back on the clipboard for operating systems which lack one.",
 164     function (I, prompt) {
 165                 var url = read_from_x_primary_selection();
 166                 // trim spaces
 167                 url = url.replace(/^\s*|\s*$/,"");
 168                 // add http:// if needed
 169                 if (url.match(/^[^:]+\./)) {
 170                         url = "http://" + url;
 171                 }
 172         try {
 173             return make_uri(url).spec;
 174         } catch (e) {
 175             throw new interactive_error("error: malformed url: "+url);
 176         }
 177     });
 178
 179 define_browser_object_class("file",
 180     "Browser object which prompts for a file name.",
 181     function (I, prompt) {
 182         var result = yield I.buffer.window.minibuffer.read_file(
 183             $prompt = prompt,
 184             $history = I.command.name+"/file",
 185             $initial_value = I.local.cwd.path);
 186         yield co_return(result);
 187     },
 188     $hint = "enter file name");
 189
 190 define_browser_object_class("alt",
 191     "Browser object class which returns the alt text of an html:img, "+
 192     "selected via hinting",
 193     function (I, prompt) {
 194         var result = yield I.buffer.window.minibuffer.read_hinted_element(
 195             $buffer = I.buffer,
 196             $prompt = prompt,
 197             $hint_xpath_expression = "//img[@alt] | //xhtml:img[@alt]");
 198         yield co_return(result.alt);
 199     },
 200     $hint = "select image for alt-text");
 201
 202 define_browser_object_class("title",
 203     "Browser object class which returns the title attribute of an element, "+
 204     "selected via hinting",
 205     function (I, prompt) {
 206         var result = yield I.buffer.window.minibuffer.read_hinted_element(
 207             $buffer = I.buffer,
 208             $prompt = prompt,
 209             $hint_xpath_expression = "//*[@title] | //xhtml:*[@title]");
 210         yield co_return(result.title);
 211     },
 212     $hint = "select element for title attribute");
 213
 214 define_browser_object_class("title-or-alt",
 215     "Browser object which is the union of browser-object-alt and "+
 216     "browser-object-title, with title having higher precedence in "+
 217     "the case of an element that has both.",
 218     function (I, prompt) {
 219         var result = yield I.buffer.window.minibuffer.read_hinted_element(
 220             $buffer = I.buffer,
 221             $prompt = prompt,
 222             $hint_xpath_expression = "//img[@alt] | //*[@title] | //xhtml:img[@alt] | //xhtml:*[@title]");
 223         yield co_return(result.title ? result.title : result.alt);
 224     },
 225     $hint = "select element for title or alt-text");
 226
 227 define_browser_object_class("scrape-url",
 228     "Browser object which lets the user choose an url from a list of "+
 229     "urls scraped from the source code of the document.",
 230     function (I, prompt) {
 231         var completions = I.buffer.document.documentElement.innerHTML
 232             .match(/https?:[^\s<>)"]*/g)
 233             .filter(remove_duplicates_filter());
 234         var completer = all_word_completer($completions = completions);
 235         var result = yield I.buffer.window.minibuffer.read(
 236             $prompt = prompt,
 237             $completer = completer,
 238             $initial_value = null,
 239             $auto_complete = "url",
 240             $select,
 241             $match_required = false);
 242         yield co_return(result);
 243     },
 244     $hint = "choose scraped URL");
 245
 246 define_browser_object_class("up-url",
 247     "Browser object which returns the url one level above the current one.",
 248     function (I, prompt) {
 249         return compute_up_url(I.buffer.current_uri);
 250     });
 251
 252 define_browser_object_class("focused-element",
 253     "Browser object which returns the focused element.",
 254     function (I, prompt) { return I.buffer.focused_element; });
 255
 256 define_browser_object_class("dom-node", null,
 257     xpath_browser_object_handler("//* | //xhtml:*"),
 258     $hint = "select DOM node");
 259
 260 define_browser_object_class("fragment-link",
 261     "Browser object class which returns a link to the specified fragment of a page",
 262     function (I, prompt) {
 263         var elem = yield I.buffer.window.minibuffer.read_hinted_element(
 264             $buffer = I.buffer,
 265             $prompt = prompt,
 266             $hint_xpath_expression = "//*[@id] | //a[@name] | //xhtml:*[@id] | //xhtml:a[@name]");
 267         yield co_return(page_fragment_load_spec(elem));
 268     },
 269     $hint = "select element to link to");
 270
 271 interactive("browser-object-text",
 272     "Composable browser object which returns the text of another object.",
 273     function (I) {
 274         // our job here is to modify the interactive context.
 275         // set I.browser_object to a browser_object which calls the
 276         // original one, then returns its text.
 277         var b = I.browser_object;
 278         I.browser_object = function (I) {
 279             I.browser_object = b;
 280             var e = yield read_browser_object(I);
 281             if (e instanceof Ci.nsIDOMHTMLImageElement)
 282                 yield co_return(e.getAttribute("alt"));
 283             yield co_return(e.textContent);
 284         };
 285     },
 286     $prefix);
 287
 288 function get_browser_object (I) {
 289     var obj = I.browser_object;
 290     var cmd = I.command;
 291
 292     // if there was no interactive browser-object,
 293     // binding_browser_object becomes the default.
 294     if (obj === undefined) {
 295         obj = I.binding_browser_object;
 296     }
 297     // if the command's default browser object is a non-null literal,
 298     // it overrides an interactive browser-object, but not a binding
 299     // browser object.
 300     if (cmd.browser_object != null &&
 301         (! (cmd.browser_object instanceof browser_object_class)) &&
 302         (I.binding_browser_object === undefined))
 303     {
 304         obj = cmd.browser_object;
 305     }
 306     // if we still have no browser-object, look for a page-mode
 307     // default, or finally the command default.
 308     if (obj === undefined) {
 309         obj = (I.buffer &&
 310                I.buffer.default_browser_object_classes[cmd.name]) ||
 311             cmd.browser_object;
 312     }
 313
 314     return obj;
 315 }
 316
 317 function read_browser_object (I) {
 318     var browser_object = get_browser_object(I);
 319     if (browser_object === undefined)
 320         throw interactive_error("No browser object");
 321
 322     var result;
 323     // literals cannot be overridden
 324     if (browser_object instanceof Function) {
 325         result = yield browser_object(I);
 326         yield co_return(result);
 327     }
 328     if (! (browser_object instanceof browser_object_class))
 329         yield co_return(browser_object);
 330
 331     var prompt = I.command.prompt;
 332     if (! prompt) {
 333         prompt = I.command.name.split(/-|_/).join(" ");
 334         prompt = prompt[0].toUpperCase() + prompt.substring(1);
 335     }
 336     if (I.target != null)
 337         prompt += TARGET_PROMPTS[I.target];
 338     if (browser_object.hint)
 339         prompt += " (" + browser_object.hint + ")";
 340     prompt += ":";
 341
 342     result = yield browser_object.handler.call(null, I, prompt);
 343     yield co_return(result);
 344 }
 345
 346
 347 /**
 348  * This is a simple wrapper function that sets focus to elem, and
 349  * bypasses the automatic focus prevention system, which might
 350  * otherwise prevent this from happening.
 351  */
 352 function browser_set_element_focus (buffer, elem, prevent_scroll) {
 353     if (! dom_node_or_window_p(elem))
 354         return;
 355     if (! elem.focus)
 356         return;
 357     if (prevent_scroll)
 358         set_focus_no_scroll(buffer.window, elem);
 359     else
 360         elem.focus();
 361 }
 362
 363 function browser_element_focus (buffer, elem) {
 364     if (! dom_node_or_window_p(elem))
 365         return;
 366
 367     if (elem instanceof Ci.nsIDOMXULTextBoxElement) {
 368         if (elem.wrappedJSObject)
 369             elem = elem.wrappedJSObject.inputField; // focus the input field
 370         else
 371             elem = elem.inputField;
 372     }
 373
 374     browser_set_element_focus(buffer, elem);
 375     if (elem instanceof Ci.nsIDOMWindow)
 376         return;
 377
 378     // If it is not a window, it must be an HTML element
 379     var x = 0;
 380     var y = 0;
 381     if (elem instanceof Ci.nsIDOMHTMLFrameElement ||
 382         elem instanceof Ci.nsIDOMHTMLIFrameElement)
 383     {
 384         elem.contentWindow.focus();
 385         return;
 386     }
 387     if (elem instanceof Ci.nsIDOMHTMLAreaElement) {
 388         var coords = elem.getAttribute("coords").split(",");
 389         x = Number(coords[0]);
 390         y = Number(coords[1]);
 391     }
 392
 393     var doc = elem.ownerDocument;
 394     var evt = doc.createEvent("MouseEvents");
 395
 396     evt.initMouseEvent("mouseover", true, true, doc.defaultView, 1, x, y, 0, 0, 0, 0, 0, 0, 0, null);
 397     elem.dispatchEvent(evt);
 398 }
 399
 400 function browser_object_follow (buffer, target, elem) {
 401     // XXX: would be better to let nsILocalFile objects be load_specs
 402     if (elem instanceof Ci.nsILocalFile)
 403         elem = elem.path;
 404
 405     var e;
 406     if (elem instanceof load_spec)
 407         e = load_spec_element(elem);
 408     if (! e)
 409         e = elem;
 410
 411     browser_set_element_focus(buffer, e, true /* no scroll */);
 412
 413     var no_click = (((elem instanceof load_spec) &&
 414                      load_spec_forced_charset(elem)) ||
 415                     (e instanceof load_spec) ||
 416                     (e instanceof Ci.nsIDOMWindow) ||
 417                     (e instanceof Ci.nsIDOMHTMLFrameElement) ||
 418                     (e instanceof Ci.nsIDOMHTMLIFrameElement) ||
 419                     (e instanceof Ci.nsIDOMHTMLLinkElement) ||
 420                     (e instanceof Ci.nsIDOMHTMLImageElement &&
 421                      !e.hasAttribute("onmousedown") && !e.hasAttribute("onclick")));
 422
 423     if (target == FOLLOW_DEFAULT && !no_click) {
 424         var x = 1, y = 1;
 425         if (e instanceof Ci.nsIDOMHTMLAreaElement) {
 426             var coords = e.getAttribute("coords").split(",");
 427             if (coords.length >= 2) {
 428                 x = Number(coords[0]) + 1;
 429                 y = Number(coords[1]) + 1;
 430             }
 431         }
 432         dom_node_click(e, x, y);
 433         return;
 434     }
 435
 436     var spec = load_spec(elem);
 437
 438     if (load_spec_uri_string(spec).match(/^\s*javascript:/)) {
 439         // it is nonsensical to follow a javascript url in a different
 440         // buffer or window
 441         target = FOLLOW_DEFAULT;
 442     } else if (!(buffer instanceof content_buffer) &&
 443         (target == FOLLOW_CURRENT_FRAME ||
 444          target == FOLLOW_DEFAULT ||
 445          target == OPEN_CURRENT_BUFFER))
 446     {
 447         target = OPEN_NEW_BUFFER;
 448     }
 449
 450     switch (target) {
 451     case FOLLOW_CURRENT_FRAME:
 452         var current_frame = load_spec_source_frame(spec);
 453         if (current_frame && current_frame != buffer.top_frame) {
 454             var target_obj = get_web_navigation_for_frame(current_frame);
 455             apply_load_spec(target_obj, spec);
 456             break;
 457         }
 458     case FOLLOW_DEFAULT:
 459     case OPEN_CURRENT_BUFFER:
 460         buffer.load(spec);
 461         break;
 462     case OPEN_NEW_WINDOW:
 463     case OPEN_NEW_BUFFER:
 464     case OPEN_NEW_BUFFER_BACKGROUND:
 465         if (dom_node_or_window_p(e))
 466             var opener = buffer;
 467         else
 468             opener = null;
 469         create_buffer(buffer.window,
 470                       buffer_creator(content_buffer,
 471                                      $opener = opener,
 472                                      $load = spec),
 473                       target);
 474     }
 475 }
 476
 477 /**
 478  * Follow a link-like element by generating fake mouse events.
 479  */
 480 function dom_node_click (elem, x, y) {
 481     var doc = elem.ownerDocument;
 482     var view = doc.defaultView;
 483
 484     var evt = doc.createEvent("MouseEvents");
 485     evt.initMouseEvent("mousedown", true, true, view, 1, x, y, 0, 0, /*ctrl*/ 0, /*event.altKey*/0,
 486                        /*event.shiftKey*/ 0, /*event.metaKey*/ 0, 0, null);
 487     elem.dispatchEvent(evt);
 488
 489     evt = doc.createEvent("MouseEvents");
 490     evt.initMouseEvent("click", true, true, view, 1, x, y, 0, 0, /*ctrl*/ 0, /*event.altKey*/0,
 491                        /*event.shiftKey*/ 0, /*event.metaKey*/ 0, 0, null);
 492     elem.dispatchEvent(evt);
 493
 494     evt = doc.createEvent("MouseEvents");
 495     evt.initMouseEvent("mouseup", true, true, view, 1, x, y, 0, 0, /*ctrl*/ 0, /*event.altKey*/0,
 496                        /*event.shiftKey*/ 0, /*event.metaKey*/ 0, 0, null);
 497     elem.dispatchEvent(evt);
 498 }
 499
 500
 501 function follow (I, target) {
 502     if (target == null)
 503         target = FOLLOW_DEFAULT;
 504     I.target = target;
 505     if (target == OPEN_CURRENT_BUFFER)
 506         check_buffer(I.buffer, content_buffer);
 507     var element = yield read_browser_object(I);
 508     try {
 509         element = load_spec(element);
 510         if (I.forced_charset)
 511             element.forced_charset = I.forced_charset;
 512     } catch (e) {}
 513     browser_object_follow(I.buffer, target, element);
 514 }
 515
 516 function follow_new_buffer (I) {
 517     yield follow(I, OPEN_NEW_BUFFER);
 518 }
 519
 520 function follow_new_buffer_background (I) {
 521     yield follow(I, OPEN_NEW_BUFFER_BACKGROUND);
 522 }
 523
 524 function follow_new_window (I) {
 525     yield follow(I, OPEN_NEW_WINDOW);
 526 }
 527
 528 function follow_current_frame (I) {
 529     yield follow(I, FOLLOW_CURRENT_FRAME);
 530 }
 531
 532 function follow_current_buffer (I) {
 533     yield follow(I, OPEN_CURRENT_BUFFER);
 534 }
 535
 536
 537 function element_get_load_target_label (element) {
 538     if (element instanceof Ci.nsIDOMWindow)
 539         return "page";
 540     if (element instanceof Ci.nsIDOMHTMLFrameElement)
 541         return "frame";
 542     if (element instanceof Ci.nsIDOMHTMLIFrameElement)
 543         return "iframe";
 544     return null;
 545 }
 546
 547 function element_get_operation_label (element, op_name, suffix) {
 548     var target_label = element_get_load_target_label(element);
 549     if (target_label != null)
 550         target_label = " " + target_label;
 551     else
 552         target_label = "";
 553
 554     if (suffix != null)
 555         suffix = " " + suffix;
 556     else
 557         suffix = "";
 558
 559     return op_name + target_label + suffix + ":";
 560 }
 561
 562
 563 function browser_element_text (buffer, elem) {
 564     try {
 565        var spec = load_spec(elem);
 566     } catch (e) {}
 567     var text = null;
 568     if (typeof elem == "string" || elem instanceof String)
 569         text = elem;
 570     else if (spec)
 571         text = load_spec_uri_string(spec);
 572     else {
 573         if (!(elem instanceof Ci.nsIDOMNode))
 574             throw interactive_error("Element has no associated text to copy.");
 575         var tag = elem.localName.toLowerCase();
 576         if ((tag == "input" || tag == "button") &&
 577             elem.type == "submit" && elem.form && elem.form.action)
 578         {
 579             text = elem.form.action;
 580         } else if (tag == "input" || tag == "textarea") {
 581             text = elem.value;
 582         } else if (tag == "select") {
 583             if (elem.selectedIndex >= 0)
 584                 text = elem.item(elem.selectedIndex).text;
 585         } else {
 586             text = elem.textContent;
 587         }
 588     }
 589     return text;
 590 }
 591
 592
 593 define_variable("copy_append_separator", "\n",
 594     "String used to separate old and new text when text is appended to clipboard");
 595
 596 function copy_text (I) {
 597     var element = yield read_browser_object(I);
 598     browser_set_element_focus(I.buffer, element);
 599     var text = browser_element_text(I.buffer, element);
 600     writeToClipboard(text);
 601     I.buffer.window.minibuffer.message("Copied: " + text);
 602 }
 603
 604 function copy_text_append (I) {
 605     var element = yield read_browser_object(I);
 606     browser_set_element_focus(I.buffer, element);
 607     var new_text = browser_element_text(I.buffer, element);
 608     var text = read_from_clipboard() + copy_append_separator + new_text;
 609     writeToClipboard(text);
 610     I.buffer.window.minibuffer.message("Copied: ..." + new_text);
 611 }
 612
 613
 614 define_variable("view_source_use_external_editor", false,
 615     "When true, the `view-source' command will send its document to "+
 616     "your external editor.");
 617
 618 define_variable("view_source_function", null,
 619     "May be set to a user-defined function for viewing source code. "+
 620     "The function should accept an nsILocalFile of the filename as "+
 621     "its one positional argument, and it will also be called with "+
 622     "the keyword `$temporary', whose value will be true if the file "+
 623     "is considered temporary, and therefore the function must take "+
 624     "responsibility for deleting it.");
 625
 626 function browser_object_view_source (buffer, target, elem) {
 627     if (view_source_use_external_editor || view_source_function) {
 628         var spec = load_spec(elem);
 629
 630         let [file, temp] = yield download_as_temporary(spec,
 631                                                        $buffer = buffer,
 632                                                        $action = "View source");
 633         if (view_source_use_external_editor)
 634             yield open_file_with_external_editor(file, $temporary = temp);
 635         else
 636             yield view_source_function(file, $temporary = temp);
 637         return;
 638     }
 639
 640     var win = null;
 641     var window = buffer.window;
 642     if (elem.localName) {
 643         switch (elem.localName.toLowerCase()) {
 644         case "frame": case "iframe":
 645             win = elem.contentWindow;
 646             break;
 647         case "math":
 648             view_mathml_source(window, charset, elem);
 649             return;
 650         default:
 651             throw new Error("Invalid browser element");
 652         }
 653     } else
 654         win = elem;
 655     win.focus();
 656
 657     var url_s = win.location.href;
 658     if (url_s.substring (0,12) != "view-source:") {
 659         try {
 660             browser_object_follow(buffer, target, "view-source:" + url_s);
 661         } catch(e) { dump_error(e); }
 662     } else {
 663         try {
 664             browser_object_follow(buffer, target, url_s.replace(/^view-source\:/, ''));
 665         } catch(e) { dump_error(e); }
 666     }
 667 }
 668
 669 function view_source (I, target) {
 670     I.target = target;
 671     if (target == null)
 672         target = OPEN_CURRENT_BUFFER;
 673     var element = yield read_browser_object(I);
 674     yield browser_object_view_source(I.buffer, target, element);
 675 }
 676
 677 function view_source_new_buffer (I) {
 678     yield view_source(I, OPEN_NEW_BUFFER);
 679 }
 680
 681 function view_source_new_window (I) {
 682     yield view_source(I, OPEN_NEW_WINDOW);
 683 }
 684
 685
 686 function browser_element_shell_command (buffer, elem, command, cwd) {
 687     var spec = load_spec(elem);
 688     yield download_as_temporary(spec,
 689                                 $buffer = buffer,
 690                                 $shell_command = command,
 691                                 $shell_command_cwd = cwd);
 692 }
 693
 694 provide("element");