diff --git a/gui/application.ini b/gui/application.ini
index 0da5e498dad..a832d9d285b 100644
--- a/gui/application.ini
+++ b/gui/application.ini
@@ -32,4 +32,4 @@ MinVersion=1.9a5
 ; This field is optional.  It specifies the maximum Gecko version that this
 ; application requires.  It should be specified if your application uses
 ; unfrozen interfaces.
-;MaxVersion=1.9.0.*
+MaxVersion=2.*
diff --git a/gui/chrome.manifest b/gui/chrome.manifest
new file mode 100644
index 00000000000..865d6a88fb4
--- /dev/null
+++ b/gui/chrome.manifest
@@ -0,0 +1 @@
+manifest chrome/chrome.manifest
diff --git a/gui/chrome/chrome.manifest b/gui/chrome/chrome.manifest
index 6b524807eaa..775445ee17b 100644
--- a/gui/chrome/chrome.manifest
+++ b/gui/chrome/chrome.manifest
@@ -1 +1 @@
-content nixos-gui content/nixos-gui/
+content nixos-gui content/
diff --git a/gui/chrome/content/nixos-gui/io.js b/gui/chrome/content/io.js
similarity index 54%
rename from gui/chrome/content/nixos-gui/io.js
rename to gui/chrome/content/io.js
index 3e3b080b814..8d9c8c17365 100644
--- a/gui/chrome/content/nixos-gui/io.js
+++ b/gui/chrome/content/io.js
@@ -1,3 +1,66 @@
+
+function inspect(obj, maxLevels, level)
+{
+  var str = '', type, msg;
+
+    // Start Input Validations
+    // Don't touch, we start iterating at level zero
+    if(level == null)  level = 0;
+
+    // At least you want to show the first level
+    if(maxLevels == null) maxLevels = 1;
+    if(maxLevels < 1)
+        return '<font color="red">Error: Levels number must be > 0</font>';
+
+    // We start with a non null object
+    if(obj == null)
+    return '<font color="red">Error: Object <b>NULL</b></font>';
+    // End Input Validations
+
+    // Each Iteration must be indented
+    str += '<ul>';
+
+    // Start iterations for all objects in obj
+    for(property in obj)
+    {
+      try
+      {
+          // Show "property" and "type property"
+          type =  typeof(obj[property]);
+          str += '<li>(' + type + ') ' + property +
+                 ( (obj[property]==null)?(': <b>null</b>'):('')) + '</li>';
+
+          // We keep iterating if this property is an Object, non null
+          // and we are inside the required number of levels
+          if((type == 'object') && (obj[property] != null) && (level+1 < maxLevels))
+          str += inspect(obj[property], maxLevels, level+1);
+      }
+      catch(err)
+      {
+        // Is there some properties in obj we can't access? Print it red.
+        if(typeof(err) == 'string') msg = err;
+        else if(err.message)        msg = err.message;
+        else if(err.description)    msg = err.description;
+        else                        msg = 'Unknown';
+
+        str += '<li><font color="red">(Error) ' + property + ': ' + msg +'</font></li>';
+      }
+    }
+
+      // Close indent
+      str += '</ul>';
+
+    return str;
+}
+
+// Run xulrunner application.ini -jsconsole -console, to see messages.
+function log(str)
+{
+  Components.classes['@mozilla.org/consoleservice;1']
+    .getService(Components.interfaces.nsIConsoleService)
+    .logStringMessage(str);
+}
+
 function makeTempFile(prefix)
 {
   var file = Components.classes["@mozilla.org/file/directory_service;1"]
@@ -29,7 +92,7 @@ function readFromFile(file)
   var sstream = Components.classes["@mozilla.org/scriptableinputstream;1"]
                           .createInstance(Components.interfaces.nsIScriptableInputStream);
   fstream.init(file, -1, 0, 0);
-  sstream.init(fstream); 
+  sstream.init(fstream);
 
   var str = sstream.read(4096);
   while (str.length > 0) {
diff --git a/gui/chrome/content/main.js b/gui/chrome/content/main.js
new file mode 100644
index 00000000000..de272e27378
--- /dev/null
+++ b/gui/chrome/content/main.js
@@ -0,0 +1,40 @@
+// global variables.
+var gNixOS;
+var gOptionView;
+
+/*
+var gProgressBar;
+function setProgress(current, max)
+{
+  if (gProgressBar) {
+    gProgressBar.value = 100 * current / max;
+    log("progress: " + gProgressBar.value + "%");
+  }
+  else
+    log("unknow progress bar");
+}
+*/
+
+function updatePanel(options)
+{
+  log("updatePanel: " + options.length);
+  var t = "";
+  for (var i = 0; i < options.length; i++)
+  {
+    log("Called with " + options[i].path);
+    t += options[i].description;
+  }
+  $("#option-desc").text(t);
+}
+
+
+function onload()
+{
+  var optionTree = document.getElementById("option-tree");
+  // gProgressBar = document.getElementById("progress-bar");
+  // setProgress(0, 1);
+
+  gNixOS = new NixOS();
+  gOptionView = new OptionView(gNixOS.option, updatePanel);
+  optionTree.view = gOptionView;
+}
diff --git a/gui/chrome/content/myviewer.xul b/gui/chrome/content/myviewer.xul
new file mode 100644
index 00000000000..23c6ce0a65d
--- /dev/null
+++ b/gui/chrome/content/myviewer.xul
@@ -0,0 +1,42 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
+
+<!DOCTYPE window>
+
+<!-- To edit this file I recommend you to use:
+     http://xulfr.org/outils/xulediteur.xul
+  -->
+
+<window
+  id     = "nixos-gui"
+  title  = "NixOS gui"
+  width  = "800"
+  height = "600"
+  xmlns  = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script src="jquery-1.3.2.js"/>
+  <script src="io.js"/>
+  <script src="nixos.js"/>
+  <script src="optionView.js"/>
+  <script src="main.js"/>
+  <columns height="580">
+    <column width = "300">
+      <tree flex="1" id="option-tree" persist="height" onselect="gOptionView.selectionChanged()">
+        <treecols>
+          <treecol persist="hidden width" flex="1" id="opt-name"
+                   label="Option" primary="true"/>
+          <!-- Uncomment the following column to see the number of option
+               printed below each options. -->
+          <!--
+          <treecol persist="hidden width" flex="1" id="dbg-size"
+                   label="Size"/>
+          -->
+        </treecols>
+        <treechildren id="first-child" flex="1"/>
+      </tree>
+    </column>
+    <column flex="1">
+      <description id="option-desc" hidden="false"></description>
+    </column>
+  </columns>
+<!--  <progressmeter id="progress-bar" value="0%"/> -->
+</window>
diff --git a/gui/chrome/content/nixos-gui/main.js b/gui/chrome/content/nixos-gui/main.js
deleted file mode 100644
index baa934e43e2..00000000000
--- a/gui/chrome/content/nixos-gui/main.js
+++ /dev/null
@@ -1,171 +0,0 @@
-var COPYCOL = 2;
-var gOptionListView = new treeView(["opt-success","opt-name","opt-desc"],
-                                   COPYCOL);
-
-// Run xulrunner application.ini -jsconsole -console, to see messages.
-function log(str)
-{
-  Components.classes['@mozilla.org/consoleservice;1']
-    .getService(Components.interfaces.nsIConsoleService)
-    .logStringMessage(str);
-}
-
-
-// return the DOM of the value returned by nix-instantiate
-function dumpOptions(path)
-{
-  var nixInstantiate = "nix-instantiate"; // "@nix@/bin/nix-instantiate";
-  var nixos = "/etc/nixos/nixos/default.nix"; // "@nixos@/default.nix";
-
-  var o = makeTempFile("nixos-options");
-
-  path = "eval.options" + (path? "." + path : "");
-  log("retrieve options from: " + path);
-
-  runProgram(nixInstantiate+" "+nixos+" -A "+path+" --eval-only --strict --xml 2>/dev/null | tr -d '' >" + o.path);
-
-  var xml = readFromFile(o);
-  o.remove(false);
-
-  // jQuery does a stack overflow when converting the XML to a DOM.
-  var dom = DOMParser().parseFromString(xml, "text/xml");
-  
-  log("return dom");
-  return dom;
-}
-
-
-// Pretty print Nix values.
-function nixPP(value, level)
-{
-  function indent(level) {  ret = ""; while (level--) ret+= "  "; return ret; }
-
-  if (!level) level = 0;
-  var ret = "<no match>";
-  if (value.is("attrs")) {
-    var content = "";
-    value.children().each(function (){
-      var name = $(this).attr("name");
-      var value = nixPP($(this).children(), level + 1);
-      content += indent(level + 1) + name + " = " + value + ";\n";
-    });
-    ret = "{\n" + content + indent(level) + "}";
-  }
-  else if (value.is("list")) {
-    var content = "";
-    value.children().each(function (){
-      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
-    });
-    ret = "[\n" + content + indent(level) + "]";
-  }
-  else if (value.is("bool"))
-    ret = (value.attr("value") == "true");
-  else if (value.is("string"))
-    ret = '"' + value.attr("value") + '"';
-  else if (value.is("path"))
-    ret = value.attr("value");
-  else if (value.is("int"))
-    ret = parseInt(value.attr("value"));
-  else if (value.is("derivation"))
-    ret = value.attr("outPath");
-  else if (value.is("function"))
-    ret = "<function>";
-  else {
-    var content = "";
-    value.children().each(function (){
-      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
-    });
-    ret = "<!--" + value.selector + "--><!--\n" + content + indent(level) + "-->";
-  }
-  return ret;
-}
-
-// Function used to reproduce the select operator on the XML DOM.
-// It return the value contained in the targeted attribute.
-function nixSelect(attrs, selector)
-{
-  var names = selector.split(".");
-  var value = $(attrs);
-  for (var i = 0; i < names.length; i++) {
-    log(nixPP(value) + "." + names[i]);
-    if (value.is("attrs"))
-      value = value.children("attr[name='" + names[i] + "']").children();
-    else {
-      log("Cannot do an attribute selection.");
-      break
-    }
-  }
-
-  log("nixSelect return: " + nixPP(value));
-
-  var ret;
-  if (value.is("attrs") || value.is("list"))
-    ret = value;
-  else if (value.is("bool"))
-    ret = value.attr("value") == "true";
-  else if (value.is("string"))
-    ret = value.attr("value");
-  else if (value.is("int"))
-    ret = parseInt(value.attr("value"));
-  else if (value.is("derivation"))
-    ret = value.attr("outPath");
-  else if (value.is("function"))
-    ret = "<function>";
-
-  return ret;
-}
-
-var gProgressBar;
-function setProgress(current, max)
-{
-  if (gProgressBar) {
-    gProgressBar.value = 100 * current / max;
-    log("progress: " + gProgressBar.value + "%");
-  }
-  else
-    log("unknow progress bar");
-}
-
-// fill the list of options
-function setOptionList(optionDOM)
-{
-  var options = $("attrs", optionDOM).filter(function () {
-    return $(this)
-      .children("attr[name='_type']")
-      .children("string[value='option']")
-      .length != 0;
-  });
-
-  var max = options.length;
-
-  log("Number of options: " + max);
-
-  setProgress(0, max);
-  gOptionListView.clear();
-  options.each(function (index){
-      var success = nixSelect(this, "config.success");
-      var name = nixSelect(this, "name");
-      var desc = nixSelect(this, "description");
-      if (success && name && desc) {
-        log("Add option '" + name + "' in the list.");
-        gOptionListView.addRow([success, name, desc]);
-      }
-      else
-        log("A problem occur while scanning an option.");
-      setProgress(index + 1, max);
-  });
-}
-
-
-function onload()
-{
-  var optionList = document.getElementById("option-list");
-  gProgressBar = document.getElementById("progress-bar");
-  setProgress(0, 1);
-  optionList.view = gOptionListView;
-
-  // try to avoid blocking the rendering, unfortunately this is not perfect.
-  setTimeout(function (){
-    setOptionList(dumpOptions("hardware"));}
-  , 100);
-}
diff --git a/gui/chrome/content/nixos-gui/myviewer.xul b/gui/chrome/content/nixos-gui/myviewer.xul
deleted file mode 100644
index c0c2bd6f822..00000000000
--- a/gui/chrome/content/nixos-gui/myviewer.xul
+++ /dev/null
@@ -1,30 +0,0 @@
-<?xml version="1.0"?>
-<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
-
-<!DOCTYPE window>
-
-<!-- To edit this file I recommend you to use: 
-     http://xulfr.org/outils/xulediteur.xul
-  -->
-
-<window
-  id     = "nixos-gui"
-  title  = "NixOS gui"
-  xmlns  = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-  <script src="jquery-1.3.2.js"/>
-  <script src="treeView.js"/>
-  <script src="main.js"/>
-  <script src="io.js"/>
-  <tree flex="1" id="option-list" persist="height">
-    <treecols>
-      <treecol persist="hidden width" flex="1" id="opt-success" label="Success"/>
-      <splitter class="tree-splitter"/>
-      <treecol persist="hidden width" flex="30" id="opt-name" label="Option"/>
-      <splitter class="tree-splitter"/>
-      <treecol persist="hidden width" flex="50" id="opt-desc" label="Description"
-               primary="true"/>
-    </treecols>
-    <treechildren id="first-child" flex="1"/>
-  </tree>
-  <progressmeter id="progress-bar" value="0%"/>
-</window>
diff --git a/gui/chrome/content/nixos-gui/treeView.js b/gui/chrome/content/nixos-gui/treeView.js
deleted file mode 100644
index 8ab7c875e68..00000000000
--- a/gui/chrome/content/nixos-gui/treeView.js
+++ /dev/null
@@ -1,117 +0,0 @@
-// Taken from pageInfo.js
-
-//******** define a js object to implement nsITreeView
-function treeView(columnids, copycol)
-{
-  // columnids is an array of strings indicating the names of the columns, in order
-  this.columnids = columnids;
-  this.colcount = columnids.length;
-
-  // copycol is the index number for the column that we want to add to
-  // the copy-n-paste buffer when the user hits accel-c
-  this.copycol = copycol;
-  this.rows = 0;
-  this.tree = null;
-  this.data = [ ];
-  this.selection = null;
-  this.sortcol = null;
-  this.sortdir = 0;
-}
-
-treeView.prototype = {
-  set rowCount(c) { throw "rowCount is a readonly property"; },
-  get rowCount() { return this.rows; },
-
-  setTree: function(tree)
-  {
-    this.tree = tree;
-  },
-
-  getCellText: function(row, column)
-  {
-    // row can be null, but js arrays are 0-indexed.
-    // colidx cannot be null, but can be larger than the number
-    // of columns in the array (when column is a string not in
-    // this.columnids.) In this case it's the fault of
-    // whoever typoed while calling this function.
-    return this.data[row][column.index] || "";
-  },
-
-  setCellValue: function(row, column, value)
-  {
-  },
-
-  setCellText: function(row, column, value)
-  {
-    this.data[row][column.index] = value;
-  },
-
-  addRow: function(row)
-  {
-    this.rows = this.data.push(row);
-    this.rowCountChanged(this.rows - 1, 1);
-  },
-
-  addRows: function(rows)
-  {
-    var length = rows.length;
-    for(var i = 0; i < length; i++)
-      this.rows = this.data.push(rows[i]);
-    this.rowCountChanged(this.rows - length, length);
-  },
-
-  rowCountChanged: function(index, count)
-  {
-    this.tree.rowCountChanged(index, count);
-  },
-
-  invalidate: function()
-  {
-    this.tree.invalidate();
-  },
-
-  clear: function()
-  {
-    if (this.tree)
-      this.tree.rowCountChanged(0, -this.rows);
-    this.rows = 0;
-    this.data = [ ];
-  },
-
-  handleCopy: function(row)
-  {
-    return (row < 0 || this.copycol < 0) ? "" : (this.data[row][this.copycol] || "");
-  },
-
-  performActionOnRow: function(action, row)
-  {
-    if (action == "copy") {
-      var data = this.handleCopy(row)
-      this.tree.treeBody.parentNode.setAttribute("copybuffer", data);
-    }
-  },
-
-  getRowProperties: function(row, prop) { },
-  getCellProperties: function(row, column, prop) { },
-  getColumnProperties: function(column, prop) { },
-  isContainer: function(index) { return false; },
-  isContainerOpen: function(index) { return false; },
-  isSeparator: function(index) { return false; },
-  isSorted: function() { },
-  canDrop: function(index, orientation) { return false; },
-  drop: function(row, orientation) { return false; },
-  getParentIndex: function(index) { return 0; },
-  hasNextSibling: function(index, after) { return false; },
-  getLevel: function(index) { return 0; },
-  getImageSrc: function(row, column) { },
-  getProgressMode: function(row, column) { },
-  getCellValue: function(row, column) { },
-  toggleOpenState: function(index) { },
-  cycleHeader: function(col) { },
-  selectionChanged: function() { },
-  cycleCell: function(row, column) { },
-  isEditable: function(row, column) { return false; },
-  isSelectable: function(row, column) { return false; },
-  performAction: function(action) { },
-  performActionOnCell: function(action, row, column) { }
-};
diff --git a/gui/chrome/content/nixos.js b/gui/chrome/content/nixos.js
new file mode 100644
index 00000000000..411dc844c4f
--- /dev/null
+++ b/gui/chrome/content/nixos.js
@@ -0,0 +1,205 @@
+
+function NixOS () {
+  var env = Components.classes["@mozilla.org/process/environment;1"].
+    getService(Components.interfaces.nsIEnvironment);
+
+  if (env.exists("NIXOS"))
+    this.nixos = env.get("NIXOS");
+  if (env.exists("NIXOS_CONFIG"))
+    this.config = env.get("NIXOS_CONFIG");
+  if (env.exists("NIXPKGS"))
+    this.nixpkgs = env.get("NIXPKGS");
+  if (env.exists("mountPoint"))
+    this.root = env.get("mountPoint");
+  if (env.exists("NIXOS_OPTION"))
+    this.optionBin = env.get("NIXOS_OPTION");
+  this.option = new Option("options", this, null);
+};
+
+NixOS.prototype = {
+  root: "",
+  nixos: "/etc/nixos/nixos",
+  nixpkgs: "/etc/nixos/nixpkgs",
+  config: "/etc/nixos/configuration.nix",
+  instantiateBin: "/var/run/current-system/sw/bin/nix-instantiate",
+  optionBin: "/var/run/current-system/sw/bin/nixos-option",
+  tmpFile: "nixos-gui",
+  option: null
+};
+
+function Option (name, context, parent) {
+  this.name = name;
+  this.context_ = context;
+  if (parent == null)
+    this.path = "";
+  else if (parent.path == "")
+    this.path = name;
+  else
+    this.path = parent.path + "." + name;
+};
+
+Option.prototype = {
+  load: function () {
+    var env = "";
+    env += "'NIXOS=" + this.context_.root + this.context_.nixos + "' ";
+    env += "'NIXOS_PKGS=" + this.context_.root + this.context_.nixpkgs + "' ";
+    env += "'NIXOS_CONFIG=" + this.context_.config + "' ";
+    var out = makeTempFile(this.context_.tmpFile);
+    var prog = this.context_.instantiateBin + " 2>&1 >" + out.path + " ";
+    var args = "";
+    args += " -A eval.options" + (this.path != "" ? "." : "") + this.path;
+    args += " --eval-only --xml --no-location";
+    args += " '" + this.context_.root + this.context_.nixos + "'";
+
+    runProgram(/*env +*/ prog + args);
+    var xml = readFromFile(out);
+    out.remove(false);
+
+    // jQuery does a stack overflow when converting a huge XML to a DOM.
+    var dom = DOMParser().parseFromString(xml, "text/xml");
+    var xmlAttrs = $("attr", dom);
+
+    this.isOption = xmlAttrs
+      .filter (
+        function (idx) {
+          return $(this).attr("name") == "_type";
+          // !!! We could not rely on the value of the attribute because it
+          // !!! may be unevaluated.
+          // $(this).children("string[value='option']").length != 0;
+        })
+      .length != 0;
+
+    if (!this.isOption)
+    {
+      var cur = this;
+      var attrs = new Array();
+
+      xmlAttrs.each(
+        function (index) {
+          var name = $(this).attr("name");
+          var attr = new Option(name, cur.context_, cur);
+          attrs.push(attr);
+        }
+      );
+
+      this.subOptions = attrs;
+    }
+    else
+    {
+      this.loadDesc();
+      // TODO: handle sub-options here.
+    }
+    this.isLoaded = true;
+  },
+
+  loadDesc:  function () {
+    var env = "";
+    env += "'NIXOS=" + this.context_.root + this.context_.nixos + "' ";
+    env += "'NIXOS_PKGS=" + this.context_.root + this.context_.nixpkgs + "' ";
+    env += "'NIXOS_CONFIG=" + this.context_.config + "' ";
+    var out = makeTempFile(this.context_.tmpFile);
+    var prog = this.context_.optionBin + " 2>&1 >" + out.path + " ";
+    var args = " -vdl " + this.path;
+
+    runProgram(/*env + */ prog + args);
+    this.description = readFromFile(out);
+    out.remove(false);
+  },
+
+  // keep the context under which this option has been used.
+  context_: null,
+  // name of the option.
+  name: "",
+  // result of nixos-option.
+  description: "",
+  // path to reach this option
+  path: "",
+
+  // list of options accessible from here.
+  isLoaded: false,
+  isOption: false,
+  subOptions: []
+};
+
+
+/*
+// Pretty print Nix values.
+function nixPP(value, level)
+{
+  function indent(level) {  ret = ""; while (level--) ret+= "  "; return ret; }
+
+  if (!level) level = 0;
+  var ret = "<no match>";
+  if (value.is("attrs")) {
+    var content = "";
+    value.children().each(function (){
+      var name = $(this).attr("name");
+      var value = nixPP($(this).children(), level + 1);
+      content += indent(level + 1) + name + " = " + value + ";\n";
+    });
+    ret = "{\n" + content + indent(level) + "}";
+  }
+  else if (value.is("list")) {
+    var content = "";
+    value.children().each(function (){
+      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
+    });
+    ret = "[\n" + content + indent(level) + "]";
+  }
+  else if (value.is("bool"))
+    ret = (value.attr("value") == "true");
+  else if (value.is("string"))
+    ret = '"' + value.attr("value") + '"';
+  else if (value.is("path"))
+    ret = value.attr("value");
+  else if (value.is("int"))
+    ret = parseInt(value.attr("value"));
+  else if (value.is("derivation"))
+    ret = value.attr("outPath");
+  else if (value.is("function"))
+    ret = "<function>";
+  else {
+    var content = "";
+    value.children().each(function (){
+      content += indent(level + 1) + "(" + nixPP($(this), level + 1) + ")\n";
+    });
+    ret = "<!--" + value.selector + "--><!--\n" + content + indent(level) + "-->";
+  }
+  return ret;
+}
+
+// Function used to reproduce the select operator on the XML DOM.
+// It return the value contained in the targeted attribute.
+function nixSelect(attrs, selector)
+{
+  var names = selector.split(".");
+  var value = $(attrs);
+  for (var i = 0; i < names.length; i++) {
+    log(nixPP(value) + "." + names[i]);
+    if (value.is("attrs"))
+      value = value.children("attr[name='" + names[i] + "']").children();
+    else {
+      log("Cannot do an attribute selection.");
+      break;
+    }
+  }
+
+  log("nixSelect return: " + nixPP(value));
+
+  var ret;
+  if (value.is("attrs") || value.is("list"))
+    ret = value;
+  else if (value.is("bool"))
+    ret = value.attr("value") == "true";
+  else if (value.is("string"))
+    ret = value.attr("value");
+  else if (value.is("int"))
+    ret = parseInt(value.attr("value"));
+  else if (value.is("derivation"))
+    ret = value.attr("outPath");
+  else if (value.is("function"))
+    ret = "<function>";
+
+  return ret;
+}
+*/
\ No newline at end of file
diff --git a/gui/chrome/content/optionView.js b/gui/chrome/content/optionView.js
new file mode 100644
index 00000000000..8e04e282828
--- /dev/null
+++ b/gui/chrome/content/optionView.js
@@ -0,0 +1,233 @@
+// extend NixOS options to handle the Tree View.  Should be better to keep a
+// separation of concern here.
+
+Option.prototype.tv_opened = false;
+Option.prototype.tv_size = 1;
+
+Option.prototype.tv_open = function () {
+  this.tv_opened = true;
+  this.tv_size = 1;
+
+  // load an option if it is not loaded yet, and initialize them to be
+  // read by the Option view.
+  if (!this.isLoaded)
+    this.load();
+
+  // If this is not an option, then add it's lits of sub-options size.
+  if (!this.isOption)
+  {
+    for (var i = 0; i < this.subOptions.length; i++)
+      this.tv_size += this.subOptions[i].tv_size;
+  }
+};
+
+Option.prototype.tv_close = function () {
+  this.tv_opened = false;
+  this.tv_size = 1;
+};
+
+
+
+
+function OptionView (root, selCallback) {
+  root.tv_open();
+  this.rootOption = root;
+  this.selCallback = selCallback;
+}
+
+OptionView.prototype = {
+  rootOption: null,
+  selCallback: null,
+
+  // This function returns the path to option which is at the specified row.
+  reach_cache: null,
+  reachRow: function (row) {
+    var o = this.rootOption; // Current option.
+    var r = 0; // Number of rows traversed.
+    var c = 0; // Child index.
+    var path = [{ row: r, opt: o }]; // new Array();
+    // hypothesis: this.rootOption.tv_size is always open and bigger than
+
+    // Use the previous returned value to avoid making to many checks and to
+    // optimize for frequent access of near rows.
+    if (this.reach_cache != null)
+    {
+      for (var i = this.reach_cache.length - 2; i >= 0; i--) {
+        var p = this.reach_cache[i];
+        // If we will have to go the same path.
+        if (row >= p.row && row < p.row + p.opt.tv_size)
+        {
+          path.unshift(p);
+          r = path[0].row;
+          o = path[0].opt;
+        }
+        else
+          break;
+      };
+    }
+
+    while (r != row)
+    {
+      // Go deeper in the child which contains the requested row.  The
+      // tv_size contains the size of the tree starting from each option.
+      c = 0;
+      while (c < o.subOptions.length && r + o.subOptions[c].tv_size < row)
+      {
+        r += o.subOptions[c].tv_size;
+        c += 1;
+      }
+      if (c < o.subOptions.length && r + o.subOptions[c].tv_size >= row)
+      {
+        // Count the current option as a row.
+        o = o.subOptions[c];
+        r += 1;
+      }
+      else
+        alert("WTF: " + o.name + " ask: " + row + " children: " + o.subOptions + " c: " + c);
+      path.unshift({ row: r, opt: o });
+    }
+
+    this.reach_cache = path;
+    return path;
+  },
+
+  // needs to return true if there is a /row/ at the same level /after/ a
+  // given row.
+  hasNextSibling: function(row, after) {
+    log("sibling " + row + " after " + after);
+    var path = reachRow(row);
+    if (path.length > 1)
+    {
+      var last = path[1].row + path[1].opt.tv_size;
+      // Has a next sibling if the row is not over the size of the
+      // parent and if the current one is not the last child.
+      return after + 1 < last && path[0].row + path[0].opt.tv_size < last;
+    }
+    else
+      // The top-level option has no sibling.
+      return false;
+  },
+
+  // Does the current row contain any sub-options?
+  isContainer: function(row) {
+    return !this.reachRow(row)[0].opt.isOption;
+  },
+  isContainerEmpty: function(row) {
+    return this.reachRow(row)[0].opt.subOptions.length == 0;
+  },
+  isContainerOpen: function(row) {
+    return this.reachRow(row)[0].opt.tv_opened;
+  },
+
+  // Open or close an option.
+  toggleOpenState: function (row) {
+    var path = this.reachRow(row);
+    var delta = -path[0].opt.tv_size;
+    if (path[0].opt.tv_opened)
+      path[0].opt.tv_close();
+    else
+      path[0].opt.tv_open();
+    delta += path[0].opt.tv_size;
+
+    // Parents are alreay opened, but we need to update the tv_size
+    // counters.  Thus we have to invalidate the reach cache.
+    this.reach_cache = null;
+    for (var i = 1; i < path.length; i++)
+      path[i].opt.tv_open();
+
+    this.tree.rowCountChanged(row + 1, delta);
+  },
+
+  // Return the identation level of the option at the line /row/.  The
+  // top-level level is 0.
+  getLevel: function(row) {
+    return this.reachRow(row).length - 1;
+  },
+
+  // Obtain the index of a parent row. If there is no parent row,
+  // returns -1.
+  getParentIndex: function(row) {
+    var path = this.reachRow(row);
+    if (path.length > 1)
+      return path[1].row;
+    else
+      return -1;
+  },
+
+
+  // Return the content of each row base on the column name.
+  getCellText: function(row, column) {
+    if (column.id == "opt-name")
+      return this.reachRow(row)[0].opt.name;
+    if (column.id == "dbg-size")
+      return this.reachRow(row)[0].opt.tv_size;
+    return "";
+  },
+
+  // We have no column with images.
+  getCellValue: function(row, column) { },
+
+
+  isSelectable: function(row, column) { return true; },
+
+  // Get the selection out of the tree and give options to the call back
+  // function.
+  selectionChanged: function() {
+    if (this.selCallback == null)
+      return;
+    var opts = [];
+    var start = new Object();
+    var end = new Object();
+    var numRanges = this.tree.view.selection.getRangeCount();
+
+    for (var t = 0; t < numRanges; t++) {
+      this.tree.view.selection.getRangeAt(t,start,end);
+      for (var v = start.value; v <= end.value; v++) {
+        var opt = this.reachRow(v)[0].opt;
+        if (!opt.isLoaded)
+          opt.load();
+        if (opt.isOption)
+          opts.push(opt);
+      }
+    }
+
+    if (opts.lenght != 0)
+      this.selCallback(opts);
+  },
+
+  set rowCount(c) { throw "rowCount is a readonly property"; },
+  get rowCount() { return this.rootOption.tv_size; },
+
+  // refuse drag-n-drop of options.
+  canDrop: function (index, orientation, dataTransfer) { return false; },
+  drop: function (index, orientation, dataTransfer) { },
+
+  // ?
+  getCellProperties: function(row, column, prop) { },
+  getColumnProperties: function(column, prop) { },
+  getRowProperties: function(row, prop) { },
+  getImageSrc: function(row, column) { },
+
+  // No progress columns are used.
+  getProgressMode: function(row, column) { },
+
+  // Do not add options yet.
+  isEditable: function(row, column) { return false; },
+  setCellValue: function(row, column, value) { },
+  setCellText: function(row, column, value) { },
+
+  // ...
+  isSeparator: function(index) { return false; },
+  isSorted: function() { return false; },
+  performAction: function(action) { },
+  performActionOnCell: function(action, row, column) { },
+  performActionOnRow: function(action, row) { }, // ??
+
+  // ??
+  cycleCell: function (row, col) { },
+  cycleHeader: function(col) { },
+
+  selection: null,
+  tree: null,
+  setTree: function(tree) { this.tree = tree; }
+};