gecko-dev/browser/base/content/socialchat.xml

<?xml version="1.0"?>

<bindings id="socialChatBindings"
    xmlns="http://www.mozilla.org/xbl"
    xmlns:xbl="http://www.mozilla.org/xbl"
    xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <binding id="chatbox">
    <content orient="vertical" mousethrough="never">
      <xul:hbox class="chat-titlebar" xbl:inherits="minimized,selected,activity" align="baseline">
        <xul:hbox flex="1" onclick="document.getBindingParent(this).onTitlebarClick(event);">
          <xul:image class="chat-status-icon" xbl:inherits="src=image"/>
          <xul:label class="chat-title" flex="1" xbl:inherits="value=label" crop="center"/>
        </xul:hbox>
        <xul:toolbarbutton anonid="notification-icon" class="notification-anchor-icon chat-toolbarbutton"
                           oncommand="document.getBindingParent(this).showNotifications(); event.stopPropagation();"/>
        <xul:toolbarbutton anonid="minimize" class="chat-minimize-button chat-toolbarbutton"
                           oncommand="document.getBindingParent(this).toggle();"/>
        <xul:toolbarbutton anonid="swap" class="chat-swap-button chat-toolbarbutton"
                           oncommand="document.getBindingParent(this).swapWindows();"/>
        <xul:toolbarbutton anonid="close" class="chat-close-button chat-toolbarbutton"
                           oncommand="document.getBindingParent(this).close();"/>
      </xul:hbox>
      <xul:browser anonid="content" class="chat-frame" flex="1"
                  context="contentAreaContextMenu"
                  disableglobalhistory="true"
                  tooltip="aHTMLTooltip"
                  xbl:inherits="src,origin" type="content"/>
    </content>

    <implementation implements="nsIDOMEventListener">
      <constructor><![CDATA[
        let Social = Components.utils.import("resource:///modules/Social.jsm", {}).Social;
        this.content.__defineGetter__("popupnotificationanchor",
                                      () => document.getAnonymousElementByAttribute(this, "anonid", "notification-icon"));
        Social.setErrorListener(this.content, function(aBrowser) {
          aBrowser.webNavigation.loadURI("about:socialerror?mode=compactInfo", null, null, null, null);
        });
        if (!this.chatbar) {
          document.getAnonymousElementByAttribute(this, "anonid", "minimize").hidden = true;
          document.getAnonymousElementByAttribute(this, "anonid", "close").hidden = true;
        }
        let contentWindow = this.contentWindow;
        this.addEventListener("DOMContentLoaded", function DOMContentLoaded(event) {
          if (event.target != this.contentDocument)
            return;
          this.removeEventListener("DOMContentLoaded", DOMContentLoaded, true);
          this.isActive = !this.minimized;
          // process this._callbacks, then set to null so the chatbox creator
          // knows to make new callbacks immediately.
          if (this._callbacks) {
            for (let callback of this._callbacks) {
              if (callback)
                callback(contentWindow);
            }
            this._callbacks = null;
          }

          // content can send a socialChatActivity event to have the UI update.
          let chatActivity = function() {
            this.setAttribute("activity", true);
            if (this.chatbar)
              this.chatbar.updateTitlebar(this);
          }.bind(this);
          contentWindow.addEventListener("socialChatActivity", chatActivity);
          contentWindow.addEventListener("unload", function unload() {
            contentWindow.removeEventListener("unload", unload);
            contentWindow.removeEventListener("socialChatActivity", chatActivity);
          });
        }, true);
        if (this.src)
          this.setAttribute("src", this.src);
      ]]></constructor>

      <field name="content" readonly="true">
        document.getAnonymousElementByAttribute(this, "anonid", "content");
      </field>

      <property name="contentWindow">
        <getter>
          return this.content.contentWindow;
        </getter>
      </property>

      <property name="contentDocument">
        <getter>
          return this.content.contentDocument;
        </getter>
      </property>

      <property name="minimized">
        <getter>
          return this.getAttribute("minimized") == "true";
        </getter>
        <setter><![CDATA[
          // Note that this.isActive is set via our transitionend handler so
          // the content doesn't see intermediate values.
          let parent = this.chatbar;
          if (val) {
            this.setAttribute("minimized", "true");
            // If this chat is the selected one a new one needs to be selected.
            if (parent && parent.selectedChat == this)
              parent._selectAnotherChat();
          } else {
            this.removeAttribute("minimized");
            // this chat gets selected.
            if (parent)
              parent.selectedChat = this;
          }
        ]]></setter>
      </property>

      <property name="chatbar">
        <getter>
          if (this.parentNode.nodeName == "chatbar")
            return this.parentNode;
          return null;
        </getter>
      </property>

      <property name="isActive">
        <getter>
          return this.content.docShell.isActive;
        </getter>
        <setter>
          this.content.docShell.isActive = !!val;

          // let the chat frame know if it is being shown or hidden
          let evt = this.contentDocument.createEvent("CustomEvent");
          evt.initCustomEvent(val ? "socialFrameShow" : "socialFrameHide", true, true, {});
          this.contentDocument.documentElement.dispatchEvent(evt);
        </setter>
      </property>
      
      <method name="showNotifications">
        <body><![CDATA[
        PopupNotifications._reshowNotifications(this.content.popupnotificationanchor,
                                                this.content);
        ]]></body>
      </method>

      <method name="swapDocShells">
        <parameter name="aTarget"/>
        <body><![CDATA[
          aTarget.setAttribute('label', this.contentDocument.title);
          aTarget.content.setAttribute("origin", this.content.getAttribute("origin"));
          aTarget.content.popupnotificationanchor.className = this.content.popupnotificationanchor.className;
          this.content.socialErrorListener.remove();
          aTarget.content.socialErrorListener.remove();
          this.content.swapDocShells(aTarget.content);
          Social.setErrorListener(this.content, function(aBrowser) {}); // 'this' will be destroyed soon.
          Social.setErrorListener(aTarget.content, function(aBrowser) {
            aBrowser.webNavigation.loadURI("about:socialerror?mode=compactInfo", null, null, null, null);
          });
        ]]></body>
      </method>

      <method name="onTitlebarClick">
        <parameter name="aEvent"/>
        <body><![CDATA[
          if (!this.chatbar)
            return;
          if (aEvent.button == 0) { // left-click: toggle minimized.
            this.toggle();
            // if we restored it, we want to focus it.
            if (!this.minimized)
              this.chatbar.focus();
          } else if (aEvent.button == 1) // middle-click: close chat
            this.close();
        ]]></body>
      </method>

      <method name="close">
        <body><![CDATA[
        if (this.chatbar)
          this.chatbar.remove(this);
        else
          window.close();
        ]]></body>
      </method>

      <method name="swapWindows">
        <body><![CDATA[
        let provider = Social._getProviderFromOrigin(this.content.getAttribute("origin"));
        if (this.chatbar) {
          this.chatbar.detachChatbox(this, { "centerscreen": "yes" }, win => {
            win.document.title = provider.name;
          });
        } else {
          // attach this chatbox to the topmost browser window
          let findChromeWindowForChats = Cu.import("resource://gre/modules/MozSocialAPI.jsm").findChromeWindowForChats;
          let win = findChromeWindowForChats();
          let chatbar = win.SocialChatBar.chatbar;
          chatbar.openChat(provider, "about:blank", win => {
            this.swapDocShells(chatbar.selectedChat);
            chatbar.focus();
            this.close();
          });
        }
        ]]></body>
      </method>

      <method name="toggle">
        <body><![CDATA[
          this.minimized = !this.minimized;
        ]]></body>
      </method>
    </implementation>

    <handlers>
      <handler event="focus" phase="capturing">
        if (this.chatbar)
          this.chatbar.selectedChat = this;
      </handler>
      <handler event="DOMTitleChanged"><![CDATA[
        this.setAttribute('label', this.contentDocument.title);
        if (this.chatbar)
          this.chatbar.updateTitlebar(this);
      ]]></handler>
      <handler event="DOMLinkAdded"><![CDATA[
        // much of this logic is from DOMLinkHandler in browser.js
        // this sets the presence icon for a chat user, we simply use favicon style updating
        let link = event.originalTarget;
        let rel = link.rel && link.rel.toLowerCase();
        if (!link || !link.ownerDocument || !rel || !link.href)
          return;
        if (link.rel.indexOf("icon") < 0)
          return;

        let uri = DOMLinkHandler.getLinkIconURI(link);
        if (!uri)
          return;

        // we made it this far, use it
        this.setAttribute('image', uri.spec);
        if (this.chatbar)
          this.chatbar.updateTitlebar(this);
      ]]></handler>
      <handler event="transitionend">
        if (this.isActive == this.minimized)
          this.isActive = !this.minimized;
      </handler>
    </handlers>
  </binding>

  <binding id="chatbar">
    <content>
      <xul:hbox align="end" pack="end" anonid="innerbox" class="chatbar-innerbox" mousethrough="always" flex="1">
        <xul:spacer flex="1" anonid="spacer" class="chatbar-overflow-spacer"/>
        <xul:toolbarbutton anonid="nub" class="chatbar-button" type="menu" collapsed="true" mousethrough="never">
          <xul:menupopup anonid="nubMenu" oncommand="document.getBindingParent(this).showChat(event.target.chat)"/>
        </xul:toolbarbutton>
        <children/>
      </xul:hbox>
    </content>

    <implementation implements="nsIDOMEventListener">
      <constructor>
        // to avoid reflows we cache the width of the nub.
        this.cachedWidthNub = 0;
        this._selectedChat = null;
      </constructor>

      <field name="innerbox" readonly="true">
        document.getAnonymousElementByAttribute(this, "anonid", "innerbox");
      </field>

      <field name="menupopup" readonly="true">
        document.getAnonymousElementByAttribute(this, "anonid", "nubMenu");
      </field>

      <field name="nub" readonly="true">
        document.getAnonymousElementByAttribute(this, "anonid", "nub");
      </field>

      <method name="focus">
        <body><![CDATA[
          if (!this.selectedChat)
            return;
          Services.focus.focusedWindow = this.selectedChat.contentWindow;
        ]]></body>
      </method>

      <method name="_isChatFocused">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          // If there are no XBL bindings for the chat it can't be focused.
          if (!aChatbox.content)
            return false;
          let fw = Services.focus.focusedWindow;
          if (!fw)
            return false;
          // We want to see if the focused window is in the subtree below our browser...
          let containingBrowser = fw.QueryInterface(Ci.nsIInterfaceRequestor)
                                    .getInterface(Ci.nsIWebNavigation)
                                    .QueryInterface(Ci.nsIDocShell)
                                    .chromeEventHandler;
          return containingBrowser == aChatbox.content;
        ]]></body>
      </method>

      <property name="selectedChat">
        <getter><![CDATA[
          return this._selectedChat;
        ]]></getter>
        <setter><![CDATA[
          // this is pretty horrible, but we:
          // * want to avoid doing touching 'selected' attribute when the
          //   specified chat is already selected.
          // * remove 'activity' attribute on newly selected tab *even if*
          //   newly selected is already selected.
          // * need to handle either current or new being null.
          if (this._selectedChat != val) {
            if (this._selectedChat) {
              this._selectedChat.removeAttribute("selected");
            }
            this._selectedChat = val;
            if (val) {
              this._selectedChat.setAttribute("selected", "true");
            }
          }
          if (val) {
            this._selectedChat.removeAttribute("activity");
          }
        ]]></setter>
      </property>

      <field name="menuitemMap">new WeakMap()</field>
      <field name="chatboxForURL">new Map();</field>

      <property name="hasCollapsedChildren">
        <getter><![CDATA[
          return !!this.querySelector("[collapsed]");
        ]]></getter>
      </property>

      <property name="collapsedChildren">
        <getter><![CDATA[
          // A generator yielding all collapsed chatboxes, in the order in
          // which they should be restored.
          let child = this.lastElementChild;
          while (child) {
            if (child.collapsed)
              yield child;
            child = child.previousElementSibling;
          }
        ]]></getter>
      </property>

      <property name="visibleChildren">
        <getter><![CDATA[
          // A generator yielding all non-collapsed chatboxes.
          let child = this.firstElementChild;
          while (child) {
            if (!child.collapsed)
              yield child;
            child = child.nextElementSibling;
          }
        ]]></getter>
      </property>

      <property name="collapsibleChildren">
        <getter><![CDATA[
          // A generator yielding all children which are able to be collapsed
          // in the order in which they should be collapsed.
          // (currently this is all visible ones other than the selected one.)
          for (let child of this.visibleChildren)
            if (child != this.selectedChat)
              yield child;
        ]]></getter>
      </property>

      <method name="_selectAnotherChat">
        <body><![CDATA[
          // Select a different chat (as the currently selected one is no
          // longer suitable as the selection - maybe it is being minimized or
          // closed.)  We only select non-minimized and non-collapsed chats,
          // and if none are found, set the selectedChat to null.
          // It's possible in the future we will track most-recently-selected
          // chats or similar to find the "best" candidate - for now though
          // the choice is somewhat arbitrary.
          let moveFocus = this.selectedChat && this._isChatFocused(this.selectedChat);
          for (let other of this.children) {
            if (other != this.selectedChat && !other.minimized && !other.collapsed) {
              this.selectedChat = other;
              if (moveFocus)
                this.focus();
              return;
            }
          }
          // can't find another - so set no chat as selected.
          this.selectedChat = null;
        ]]></body>
      </method>

      <method name="updateTitlebar">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          if (aChatbox.collapsed) {
            let menuitem = this.menuitemMap.get(aChatbox);
            if (aChatbox.getAttribute("activity")) {
              menuitem.setAttribute("activity", true);
              this.nub.setAttribute("activity", true);
            }
            menuitem.setAttribute("label", aChatbox.getAttribute("label"));
            menuitem.setAttribute("image", aChatbox.getAttribute("image"));
          }
        ]]></body>
      </method>

      <method name="calcTotalWidthOf">
        <parameter name="aElement"/>
        <body><![CDATA[
          let cs = document.defaultView.getComputedStyle(aElement);
          let margins = parseInt(cs.marginLeft) + parseInt(cs.marginRight);
          return aElement.getBoundingClientRect().width + margins;
        ]]></body>
      </method>

      <method name="getTotalChildWidth">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          // These are from the CSS for the chatbox and must be kept in sync.
          // We can't use calcTotalWidthOf due to the transitions...
          const CHAT_WIDTH_OPEN = 260;
          const CHAT_WIDTH_MINIMIZED = 160;
          return aChatbox.minimized ? CHAT_WIDTH_MINIMIZED : CHAT_WIDTH_OPEN;
        ]]></body>
      </method>

      <method name="collapseChat">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          // we ensure that the cached width for a child of this type is
          // up-to-date so we can use it when resizing.
          this.getTotalChildWidth(aChatbox);
          aChatbox.collapsed = true;
          aChatbox.isActive = false;
          let menu = document.createElementNS("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", "menuitem");
          menu.setAttribute("class", "menuitem-iconic");
          menu.setAttribute("label", aChatbox.contentDocument.title);
          menu.setAttribute("image", aChatbox.getAttribute("image"));
          menu.chat = aChatbox;
          this.menuitemMap.set(aChatbox, menu);
          this.menupopup.appendChild(menu);
          this.nub.collapsed = false;
        ]]></body>
      </method>

      <method name="showChat">
        <parameter name="aChatbox"/>
        <parameter name="aMode"/>
        <body><![CDATA[
          if ((aMode != "minimized") && aChatbox.minimized)
            aChatbox.minimized = false;
          if (this.selectedChat != aChatbox)
            this.selectedChat = aChatbox;
          if (!aChatbox.collapsed)
            return; // already showing - no more to do.
          this._showChat(aChatbox);
          // showing a collapsed chat might mean another needs to be collapsed
          // to make room...
          this.resize();
        ]]></body>
      </method>

      <method name="_showChat">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          // the actual implementation - doesn't check for overflow, assumes
          // collapsed, etc.
          let menuitem = this.menuitemMap.get(aChatbox);
          this.menuitemMap.delete(aChatbox);
          this.menupopup.removeChild(menuitem);
          aChatbox.collapsed = false;
          aChatbox.isActive = !aChatbox.minimized;
        ]]></body>
      </method>

      <method name="remove">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          this._remove(aChatbox);
          // The removal of a chat may mean a collapsed one can spring up,
          // or that the popup should be hidden.  We also defer the selection
          // of another chat until after a resize, as a new candidate may
          // become uncollapsed after the resize.
          this.resize();
          if (this.selectedChat == aChatbox) {
            this._selectAnotherChat();
          }
        ]]></body>
      </method>

      <method name="_remove">
        <parameter name="aChatbox"/>
        <body><![CDATA[
          aChatbox.content.socialErrorListener.remove();
          this.removeChild(aChatbox);
          // child might have been collapsed.
          let menuitem = this.menuitemMap.get(aChatbox);
          if (menuitem) {
            this.menuitemMap.delete(aChatbox);
            this.menupopup.removeChild(menuitem);
          }
          this.chatboxForURL.delete(aChatbox.getAttribute('src'));
        ]]></body>
      </method>

      <method name="removeAll">
        <body><![CDATA[
          this.selectedChat = null;
          while (this.firstElementChild) {
            this._remove(this.firstElementChild);
          }
          // and the nub/popup must also die.
          this.nub.collapsed = true;
        ]]></body>
      </method>

      <method name="openChat">
        <parameter name="aProvider"/>
        <parameter name="aURL"/>
        <parameter name="aCallback"/>
        <parameter name="aMode"/>
        <body><![CDATA[
          let cb = this.chatboxForURL.get(aURL);
          if (cb) {
            cb = cb.get();
            if (cb.parentNode) {
              this.showChat(cb, aMode);
              if (aCallback) {
                if (cb._callbacks == null) {
                  // DOMContentLoaded has already fired, so callback now.
                  aCallback(cb.contentWindow);
                } else {
                  // DOMContentLoaded for this chat is yet to fire...
                  cb._callbacks.push(aCallback);
                }
              }
              return;
            }
            this.chatboxForURL.delete(aURL);
          }
          cb = document.createElementNS("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", "chatbox");
          // _callbacks is a javascript property instead of a <field> as it
          // must exist before the (possibly delayed) bindings are created.
          cb._callbacks = [aCallback];
          // src also a javascript property; the src attribute is set in the ctor.
          cb.src = aURL;
          if (aMode == "minimized")
            cb.setAttribute("minimized", "true");
          cb.setAttribute("origin", aProvider.origin);
          this.insertBefore(cb, this.firstChild);
          this.selectedChat = cb;
          this.chatboxForURL.set(aURL, Cu.getWeakReference(cb));
          this.resize();
        ]]></body>
      </method>

      <method name="resize">
        <body><![CDATA[
        // Checks the current size against the collapsed state of children
        // and collapses or expands as necessary such that as many as possible
        // are shown.
        // So 2 basic strategies:
        // * Collapse/Expand one at a time until we can't collapse/expand any
        //   more - but this is one reflow per change.
        // * Calculate the dimensions ourself and choose how many to collapse
        //   or expand based on this, then do them all in one go.  This is one
        //   reflow regardless of how many we change.
        // So we go the more complicated but more efficient second option...
        let availWidth = this.getBoundingClientRect().width;
        let currentWidth = 0;
        if (!this.nub.collapsed) { // the nub is visible.
          if (!this.cachedWidthNub)
            this.cachedWidthNub = this.calcTotalWidthOf(this.nub);
          currentWidth += this.cachedWidthNub;
        }
        for (let child of this.visibleChildren) {
          currentWidth += this.getTotalChildWidth(child);
        }

        if (currentWidth > availWidth) {
          // we need to collapse some.
          let toCollapse = [];
          for (let child of this.collapsibleChildren) {
            if (currentWidth <= availWidth)
              break;
            toCollapse.push(child);
            currentWidth -= this.getTotalChildWidth(child);
          }
          if (toCollapse.length) {
            for (let child of toCollapse)
              this.collapseChat(child);
          }
        } else if (currentWidth < availWidth) {
          // we *might* be able to expand some - see how many.
          // XXX - if this was clever, it could know when removing the nub
          // leaves enough space to show all collapsed
          let toShow = [];
          for (let child of this.collapsedChildren) {
            currentWidth += this.getTotalChildWidth(child);
            if (currentWidth > availWidth)
              break;
            toShow.push(child);
          }
          for (let child of toShow)
            this._showChat(child);

          // If none remain collapsed remove the nub.
          if (!this.hasCollapsedChildren) {
            this.nub.collapsed = true;
          }
        }
        // else: achievement unlocked - we are pixel-perfect!
        ]]></body>
      </method>

      <method name="handleEvent">
        <parameter name="aEvent"/>
        <body><![CDATA[
          if (aEvent.type == "resize" && aEvent.eventPhase == aEvent.AT_TARGET) {
            this.resize();
          }
        ]]></body>
      </method>

      <method name="_getDragTarget">
        <parameter name="event"/>
        <body><![CDATA[
          return event.target.localName == "chatbox" ? event.target : null;
        ]]></body>
      </method>

      <!-- Moves a chatbox to a new window. -->
      <method name="detachChatbox">
        <parameter name="aChatbox"/>
        <parameter name="aOptions"/>
        <parameter name="aCallback"/>
        <body><![CDATA[
          let options = "";
          for (let name in aOptions)
            options += "," + name + "=" + aOptions[name];

          let otherWin = window.openDialog("chrome://browser/content/chatWindow.xul", null, "chrome,all" + options);

          otherWin.addEventListener("load", function _chatLoad(event) {
            if (event.target != otherWin.document)
              return;

            otherWin.removeEventListener("load", _chatLoad, true);
            let otherChatbox = otherWin.document.getElementById("chatter");
            aChatbox.swapDocShells(otherChatbox);
            aChatbox.close();
            if (aCallback)
              aCallback(otherWin);
          }, true);
        ]]></body>
      </method>

    </implementation>

    <handlers>
      <handler event="popupshown"><![CDATA[
        this.nub.removeAttribute("activity");
      ]]></handler>
      <handler event="load"><![CDATA[
        window.addEventListener("resize", this);
      ]]></handler>
      <handler event="unload"><![CDATA[
        window.removeEventListener("resize", this);
      ]]></handler>

      <handler event="dragstart"><![CDATA[
        // chat window dragging is essentially duplicated from tabbrowser.xml
        // to acheive the same visual experience
        let chatbox = this._getDragTarget(event);
        if (!chatbox) {
          return;
        }

        let dt = event.dataTransfer;
        // we do not set a url in the drag data to prevent moving to tabbrowser
        // or otherwise having unexpected drop handlers do something with our
        // chatbox
        dt.mozSetDataAt("application/x-moz-chatbox", chatbox, 0);

        // Set the cursor to an arrow during tab drags.
        dt.mozCursor = "default";

        // Create a canvas to which we capture the current tab.
        // Until canvas is HiDPI-aware (bug 780362), we need to scale the desired
        // canvas size (in CSS pixels) to the window's backing resolution in order
        // to get a full-resolution drag image for use on HiDPI displays.
        let windowUtils = window.getInterface(Ci.nsIDOMWindowUtils);
        let scale = windowUtils.screenPixelsPerCSSPixel / windowUtils.fullZoom;
        let canvas = document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
        canvas.mozOpaque = true;
        canvas.width = 160 * scale;
        canvas.height = 90 * scale;
        PageThumbs.captureToCanvas(chatbox.contentWindow, canvas);
        dt.setDragImage(canvas, -16 * scale, -16 * scale);

        event.stopPropagation();
      ]]></handler>

      <handler event="dragend"><![CDATA[
        let dt = event.dataTransfer;
        let draggedChat = dt.mozGetDataAt("application/x-moz-chatbox", 0);
        if (dt.mozUserCancelled || dt.dropEffect != "none") {
          return;
        }

        let eX = event.screenX;
        let eY = event.screenY;
        // screen.availLeft et. al. only check the screen that this window is on,
        // but we want to look at the screen the tab is being dropped onto.
        let sX = {}, sY = {}, sWidth = {}, sHeight = {};
        Cc["@mozilla.org/gfx/screenmanager;1"]
          .getService(Ci.nsIScreenManager)
          .screenForRect(eX, eY, 1, 1)
          .GetAvailRect(sX, sY, sWidth, sHeight);
        // default size for the chat window as used in chatWindow.xul, use them
        // here to attempt to keep the window fully within the screen when
        // opening at the drop point. If the user has resized the window to
        // something larger (which gets persisted), at least a good portion of
        // the window should still be within the screen.
        let winWidth = 400;
        let winHeight = 420;
        // ensure new window entirely within screen
        let left = Math.min(Math.max(eX, sX.value),
                            sX.value + sWidth.value - winWidth);
        let top = Math.min(Math.max(eY, sY.value),
                           sY.value + sHeight.value - winHeight);

        let provider = Social._getProviderFromOrigin(draggedChat.content.getAttribute("origin"));
        this.detachChatbox(draggedChat, { screenX: left, screenY: top }, win => {
          win.document.title = provider.name;
        });

        event.stopPropagation();
      ]]></handler>
    </handlers>
  </binding>

</bindings>