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 /* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ft=javascript ts=2 et sw=2 tw=80: */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 "use strict";

 const EventEmitter = require("devtools/toolkit/event-emitter");

 const { Cu, Ci } = require("chrome");

 const { ViewHelpers } = Cu.import("resource:///modules/devtools/ViewHelpers.jsm", {});

 /**

  * A list menu widget that attempts to be very fast.

  *

  * Note: this widget should be used in tandem with the WidgetMethods in

  * ViewHelpers.jsm.

  *

  * @param nsIDOMNode aNode

  *        The element associated with the widget.

  */

 const FastListWidget = module.exports = function FastListWidget(aNode) {

   this.document = aNode.ownerDocument;

   this.window = this.document.defaultView;

   this._parent = aNode;

   this._fragment = this.document.createDocumentFragment();

   // This is a prototype element that each item added to the list clones.

   this._templateElement = this.document.createElement("hbox");

   // Create an internal scrollbox container.

   this._list = this.document.createElement("scrollbox");

   this._list.className = "fast-list-widget-container theme-body";

   this._list.setAttribute("flex", "1");

   this._list.setAttribute("orient", "vertical");

   this._list.setAttribute("tabindex", "0");

   this._list.addEventListener("keypress", e => this.emit("keyPress", e), false);

   this._list.addEventListener("mousedown", e => this.emit("mousePress", e), false);

   this._parent.appendChild(this._list);

   this._orderedMenuElementsArray = [];

   this._itemsByElement = new Map();

   // This widget emits events that can be handled in a MenuContainer.

   EventEmitter.decorate(this);

   // Delegate some of the associated node's methods to satisfy the interface

   // required by MenuContainer instances.

   ViewHelpers.delegateWidgetAttributeMethods(this, aNode);

   ViewHelpers.delegateWidgetEventMethods(this, aNode);

 }

 FastListWidget.prototype = {

   /**

    * Inserts an item in this container at the specified index, optionally

    * grouping by name.

    *

    * @param number aIndex

    *        The position in the container intended for this item.

    * @param nsIDOMNode aContents

    *        The node to be displayed in the container.

    * @param Object aAttachment [optional]

    *        Extra data for the user.

    * @return nsIDOMNode

    *         The element associated with the displayed item.

    */

   insertItemAt: function(aIndex, aContents, aAttachment={}) {

     let element = this._templateElement.cloneNode();

     element.appendChild(aContents);

     if (aIndex >= 0) {

       throw new Error("FastListWidget only supports appending items.");

     }

     this._fragment.appendChild(element);

     this._orderedMenuElementsArray.push(element);

     this._itemsByElement.set(element, this);

     return element;

   },

   /**

    * This is a non-standard widget implementation method. When appending items,

    * they are queued in a document fragment. This method appends the document

    * fragment to the dom.

    */

   flush: function() {

     this._list.appendChild(this._fragment);

   },

   /**

    * Removes all of the child nodes from this container.

    */

   removeAllItems: function() {

     let parent = this._parent;

     let list = this._list;

     while (list.hasChildNodes()) {

       list.firstChild.remove();

     }

     this._selectedItem = null;

     this._orderedMenuElementsArray.length = 0;

     this._itemsByElement.clear();

   },

   /**

    * Remove the given item.

    */

   removeChild: function(child) {

     throw new Error("Not yet implemented");

   },

   /**

    * Gets the currently selected child node in this container.

    * @return nsIDOMNode

    */

   get selectedItem() {

     return this._selectedItem;

   },

   /**

    * Sets the currently selected child node in this container.

    * @param nsIDOMNode child

    */

   set selectedItem(child) {

     let menuArray = this._orderedMenuElementsArray;

     if (!child) {

       this._selectedItem = null;

     }

     for (let node of menuArray) {

       if (node == child) {

         node.classList.add("selected");

         this._selectedItem = node;

       } else {

         node.classList.remove("selected");

       }

     }

     this.ensureElementIsVisible(this.selectedItem);

   },

   /**

    * Returns the child node in this container situated at the specified index.

    *

    * @param number index

    *        The position in the container intended for this item.

    * @return nsIDOMNode

    *         The element associated with the displayed item.

    */

   getItemAtIndex: function(index) {

     return this._orderedMenuElementsArray[index];

   },

   /**

    * Adds a new attribute or changes an existing attribute on this container.

    *

    * @param string name

    *        The name of the attribute.

    * @param string value

    *        The desired attribute value.

    */

   setAttribute: function(name, value) {

     this._parent.setAttribute(name, value);

     if (name == "emptyText") {

       this._textWhenEmpty = value;

     }

   },

   /**

    * Removes an attribute on this container.

    *

    * @param string name

    *        The name of the attribute.

    */

   removeAttribute: function(name) {

     this._parent.removeAttribute(name);

     if (name == "emptyText") {

       this._removeEmptyText();

     }

   },

   /**

    * Ensures the specified element is visible.

    *

    * @param nsIDOMNode element

    *        The element to make visible.

    */

   ensureElementIsVisible: function(element) {

     if (!element) {

       return;

     }

     // Ensure the element is visible but not scrolled horizontally.

     let boxObject = this._list.boxObject.QueryInterface(Ci.nsIScrollBoxObject);

     boxObject.ensureElementIsVisible(element);

     boxObject.scrollBy(-this._list.clientWidth, 0);

   },

   /**

    * Sets the text displayed in this container when empty.

    * @param string aValue

    */

   set _textWhenEmpty(aValue) {

     if (this._emptyTextNode) {

       this._emptyTextNode.setAttribute("value", aValue);

     }

     this._emptyTextValue = aValue;

     this._showEmptyText();

   },

   /**

    * Creates and appends a label signaling that this container is empty.

    */

   _showEmptyText: function() {

     if (this._emptyTextNode || !this._emptyTextValue) {

       return;

     }

     let label = this.document.createElement("label");

     label.className = "plain fast-list-widget-empty-text";

     label.setAttribute("value", this._emptyTextValue);

     this._parent.insertBefore(label, this._list);

     this._emptyTextNode = label;

   },

   /**

    * Removes the label signaling that this container is empty.

    */

   _removeEmptyText: function() {

     if (!this._emptyTextNode) {

       return;

     }

     this._parent.removeChild(this._emptyTextNode);

     this._emptyTextNode = null;

   },

   window: null,

   document: null,

   _parent: null,

   _list: null,

   _selectedItem: null,

   _orderedMenuElementsArray: null,

   _itemsByElement: null,

   _emptyTextNode: null,

   _emptyTextValue: ""

 };