Make ol.style.Image loadable

src/ol/style/imagestyle.js

@@ -1,15 +1,36 @@
 // FIXME decide default value for snapToPixel
 
 goog.provide('ol.style.Image');
+goog.provide('ol.style.ImageState');
+
+goog.require('goog.array');
+goog.require('goog.asserts');
+goog.require('goog.events');
+goog.require('goog.events.EventTarget');
+goog.require('goog.events.EventType');
+
+
+/**
+ * @enum {number}
+ */
+ol.style.ImageState = {
+  IDLE: 0,
+  LOADING: 1,
+  LOADED: 2,
+  ERROR: 3
+};
 
 
 
 /**
  * @constructor
  * @param {ol.style.ImageOptions} options Options.
+ * @extends {goog.events.EventTarget}
  */
 ol.style.Image = function(options) {
 
+  goog.base(this);
+
   /**
    * @type {ol.Pixel}
    */
@@ -18,7 +39,17 @@ ol.style.Image = function(options) {
   /**
    * @type {HTMLCanvasElement|HTMLVideoElement|Image}
    */
-  this.image = options.image;
+  this.image = goog.isDefAndNotNull(options.image) ?
+      options.image : new Image();
+  if (!goog.isNull(options.crossOrigin)) {
+    this.image.crossOrigin = options.crossOrigin;
+  }
+
+  /**
+   * @type {ol.style.ImageState}
+   */
+  this.imageState = goog.isDef(options.imageState) ?
+      options.imageState : ol.style.ImageState.IDLE;
 
   /**
    * @type {number|undefined}
@@ -40,4 +71,80 @@ ol.style.Image = function(options) {
    */
   this.subtractViewRotation = options.subtractViewRotation;
 
+  /**
+   * @private
+   * @type {Array.<number>}
+   */
+  this.imageListenerKeys_ = null;
+
+  /**
+   * @private
+   * @type {string|undefined}
+   */
+  this.src_ = options.src;
+
+};
+goog.inherits(ol.style.Image, goog.events.EventTarget);
+
+
+/**
+ * @private
+ */
+ol.style.Image.prototype.dispatchChangeEvent_ = function() {
+  this.dispatchEvent(goog.events.EventType.CHANGE);
+};
+
+
+/**
+ * Tracks loading or read errors.
+ *
+ * @private
+ */
+ol.style.Image.prototype.handleImageError_ = function() {
+  this.imageState = ol.style.ImageState.ERROR;
+  this.unlistenImage_();
+  this.dispatchChangeEvent_();
+};
+
+
+/**
+ * Tracks successful image load.
+ *
+ * @private
+ */
+ol.style.Image.prototype.handleImageLoad_ = function() {
+  this.imageState = ol.style.ImageState.LOADED;
+  this.unlistenImage_();
+  this.dispatchChangeEvent_();
+};
+
+
+/**
+ * Load not yet loaded URI.
+ */
+ol.style.Image.prototype.load = function() {
+  if (this.imageState == ol.style.ImageState.IDLE) {
+    goog.asserts.assert(goog.isDef(this.src_));
+    goog.asserts.assert(goog.isNull(this.imageListenerKeys_));
+    this.imageState = ol.style.ImageState.LOADING;
+    this.imageListenerKeys_ = [
+      goog.events.listenOnce(this.image, goog.events.EventType.ERROR,
+          this.handleImageError_, false, this),
+      goog.events.listenOnce(this.image, goog.events.EventType.LOAD,
+          this.handleImageLoad_, false, this)
+    ];
+    this.image.src = this.src_;
+  }
+};
+
+
+/**
+ * Discards event handlers which listen for load completion or errors.
+ *
+ * @private
+ */
+ol.style.Image.prototype.unlistenImage_ = function() {
+  goog.asserts.assert(!goog.isNull(this.imageListenerKeys_));
+  goog.array.forEach(this.imageListenerKeys_, goog.events.unlistenByKey);
+  this.imageListenerKeys_ = null;
 };