Allow source to be set after layer construction

src/ol/control/attributioncontrol.js

@@ -169,6 +169,9 @@ ol.control.Attribution.prototype.getSourceAttributions = function(frameState) {
   var hiddenAttributions = {};
   for (i = 0, ii = layerStatesArray.length; i < ii; i++) {
     source = layerStatesArray[i].layer.getSource();
+    if (goog.isNull(source)) {
+      continue;
+    }
     sourceKey = goog.getUid(source).toString();
     sourceAttributions = source.getAttributions();
     if (goog.isNull(sourceAttributions)) {

src/ol/layer/imagelayer.js

@@ -15,10 +15,11 @@ goog.require('ol.layer.Layer');
  * @constructor
  * @extends {ol.layer.Layer}
  * @fires ol.render.Event
- * @param {olx.layer.ImageOptions} options Layer options.
+ * @param {olx.layer.ImageOptions=} opt_options Layer options.
  * @api stable
  */
-ol.layer.Image = function(options) {
+ol.layer.Image = function(opt_options) {
+  var options = goog.isDef(opt_options) ? opt_options : {};
   goog.base(this,  /** @type {olx.layer.LayerOptions} */ (options));
 };
 goog.inherits(ol.layer.Image, ol.layer.Layer);

src/ol/layer/layer.js

@@ -7,6 +7,7 @@ goog.require('goog.object');
 goog.require('ol.Object');
 goog.require('ol.layer.Base');
 goog.require('ol.layer.LayerProperty');
+goog.require('ol.source.State');
 
 
 
@@ -42,7 +43,8 @@ ol.layer.Layer = function(options) {
       ol.Object.getChangeEventType(ol.layer.LayerProperty.SOURCE),
       this.handleSourcePropertyChange_, false, this);
 
-  this.setSource(options.source);
+  var source = goog.isDef(options.source) ? options.source : null;
+  this.setSource(source);
 };
 goog.inherits(ol.layer.Layer, ol.layer.Base);
 
@@ -83,7 +85,7 @@ ol.layer.Layer.prototype.getLayerStatesArray = function(opt_states) {
 
 /**
  * Get the layer source.
- * @return {ol.source.Source} Source.
+ * @return {ol.source.Source} The layer source (or `null` if not yet set).
  * @observable
  * @api stable
  */
@@ -102,7 +104,14 @@ goog.exportProperty(
   * @inheritDoc
   */
 ol.layer.Layer.prototype.getSourceState = function() {
-  return this.getSource().getState();
+  var source = this.getSource();
+  var state;
+  if (!goog.isNull(source)) {
+    state = source.getState();
+  } else {
+    state = ol.source.State.UNDEFINED;
+  }
+  return state;
 };
 
 

src/ol/layer/tilelayer.js

@@ -24,10 +24,11 @@ ol.layer.TileProperty = {
  * @constructor
  * @extends {ol.layer.Layer}
  * @fires ol.render.Event
- * @param {olx.layer.TileOptions} options Tile layer options.
+ * @param {olx.layer.TileOptions=} opt_options Tile layer options.
  * @api stable
  */
-ol.layer.Tile = function(options) {
+ol.layer.Tile = function(opt_options) {
+  var options = goog.isDef(opt_options) ? opt_options : {};
   goog.base(this,  /** @type {olx.layer.LayerOptions} */ (options));
 };
 goog.inherits(ol.layer.Tile, ol.layer.Layer);

src/ol/renderer/dom/domimagelayerrenderer.js

@@ -69,6 +69,15 @@ ol.renderer.dom.ImageLayer.prototype.forEachFeatureAtPixel =
 };
 
 
+/**
+ * @inheritDoc
+ */
+ol.renderer.dom.ImageLayer.prototype.clearFrame = function() {
+  goog.dom.removeChildren(this.target);
+  this.image_ = null;
+};
+
+
 /**
  * @inheritDoc
  */

src/ol/renderer/dom/domlayerrenderer.js

@@ -27,6 +27,12 @@ ol.renderer.dom.Layer = function(mapRenderer, layer, target) {
 goog.inherits(ol.renderer.dom.Layer, ol.renderer.Layer);
 
 
+/**
+ * Clear rendered elements.
+ */
+ol.renderer.dom.Layer.prototype.clearFrame = goog.nullFunction;
+
+
 /**
  * @param {olx.FrameState} frameState Frame state.
  * @param {ol.layer.LayerState} layerState Layer state.

src/ol/renderer/dom/dommaprenderer.js

@@ -244,6 +244,8 @@ ol.renderer.dom.Map.prototype.renderFrame = function(frameState) {
       if (layerRenderer.prepareFrame(frameState, layerState)) {
         layerRenderer.composeFrame(frameState, layerState);
       }
+    } else {
+      layerRenderer.clearFrame();
     }
   }
 

src/ol/renderer/dom/domtilelayerrenderer.js

@@ -74,6 +74,15 @@ ol.renderer.dom.TileLayer = function(mapRenderer, tileLayer) {
 goog.inherits(ol.renderer.dom.TileLayer, ol.renderer.dom.Layer);
 
 
+/**
+ * @inheritDoc
+ */
+ol.renderer.dom.TileLayer.prototype.clearFrame = function() {
+  goog.dom.removeChildren(this.target);
+  this.renderedRevision_ = 0;
+};
+
+
 /**
  * @inheritDoc
  */

src/ol/source/source.js

@@ -9,11 +9,12 @@ goog.require('ol.proj');
 
 
 /**
- * State of the source, one of 'loading', 'ready' or 'error'.
+ * State of the source, one of 'undefined', 'loading', 'ready' or 'error'.
  * @enum {string}
  * @api
  */
 ol.source.State = {
+  UNDEFINED: 'undefined',
   LOADING: 'loading',
   READY: 'ready',
   ERROR: 'error'