Initial composite map renderer.

src/ol/renderer/Composite.js

@@ -0,0 +1,103 @@
+goog.provide('ol.renderer.Composite');
+
+goog.require('goog.dom');
+goog.require('ol.layer.Layer');
+goog.require('ol.Loc');
+
+/**
+ * @constructor
+ * @param {string|Element} target
+ */
+ol.renderer.Composite = function(target) {
+    
+    /**
+     * @type Element
+     * @private
+     */
+    this.target_ = goog.dom.getElement(target);
+    
+    /**
+     * @type Array.<ol.renderer.LayerRenderer>
+     * @private
+     */
+    this.renderers_ = [];
+    
+};
+
+/**
+ * @param {Array.<ol.layer.Layer>} layers
+ * @param {ol.Loc} center
+ * @param {number} resolution
+ */
+ol.renderer.Composite.prototype.draw = function(layers, center, resolution) {
+};
+
+/**
+ * @param {ol.layer.Layer} layer
+ */
+ol.renderer.Composite.prototype.getRenderer = function(layer) {
+    function finder(candidate) {
+        return candidate.getLayer() === layer;
+    }
+    return goog.array.find(this.renderers_, finder);
+};
+
+/**
+ * @param {ol.layer.Layer} layer
+ */
+ol.renderer.Composite.prototype.createRenderer = function(layer) {
+};
+
+/**
+ * List of preferred renderer types.  Layer renderers have a getType method
+ * that returns a string describing their type.  This list determines the 
+ * preferences for picking a layer renderer.
+ *
+ * @type {Array.<string>}
+ */
+ol.renderer.Composite.preferredRenderers = ["svg", "canvas", "vml"];
+
+/**
+ * @param {ol.layer.Layer} layer
+ * @returns {Function}
+ */
+ol.renderer.Composite.prototype.pickRendererType = function(layer) {
+    // maps candidate renderer types to candidate renderers
+    var types = {};
+
+    function picker(Candidate) {
+        var supports = Candidate.isSupported() && Candidate.canRender(layer);
+        if (supports) {
+            types[Candidate.getType()] = Candidate;
+        }
+        return supports;
+    }
+    var Candidates = goog.array.some(ol.renderer.Composite.registry_, picker);
+    
+    // check to see if any preferred renderers are available
+    var preferences = ol.renderer.Composite.preferredRenderers;
+
+    var Renderer;
+    for (var i=0, ii=preferences.length; i<ii; ++i) {
+        Renderer = preferences[i];
+        if (Renderer) {
+            break;
+        }
+    }
+    
+    // if we didn't find any of the preferred renderers, use the first
+    return Renderer || Candidates[0] || null;
+};
+
+/**
+ * @type {Array.<Function>}
+ * @private
+ */
+ol.renderer.Composite.registry_ = [];
+
+/**
+ * @param {Function} Renderer
+ */
+ol.renderer.Composite.register = function(Renderer) {
+    ol.renderer.Composite.registry_.push(Renderer);
+};