Allow geometries to use a shared vertex array

The ol.geom.SharedVertices structure represents a flattened array of vertex coordinates.  This is intended to support optimal WebGL rendering.

src/ol/geom/linestring.js

@@ -2,44 +2,47 @@ goog.provide('ol.geom.LineString');
 
 goog.require('goog.asserts');
 goog.require('ol.Extent');
-goog.require('ol.geom.CoordinateArray');
 goog.require('ol.geom.Geometry');
 goog.require('ol.geom.GeometryType');
+goog.require('ol.geom.SharedVertices');
+goog.require('ol.geom.VertexArray');
 
 
 
 /**
  * @constructor
  * @extends {ol.geom.Geometry}
- * @param {ol.geom.CoordinateArray} coordinates Coordinates array (e.g.
+ * @param {ol.geom.VertexArray} coordinates Vertex array (e.g.
  *    [[x0, y0], [x1, y1]]).
+ * @param {ol.geom.SharedVertices=} opt_shared Shared vertices.
  */
-ol.geom.LineString = function(coordinates) {
-
+ol.geom.LineString = function(coordinates, opt_shared) {
   goog.base(this);
+  goog.asserts.assert(goog.isArray(coordinates[0]));
 
-  // assume the same dimension for all coordinates
-  var dimension = coordinates[0].length,
-      count = coordinates.length,
-      length = count * dimension;
+  var vertices = opt_shared,
+      dimension;
+
+  if (!goog.isDef(vertices)) {
+    dimension = coordinates[0].length;
+    vertices = new ol.geom.SharedVertices({dimension: dimension});
+  }
 
   /**
-   * @type {Array}
+   * @type {ol.geom.SharedVertices}
    */
-  this.coordinates = new Array(length);
-  var i, offset, j;
-  for (i = 0; i < count; ++i) {
-    goog.asserts.assert(coordinates[i].length === dimension);
-    offset = i * dimension;
-    for (j = 0; j < dimension; ++j) {
-      this.coordinates[offset + j] = coordinates[i][j];
-    }
-  }
+  this.vertices = vertices;
+
+  /**
+   * @type {string}
+   * @private
+   */
+  this.sharedId_ = vertices.add(coordinates);
 
   /**
    * @type {number}
    */
-  this.dimension = dimension;
+  this.dimension = vertices.getDimension();
   goog.asserts.assert(this.dimension >= 2);
 
   /**
@@ -52,6 +55,45 @@ ol.geom.LineString = function(coordinates) {
 goog.inherits(ol.geom.LineString, ol.geom.Geometry);
 
 
+/**
+ * Get a vertex coordinate value for the given dimension.
+ * @param {number} index Vertex index.
+ * @param {number} dim Coordinate dimension.
+ * @return {number} The vertex coordinate value.
+ */
+ol.geom.LineString.prototype.get = function(index, dim) {
+  return this.vertices.get(this.sharedId_, index, dim);
+};
+
+
+/**
+ * @inheritDoc
+ * @return {ol.geom.VertexArray} Coordinates array.
+ */
+ol.geom.LineString.prototype.getCoordinates = function() {
+  var count = this.getCount();
+  var coordinates = new Array(count);
+  var vertex;
+  for (var i = 0; i < count; ++i) {
+    vertex = new Array(this.dimension);
+    for (var j = 0; j < this.dimension; ++j) {
+      vertex[j] = this.get(i, j);
+    }
+    coordinates[i] = vertex;
+  }
+  return coordinates;
+};
+
+
+/**
+ * Get the count of vertices in this linestring.
+ * @return {number} The vertex count.
+ */
+ol.geom.LineString.prototype.getCount = function() {
+  return this.vertices.getCount(this.sharedId_);
+};
+
+
 /**
  * @inheritDoc
  */
@@ -61,14 +103,15 @@ ol.geom.LineString.prototype.getBounds = function() {
         minY = minX = Number.POSITIVE_INFINITY,
         maxX,
         maxY = maxX = Number.NEGATIVE_INFINITY,
-        coordinates = this.coordinates,
-        len = coordinates.length,
-        dim = this.dimension,
+        vertices = this.vertices,
+        id = this.sharedId_,
+        count = vertices.getCount(id),
+        dimension = this.dimension,
         x, y, i;
 
-    for (i = 0; i < len; i += dim) {
-      x = coordinates[i];
-      y = coordinates[i + 1];
+    for (i = 0; i < count; ++i) {
+      x = vertices.get(id, i, 0);
+      y = vertices.get(id, i, 1);
       minX = Math.min(minX, x);
       minY = Math.min(minY, y);
       maxX = Math.max(maxX, x);
@@ -86,3 +129,12 @@ ol.geom.LineString.prototype.getBounds = function() {
 ol.geom.LineString.prototype.getType = function() {
   return ol.geom.GeometryType.LINESTRING;
 };
+
+
+/**
+ * Get the identifier used to mark this line in the shared vertices structure.
+ * @return {string} The identifier.
+ */
+ol.geom.LineString.prototype.getSharedId = function() {
+  return this.sharedId_;
+};