Replace PointerMap with potentially-sparse-array-based Map polyfill

Closes gh-190

Author: stuartpb

src/pointermap.js

@@ -2,55 +2,47 @@
  * This module implements an map of pointer states
  */
 var USE_MAP = window.Map && window.Map.prototype.forEach;
-var POINTERS_FN = function() { return this.size; };
 function PointerMap() {
-  if (USE_MAP) {
-    var m = new Map();
-    m.pointers = POINTERS_FN;
-    return m;
-  } else {
-    this.keys = [];
-    this.values = [];
-  }
+  return USE_MAP ? new Map() : new SparseArrayMap();
+}
+
+function SparseArrayMap() {
+  this.array = [];
+  this.size = 0;
 }
 
-PointerMap.prototype = {
-  set: function(inId, inEvent) {
-    var i = this.keys.indexOf(inId);
-    if (i > -1) {
-      this.values[i] = inEvent;
-    } else {
-      this.keys.push(inId);
-      this.values.push(inEvent);
+SparseArrayMap.prototype = {
+  set: function(k, v) {
+    if (v === undefined) {
+      return this.delete(k);
     }
+    if (!this.has(k)) {
+      this.size++;
+    }
+    this.array[k] = v;
   },
-  has: function(inId) {
-    return this.keys.indexOf(inId) > -1;
+  has: function(k) {
+    return this.array[k] !== undefined;
   },
-  delete: function(inId) {
-    var i = this.keys.indexOf(inId);
-    if (i > -1) {
-      this.keys.splice(i, 1);
-      this.values.splice(i, 1);
+  delete: function(k) {
+    if (this.has(k)) {
+      delete this.array[k];
+      this.size--;
     }
   },
-  get: function(inId) {
-    var i = this.keys.indexOf(inId);
-    return this.values[i];
+  get: function(k) {
+    return this.array[k];
   },
   clear: function() {
-    this.keys.length = 0;
-    this.values.length = 0;
+    this.array.length = 0;
+    this.size = 0;
   },
 
   // return value, key, map
   forEach: function(callback, thisArg) {
-    this.values.forEach(function(v, i) {
-      callback.call(thisArg, v, this.keys[i], this);
+    return this.array.forEach(function(v, k) {
+      callback.call(thisArg, v, k, this);
     }, this);
-  },
-  pointers: function() {
-    return this.keys.length;
   }
 };
 

src/touch.js

@@ -112,7 +112,7 @@ var touchEvents = {
   setPrimaryTouch: function(inTouch) {
 
     // set primary touch if there no pointers, or the only pointer is the mouse
-    if (pointermap.pointers() === 0 || (pointermap.pointers() === 1 && pointermap.has(1))) {
+    if (pointermap.size === 0 || (pointermap.size === 1 && pointermap.has(1))) {
       this.firstTouch = inTouch.identifier;
       this.firstXY = { X: inTouch.clientX, Y: inTouch.clientY };
       this.scrolling = false;
@@ -233,9 +233,9 @@ var touchEvents = {
   vacuumTouches: function(inEvent) {
     var tl = inEvent.touches;
 
-    // pointermap.pointers() should be < tl.length here, as the touchstart has not
+    // pointermap.size should be < tl.length here, as the touchstart has not
     // been processed yet.
-    if (pointermap.pointers() >= tl.length) {
+    if (pointermap.size >= tl.length) {
       var d = [];
       pointermap.forEach(function(value, key) {
 

tests/unit/pointermap.js

@@ -14,7 +14,7 @@ define([
         'get',
         'has',
         'delete',
-        'pointers',
+        'size',
         'clear',
         'forEach'
       ];
@@ -26,20 +26,16 @@ define([
     test('PointerMap .set', function() {
       var p = new PointerMap();
       p.set(1, true);
-      if (!window.Map || !(p instanceof Map)) {
-        expect(p.keys).to.have.length(1);
-        expect(p.values).to.have.length(1);
-      }
-      expect(p.pointers()).to.equal(1);
+      expect(p.size).to.equal(1);
     });
-    test('PointerMap .pointers', function() {
+    test('PointerMap .size', function() {
       var p = new PointerMap();
-      expect(p.pointers).to.be.a('function');
-      expect(p.pointers()).to.equal(0);
+      expect(p.size).to.be.a('number');
+      expect(p.size).to.equal(0);
       p.set(1, true);
-      expect(p.pointers()).to.equal(1);
+      expect(p.size).to.equal(1);
       p.set(1, false);
-      expect(p.pointers()).to.equal(1);
+      expect(p.size).to.equal(1);
     });
     test('PointerMap .has', function() {
       var p = new PointerMap();
@@ -51,16 +47,16 @@ define([
       var p = new PointerMap();
       p.set(1, true);
       p.set(2, false);
-      expect(p.pointers()).to.equal(2);
+      expect(p.size).to.equal(2);
       p.delete(1);
-      expect(p.pointers()).to.equal(1);
+      expect(p.size).to.equal(1);
       expect(p.get(2)).to.equal(false);
     });
     test('PointerMap .clear', function() {
       var p = new PointerMap();
       p.set(1, true);
       p.clear();
-      expect(p.pointers()).to.equal(0);
+      expect(p.size).to.equal(0);
     });
     test('PointerMap .forEach', function() {
       var p = new PointerMap();