Improve performance

- Use raw Event objects with assignments
  - Significantly faster than new MouseEvent and defineProperty
  - Break spec compatibility about "readonly" properties
- Remove WeakMap Dependency
- Forward pageX/pageY

Author: dfreedm

bower.json

@@ -9,9 +9,6 @@
   "keywords": [
     "PointerEvents"
   ],
-  "dependencies": {
-    "WeakMap": "Polymer/WeakMap#master"
-  },
   "license": "BSD",
   "private": true,
   "ignore": [

build.json

@@ -1,5 +1,4 @@
 [
-  "../WeakMap/weakmap.js",
   "src/boot.js",
   "src/touch-action.js",
   "src/PointerEvent.js",

pointerevents.js

@@ -7,7 +7,6 @@
   var thisFile = 'pointerevents.js';
   var scopeName = 'PointerEventsPolyfill';
   var modules = [
-    '../WeakMap/weakmap.js',
     'src/boot.js',
     'src/touch-action.js',
     'src/PointerEvent.js',

src/PointerEvent.js

@@ -19,16 +19,6 @@
  * @return {Event} A new PointerEvent of type `inType` and initialized with properties from `inDict`.
  */
 (function(scope) {
-  // test for DOM Level 4 Events
-  var NEW_MOUSE_EVENT = false;
-  var HAS_BUTTONS = false;
-  try {
-    var ev = new MouseEvent('click', {buttons: 1});
-    NEW_MOUSE_EVENT = true;
-    HAS_BUTTONS = ev.buttons === 1;
-    ev = null;
-  } catch(e) {
-  }
 
   var MOUSE_PROPS = [
     'bubbles',
@@ -45,6 +35,8 @@
     'metaKey',
     'button',
     'relatedTarget',
+    'pageX',
+    'pageY'
   ];
 
   var MOUSE_DEFAULTS = [
@@ -61,101 +53,46 @@
     false,
     false,
     0,
-    null
+    null,
+    0,
+    0
   ];
 
   function PointerEvent(inType, inDict) {
-    inDict = inDict || {};
-    // According to the w3c spec,
-    // http://www.w3.org/TR/DOM-Level-3-Events/#events-MouseEvent-button
-    // MouseEvent.button == 0 can mean either no mouse button depressed, or the
-    // left mouse button depressed.
-    //
-    // As of now, the only way to distinguish between the two states of
-    // MouseEvent.button is by using the deprecated MouseEvent.which property, as
-    // this maps mouse buttons to positive integers > 0, and uses 0 to mean that
-    // no mouse button is held.
-    //
-    // MouseEvent.which is derived from MouseEvent.button at MouseEvent creation,
-    // but initMouseEvent does not expose an argument with which to set
-    // MouseEvent.which. Calling initMouseEvent with a buttonArg of 0 will set
-    // MouseEvent.button == 0 and MouseEvent.which == 1, breaking the expectations
-    // of app developers.
-    //
-    // The only way to propagate the correct state of MouseEvent.which and
-    // MouseEvent.button to a new MouseEvent.button == 0 and MouseEvent.which == 0
-    // is to call initMouseEvent with a buttonArg value of -1.
-    //
-    // This is fixed with DOM Level 4's use of buttons
-    var buttons = inDict.buttons;
-    // touch has two possible buttons state: 0 and 1, rely on being told the right one
-    if (!HAS_BUTTONS && !buttons && inType !== 'touch') {
-      switch (inDict.which) {
-        case 1: buttons = 1; break;
-        case 2: buttons = 4; break;
-        case 3: buttons = 2; break;
-        default: buttons = 0;
-      }
-    }
-
-    var e;
-    if (NEW_MOUSE_EVENT) {
-      e = new MouseEvent(inType, inDict);
-    } else {
-      e = document.createEvent('MouseEvent');
+    inDict = inDict || Object.create(null);
 
-      // import values from the given dictionary
-      var props = {}, p;
-      for(var i = 0; i < MOUSE_PROPS.length; i++) {
-        p = MOUSE_PROPS[i];
-        props[p] = inDict[p] || MOUSE_DEFAULTS[i];
-      }
+    var e = document.createEvent('Event');
+    e.initEvent(inType, inDict.bubbles || false, inDict.cancelable || false);
 
-      // define the properties inherited from MouseEvent
-      e.initMouseEvent(
-        inType, props.bubbles, props.cancelable, props.view, props.detail,
-        props.screenX, props.screenY, props.clientX, props.clientY, props.ctrlKey,
-        props.altKey, props.shiftKey, props.metaKey, props.button, props.relatedTarget
-      );
-    }
-
-    // make the event pass instanceof checks
-    e.__proto__ = PointerEvent.prototype;
-
-    // define the buttons property according to DOM Level 3 spec
-    if (!HAS_BUTTONS) {
-      // IE 10 has buttons on MouseEvent.prototype as a getter w/o any setting
-      // mechanism
-      Object.defineProperty(e, 'buttons', {get: function(){ return buttons; }, enumerable: true});
+    // define inherited MouseEvent properties
+    for(var i = 0, p; i < MOUSE_PROPS.length; i++) {
+      p = MOUSE_PROPS[i];
+      e[p] = inDict[p] || MOUSE_DEFAULTS[i];
     }
+    e.buttons = inDict.buttons || 0;
 
     // Spec requires that pointers without pressure specified use 0.5 for down
     // state and 0 for up state.
     var pressure = 0;
     if (inDict.pressure) {
       pressure = inDict.pressure;
     } else {
-      pressure = buttons ? 0.5 : 0;
+      pressure = e.buttons ? 0.5 : 0;
     }
 
     // define the properties of the PointerEvent interface
-    Object.defineProperties(e, {
-      pointerId: { value: inDict.pointerId || 0, enumerable: true },
-      width: { value: inDict.width || 0, enumerable: true },
-      height: { value: inDict.height || 0, enumerable: true },
-      pressure: { value: pressure, enumerable: true },
-      tiltX: { value: inDict.tiltX || 0, enumerable: true },
-      tiltY: { value: inDict.tiltY || 0, enumerable: true },
-      pointerType: { value: inDict.pointerType || '', enumerable: true },
-      hwTimestamp: { value: inDict.hwTimestamp || 0, enumerable: true },
-      isPrimary: { value: inDict.isPrimary || false, enumerable: true }
-    });
+    e.pointerId = inDict.pointerId || 0;
+    e.width = inDict.width || 0;
+    e.height = inDict.height || 0;
+    e.pressure = pressure;
+    e.tiltX = inDict.tiltX || 0;
+    e.tiltY = inDict.tiltY || 0;
+    e.pointerType = inDict.pointerType || '';
+    e.hwTimestamp = inDict.hwTimestamp || 0;
+    e.isPrimary = inDict.isPrimary || false;
     return e;
   }
 
-  // PointerEvent extends MouseEvent
-  PointerEvent.prototype = Object.create(MouseEvent.prototype);
-
   // attach to window
   if (!scope.PointerEvent) {
     scope.PointerEvent = PointerEvent;

src/dispatcher.js

@@ -37,7 +37,9 @@
     'type',
     'target',
     'currentTarget',
-    'which'
+    'which',
+    'pageX',
+    'pageY'
   ];
 
   var CLONE_DEFAULTS = [
@@ -72,6 +74,8 @@
     '',
     null,
     null,
+    0,
+    0,
     0
   ];
 
@@ -90,13 +94,11 @@
    *   - pointercancel: a pointer will no longer generate events
    */
   var dispatcher = {
-    targets: new WeakMap(),
-    handledEvents: new WeakMap(),
     pointermap: new scope.PointerMap(),
     eventMap: {},
     // Scope objects for native events.
     // This exists for ease of testing.
-    eventSources: {},
+    eventSources: Object.create(null),
     eventSourceList: [],
     /**
      * Add a new event source that will generate pointer events.
@@ -186,15 +188,15 @@
       // This is used to prevent multiple dispatch of pointerevents from
       // platform events. This can happen when two elements in different scopes
       // are set up to create pointer events, which is relevant to Shadow DOM.
-      if (this.handledEvents.get(inEvent)) {
+      if (inEvent._handledByPE) {
         return;
       }
       var type = inEvent.type;
       var fn = this.eventMap && this.eventMap[type];
       if (fn) {
         fn(inEvent);
       }
-      this.handledEvents.set(inEvent, true);
+      inEvent._handledByPE = true;
     },
     // set up event listeners
     listen: function(target, events) {
@@ -232,7 +234,7 @@
       if (inEvent.preventDefault) {
         e.preventDefault = inEvent.preventDefault;
       }
-      this.targets.set(e, this.targets.get(inEvent) || inEvent.target);
+      e._target = e._target || inEvent.target;
       return e;
     },
     // make and dispatch an event in one call
@@ -248,7 +250,7 @@
      *    properties.
      */
     cloneEvent: function(inEvent) {
-      var eventCopy = {}, p;
+      var eventCopy = Object.create(null), p;
       for (var i = 0; i < CLONE_PROPS.length; i++) {
         p = CLONE_PROPS[i];
         eventCopy[p] = inEvent[p] || CLONE_DEFAULTS[i];
@@ -277,7 +279,7 @@
           return this.captureInfo.target;
         }
       }
-      return this.targets.get(inEvent);
+      return inEvent._target;
     },
     setCapture: function(inPointerId, inTarget) {
       if (this.captureInfo) {
@@ -288,7 +290,7 @@
       this.implicitRelease = this.releaseCapture.bind(this, inPointerId);
       document.addEventListener('pointerup', this.implicitRelease);
       document.addEventListener('pointercancel', this.implicitRelease);
-      this.targets.set(e, inTarget);
+      e._target = inTarget;
       this.asyncDispatchEvent(e);
     },
     releaseCapture: function(inPointerId) {
@@ -298,7 +300,7 @@
         this.captureInfo = null;
         document.removeEventListener('pointerup', this.implicitRelease);
         document.removeEventListener('pointercancel', this.implicitRelease);
-        this.targets.set(e, t);
+        e._target = t;
         this.asyncDispatchEvent(e);
       }
     },

src/mouse.js

@@ -10,6 +10,13 @@
   // radius around touchend that swallows mouse events
   var DEDUP_DIST = 25;
 
+  var WHICH_TO_BUTTONS = [0, 1, 4, 2];
+
+  var HAS_BUTTONS = false;
+  try {
+    HAS_BUTTONS = new MouseEvent('test', {buttons: 1}).buttons === 1;
+  } catch (e) {}
+
   // handler block for native mouse events
   var mouseEvents = {
     POINTER_ID: 1,
@@ -51,6 +58,9 @@
       e.pointerId = this.POINTER_ID;
       e.isPrimary = true;
       e.pointerType = this.POINTER_TYPE;
+      if (!HAS_BUTTONS) {
+        e.buttons = WHICH_TO_BUTTONS[e.which] || 0;
+      }
       return e;
     },
     mousedown: function(inEvent) {