Event: Remove fixHooks, propHooks; switch to ES5 getter with addProp

Fixes gh-3103
Fixes gh-1746
Closes gh-2860

- Removes the copy loop in jQuery.event.fix
- Avoids accessing properties such as client/offset/page/screen X/Y
  which may cause style recalc or layouts
- Simplifies adding property hooks to event object

src/event.js

@@ -398,90 +398,38 @@ jQuery.event = {
 		return handlerQueue;
 	},
 
-	// Includes some event props shared by KeyEvent and MouseEvent
-	props: ( "altKey bubbles cancelable ctrlKey currentTarget detail eventPhase " +
-		"metaKey relatedTarget shiftKey target timeStamp view which" ).split( " " ),
+	addProp: function( name, hook ) {
+		Object.defineProperty( jQuery.Event.prototype, name, {
+			enumerable: true,
+			configurable: true,
 
-	fixHooks: {},
+			get: jQuery.isFunction( hook ) ?
+				function() {
+					if ( this.originalEvent ) {
+							return hook( this.originalEvent );
+					}
+				} :
+				function() {
+					if ( this.originalEvent ) {
+							return this.originalEvent[ name ];
+					}
+				},
 
-	keyHooks: {
-		props: "char charCode key keyCode".split( " " ),
-		filter: function( event, original ) {
-
-			// Add which for key events
-			if ( event.which == null ) {
-				event.which = original.charCode != null ? original.charCode : original.keyCode;
+			set: function( value ) {
+				Object.defineProperty( this, name, {
+					enumerable: true,
+					configurable: true,
+					writable: true,
+					value: value
+				} );
 			}
-
-			return event;
-		}
+		} );
 	},
 
-	mouseHooks: {
-		props: ( "button buttons clientX clientY offsetX offsetY pageX pageY " +
-			"screenX screenY toElement" ).split( " " ),
-		filter: function( event, original ) {
-			var eventDoc, doc, body,
-				button = original.button;
-
-			// Calculate pageX/Y if missing and clientX/Y available
-			if ( event.pageX == null && original.clientX != null ) {
-				eventDoc = event.target.ownerDocument || document;
-				doc = eventDoc.documentElement;
-				body = eventDoc.body;
-
-				event.pageX = original.clientX +
-					( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) -
-					( doc && doc.clientLeft || body && body.clientLeft || 0 );
-				event.pageY = original.clientY +
-					( doc && doc.scrollTop  || body && body.scrollTop  || 0 ) -
-					( doc && doc.clientTop  || body && body.clientTop  || 0 );
-			}
-
-			// Add which for click: 1 === left; 2 === middle; 3 === right
-			// Note: button is not normalized, so don't use it
-			if ( !event.which && button !== undefined ) {
-				event.which = ( button & 1 ? 1 : ( button & 2 ? 3 : ( button & 4 ? 2 : 0 ) ) );
-			}
-
-			return event;
-		}
-	},
-
-	fix: function( event ) {
-		if ( event[ jQuery.expando ] ) {
-			return event;
-		}
-
-		// Create a writable copy of the event object and normalize some properties
-		var i, prop, copy,
-			type = event.type,
-			originalEvent = event,
-			fixHook = this.fixHooks[ type ];
-
-		if ( !fixHook ) {
-			this.fixHooks[ type ] = fixHook =
-				rmouseEvent.test( type ) ? this.mouseHooks :
-				rkeyEvent.test( type ) ? this.keyHooks :
-				{};
-		}
-		copy = fixHook.props ? this.props.concat( fixHook.props ) : this.props;
-
-		event = new jQuery.Event( originalEvent );
-
-		i = copy.length;
-		while ( i-- ) {
-			prop = copy[ i ];
-			event[ prop ] = originalEvent[ prop ];
-		}
-
-		// Support: Safari <=6 - 7 only
-		// Target should not be a text node (#504, #13143)
-		if ( event.target.nodeType === 3 ) {
-			event.target = event.target.parentNode;
-		}
-
-		return fixHook.filter ? fixHook.filter( event, originalEvent ) : event;
+	fix: function( originalEvent ) {
+		return originalEvent[ jQuery.expando ] ?
+			originalEvent :
+			new jQuery.Event( originalEvent );
 	},
 
 	special: {
@@ -569,6 +517,16 @@ jQuery.Event = function( src, props ) {
 			returnTrue :
 			returnFalse;
 
+		// Create target properties
+		// Support: Safari <=6 - 7 only
+		// Target should not be a text node (#504, #13143)
+		this.target = ( src.target.nodeType === 3 ) ?
+			src.target.parentNode :
+			src.target;
+
+		this.currentTarget = src.currentTarget;
+		this.relatedTarget = src.relatedTarget;
+
 	// Event type
 	} else {
 		this.type = src;
@@ -625,6 +583,82 @@ jQuery.Event.prototype = {
 	}
 };
 
+// Includes all common event props including KeyEvent and MouseEvent specific props
+jQuery.each( {
+	altKey: true,
+	bubbles: true,
+	cancelable: true,
+	ctrlKey: true,
+	detail: true,
+	eventPhase: true,
+	metaKey: true,
+	shiftKey: true,
+	view: true,
+	"char": true,
+	charCode: true,
+	key: true,
+	keyCode: true,
+	button: true,
+	buttons: true,
+	clientX: true,
+	clientY: true,
+	offsetX: true,
+	offsetY: true,
+	screenX: true,
+	screenY: true,
+	toElement: true,
+
+	which: function( event ) {
+		var button = event.button;
+
+		// Add which for key events
+		if ( event.which == null && rkeyEvent.test( event.type ) ) {
+			return event.charCode != null ? event.charCode : event.keyCode;
+		}
+
+		// Add which for click: 1 === left; 2 === middle; 3 === right
+		if ( !event.which && button !== undefined && rmouseEvent.test( event.type ) ) {
+			return ( button & 1 ? 1 : ( button & 2 ? 3 : ( button & 4 ? 2 : 0 ) ) );
+		}
+
+		return event.which;
+	},
+
+	pageX: function( event ) {
+		var eventDoc, doc, body;
+
+		// Calculate pageX if missing and clientX available
+		if ( event.pageX == null && event.clientX != null ) {
+			eventDoc = event.target.ownerDocument || document;
+			doc = eventDoc.documentElement;
+			body = eventDoc.body;
+
+			return event.clientX +
+				( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) -
+				( doc && doc.clientLeft || body && body.clientLeft || 0 );
+		}
+
+		return event.pageX;
+	},
+
+	pageY: function( event ) {
+		var eventDoc, doc, body;
+
+		// Calculate pageY if missing and clientY available
+		if ( event.pageY == null && event.clientY != null ) {
+			eventDoc = event.target.ownerDocument || document;
+			doc = eventDoc.documentElement;
+			body = eventDoc.body;
+
+			return event.clientY +
+				( doc && doc.scrollTop || body && body.scrollTop || 0 ) -
+				( doc && doc.clientTop || body && body.clientTop || 0 );
+		}
+
+		return event.pageY;
+	}
+}, jQuery.event.addProp );
+
 // Create mouseenter/leave events using mouseover/out and event-time checks
 // so that event delegation works in jQuery.
 // Do the same for pointerenter/pointerleave and pointerover/pointerout

test/unit/event.js

@@ -2410,36 +2410,28 @@ QUnit.test( "event object properties on natively-triggered event", function( ass
 	$link.off( "click" ).remove();
 } );
 
-QUnit.test( "fixHooks extensions", function( assert ) {
+QUnit.test( "addProp extensions", function( assert ) {
 	assert.expect( 2 );
 
-	// IE requires focusable elements to be visible, so append to body
-	var $fixture = jQuery( "<input type='text' id='hook-fixture' />" ).appendTo( "body" ),
-		saved = jQuery.event.fixHooks.click;
+	var $fixture = jQuery( "<div>" ).appendTo( "#qunit-fixture" );
 
 	// Ensure the property doesn't exist
 	$fixture.on( "click", function( event ) {
-		assert.ok( !( "blurrinessLevel" in event ), "event.blurrinessLevel does not exist" );
+		assert.ok( !( "testProperty" in event ), "event.testProperty does not exist" );
 	} );
 	fireNative( $fixture[ 0 ], "click" );
 	$fixture.off( "click" );
 
-	jQuery.event.fixHooks.click = {
-		filter: function( event ) {
-			event.blurrinessLevel = 42;
-			return event;
-		}
-	};
+	jQuery.event.addProp( "testProperty", function() { return 42; } );
 
 	// Trigger a native click and ensure the property is set
 	$fixture.on( "click", function( event ) {
-		assert.equal( event.blurrinessLevel, 42, "event.blurrinessLevel was set" );
+		assert.equal( event.testProperty, 42, "event.testProperty getter was invoked" );
 	} );
 	fireNative( $fixture[ 0 ], "click" );
+	$fixture.off( "click" );
 
-	delete jQuery.event.fixHooks.click;
-	$fixture.off( "click" ).remove();
-	jQuery.event.fixHooks.click = saved;
+	$fixture.remove();
 } );
 
 QUnit.test( "drag/drop events copy mouse-related event properties (gh-1925, gh-2009)", function( assert ) {