Fix #2089. Feature detect for mouseenter and (assume) mouseleave.

Source/Element/Element.Event.js

@@ -3,7 +3,7 @@
 
 name: Element.Event
 
-description: Contains Element methods for dealing with events. This file also includes mouseenter and mouseleave custom Element Events.
+description: Contains Element methods for dealing with events. This file also includes mouseenter and mouseleave custom Element Events, if necessary.
 
 license: MIT-style license.
 
@@ -141,30 +141,30 @@ Element.NativeEvents = {
 	error: 1, abort: 1, scroll: 1 //misc
 };
 
-var check = function(event){
-	var related = event.relatedTarget;
-	if (related == null) return true;
-	if (!related) return false;
-	return (related != this && related.prefix != 'xul' && typeOf(this) != 'document' && !this.contains(related));
-};
-
-Element.Events = {
+Element.Events = {mousewheel: {
+	base: (Browser.firefox) ? 'DOMMouseScroll' : 'mousewheel'
+}};
 
-	mouseenter: {
+if ('onmouseenter' in document.documentElement){
+	Element.NativeEvents.mouseenter = Element.NativeEvents.mouseleave = 2;
+} else {
+	var check = function(event){
+		var related = event.relatedTarget;
+		if (related == null) return true;
+		if (!related) return false;
+		return (related != this && related.prefix != 'xul' && typeOf(this) != 'document' && !this.contains(related));
+	};
+
+	Element.Events.mouseenter = {
 		base: 'mouseover',
 		condition: check
-	},
+	};
 
-	mouseleave: {
+	Element.Events.mouseleave = {
 		base: 'mouseout',
 		condition: check
-	},
-
-	mousewheel: {
-		base: (Browser.firefox) ? 'DOMMouseScroll' : 'mousewheel'
-	}
-
-};
+	};
+}
 
 /*<ltIE9>*/
 if (!window.addEventListener){