From c480bd7b97f6c7ca2d49f8649320436eea7f0aed Mon Sep 17 00:00:00 2001
From: Juriy Zaytsev <juriy@kangax.local>
Date: Sat, 28 Mar 2009 19:45:33 -0400
Subject: [PATCH] Do not sniff when testing for IE's proprietary
 mouseenter/mouseleave events support. Use more robust inference instead.

---
 CHANGELOG        | 2 ++
 src/dom/event.js | 8 ++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index e08a3df..dc1c89c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Do not sniff when testing for IE's proprietary mouseenter/mouseleave events support. Use more robust inference instead. (kangax)
+
 * Use `Prototype.emptyFunction` consistently throughout unit tests. [#253 state:resolved] (Michael M Slusarz, John David Dalton, kangax)
 
 * deprecation extension: mark Array#reduce() as removed. [#569 state:resolved] (Tobie Langel)
diff --git a/src/dom/event.js b/src/dom/event.js
index 5e56184..3a08d6c 100644
--- a/src/dom/event.js
+++ b/src/dom/event.js
@@ -49,6 +49,10 @@
 
     cache: {}
   };
+  
+  var docEl = document.documentElement;
+  var MOUSEENTER_MOUSELEAVE_EVENTS_SUPPORTED = 'onmouseenter' in docEl
+    && 'onmouseleave' in docEl;
 
   var _isButton;
   if (Prototype.Browser.IE) {
@@ -320,7 +324,7 @@
       };
     } else {
       // Non-custom event.
-      if (!Prototype.Browser.IE &&
+      if (!MOUSEENTER_MOUSELEAVE_EVENTS_SUPPORTED &&
        (eventName === "mouseenter" || eventName === "mouseleave")) {
         // If we're dealing with mouseenter or mouseleave in a non-IE browser,
         // we create a custom responder that mimics their behavior within
@@ -376,7 +380,7 @@
     
   var _getDOMEventName = Prototype.K;
   
-  if (!Prototype.Browser.IE) {
+  if (!MOUSEENTER_MOUSELEAVE_EVENTS_SUPPORTED) {
     _getDOMEventName = function(eventName) {
       var translations = { mouseenter: "mouseover", mouseleave: "mouseout" };      
       return eventName in translations ? translations[eventName] : eventName;