From 8c21f2e1717a87a88a0507f090b1a5572c1d1799 Mon Sep 17 00:00:00 2001
From: Daniel Freedman <dfreedm@google.com>
Date: Fri, 13 Nov 2015 12:15:21 -0800
Subject: [PATCH] Make sure fixed preventDefault can be called multiple times

Fixes #441 Interact .draggable and webcomponentsjs conflict in IE
---
 src/ShadowDOM/wrappers/events.js  | 15 ++++++++++-----
 src/WebComponents/dom.js          | 17 +++++++++++------
 tests/WebComponents/html/dom.html |  2 ++
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/ShadowDOM/wrappers/events.js b/src/ShadowDOM/wrappers/events.js
index 0e9d2ff..6ddfeb2 100644
--- a/src/ShadowDOM/wrappers/events.js
+++ b/src/ShadowDOM/wrappers/events.js
@@ -534,12 +534,17 @@
     Event.prototype.preventDefault = function() {
       if (!this.cancelable)
         return;
+
       unsafeUnwrap(this).preventDefault();
-      Object.defineProperty(this, 'defaultPrevented', {
-        get: function() {
-          return true;
-        }
-      });
+
+      if (!this.defaultPrevented) {
+        Object.defineProperty(this, 'defaultPrevented', {
+          get: function() {
+            return true;
+          },
+          configurable: true
+        });
+      }
     };
   }
 
diff --git a/src/WebComponents/dom.js b/src/WebComponents/dom.js
index b713380..d082afd 100644
--- a/src/WebComponents/dom.js
+++ b/src/WebComponents/dom.js
@@ -17,7 +17,7 @@
   if (!window.performance) {
     var start = Date.now();
     // only at millisecond precision
-    window.performance = {now: function(){ return Date.now() - start }};
+    window.performance = {now: function(){ return Date.now() - start; }};
   }
 
   // polyfill for requestAnimationFrame
@@ -64,12 +64,17 @@
       if (!this.cancelable) {
         return;
       }
+
       origPreventDefault.call(this);
-      Object.defineProperty(this, 'defaultPrevented', {
-        get: function() {
-          return true;
-        }
-      });
+
+      if (!this.defaultPrevented) {
+        Object.defineProperty(this, 'defaultPrevented', {
+          get: function() {
+            return true;
+          },
+          configurable: true
+        });
+      }
     };
   }
 
diff --git a/tests/WebComponents/html/dom.html b/tests/WebComponents/html/dom.html
index 990c3d5..7262262 100644
--- a/tests/WebComponents/html/dom.html
+++ b/tests/WebComponents/html/dom.html
@@ -87,6 +87,8 @@
       var e = new Event('foo', {cancelable: true});
       e.preventDefault();
       assert.isTrue(e.defaultPrevented);
+      // call again, just in case
+      assert.doesNotThrow(e.preventDefault);
     });
   });
 </script>