From 75402fe277c05a540567da4476e1879fc7a00bc7 Mon Sep 17 00:00:00 2001
From: jdotzki <joerg.dotzki@zalando.de>
Date: Wed, 9 Jul 2014 15:07:29 +0200
Subject: [PATCH] fix(zoomscroll): fix using of incorrect offsetX/Y values for
 zoom on Gecko Browsers

close #83
---
 lib/features/zoomscroll/ZoomScroll.js | 47 +++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/lib/features/zoomscroll/ZoomScroll.js b/lib/features/zoomscroll/ZoomScroll.js
index 3f774706..78294f78 100644
--- a/lib/features/zoomscroll/ZoomScroll.js
+++ b/lib/features/zoomscroll/ZoomScroll.js
@@ -51,8 +51,23 @@ function ZoomScroll(events, canvas) {
 
         canvas.scroll(delta);
       } else {
+        var offset = {};
+
+        // Gecko Browser should use _offsetX
+        if(!event.originalEvent.offsetX) {
+          offset = {
+            x: event.originalEvent._offsetX,
+            y: event.originalEvent._offsetY
+          };
+        } else {
+          offset = {
+            x: event.offsetX,
+            y: event.offsetY
+          };
+        }
+
         // zoom in relative to diagram {x,y} coordinates
-        zoom(y, { x: event.offsetX, y: event.offsetY });
+        zoom(y, offset);
       }
 
       event.preventDefault();
@@ -71,4 +86,32 @@ function ZoomScroll(events, canvas) {
 
 ZoomScroll.$inject = [ 'eventBus', 'canvas' ];
 
-module.exports = ZoomScroll;
\ No newline at end of file
+module.exports = ZoomScroll;
+
+// Thx to https://bugzilla.mozilla.org/show_bug.cgi?id=69787#c37
+// for providing a work around for missing offsetX in Gecko
+Object.defineProperties(MouseEvent.prototype, {
+  _offsetRelativeElement: {
+    get: function() {
+      var element = this.target;
+      while (['block', 'inline-block', 'list-item', 'table', 'inline-table', 'table-caption',
+        'table-column', 'table-colgroup', 'table-header-group', 'table-row-group', 'table-footer-group',
+        'table-row', 'table-cell'].indexOf(window.getComputedStyle(element).display) === -1) {
+
+        element = element.parentNode;
+      }
+
+      return element;
+    }
+  },
+  _offsetX: {
+    get: function() {
+      return this.clientX - this._offsetRelativeElement.getBoundingClientRect().left;
+    }
+  },
+  _offsetY: {
+    get: function() {
+      return this.clientY - this._offsetRelativeElement.getBoundingClientRect().top;
+    }
+  }
+});
\ No newline at end of file