From bd029dfebd07ae4a6e188e8623cf99b228e5d577 Mon Sep 17 00:00:00 2001
From: Peter Chiocchetti
Date: Sat, 13 Dec 2014 12:38:32 +0100
Subject: js/CGP: scroll wheel zoom center position

Closes #111
---
 js/CGP.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/js/CGP.js b/js/CGP.js
index a83380f..5ed729b 100644
--- a/js/CGP.js
+++ b/js/CGP.js
@@ -44,8 +44,10 @@ var CGP = (function() {
             if (this.stidx < 0) this.stidx = 0;
         }
         if (cstime !== this.stime[this.stidx]) {
-            var middle = this.rrdgraph.start + Math.abs(Math.round((this.rrdgraph.end - this.rrdgraph.start) / 2));
-            this.rrdgraph.start = Math.round(middle - this.stime[this.stidx] / 2);
+            var posx = e.clientX - e.target.getBoundingClientRect().left - this.rrdgraph.xorigin;
+            var relx = this.rrdgraph.xsize / Math.min(Math.max(posx, 0), this.rrdgraph.xsize);
+            var cntr = this.rrdgraph.start + Math.abs(Math.round((this.rrdgraph.end - this.rrdgraph.start) / relx));
+            this.rrdgraph.start = Math.round(cntr - this.stime[this.stidx] / relx);
             this.rrdgraph.end = this.rrdgraph.start + this.stime[this.stidx];
 
             try {
-- 
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