From 2ee5aeec56876793334d3bb2f89276c76a70adae Mon Sep 17 00:00:00 2001
From: wp <wp.no-reply@lazarus-ide-org>
Date: Wed, 10 Feb 2016 21:45:34 +0000
Subject: [PATCH] TAChart: Fix mouse-wheel-zooming with fixed chart center.

git-svn-id: trunk@51585 -
---
 components/tachart/tatools.pas | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/components/tachart/tatools.pas b/components/tachart/tatools.pas
index 2ebbfb6ea6..0b5715e6a3 100644
--- a/components/tachart/tatools.pas
+++ b/components/tachart/tatools.pas
@@ -1337,12 +1337,14 @@ var
   ext: TDoubleRect;
 begin
   ext := FChart.LogicalExtent;
-  center := FChart.ImageToGraph(APoint);
   sz := ext.b - ext.a;
-  if FixedPoint and (sz.X <> 0) and (sz.Y <> 0) then
-    ratio := (center - ext.a) / sz
-  else
+  if FixedPoint and (sz.X <> 0) and (sz.Y <> 0) then begin
+    center := FChart.ImageToGraph(APoint);
+    ratio := (center - ext.a) / sz;
+  end else begin
+    center := DoublePoint((ext.a.x + ext.b.X) / 2, (ext.a.y + ext.b.y) / 2);
     ratio := DoublePoint(0.5, 0.5);
+  end;
   ext.a := center - sz * ratio / AFactor;
   ext.b := center + sz * (DoublePoint(1, 1) - ratio) / AFactor;
   DoZoom(ext, false);