From d84ea36159dc948383c41f173ef510a3899b51bf Mon Sep 17 00:00:00 2001
From: Laurent Le Goff <legoff.laurent@gmail.com>
Date: Thu, 14 Apr 2011 15:01:10 +0200
Subject: [PATCH] resolve bug on transformation matrix

---
 draw2d/transform.go | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/draw2d/transform.go b/draw2d/transform.go
index a794483..ce3e80e 100644
--- a/draw2d/transform.go
+++ b/draw2d/transform.go
@@ -144,33 +144,30 @@ func (tr1 MatrixTransform) Multiply(tr2 MatrixTransform) MatrixTransform {
 
 
 func (tr *MatrixTransform) Scale(sx, sy float64) *MatrixTransform {
-	tr[0] = tr[0] * sx
-	tr[1] = tr[1] * sx
-	tr[4] = tr[4] * sx
-	tr[2] = tr[2] * sy
-	tr[3] = tr[3] * sy
-	tr[5] = tr[5] * sy
+	tr[0] = sx*tr[0]
+	tr[1] = sx*tr[1]
+	tr[2] = sy*tr[2]
+	tr[3] = sy*tr[3]
 	return tr
 }
 
 func (tr *MatrixTransform) Translate(tx, ty float64) *MatrixTransform {
-	tr[4] = tr[4] + tx
-	tr[5] = tr[5] + ty
+	tr[4] = tx*tr[0] + ty*tr[2] + tr[4]
+	tr[5] = ty*tr[3] + tx*tr[1] + tr[5]
 	return tr
 }
 
 func (tr *MatrixTransform) Rotate(angle float64) *MatrixTransform {
-	ca := math.Cos(angle)
-	sa := math.Sin(angle)
-	t0 := tr[0]*ca - tr[1]*sa
-	t2 := tr[1]*ca - tr[3]*sa
-	t4 := tr[4]*ca - tr[5]*sa
-	tr[1] = tr[0]*sa + tr[1]*ca
-	tr[3] = tr[2]*sa + tr[3]*ca
-	tr[5] = tr[4]*sa + tr[5]*ca
+	c := math.Cos(angle)
+	s := math.Sin(angle)
+	t0 := c*tr[0] + s*tr[2]
+	t1 := s*tr[3] + c*tr[1]
+	t2 := c*tr[2] - s*tr[0]
+	t3 := c*tr[3] - s*tr[1]
 	tr[0] = t0
+	tr[1] = t1
 	tr[2] = t2
-	tr[4] = t4
+	tr[3] = t3
 	return tr
 }