From dad427920d87837025e5b613e498a75de7a3164d Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 25 May 2017 22:50:47 +0900
Subject: [PATCH] affine: Add Reset function

---
 colorm.go                 | 5 +++++
 examples/sprites/main.go  | 2 +-
 geom.go                   | 5 +++++
 internal/affine/colorm.go | 4 ++++
 internal/affine/geom.go   | 4 ++++
 5 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/colorm.go b/colorm.go
index 57be2f31e..332413f81 100644
--- a/colorm.go
+++ b/colorm.go
@@ -33,6 +33,11 @@ type ColorM struct {
 	impl affine.ColorM
 }
 
+// Reset resets the ColorM as identity.
+func (c *ColorM) Reset() {
+	c.impl.Reset()
+}
+
 // Concat multiplies a color matrix with the other color matrix.
 // This is same as muptiplying the matrix other and the matrix c in this order.
 func (c *ColorM) Concat(other ColorM) {
diff --git a/examples/sprites/main.go b/examples/sprites/main.go
index 281606ca7..2350937a6 100644
--- a/examples/sprites/main.go
+++ b/examples/sprites/main.go
@@ -110,7 +110,7 @@ func update(screen *ebiten.Image) error {
 	}
 	for i := 0; i < sprites.num; i++ {
 		s := sprites.sprites[i]
-		op.GeoM = ebiten.GeoM{}
+		op.GeoM.Reset()
 		op.GeoM.Translate(float64(s.x), float64(s.y))
 		screen.DrawImage(ebitenImage, op)
 	}
diff --git a/geom.go b/geom.go
index fb54a16ee..433218d2e 100644
--- a/geom.go
+++ b/geom.go
@@ -28,6 +28,11 @@ type GeoM struct {
 	impl affine.GeoM
 }
 
+// Reset resets the GeoM as identity.
+func (g *GeoM) Reset() {
+	g.impl.Reset()
+}
+
 // Element returns a value of a matrix at (i, j).
 func (g *GeoM) Element(i, j int) float64 {
 	a, b, c, d, tx, ty := g.impl.Elements()
diff --git a/internal/affine/colorm.go b/internal/affine/colorm.go
index c14632091..bd13c5ab9 100644
--- a/internal/affine/colorm.go
+++ b/internal/affine/colorm.go
@@ -44,6 +44,10 @@ type ColorM struct {
 	elements []float64
 }
 
+func (c *ColorM) Reset() {
+	c.elements = nil
+}
+
 func (c *ColorM) UnsafeElements() []float64 {
 	if c.elements == nil {
 		c.elements = colorMIdentityElements
diff --git a/internal/affine/geom.go b/internal/affine/geom.go
index 3cfa30a04..68ea30b15 100644
--- a/internal/affine/geom.go
+++ b/internal/affine/geom.go
@@ -34,6 +34,10 @@ type GeoM struct {
 	inited bool
 }
 
+func (g *GeoM) Reset() {
+	g.inited = false
+}
+
 func (g *GeoM) Elements() (a, b, c, d, tx, ty float64) {
 	if !g.inited {
 		return 1, 0, 0, 1, 0, 0