From 3678b20c5d88b649d5b18624da01994c59a9d034 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sun, 27 Aug 2023 01:40:37 +0900
Subject: [PATCH] ebiten: bug fix: DrawImage/DrawRectShader unexpectedly
 modified the given options

Closes #2733
---
 image.go      | 12 +++++++-----
 image_test.go | 28 ++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/image.go b/image.go
index 95b74835b..23010553d 100644
--- a/image.go
+++ b/image.go
@@ -240,10 +240,11 @@ func (i *Image) DrawImage(img *Image, options *DrawImageOptions) {
 	}
 	filter := builtinshader.Filter(options.Filter)
 
+	geoM := options.GeoM
 	if offsetX, offsetY := i.adjustPosition(0, 0); offsetX != 0 || offsetY != 0 {
-		options.GeoM.Translate(float64(offsetX), float64(offsetY))
+		geoM.Translate(float64(offsetX), float64(offsetY))
 	}
-	a, b, c, d, tx, ty := options.GeoM.elements32()
+	a, b, c, d, tx, ty := geoM.elements32()
 
 	bounds := img.Bounds()
 	sx0, sy0 := img.adjustPosition(bounds.Min.X, bounds.Min.Y)
@@ -269,7 +270,7 @@ func (i *Image) DrawImage(img *Image, options *DrawImageOptions) {
 		})
 	}
 
-	i.image.DrawTriangles(srcs, vs, is, blend, i.adjustedRegion(), img.adjustedRegion(), [graphics.ShaderImageCount - 1][2]float32{}, shader.shader, i.tmpUniforms, false, canSkipMipmap(options.GeoM, filter), false)
+	i.image.DrawTriangles(srcs, vs, is, blend, i.adjustedRegion(), img.adjustedRegion(), [graphics.ShaderImageCount - 1][2]float32{}, shader.shader, i.tmpUniforms, false, canSkipMipmap(geoM, filter), false)
 }
 
 // Vertex represents a vertex passed to DrawTriangles.
@@ -792,10 +793,11 @@ func (i *Image) DrawRectShader(width, height int, shader *Shader, options *DrawR
 		}
 	}
 
+	geoM := options.GeoM
 	if offsetX, offsetY := i.adjustPosition(0, 0); offsetX != 0 || offsetY != 0 {
-		options.GeoM.Translate(float64(offsetX), float64(offsetY))
+		geoM.Translate(float64(offsetX), float64(offsetY))
 	}
-	a, b, c, d, tx, ty := options.GeoM.elements32()
+	a, b, c, d, tx, ty := geoM.elements32()
 	cr, cg, cb, ca := options.ColorScale.elements()
 	vs := i.ensureTmpVertices(4 * graphics.VertexFloatCount)
 	graphics.QuadVertices(vs, float32(sx), float32(sy), float32(sx+width), float32(sy+height), a, b, c, d, tx, ty, cr, cg, cb, ca)
diff --git a/image_test.go b/image_test.go
index 1755bcbba..63d9afe70 100644
--- a/image_test.go
+++ b/image_test.go
@@ -4203,3 +4203,31 @@ func TestImageDrawTrianglesShaderWithTooBigIndex(t *testing.T) {
 	}
 	dst.DrawTrianglesShader(vs, is, shader, nil)
 }
+
+// Issue #2733
+func TestImageGeoMAfterDraw(t *testing.T) {
+	src := ebiten.NewImage(1, 1)
+	dst := ebiten.NewImageWithOptions(image.Rect(-1, -1, 0, 0), nil)
+	op0 := &ebiten.DrawImageOptions{}
+	dst.DrawImage(src, op0)
+	if x, y := op0.GeoM.Apply(0, 0); x != 0 || y != 0 {
+		t.Errorf("got: (%0.2f, %0.2f), want: (0, 0)", x, y)
+	}
+
+	s, err := ebiten.NewShader([]byte(`//kage:unit pixels
+
+package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	return vec4(1)
+}
+`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	op1 := &ebiten.DrawRectShaderOptions{}
+	dst.DrawRectShader(1, 1, s, op1)
+	if x, y := op1.GeoM.Apply(0, 0); x != 0 || y != 0 {
+		t.Errorf("got: (%0.2f, %0.2f), want: (0, 0)", x, y)
+	}
+}