From 674802d2f54a06d5aaca1894c7096c8848fbe31c Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Mon, 5 Jul 2021 18:08:52 +0900
Subject: [PATCH] ebiten: Bug fix: Draw commands with EvenOdd should not be
 merged

Updates #1684
---
 image_test.go                             | 40 ++++++++++++++++++++++-
 internal/graphicscommand/command.go       |  2 +-
 internal/graphicsdriver/metal/graphics.go | 14 +++-----
 3 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/image_test.go b/image_test.go
index 38797af0b..de421d296 100644
--- a/image_test.go
+++ b/image_test.go
@@ -2332,7 +2332,7 @@ func TestImageEvenOdd(t *testing.T) {
 		}
 	}
 
-	// Do the same thing with a little shift. This confirms that the underlying stencil buffer is cleared correctly.
+	// Do the same thing but with a little shift. This confirms that the underlying stencil buffer is cleared correctly.
 	for i := range vs0 {
 		vs0[i].DstX++
 		vs0[i].DstY++
@@ -2366,4 +2366,42 @@ func TestImageEvenOdd(t *testing.T) {
 			}
 		}
 	}
+
+	// Do the same thing but with split DrawTriangle calls. This confirms that the even-odd rule is applied for one call.
+	for i := range vs0 {
+		vs0[i].DstX--
+		vs0[i].DstY--
+	}
+	for i := range vs1 {
+		vs1[i].DstX--
+		vs1[i].DstY--
+	}
+	for i := range vs2 {
+		vs2[i].DstX--
+		vs2[i].DstY--
+	}
+	dst.Clear()
+	// Use the first indices set.
+	dst.DrawTriangles(vs0, is0, emptySubImage, op)
+	dst.DrawTriangles(vs1, is0, emptySubImage, op)
+	dst.DrawTriangles(vs2, is0, emptySubImage, op)
+	for j := 0; j < 16; j++ {
+		for i := 0; i < 16; i++ {
+			got := dst.At(i, j)
+			var want color.RGBA
+			switch {
+			case 3 <= i && i < 13 && 3 <= j && j < 13:
+				want = color.RGBA{0, 0, 0xff, 0xff}
+			case 2 <= i && i < 14 && 2 <= j && j < 14:
+				want = color.RGBA{0, 0xff, 0, 0xff}
+			case 1 <= i && i < 15 && 1 <= j && j < 15:
+				want = color.RGBA{0xff, 0, 0, 0xff}
+			default:
+				want = color.RGBA{0, 0, 0, 0}
+			}
+			if got != want {
+				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
+			}
+		}
+	}
 }
diff --git a/internal/graphicscommand/command.go b/internal/graphicscommand/command.go
index b9d9cbd45..d21163a14 100644
--- a/internal/graphicscommand/command.go
+++ b/internal/graphicscommand/command.go
@@ -482,7 +482,7 @@ func (c *drawTrianglesCommand) CanMergeWithDrawTrianglesCommand(dst *Image, srcs
 	if c.srcRegion != srcRegion {
 		return false
 	}
-	if c.evenOdd != evenOdd {
+	if c.evenOdd || evenOdd {
 		return false
 	}
 	return true
diff --git a/internal/graphicsdriver/metal/graphics.go b/internal/graphicsdriver/metal/graphics.go
index 86a0c7682..affaa7ea8 100644
--- a/internal/graphicsdriver/metal/graphics.go
+++ b/internal/graphicsdriver/metal/graphics.go
@@ -316,7 +316,6 @@ type Graphics struct {
 	screenDrawable ca.MetalDrawable
 
 	lastDstTexture mtl.Texture
-	lastStencilUse bool
 
 	vb mtl.Buffer
 	ib mtl.Buffer
@@ -345,10 +344,6 @@ const (
 	noStencil
 )
 
-func (s stencilMode) useStencil() bool {
-	return s != noStencil
-}
-
 var theGraphics Graphics
 
 func Get() *Graphics {
@@ -645,11 +640,13 @@ func (g *Graphics) flushRenderCommandEncoderIfNeeded() {
 	g.rce.EndEncoding()
 	g.rce = mtl.RenderCommandEncoder{}
 	g.lastDstTexture = mtl.Texture{}
-	g.lastStencilUse = false
 }
 
 func (g *Graphics) draw(rps mtl.RenderPipelineState, dst *Image, dstRegion driver.Region, srcs [graphics.ShaderImageNum]*Image, indexLen int, indexOffset int, uniforms []interface{}, stencilMode stencilMode) error {
-	if g.lastDstTexture != dst.mtlTexture() || g.lastStencilUse != stencilMode.useStencil() {
+	// When prepareing a stencil buffer, flush the current render command encoder
+	// to make sure the stencil buffer is cleared when loading.
+	// TODO: What about clearing the stencil buffer by vertices?
+	if g.lastDstTexture != dst.mtlTexture() || stencilMode == prepareStencil {
 		g.flushRenderCommandEncoderIfNeeded()
 	}
 
@@ -668,7 +665,7 @@ func (g *Graphics) draw(rps mtl.RenderPipelineState, dst *Image, dstRegion drive
 		rpd.ColorAttachments[0].Texture = t
 		rpd.ColorAttachments[0].ClearColor = mtl.ClearColor{}
 
-		if stencilMode.useStencil() {
+		if stencilMode == prepareStencil {
 			dst.ensureStencil()
 			rpd.StencilAttachment.LoadAction = mtl.LoadActionClear
 			rpd.StencilAttachment.StoreAction = mtl.StoreActionDontCare
@@ -680,7 +677,6 @@ func (g *Graphics) draw(rps mtl.RenderPipelineState, dst *Image, dstRegion drive
 		}
 		g.rce = g.cb.MakeRenderCommandEncoder(rpd)
 	}
-	g.lastStencilUse = stencilMode.useStencil()
 
 	g.rce.SetRenderPipelineState(rps)