internal/graphicsdriver/metal: bug fix: need to commit replace-pixels commands at DrawTriangles

Closes #2154

internal/graphicsdriver/metal/graphics_darwin.go

@@ -334,6 +334,7 @@ type Graphics struct {
 	transparent             bool
 	maxImageSize            int
 	tmpTextures             []mtl.Texture
+	needCommitReplacePixels bool
 
 	pool unsafe.Pointer
 }
@@ -878,6 +879,17 @@ func (g *Graphics) draw(rps mtl.RenderPipelineState, dst *Image, dstRegion graph
 }
 
 func (g *Graphics) DrawTriangles(dstID graphicsdriver.ImageID, srcIDs [graphics.ShaderImageNum]graphicsdriver.ImageID, offsets [graphics.ShaderImageNum - 1][2]float32, shaderID graphicsdriver.ShaderID, indexLen int, indexOffset int, mode graphicsdriver.CompositeMode, colorM graphicsdriver.ColorM, filter graphicsdriver.Filter, address graphicsdriver.Address, dstRegion, srcRegion graphicsdriver.Region, uniforms [][]float32, evenOdd bool) error {
+	// Resolve all the replace-pixels commands before rendering with vertices (#2154).
+	// TODO: Find a better way to sync a copy-engine and a draw-engine with MTLFence.
+	if g.needCommitReplacePixels {
+		if g.cb != (mtl.CommandBuffer{}) {
+			g.cb.Commit()
+			g.cb.WaitUntilCompleted()
+			g.cb = mtl.CommandBuffer{}
+		}
+		g.needCommitReplacePixels = false
+	}
+
 	dst := g.images[dstID]
 
 	if dst.screen {
@@ -1266,6 +1278,7 @@ func (i *Image) ReplacePixels(args []*graphicsdriver.ReplacePixelsArgs) error {
 		bce.CopyFromTexture(t, 0, 0, so, ss, i.texture, 0, 0, do)
 	}
 	bce.EndEncoding()
+	g.needCommitReplacePixels = true
 
 	return nil
 }

internal/processtest/testdata/issue2154.go

@@ -0,0 +1,91 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"image/color"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+var regularTermination = errors.New("regular termination")
+
+var src *ebiten.Image
+
+func init() {
+	const (
+		w = 2
+		h = 2
+	)
+
+	src0 := ebiten.NewImage(w, h)
+	src0.Fill(color.RGBA{0xff, 0xff, 0xff, 0xff})
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			src0.Set(i, j, color.RGBA{0, 0, 0, 0xff})
+		}
+	}
+
+	src1 := ebiten.NewImage(w, h)
+	src1.DrawImage(src0, nil)
+
+	src = src1
+}
+
+type Game struct {
+	count int
+	dst   *ebiten.Image
+}
+
+func (g *Game) Update() error {
+	g.count++
+	if g.count == 16 {
+		return regularTermination
+	}
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	screen.Fill(color.RGBA{0xff, 0xff, 0xff, 0xff})
+	screen.DrawImage(src, nil)
+
+	if g.dst == nil {
+		g.dst = ebiten.NewImage(screen.Size())
+		return
+	}
+
+	// Get the pixel at the next frame.
+	g.dst.DrawImage(screen, nil)
+	got := g.dst.At(0, 0)
+	want := color.RGBA{0, 0, 0, 0xff}
+	if got != want {
+		panic(fmt.Sprintf("got: %v, want: %v", got, want))
+	}
+}
+
+func (g *Game) Layout(width, height int) (int, int) {
+	return width, height
+}
+
+func main() {
+	if err := ebiten.RunGame(&Game{}); err != nil && err != regularTermination {
+		panic(err)
+	}
+}