vector: reduce allocations

This is a preparation for #2884.

Updates #2884

.github/workflows/test.yml

@@ -153,7 +153,7 @@ jobs:
         if: runner.os == 'Linux'
         run: |
           sudo apt-get install libgles2-mesa-dev
-          env EBITENGINE_GRAPHICS_LIBRARY=opengl EBITENGINE_OPENGL=es go test -shuffle=on -v -p=1 ./...
+          env EBITENGINE_GRAPHICS_LIBRARY=opengl go test -shuffle=on -v -p=1 ./...
 
       - name: go test (Windows)
         if: runner.os == 'Windows'
@@ -168,7 +168,7 @@ jobs:
           env GOARCH=386 EBITENGINE_DIRECTX=version=12 go test -shuffle=on -v ./...
 
       - name: go test (Wasm)
-        if: ${{ runner.os != 'macOS' }}
+        if: runner.os != 'macOS'
         run: |
           # Wasm tests don't work on macOS with the headless mode enabled, but the headless mode cannot be disabled in GitHub Actions (#2972).
           env GOOS=js GOARCH=wasm cleanenv -remove-prefix GITHUB_ -remove-prefix JAVA_ -remove-prefix PSModulePath -remove-prefix STATS_ -remove-prefix RUNNER_ -- go test -shuffle=on -v ./...

doc.go

@@ -93,11 +93,6 @@
 // The option "featurelevel" is valid only for DirectX 12.
 // The possible values are "11_0", "11_1", "12_0", "12_1", and "12_2". The default value is "11_0".
 //
-// `EBITENGINE_OPENGL` environment variable specifies various parameters for OpenGL.
-// You can specify multiple values separated by a comma. The default value is empty (i.e. no parameters).
-//
-//	"es": Use OpenGL ES. Without this, OpenGL and OpenGL ES are automatically chosen.
-//
 // # Build tags
 //
 // `ebitenginedebug` outputs a log of graphics commands. This is useful to know what happens in Ebitengine. In general, the

examples/vector/main.go

@@ -44,7 +44,17 @@ const (
 	screenHeight = 480
 )
 
-func drawEbitenText(screen *ebiten.Image, x, y int, aa bool, line bool) {
+type Game struct {
+	counter int
+
+	aa   bool
+	line bool
+
+	vertices []ebiten.Vertex
+	indices  []uint16
+}
+
+func (g *Game) drawEbitenText(screen *ebiten.Image, x, y int, aa bool, line bool) {
 	var path vector.Path
 
 	// E
@@ -116,26 +126,24 @@ func drawEbitenText(screen *ebiten.Image, x, y int, aa bool, line bool) {
 	path.LineTo(290, 20)
 	path.Close()
 
-	var vs []ebiten.Vertex
-	var is []uint16
 	if line {
 		op := &vector.StrokeOptions{}
 		op.Width = 5
 		op.LineJoin = vector.LineJoinRound
-		vs, is = path.AppendVerticesAndIndicesForStroke(nil, nil, op)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForStroke(g.vertices[:0], g.indices[:0], op)
 	} else {
-		vs, is = path.AppendVerticesAndIndicesForFilling(nil, nil)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForFilling(g.vertices[:0], g.indices[:0])
 	}
 
-	for i := range vs {
+	for i := range g.vertices {
-		vs[i].DstX = (vs[i].DstX + float32(x))
+		g.vertices[i].DstX = (g.vertices[i].DstX + float32(x))
-		vs[i].DstY = (vs[i].DstY + float32(y))
+		g.vertices[i].DstY = (g.vertices[i].DstY + float32(y))
-		vs[i].SrcX = 1
+		g.vertices[i].SrcX = 1
-		vs[i].SrcY = 1
+		g.vertices[i].SrcY = 1
-		vs[i].ColorR = 0xdb / float32(0xff)
+		g.vertices[i].ColorR = 0xdb / float32(0xff)
-		vs[i].ColorG = 0x56 / float32(0xff)
+		g.vertices[i].ColorG = 0x56 / float32(0xff)
-		vs[i].ColorB = 0x20 / float32(0xff)
+		g.vertices[i].ColorB = 0x20 / float32(0xff)
-		vs[i].ColorA = 1
+		g.vertices[i].ColorA = 1
 	}
 
 	op := &ebiten.DrawTrianglesOptions{}
@@ -150,10 +158,10 @@ func drawEbitenText(screen *ebiten.Image, x, y int, aa bool, line bool) {
 	// For simplicity, this example always uses FillRuleNonZero, whichever strokes or filling is done.
 	op.FillRule = ebiten.FillRuleNonZero
 
-	screen.DrawTriangles(vs, is, whiteSubImage, op)
+	screen.DrawTriangles(g.vertices, g.indices, whiteSubImage, op)
 }
 
-func drawEbitenLogo(screen *ebiten.Image, x, y int, aa bool, line bool) {
+func (g *Game) drawEbitenLogo(screen *ebiten.Image, x, y int, aa bool, line bool) {
 	const unit = 16
 
 	var path vector.Path
@@ -179,35 +187,33 @@ func drawEbitenLogo(screen *ebiten.Image, x, y int, aa bool, line bool) {
 	path.LineTo(unit, 4*unit)
 	path.Close()
 
-	var vs []ebiten.Vertex
-	var is []uint16
 	if line {
 		op := &vector.StrokeOptions{}
 		op.Width = 5
 		op.LineJoin = vector.LineJoinRound
-		vs, is = path.AppendVerticesAndIndicesForStroke(nil, nil, op)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForStroke(g.vertices[:0], g.indices[:0], op)
 	} else {
-		vs, is = path.AppendVerticesAndIndicesForFilling(nil, nil)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForFilling(g.vertices[:0], g.indices[:0])
 	}
 
-	for i := range vs {
+	for i := range g.vertices {
-		vs[i].DstX = (vs[i].DstX + float32(x))
+		g.vertices[i].DstX = (g.vertices[i].DstX + float32(x))
-		vs[i].DstY = (vs[i].DstY + float32(y))
+		g.vertices[i].DstY = (g.vertices[i].DstY + float32(y))
-		vs[i].SrcX = 1
+		g.vertices[i].SrcX = 1
-		vs[i].SrcY = 1
+		g.vertices[i].SrcY = 1
-		vs[i].ColorR = 0xdb / float32(0xff)
+		g.vertices[i].ColorR = 0xdb / float32(0xff)
-		vs[i].ColorG = 0x56 / float32(0xff)
+		g.vertices[i].ColorG = 0x56 / float32(0xff)
-		vs[i].ColorB = 0x20 / float32(0xff)
+		g.vertices[i].ColorB = 0x20 / float32(0xff)
-		vs[i].ColorA = 1
+		g.vertices[i].ColorA = 1
 	}
 
 	op := &ebiten.DrawTrianglesOptions{}
 	op.AntiAlias = aa
 	op.FillRule = ebiten.FillRuleNonZero
-	screen.DrawTriangles(vs, is, whiteSubImage, op)
+	screen.DrawTriangles(g.vertices, g.indices, whiteSubImage, op)
 }
 
-func drawArc(screen *ebiten.Image, count int, aa bool, line bool) {
+func (g *Game) drawArc(screen *ebiten.Image, count int, aa bool, line bool) {
 	var path vector.Path
 
 	path.MoveTo(350, 100)
@@ -223,37 +229,35 @@ func drawArc(screen *ebiten.Image, count int, aa bool, line bool) {
 	path.Arc(550, 100, 50, float32(theta1), float32(theta2), vector.Clockwise)
 	path.Close()
 
-	var vs []ebiten.Vertex
-	var is []uint16
 	if line {
 		op := &vector.StrokeOptions{}
 		op.Width = 5
 		op.LineJoin = vector.LineJoinRound
-		vs, is = path.AppendVerticesAndIndicesForStroke(nil, nil, op)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForStroke(g.vertices[:0], g.indices[:0], op)
 	} else {
-		vs, is = path.AppendVerticesAndIndicesForFilling(nil, nil)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForFilling(g.vertices[:0], g.indices[:0])
 	}
 
-	for i := range vs {
+	for i := range g.vertices {
-		vs[i].SrcX = 1
+		g.vertices[i].SrcX = 1
-		vs[i].SrcY = 1
+		g.vertices[i].SrcY = 1
-		vs[i].ColorR = 0x33 / float32(0xff)
+		g.vertices[i].ColorR = 0x33 / float32(0xff)
-		vs[i].ColorG = 0xcc / float32(0xff)
+		g.vertices[i].ColorG = 0xcc / float32(0xff)
-		vs[i].ColorB = 0x66 / float32(0xff)
+		g.vertices[i].ColorB = 0x66 / float32(0xff)
-		vs[i].ColorA = 1
+		g.vertices[i].ColorA = 1
 	}
 
 	op := &ebiten.DrawTrianglesOptions{}
 	op.AntiAlias = aa
 	op.FillRule = ebiten.FillRuleNonZero
-	screen.DrawTriangles(vs, is, whiteSubImage, op)
+	screen.DrawTriangles(g.vertices, g.indices, whiteSubImage, op)
 }
 
 func maxCounter(index int) int {
 	return 128 + (17*index+32)%64
 }
 
-func drawWave(screen *ebiten.Image, counter int, aa bool, line bool) {
+func (g *Game) drawWave(screen *ebiten.Image, counter int, aa bool, line bool) {
 	var path vector.Path
 
 	const npoints = 8
@@ -278,37 +282,28 @@ func drawWave(screen *ebiten.Image, counter int, aa bool, line bool) {
 	path.LineTo(screenWidth, screenHeight)
 	path.LineTo(0, screenHeight)
 
-	var vs []ebiten.Vertex
-	var is []uint16
 	if line {
 		op := &vector.StrokeOptions{}
 		op.Width = 5
 		op.LineJoin = vector.LineJoinRound
-		vs, is = path.AppendVerticesAndIndicesForStroke(nil, nil, op)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForStroke(g.vertices[:0], g.indices[:0], op)
 	} else {
-		vs, is = path.AppendVerticesAndIndicesForFilling(nil, nil)
+		g.vertices, g.indices = path.AppendVerticesAndIndicesForFilling(g.vertices[:0], g.indices[:0])
 	}
 
-	for i := range vs {
+	for i := range g.vertices {
-		vs[i].SrcX = 1
+		g.vertices[i].SrcX = 1
-		vs[i].SrcY = 1
+		g.vertices[i].SrcY = 1
-		vs[i].ColorR = 0x33 / float32(0xff)
+		g.vertices[i].ColorR = 0x33 / float32(0xff)
-		vs[i].ColorG = 0x66 / float32(0xff)
+		g.vertices[i].ColorG = 0x66 / float32(0xff)
-		vs[i].ColorB = 0xff / float32(0xff)
+		g.vertices[i].ColorB = 0xff / float32(0xff)
-		vs[i].ColorA = 1
+		g.vertices[i].ColorA = 1
 	}
 
 	op := &ebiten.DrawTrianglesOptions{}
 	op.AntiAlias = aa
 	op.FillRule = ebiten.FillRuleNonZero
-	screen.DrawTriangles(vs, is, whiteSubImage, op)
+	screen.DrawTriangles(g.vertices, g.indices, whiteSubImage, op)
-}
-
-type Game struct {
-	counter int
-
-	aa   bool
-	line bool
 }
 
 func (g *Game) Update() error {
@@ -331,10 +326,10 @@ func (g *Game) Draw(screen *ebiten.Image) {
 	dst := screen
 
 	dst.Fill(color.RGBA{0xe0, 0xe0, 0xe0, 0xff})
-	drawEbitenText(dst, 0, 50, g.aa, g.line)
+	g.drawEbitenText(dst, 0, 50, g.aa, g.line)
-	drawEbitenLogo(dst, 20, 150, g.aa, g.line)
+	g.drawEbitenLogo(dst, 20, 150, g.aa, g.line)
-	drawArc(dst, g.counter, g.aa, g.line)
+	g.drawArc(dst, g.counter, g.aa, g.line)
-	drawWave(dst, g.counter, g.aa, g.line)
+	g.drawWave(dst, g.counter, g.aa, g.line)
 
 	msg := fmt.Sprintf("TPS: %0.2f\nFPS: %0.2f", ebiten.ActualTPS(), ebiten.ActualFPS())
 	msg += "\nPress A to switch anti-alias."

internal/graphicsdriver/opengl/gl/procaddr_linbsd.go

@@ -18,8 +18,6 @@ package gl
 
 import (
 	"fmt"
-	"os"
-	"runtime"
 	"strings"
 
 	"github.com/ebitengine/purego"
@@ -31,40 +29,10 @@ var (
 )
 
 func (c *defaultContext) init() error {
-	var preferES bool
-	if runtime.GOOS == "android" {
-		preferES = true
-	}
-	if !preferES {
-		for _, t := range strings.Split(os.Getenv("EBITENGINE_OPENGL"), ",") {
-			switch strings.TrimSpace(t) {
-			case "es":
-				preferES = true
-				break
-			}
-		}
-	}
-
 	// TODO: Use multiple %w-s as of Go 1.20.
 	var errors []string
 
-	// Try OpenGL first. OpenGL is preferable as this doesn't cause context losses.
+	// Try OpenGL ES first. Some machines like Android and Raspberry Pi might work only with OpenGL ES.
-	if !preferES {
-		// Usually libGL.so or libGL.so.1 is used. libGL.so.2 might exist only on NetBSD.
-		// TODO: Should "libOpenGL.so.0" [1] and "libGLX.so.0" [2] be added? These were added as of GLFW 3.3.9.
-		// [1] https://github.com/glfw/glfw/commit/55aad3c37b67f17279378db52da0a3ab81bbf26d
-		// [2] https://github.com/glfw/glfw/commit/c18851f52ec9704eb06464058a600845ec1eada1
-		for _, name := range []string{"libGL.so", "libGL.so.2", "libGL.so.1", "libGL.so.0"} {
-			lib, err := purego.Dlopen(name, purego.RTLD_LAZY|purego.RTLD_GLOBAL)
-			if err == nil {
-				libGL = lib
-				return nil
-			}
-			errors = append(errors, fmt.Sprintf("%s: %v", name, err))
-		}
-	}
-
-	// Try OpenGL ES.
 	for _, name := range []string{"libGLESv2.so", "libGLESv2.so.2", "libGLESv2.so.1", "libGLESv2.so.0"} {
 		lib, err := purego.Dlopen(name, purego.RTLD_LAZY|purego.RTLD_GLOBAL)
 		if err == nil {
@@ -75,6 +43,20 @@ func (c *defaultContext) init() error {
 		errors = append(errors, fmt.Sprintf("%s: %v", name, err))
 	}
 
+	// Try OpenGL next.
+	// Usually libGL.so or libGL.so.1 is used. libGL.so.2 might exist only on NetBSD.
+	// TODO: Should "libOpenGL.so.0" [1] and "libGLX.so.0" [2] be added? These were added as of GLFW 3.3.9.
+	// [1] https://github.com/glfw/glfw/commit/55aad3c37b67f17279378db52da0a3ab81bbf26d
+	// [2] https://github.com/glfw/glfw/commit/c18851f52ec9704eb06464058a600845ec1eada1
+	for _, name := range []string{"libGL.so", "libGL.so.2", "libGL.so.1", "libGL.so.0"} {
+		lib, err := purego.Dlopen(name, purego.RTLD_LAZY|purego.RTLD_GLOBAL)
+		if err == nil {
+			libGL = lib
+			return nil
+		}
+		errors = append(errors, fmt.Sprintf("%s: %v", name, err))
+	}
+
 	return fmt.Errorf("gl: failed to load libGL.so and libGLESv2.so: %s", strings.Join(errors, ", "))
 }
 

vector/path.go

@@ -31,6 +31,23 @@ const (
 	CounterClockwise
 )
 
+type opType int
+
+const (
+	opTypeMoveTo opType = iota
+	opTypeLineTo
+	opTypeQuadTo
+	opTypeCubicTo
+	opTypeClose
+)
+
+type op struct {
+	typ opType
+	p1  point
+	p2  point
+	p3  point
+}
+
 func abs(x float32) float32 {
 	if x < 0 {
 		return -x
@@ -48,16 +65,6 @@ type subpath struct {
 	closed bool
 }
 
-func (s *subpath) currentPosition() (point, bool) {
-	if len(s.points) == 0 {
-		return point{}, false
-	}
-	if s.closed {
-		return point{}, false
-	}
-	return s.points[len(s.points)-1], true
-}
-
 func (s *subpath) pointCount() int {
 	return len(s.points)
 }
@@ -91,15 +98,51 @@ func (s *subpath) close() {
 
 // Path represents a collection of path subpathments.
 type Path struct {
+	ops []op
+
 	subpaths []*subpath
 }
 
+func (p *Path) ensureSubpaths() []*subpath {
+	// TODO: Probably it is better to avoid returning a slice since allocation is heavy.
+	// What about walkSubpaths(func(*subpath))?
+
+	if len(p.subpaths) > 0 || len(p.ops) == 0 {
+		return p.subpaths
+	}
+
+	var cur point
+	for _, op := range p.ops {
+		switch op.typ {
+		case opTypeMoveTo:
+			p.subpaths = append(p.subpaths, &subpath{
+				points: []point{op.p1},
+			})
+			cur = op.p1
+		case opTypeLineTo:
+			p.lineTo(op.p1)
+			cur = op.p1
+		case opTypeQuadTo:
+			p.quadTo(cur, op.p1, op.p2, 0)
+			cur = op.p2
+		case opTypeCubicTo:
+			p.cubicTo(cur, op.p1, op.p2, op.p3, 0)
+			cur = op.p3
+		case opTypeClose:
+			p.close()
+			cur = point{}
+		}
+	}
+
+	return p.subpaths
+}
+
 // MoveTo starts a new subpath with the given position (x, y) without adding a subpath,
 func (p *Path) MoveTo(x, y float32) {
-	p.subpaths = append(p.subpaths, &subpath{
+	p.subpaths = p.subpaths[:0]
-		points: []point{
+	p.ops = append(p.ops, op{
-			{x: x, y: y},
+		typ: opTypeMoveTo,
-		},
+		p1:  point{x: x, y: y},
 	})
 }
 
@@ -107,22 +150,54 @@ func (p *Path) MoveTo(x, y float32) {
 // and ends to the given position (x, y).
 // If p doesn't have any subpaths or the last subpath is closed, LineTo sets (x, y) as the start position of a new subpath.
 func (p *Path) LineTo(x, y float32) {
-	if len(p.subpaths) == 0 || p.subpaths[len(p.subpaths)-1].closed {
+	p.subpaths = p.subpaths[:0]
-		p.subpaths = append(p.subpaths, &subpath{
+	p.ops = append(p.ops, op{
-			points: []point{
+		typ: opTypeLineTo,
-				{x: x, y: y},
+		p1:  point{x: x, y: y},
-			},
+	})
-		})
-		return
-	}
-
-	p.subpaths[len(p.subpaths)-1].appendPoint(point{x: x, y: y})
 }
 
 // QuadTo adds a quadratic Bézier curve to the path.
 // (x1, y1) is the control point, and (x2, y2) is the destination.
 func (p *Path) QuadTo(x1, y1, x2, y2 float32) {
-	p.quadTo(point{x: x1, y: y1}, point{x: x2, y: y2}, 0)
+	p.subpaths = p.subpaths[:0]
+	p.ops = append(p.ops, op{
+		typ: opTypeQuadTo,
+		p1:  point{x: x1, y: y1},
+		p2:  point{x: x2, y: y2},
+	})
+}
+
+// CubicTo adds a cubic Bézier curve to the path.
+// (x1, y1) and (x2, y2) are the control points, and (x3, y3) is the destination.
+func (p *Path) CubicTo(x1, y1, x2, y2, x3, y3 float32) {
+	p.subpaths = p.subpaths[:0]
+	p.ops = append(p.ops, op{
+		typ: opTypeCubicTo,
+		p1:  point{x: x1, y: y1},
+		p2:  point{x: x2, y: y2},
+		p3:  point{x: x3, y: y3},
+	})
+}
+
+// Close adds a new line from the last position of the current subpath to the first position of the current subpath,
+// and marks the current subpath closed.
+// Following operations for this path will start with a new subpath.
+func (p *Path) Close() {
+	p.subpaths = p.subpaths[:0]
+	p.ops = append(p.ops, op{
+		typ: opTypeClose,
+	})
+}
+
+func (p *Path) lineTo(pt point) {
+	if len(p.subpaths) == 0 || p.subpaths[len(p.subpaths)-1].closed {
+		p.subpaths = append(p.subpaths, &subpath{
+			points: []point{pt},
+		})
+		return
+	}
+	p.subpaths[len(p.subpaths)-1].appendPoint(pt)
 }
 
 // lineForTwoPoints returns parameters for a line passing through p0 and p1.
@@ -154,24 +229,13 @@ func crossingPointForTwoLines(p00, p01, p10, p11 point) point {
 	}
 }
 
-func (p *Path) currentPosition() (point, bool) {
+func (p *Path) quadTo(p0, p1, p2 point, level int) {
-	if len(p.subpaths) == 0 {
-		return point{}, false
-	}
-	return p.subpaths[len(p.subpaths)-1].currentPosition()
-}
-
-func (p *Path) quadTo(p1, p2 point, level int) {
 	if level > 10 {
 		return
 	}
 
-	p0, ok := p.currentPosition()
-	if !ok {
-		p0 = p1
-	}
 	if isPointCloseToSegment(p1, p0, p2, 0.5) {
-		p.LineTo(p2.x, p2.y)
+		p.lineTo(p2)
 		return
 	}
 
@@ -187,27 +251,17 @@ func (p *Path) quadTo(p1, p2 point, level int) {
 		x: (p01.x + p12.x) / 2,
 		y: (p01.y + p12.y) / 2,
 	}
-	p.quadTo(p01, p012, level+1)
+	p.quadTo(p0, p01, p012, level+1)
-	p.quadTo(p12, p2, level+1)
+	p.quadTo(p012, p12, p2, level+1)
 }
 
-// CubicTo adds a cubic Bézier curve to the path.
+func (p *Path) cubicTo(p0, p1, p2, p3 point, level int) {
-// (x1, y1) and (x2, y2) are the control points, and (x3, y3) is the destination.
-func (p *Path) CubicTo(x1, y1, x2, y2, x3, y3 float32) {
-	p.cubicTo(point{x: x1, y: y1}, point{x: x2, y: y2}, point{x: x3, y: y3}, 0)
-}
-
-func (p *Path) cubicTo(p1, p2, p3 point, level int) {
 	if level > 10 {
 		return
 	}
 
-	p0, ok := p.currentPosition()
-	if !ok {
-		p0 = p1
-	}
 	if isPointCloseToSegment(p1, p0, p3, 0.5) && isPointCloseToSegment(p2, p0, p3, 0.5) {
-		p.LineTo(p3.x, p3.y)
+		p.lineTo(p3)
 		return
 	}
 
@@ -235,8 +289,8 @@ func (p *Path) cubicTo(p1, p2, p3 point, level int) {
 		x: (p012.x + p123.x) / 2,
 		y: (p012.y + p123.y) / 2,
 	}
-	p.cubicTo(p01, p012, p0123, level+1)
+	p.cubicTo(p0, p01, p012, p0123, level+1)
-	p.cubicTo(p123, p23, p3, level+1)
+	p.cubicTo(p0123, p123, p23, p3, level+1)
 }
 
 func normalize(p point) point {
@@ -248,6 +302,26 @@ func cross(p0, p1 point) float32 {
 	return p0.x*p1.y - p1.x*p0.y
 }
 
+func (p *Path) currentPosition() (point, bool) {
+	if len(p.ops) == 0 {
+		return point{}, false
+	}
+	op := p.ops[len(p.ops)-1]
+	switch op.typ {
+	case opTypeMoveTo:
+		return op.p1, true
+	case opTypeLineTo:
+		return op.p1, true
+	case opTypeQuadTo:
+		return op.p2, true
+	case opTypeCubicTo:
+		return op.p3, true
+	case opTypeClose:
+		return point{}, false
+	}
+	return point{}, false
+}
+
 // ArcTo adds an arc curve to the path.
 // (x1, y1) is the first control point, and (x2, y2) is the second control point.
 func (p *Path) ArcTo(x1, y1, x2, y2, radius float32) {
@@ -362,7 +436,7 @@ func (p *Path) Arc(x, y, radius, startAngle, endAngle float32, dir Direction) {
 	p.LineTo(x0, y0)
 
 	// Calculate the control points for an approximated Bézier curve.
-	// See https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/curves/beziers.
+	// See https://learn.microsoft.com/en-us/previous-versions/xamarin/xamarin-forms/user-interface/graphics/skiasharp/curves/beziers.
 	l := radius * float32(math.Tan(da/4)*4/3)
 	var cx0, cy0, cx1, cy1 float32
 	if dir == Clockwise {
@@ -379,10 +453,7 @@ func (p *Path) Arc(x, y, radius, startAngle, endAngle float32, dir Direction) {
 	p.CubicTo(cx0, cy0, cx1, cy1, x1, y1)
 }
 
-// Close adds a new line from the last position of the current subpath to the first position of the current subpath,
+func (p *Path) close() {
-// and marks the current subpath closed.
-// Following operations for this path will start with a new subpath.
-func (p *Path) Close() {
 	if len(p.subpaths) == 0 {
 		return
 	}
@@ -405,7 +476,7 @@ func (p *Path) AppendVerticesAndIndicesForFilling(vertices []ebiten.Vertex, indi
 	// TODO: Add tests.
 
 	base := uint16(len(vertices))
-	for _, subpath := range p.subpaths {
+	for _, subpath := range p.ensureSubpaths() {
 		if subpath.pointCount() < 3 {
 			continue
 		}
@@ -486,12 +557,13 @@ func (p *Path) AppendVerticesAndIndicesForStroke(vertices []ebiten.Vertex, indic
 		return vertices, indices
 	}
 
-	for _, subpath := range p.subpaths {
+	var rects [][4]point
+	for _, subpath := range p.ensureSubpaths() {
 		if subpath.pointCount() < 2 {
 			continue
 		}
 
-		var rects [][4]point
+		rects = rects[:0]
 		for i := 0; i < subpath.pointCount()-1; i++ {
 			pt := subpath.points[i]
 

vector/util.go

@@ -18,6 +18,7 @@ import (
 	"image"
 	"image/color"
 	"math"
+	"sync"
 
 	"github.com/hajimehoshi/ebiten/v2"
 )
@@ -27,6 +28,18 @@ var (
 	whiteSubImage = whiteImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
 )
 
+var (
+	cachedVertices []ebiten.Vertex
+	cachedIndices  []uint16
+	cacheM         sync.Mutex
+)
+
+func useCachedVerticesAndIndices(fn func([]ebiten.Vertex, []uint16) (vs []ebiten.Vertex, is []uint16)) {
+	cacheM.Lock()
+	defer cacheM.Unlock()
+	cachedVertices, cachedIndices = fn(cachedVertices[:0], cachedIndices[:0])
+}
+
 func init() {
 	b := whiteImage.Bounds()
 	pix := make([]byte, 4*b.Dx()*b.Dy())
@@ -63,9 +76,12 @@ func StrokeLine(dst *ebiten.Image, x0, y0, x1, y1 float32, strokeWidth float32,
 	path.LineTo(x1, y1)
 	strokeOp := &StrokeOptions{}
 	strokeOp.Width = strokeWidth
-	vs, is := path.AppendVerticesAndIndicesForStroke(nil, nil, strokeOp)
 
-	drawVerticesForUtil(dst, vs, is, clr, antialias)
+	useCachedVerticesAndIndices(func(vs []ebiten.Vertex, is []uint16) ([]ebiten.Vertex, []uint16) {
+		vs, is = path.AppendVerticesAndIndicesForStroke(vs, is, strokeOp)
+		drawVerticesForUtil(dst, vs, is, clr, antialias)
+		return vs, is
+	})
 }
 
 // DrawFilledRect fills a rectangle with the specified width and color.
@@ -75,9 +91,12 @@ func DrawFilledRect(dst *ebiten.Image, x, y, width, height float32, clr color.Co
 	path.LineTo(x, y+height)
 	path.LineTo(x+width, y+height)
 	path.LineTo(x+width, y)
-	vs, is := path.AppendVerticesAndIndicesForFilling(nil, nil)
 
-	drawVerticesForUtil(dst, vs, is, clr, antialias)
+	useCachedVerticesAndIndices(func(vs []ebiten.Vertex, is []uint16) ([]ebiten.Vertex, []uint16) {
+		vs, is = path.AppendVerticesAndIndicesForFilling(vs, is)
+		drawVerticesForUtil(dst, vs, is, clr, antialias)
+		return vs, is
+	})
 }
 
 // StrokeRect strokes a rectangle with the specified width and color.
@@ -94,18 +113,24 @@ func StrokeRect(dst *ebiten.Image, x, y, width, height float32, strokeWidth floa
 	strokeOp := &StrokeOptions{}
 	strokeOp.Width = strokeWidth
 	strokeOp.MiterLimit = 10
-	vs, is := path.AppendVerticesAndIndicesForStroke(nil, nil, strokeOp)
 
-	drawVerticesForUtil(dst, vs, is, clr, antialias)
+	useCachedVerticesAndIndices(func(vs []ebiten.Vertex, is []uint16) ([]ebiten.Vertex, []uint16) {
+		vs, is = path.AppendVerticesAndIndicesForStroke(vs, is, strokeOp)
+		drawVerticesForUtil(dst, vs, is, clr, antialias)
+		return vs, is
+	})
 }
 
 // DrawFilledCircle fills a circle with the specified center position (cx, cy), the radius (r), width and color.
 func DrawFilledCircle(dst *ebiten.Image, cx, cy, r float32, clr color.Color, antialias bool) {
 	var path Path
 	path.Arc(cx, cy, r, 0, 2*math.Pi, Clockwise)
-	vs, is := path.AppendVerticesAndIndicesForFilling(nil, nil)
 
-	drawVerticesForUtil(dst, vs, is, clr, antialias)
+	useCachedVerticesAndIndices(func(vs []ebiten.Vertex, is []uint16) ([]ebiten.Vertex, []uint16) {
+		vs, is = path.AppendVerticesAndIndicesForFilling(vs, is)
+		drawVerticesForUtil(dst, vs, is, clr, antialias)
+		return vs, is
+	})
 }
 
 // StrokeCircle strokes a circle with the specified center position (cx, cy), the radius (r), width and color.
@@ -118,7 +143,10 @@ func StrokeCircle(dst *ebiten.Image, cx, cy, r float32, strokeWidth float32, clr
 
 	strokeOp := &StrokeOptions{}
 	strokeOp.Width = strokeWidth
-	vs, is := path.AppendVerticesAndIndicesForStroke(nil, nil, strokeOp)
 
-	drawVerticesForUtil(dst, vs, is, clr, antialias)
+	useCachedVerticesAndIndices(func(vs []ebiten.Vertex, is []uint16) ([]ebiten.Vertex, []uint16) {
+		vs, is = path.AppendVerticesAndIndicesForStroke(vs, is, strokeOp)
+		drawVerticesForUtil(dst, vs, is, clr, antialias)
+		return vs, is
+	})
 }