Remove GraphicsContext; Add rendering methods to RenderTarget (#26)

ebitenutil/debugprint.go

@@ -24,17 +24,17 @@ import (
 
 type debugPrintState struct {
 	textTexture            *ebiten.Texture
-	debugPrintRenderTarget *ebiten.RenderTarget
+	debugPrintRenderTarget ebiten.RenderTarget
 	y                      int
 }
 
 var defaultDebugPrintState = new(debugPrintState)
 
-func DebugPrint(gr ebiten.GraphicsContext, str string) {
+func DebugPrint(r ebiten.RenderTarget, str string) {
-	defaultDebugPrintState.DebugPrint(gr, str)
+	defaultDebugPrintState.DebugPrint(r, str)
 }
 
-func (d *debugPrintState) drawText(gr ebiten.GraphicsContext, str string, x, y int, clr color.Color) {
+func (d *debugPrintState) drawText(r ebiten.RenderTarget, str string, x, y int, clr color.Color) {
 	parts := []ebiten.TexturePart{}
 	locationX, locationY := 0, 0
 	for _, c := range str {
@@ -57,10 +57,10 @@ func (d *debugPrintState) drawText(gr ebiten.GraphicsContext, str string, x, y i
 	geom.Concat(ebiten.TranslateGeometry(float64(x)+1, float64(y)))
 	clrm := ebiten.ColorMatrixI()
 	clrm.Concat(ebiten.ScaleColor(clr))
-	gr.DrawTexture(d.textTexture, parts, geom, clrm)
+	r.DrawTexture(d.textTexture, parts, geom, clrm)
 }
 
-func (d *debugPrintState) DebugPrint(gr ebiten.GraphicsContext, str string) {
+func (d *debugPrintState) DebugPrint(r ebiten.RenderTarget, str string) {
 	if d.textTexture == nil {
 		img, err := assets.TextImage()
 		if err != nil {
@@ -79,6 +79,6 @@ func (d *debugPrintState) DebugPrint(gr ebiten.GraphicsContext, str string) {
 			panic(err)
 		}
 	}
-	d.drawText(gr, str, 1, d.y+1, &color.RGBA{0x00, 0x00, 0x00, 0x80})
+	d.drawText(r, str, 1, d.y+1, &color.RGBA{0x00, 0x00, 0x00, 0x80})
-	d.drawText(gr, str, 0, d.y, &color.RGBA{0xff, 0xff, 0xff, 0xff})
+	d.drawText(r, str, 0, d.y, &color.RGBA{0xff, 0xff, 0xff, 0xff})
 }

example/alphablending/main.go

@@ -31,11 +31,11 @@ const (
 
 type Game struct {
 	count           int
-	tmpRenderTarget *ebiten.RenderTarget
+	tmpRenderTarget ebiten.RenderTarget
 	ebitenTexture   *ebiten.Texture
 }
 
-func (g *Game) Update(gr ebiten.GraphicsContext) error {
+func (g *Game) Update(r ebiten.RenderTarget) error {
 	g.count++
 	g.count %= 600
 	diff := float64(g.count) * 0.2
@@ -45,21 +45,26 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 	case 240 < g.count:
 		diff = float64(480-g.count) * 0.2
 	}
+	_ = diff
 
-	gr.PushRenderTarget(g.tmpRenderTarget)
+	if err := g.tmpRenderTarget.Clear(); err != nil {
-	gr.Clear()
+		return err
+	}
 	for i := 0; i < 10; i++ {
 		geo := ebiten.TranslateGeometry(15+float64(i)*(diff), 20)
 		clr := ebiten.ScaleColor(color.RGBA{0xff, 0xff, 0xff, 0x80})
-		ebiten.DrawWholeTexture(gr, g.ebitenTexture, geo, clr)
+		if err := ebiten.DrawWholeTexture(g.tmpRenderTarget, g.ebitenTexture, geo, clr); err != nil {
+			return err
+		}
 	}
-	gr.PopRenderTarget()
 
-	gr.Fill(color.RGBA{0x00, 0x00, 0x80, 0xff})
+	r.Fill(color.RGBA{0x00, 0x00, 0x80, 0xff})
 	for i := 0; i < 10; i++ {
 		geo := ebiten.TranslateGeometry(0, float64(i)*(diff))
 		clr := ebiten.ColorMatrixI()
-		ebiten.DrawWholeTexture(gr, g.tmpRenderTarget.Texture(), geo, clr)
+		if err := ebiten.DrawWholeTexture(r, g.tmpRenderTarget.Texture(), geo, clr); err != nil {
+			return err
+		}
 	}
 	return nil
 }

example/blocks/blocks/field.go

@@ -112,11 +112,11 @@ func (f *Field) flushLine(j int) bool {
 	return true
 }
 
-func (f *Field) Draw(context ebiten.GraphicsContext, textures *Textures, geo ebiten.GeometryMatrix) {
+func (f *Field) Draw(r ebiten.RenderTarget, textures *Textures, geo ebiten.GeometryMatrix) {
 	blocks := make([][]BlockType, len(f.blocks))
 	for i, blockCol := range f.blocks {
 		blocks[i] = make([]BlockType, len(blockCol))
 		copy(blocks[i], blockCol[:])
 	}
-	drawBlocks(context, textures, blocks, geo)
+	drawBlocks(r, textures, blocks, geo)
 }

example/blocks/blocks/font.go

@@ -32,7 +32,7 @@ func textWidth(str string) int {
 	return charWidth * len(str)
 }
 
-func drawText(context ebiten.GraphicsContext, textures *Textures, str string, ox, oy, scale int, clr color.Color) {
+func drawText(r ebiten.RenderTarget, textures *Textures, str string, ox, oy, scale int, clr color.Color) {
 	fontTextureId := textures.GetTexture("font")
 	parts := []ebiten.TexturePart{}
 
@@ -56,10 +56,10 @@ func drawText(context ebiten.GraphicsContext, textures *Textures, str string, ox
 	geoMat := ebiten.ScaleGeometry(float64(scale), float64(scale))
 	geoMat.Concat(ebiten.TranslateGeometry(float64(ox), float64(oy)))
 	clrMat := ebiten.ScaleColor(clr)
-	context.DrawTexture(fontTextureId, parts, geoMat, clrMat)
+	r.DrawTexture(fontTextureId, parts, geoMat, clrMat)
 }
 
-func drawTextWithShadow(context ebiten.GraphicsContext, textures *Textures, str string, x, y, scale int, clr color.Color) {
+func drawTextWithShadow(r ebiten.RenderTarget, textures *Textures, str string, x, y, scale int, clr color.Color) {
-	drawText(context, textures, str, x+1, y+1, scale, color.RGBA{0, 0, 0, 0x80})
+	drawText(r, textures, str, x+1, y+1, scale, color.RGBA{0, 0, 0, 0x80})
-	drawText(context, textures, str, x, y, scale, clr)
+	drawText(r, textures, str, x, y, scale, clr)
 }

example/blocks/blocks/game.go

@@ -70,7 +70,7 @@ func (game *Game) isInitialized() bool {
 	return true
 }
 
-func (game *Game) Update(g ebiten.GraphicsContext) error {
+func (game *Game) Update(r ebiten.RenderTarget) error {
 	game.once.Do(func() {
 		game.textures = NewTextures()
 		for name, path := range texturePaths {
@@ -88,6 +88,6 @@ func (game *Game) Update(g ebiten.GraphicsContext) error {
 		SceneManager: game.sceneManager,
 		Input:        game.input,
 	})
-	game.sceneManager.Draw(g, game.textures)
+	game.sceneManager.Draw(r, game.textures)
 	return nil
 }

example/blocks/blocks/gamescene.go

@@ -109,21 +109,21 @@ func (s *GameScene) Update(state *GameState) {
 	}
 }
 
-func (s *GameScene) Draw(context ebiten.GraphicsContext, textures *Textures) {
+func (s *GameScene) Draw(r ebiten.RenderTarget, textures *Textures) {
-	context.Fill(color.White)
+	r.Fill(color.White)
 
 	field := textures.GetTexture("empty")
 	w, h := field.Size()
 	geoMat := ebiten.ScaleGeometry(float64(fieldWidth)/float64(w), float64(fieldHeight)/float64(h))
 	geoMat.Concat(ebiten.TranslateGeometry(20, 20)) // TODO: magic number?
 	colorMat := ebiten.ScaleColor(color.RGBA{0, 0, 0, 0x80})
-	ebiten.DrawWholeTexture(context, field, geoMat, colorMat)
+	ebiten.DrawWholeTexture(r, field, geoMat, colorMat)
 
 	geoMat = ebiten.GeometryMatrixI()
 	geoMat.Concat(ebiten.TranslateGeometry(20, 20))
-	s.field.Draw(context, textures, geoMat)
+	s.field.Draw(r, textures, geoMat)
 
 	if s.currentPiece != nil {
-		s.currentPiece.Draw(context, textures, 20, 20, s.currentPieceX, s.currentPieceY, s.currentPieceAngle)
+		s.currentPiece.Draw(r, textures, 20, 20, s.currentPieceX, s.currentPieceY, s.currentPieceAngle)
 	}
 }

example/blocks/blocks/piece.go

@@ -138,7 +138,7 @@ const blockHeight = 10
 const fieldBlockNumX = 10
 const fieldBlockNumY = 20
 
-func drawBlocks(context ebiten.GraphicsContext, textures *Textures, blocks [][]BlockType, geo ebiten.GeometryMatrix) {
+func drawBlocks(r ebiten.RenderTarget, textures *Textures, blocks [][]BlockType, geo ebiten.GeometryMatrix) {
 	parts := []ebiten.TexturePart{}
 	for i, blockCol := range blocks {
 		for j, block := range blockCol {
@@ -153,7 +153,7 @@ func drawBlocks(context ebiten.GraphicsContext, textures *Textures, blocks [][]B
 		}
 	}
 	blocksTexture := textures.GetTexture("blocks")
-	context.DrawTexture(blocksTexture, parts, geo, ebiten.ColorMatrixI())
+	r.DrawTexture(blocksTexture, parts, geo, ebiten.ColorMatrixI())
 }
 
 func (p *Piece) InitialPosition() (int, int) {
@@ -213,7 +213,7 @@ func (p *Piece) AbsorbInto(field *Field, x, y int, angle Angle) {
 	}
 }
 
-func (p *Piece) Draw(context ebiten.GraphicsContext, textures *Textures, fieldX, fieldY int, pieceX, pieceY int, angle Angle) {
+func (p *Piece) Draw(r ebiten.RenderTarget, textures *Textures, fieldX, fieldY int, pieceX, pieceY int, angle Angle) {
 	size := len(p.blocks)
 	blocks := make([][]BlockType, size)
 	for i := range p.blocks {
@@ -230,5 +230,5 @@ func (p *Piece) Draw(context ebiten.GraphicsContext, textures *Textures, fieldX,
 	y := fieldY + pieceY*blockHeight
 	geoMat.Concat(ebiten.TranslateGeometry(float64(x), float64(y)))
 
-	drawBlocks(context, textures, blocks, geoMat)
+	drawBlocks(r, textures, blocks, geoMat)
 }

example/blocks/blocks/scenemanager.go

@@ -29,7 +29,7 @@ func init() {
 
 type Scene interface {
 	Update(state *GameState)
-	Draw(context ebiten.GraphicsContext, textures *Textures)
+	Draw(r ebiten.RenderTarget, textures *Textures)
 }
 
 const transitionMaxCount = 20
@@ -60,29 +60,25 @@ func (s *SceneManager) Update(state *GameState) {
 	}
 }
 
-func (s *SceneManager) Draw(context ebiten.GraphicsContext, textures *Textures) {
+func (s *SceneManager) Draw(r ebiten.RenderTarget, textures *Textures) {
 	if s.transitionCount == -1 {
-		s.current.Draw(context, textures)
+		s.current.Draw(r, textures)
 		return
 	}
 	from := textures.GetRenderTarget("scene_manager_transition_from")
-	context.PushRenderTarget(from)
+	from.Clear()
-	context.Clear()
+	s.current.Draw(from, textures)
-	s.current.Draw(context, textures)
-	context.PopRenderTarget()
 
 	to := textures.GetRenderTarget("scene_manager_transition_to")
-	context.PushRenderTarget(to)
+	to.Clear()
-	context.Clear()
+	s.next.Draw(to, textures)
-	s.next.Draw(context, textures)
-	context.PopRenderTarget()
 
 	color := ebiten.ColorMatrixI()
-	ebiten.DrawWholeTexture(context, from.Texture(), ebiten.GeometryMatrixI(), color)
+	ebiten.DrawWholeTexture(r, from.Texture(), ebiten.GeometryMatrixI(), color)
 
 	alpha := float64(s.transitionCount) / float64(transitionMaxCount)
 	color.Elements[3][3] = alpha
-	ebiten.DrawWholeTexture(context, to.Texture(), ebiten.GeometryMatrixI(), color)
+	ebiten.DrawWholeTexture(r, to.Texture(), ebiten.GeometryMatrixI(), color)
 }
 
 func (s *SceneManager) GoTo(scene Scene) {

example/blocks/blocks/textures.go

@@ -38,7 +38,7 @@ type Textures struct {
 	texturePaths      chan namePath
 	renderTargetSizes chan nameSize
 	textures          map[string]*ebiten.Texture
-	renderTargets     map[string]*ebiten.RenderTarget
+	renderTargets     map[string]ebiten.RenderTarget
 	sync.RWMutex
 }
 
@@ -47,7 +47,7 @@ func NewTextures() *Textures {
 		texturePaths:      make(chan namePath),
 		renderTargetSizes: make(chan nameSize),
 		textures:          map[string]*ebiten.Texture{},
-		renderTargets:     map[string]*ebiten.RenderTarget{},
+		renderTargets:     map[string]ebiten.RenderTarget{},
 	}
 	go func() {
 		for {
@@ -129,7 +129,7 @@ func (t *Textures) GetTexture(name string) *ebiten.Texture {
 	return t.textures[name]
 }
 
-func (t *Textures) GetRenderTarget(name string) *ebiten.RenderTarget {
+func (t *Textures) GetRenderTarget(name string) ebiten.RenderTarget {
 	t.RLock()
 	defer t.RUnlock()
 	return t.renderTargets[name]

example/blocks/blocks/titlescene.go

@@ -40,17 +40,17 @@ func (s *TitleScene) Update(state *GameState) {
 	}
 }
 
-func (s *TitleScene) Draw(context ebiten.GraphicsContext, textures *Textures) {
+func (s *TitleScene) Draw(r ebiten.RenderTarget, textures *Textures) {
-	drawTitleBackground(context, textures, s.count)
+	drawTitleBackground(r, textures, s.count)
-	drawLogo(context, textures, "BLOCKS")
+	drawLogo(r, textures, "BLOCKS")
 
 	message := "PRESS SPACE TO START"
 	x := (ScreenWidth - textWidth(message)) / 2
 	y := ScreenHeight - 48
-	drawTextWithShadow(context, textures, message, x, y, 1, color.RGBA{0x80, 0, 0, 0xff})
+	drawTextWithShadow(r, textures, message, x, y, 1, color.RGBA{0x80, 0, 0, 0xff})
 }
 
-func drawTitleBackground(context ebiten.GraphicsContext, textures *Textures, c int) {
+func drawTitleBackground(r ebiten.RenderTarget, textures *Textures, c int) {
 	const textureWidth = 32
 	const textureHeight = 32
 
@@ -70,13 +70,13 @@ func drawTitleBackground(context ebiten.GraphicsContext, textures *Textures, c i
 	geo := ebiten.GeometryMatrixI()
 	geo.Concat(ebiten.TranslateGeometry(float64(dx), float64(dy)))
 	clr := ebiten.ColorMatrixI()
-	context.DrawTexture(backgroundTexture, parts, geo, clr)
+	r.DrawTexture(backgroundTexture, parts, geo, clr)
 }
 
-func drawLogo(context ebiten.GraphicsContext, textures *Textures, str string) {
+func drawLogo(r ebiten.RenderTarget, textures *Textures, str string) {
 	scale := 4
 	textWidth := textWidth(str) * scale
 	x := (ScreenWidth - textWidth) / 2
 	y := 32
-	drawTextWithShadow(context, textures, str, x, y, scale, color.RGBA{0x00, 0x00, 0x80, 0xff})
+	drawTextWithShadow(r, textures, str, x, y, scale, color.RGBA{0x00, 0x00, 0x80, 0xff})
 }

example/image/main.go

@@ -36,7 +36,7 @@ type Game struct {
 	gophersTexture  *ebiten.Texture
 }
 
-func (g *Game) Update(gr ebiten.GraphicsContext) error {
+func (g *Game) Update(r ebiten.RenderTarget) error {
 	g.count++
 	if ebiten.IsKeyPressed(ebiten.KeyLeft) {
 		g.horizontalCount--
@@ -60,7 +60,7 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 	geo.Concat(ebiten.TranslateGeometry(screenWidth/2, screenHeight/2))
 	//clr := ebiten.RotateHue(float64(g.count%180) * 2 * math.Pi / 180)
 	clr := ebiten.ColorMatrixI()
-	ebiten.DrawWholeTexture(gr, g.gophersTexture, geo, clr)
+	ebiten.DrawWholeTexture(r, g.gophersTexture, geo, clr)
 	return nil
 }
 

example/mosaic/main.go

@@ -32,17 +32,15 @@ const mosaicRatio = 16
 
 type Game struct {
 	gophersTexture      *ebiten.Texture
-	gophersRenderTarget *ebiten.RenderTarget
+	gophersRenderTarget ebiten.RenderTarget
 }
 
-func (g *Game) Update(gr ebiten.GraphicsContext) error {
+func (g *Game) Update(r ebiten.RenderTarget) error {
-	gr.PushRenderTarget(g.gophersRenderTarget)
 	geo := ebiten.ScaleGeometry(1.0/mosaicRatio, 1.0/mosaicRatio)
-	ebiten.DrawWholeTexture(gr, g.gophersTexture, geo, ebiten.ColorMatrixI())
+	ebiten.DrawWholeTexture(g.gophersRenderTarget, g.gophersTexture, geo, ebiten.ColorMatrixI())
-	gr.PopRenderTarget()
 
 	geo = ebiten.ScaleGeometry(mosaicRatio/2.0, mosaicRatio/2.0)
-	ebiten.DrawWholeTexture(gr, g.gophersRenderTarget.Texture(), geo, ebiten.ColorMatrixI())
+	ebiten.DrawWholeTexture(r, g.gophersRenderTarget.Texture(), geo, ebiten.ColorMatrixI())
 	return nil
 }
 

example/paint/main.go

@@ -33,39 +33,33 @@ const (
 type Game struct {
 	inited             bool
 	count              int
-	brushRenderTarget  *ebiten.RenderTarget
+	brushRenderTarget  ebiten.RenderTarget
-	canvasRenderTarget *ebiten.RenderTarget
+	canvasRenderTarget ebiten.RenderTarget
 }
 
-func (g *Game) Update(gr ebiten.GraphicsContext) error {
+func (g *Game) Update(r ebiten.RenderTarget) error {
 	if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
 		g.count++
 	}
 	if !g.inited {
-		gr.PushRenderTarget(g.brushRenderTarget)
+		g.brushRenderTarget.Fill(color.White)
-		gr.Fill(color.White)
+		g.canvasRenderTarget.Fill(color.White)
-		gr.PopRenderTarget()
-		gr.PushRenderTarget(g.canvasRenderTarget)
-		gr.Fill(color.White)
-		gr.PopRenderTarget()
 		g.inited = true
 	}
 
 	mx, my := ebiten.CursorPosition()
 
 	if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
-		gr.PushRenderTarget(g.canvasRenderTarget)
 		geo := ebiten.TranslateGeometry(float64(mx), float64(my))
 		clr := ebiten.ScaleColor(color.RGBA{0xff, 0x40, 0x40, 0xff})
 		theta := 2.0 * math.Pi * float64(g.count%60) / 60.0
 		clr.Concat(ebiten.RotateHue(theta))
-		ebiten.DrawWholeTexture(gr, g.brushRenderTarget.Texture(), geo, clr)
+		ebiten.DrawWholeTexture(g.canvasRenderTarget, g.brushRenderTarget.Texture(), geo, clr)
-		gr.PopRenderTarget()
 	}
 
-	ebiten.DrawWholeTexture(gr, g.canvasRenderTarget.Texture(), ebiten.GeometryMatrixI(), ebiten.ColorMatrixI())
+	ebiten.DrawWholeTexture(r, g.canvasRenderTarget.Texture(), ebiten.GeometryMatrixI(), ebiten.ColorMatrixI())
 
-	ebitenutil.DebugPrint(gr, fmt.Sprintf("(%d, %d)", mx, my))
+	ebitenutil.DebugPrint(r, fmt.Sprintf("(%d, %d)", mx, my))
 	return nil
 }
 

example/perspective/main.go

@@ -32,7 +32,7 @@ type Game struct {
 	gophersTexture *ebiten.Texture
 }
 
-func (g *Game) Update(gr ebiten.GraphicsContext) error {
+func (g *Game) Update(r ebiten.RenderTarget) error {
 	parts := []ebiten.TexturePart{}
 	w, h := g.gophersTexture.Size()
 	for i := 0; i < h; i++ {
@@ -48,7 +48,7 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 	geo := ebiten.TranslateGeometry(-maxWidth/2, -float64(h)/2)
 	geo.Concat(ebiten.ScaleGeometry(0.4, 0.4))
 	geo.Concat(ebiten.TranslateGeometry(screenWidth/2, screenHeight/2))
-	gr.DrawTexture(g.gophersTexture, parts, geo, ebiten.ColorMatrixI())
+	r.DrawTexture(g.gophersTexture, parts, geo, ebiten.ColorMatrixI())
 	return nil
 }
 

gamecontext.go

@@ -48,7 +48,7 @@ func glFilter(f Filter) int {
 }
 
 // NewRenderTarget returns a new RenderTarget.
-func NewRenderTarget(width, height int, filter Filter) (*RenderTarget, error) {
+func NewRenderTarget(width, height int, filter Filter) (RenderTarget, error) {
 	return currentUI.newRenderTarget(width, height, glFilter(filter))
 }
 

graphics.go

@@ -18,7 +18,6 @@ package ebiten
 
 import (
 	"github.com/hajimehoshi/ebiten/internal/opengl"
-	"image/color"
 )
 
 // A Rect represents a rectangle.
@@ -36,22 +35,12 @@ type TexturePart struct {
 }
 
 // DrawWholeTexture draws the whole texture.
-func DrawWholeTexture(g GraphicsContext, texture *Texture, geo GeometryMatrix, color ColorMatrix) error {
+func DrawWholeTexture(r RenderTarget, texture *Texture, geo GeometryMatrix, color ColorMatrix) error {
 	w, h := texture.Size()
 	parts := []TexturePart{
 		{Rect{0, 0, float64(w), float64(h)}, Rect{0, 0, float64(w), float64(h)}},
 	}
-	return g.DrawTexture(texture, parts, geo, color)
+	return r.DrawTexture(texture, parts, geo, color)
-}
-
-// A GraphicsContext is the interface that means a context of rendering.
-type GraphicsContext interface {
-	Clear() error
-	Fill(clr color.Color) error
-	DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error
-	// TODO: ScreenRenderTarget() Drawer
-	PushRenderTarget(id *RenderTarget)
-	PopRenderTarget()
 }
 
 // Filter represents the type of filter to be used when a texture is maginified or minified.
@@ -72,19 +61,3 @@ type Texture struct {
 func (t *Texture) Size() (width int, height int) {
 	return t.glTexture.Width(), t.glTexture.Height()
 }
-
-// RenderTarget represents a render target.
-type RenderTarget struct {
-	glRenderTarget *opengl.RenderTarget
-	texture        *Texture
-}
-
-// Texture returns the texture of the render target.
-func (r *RenderTarget) Texture() *Texture {
-	return r.texture
-}
-
-// Size returns the size of the render target.
-func (r *RenderTarget) Size() (width int, height int) {
-	return r.glRenderTarget.Width(), r.glRenderTarget.Height()
-}

graphicscontext.go

@@ -19,7 +19,6 @@ package ebiten
 import (
 	"github.com/go-gl/gl"
 	"github.com/hajimehoshi/ebiten/internal/opengl"
-	"image/color"
 )
 
 func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsContext, error) {
@@ -28,32 +27,24 @@ func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsCo
 		return nil, err
 	}
 
-	screen, err := idsInstance.createRenderTarget(screenWidth, screenHeight, gl.NEAREST)
+	screen, err := newRenderTarget(screenWidth, screenHeight, gl.NEAREST)
 	if err != nil {
 		return nil, err
 	}
 	c := &graphicsContext{
-		currents:     make([]*RenderTarget, 1),
+		defaultR:    &renderTarget{r, nil},
-		defaultR:     &RenderTarget{r, nil},
 		screen:      screen,
-		screenWidth:  screenWidth,
-		screenHeight: screenHeight,
 		screenScale: screenScale,
 	}
 	return c, nil
 }
 
 type graphicsContext struct {
-	screen       *RenderTarget
+	screen      *renderTarget
-	defaultR     *RenderTarget
+	defaultR    *renderTarget
-	currents     []*RenderTarget
-	screenWidth  int
-	screenHeight int
 	screenScale int
 }
 
-var _ GraphicsContext = new(graphicsContext)
-
 func (c *graphicsContext) dispose() {
 	// NOTE: Now this method is not used anywhere.
 	glRenderTarget := c.screen.glRenderTarget
@@ -64,44 +55,20 @@ func (c *graphicsContext) dispose() {
 	glTexture.Dispose()
 }
 
-func (c *graphicsContext) Clear() error {
+func (c *graphicsContext) preUpdate() error {
-	return c.Fill(color.RGBA{0, 0, 0, 0})
+	return c.screen.Clear()
 }
 
-func (c *graphicsContext) Fill(clr color.Color) error {
+func (c *graphicsContext) postUpdate() error {
-	return idsInstance.fillRenderTarget(c.currents[len(c.currents)-1], clr)
-}
-
-func (c *graphicsContext) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error {
-	current := c.currents[len(c.currents)-1]
-	return idsInstance.drawTexture(current, texture, parts, geo, color)
-}
-
-func (c *graphicsContext) PushRenderTarget(renderTarget *RenderTarget) {
-	c.currents = append(c.currents, renderTarget)
-}
-
-func (c *graphicsContext) PopRenderTarget() {
-	c.currents = c.currents[:len(c.currents)-1]
-}
-
-func (c *graphicsContext) preUpdate() {
-	c.currents = c.currents[0:1]
-	c.currents[0] = c.defaultR
-
-	c.PushRenderTarget(c.screen)
-	c.Clear()
-}
-
-func (c *graphicsContext) postUpdate() {
-	c.PopRenderTarget()
-
 	// We don't need to clear the default render target (framebuffer).
 	// For the default framebuffer, a special shader is used.
 	scale := float64(c.screenScale)
 	geo := ScaleGeometry(scale, scale)
 	clr := ColorMatrixI()
-	DrawWholeTexture(c, c.screen.texture, geo, clr)
+	if err := DrawWholeTexture(c.defaultR, c.screen.texture, geo, clr); err != nil {
+		return err
+	}
 
 	gl.Flush()
+	return nil
 }

internal/opengl/rendertarget.go

@@ -73,16 +73,11 @@ func (r *RenderTarget) Height() int {
 	return r.height
 }
 
-func (r *RenderTarget) FlipY() bool {
-	return r.flipY
-}
-
 func (r *RenderTarget) Dispose() {
 	r.framebuffer.Delete()
 }
 
 func createFramebuffer(nativeTexture gl.Texture) (gl.Framebuffer, error) {
-	// TODO: Does this affect the current rendering target?
 	framebuffer := gl.GenFramebuffer()
 	framebuffer.Bind()
 
@@ -102,7 +97,10 @@ func (r *RenderTarget) SetAsViewport() error {
 	r.framebuffer.Bind()
 	err := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
 	if err != gl.FRAMEBUFFER_COMPLETE {
-		return errors.New(fmt.Sprintf("glBindFramebuffer failed: %d", err))
+		if gl.GetError() != 0 {
+			return errors.New(fmt.Sprintf("glBindFramebuffer failed: %d", gl.GetError()))
+		}
+		return errors.New("glBindFramebuffer failed: the context is different?")
 	}
 
 	width := internal.AdjustSizeForTexture(r.width)

rendertarget.go

@@ -25,72 +25,79 @@ import (
 	"math"
 )
 
-// ids manages the current render target to be used.
+// TODO: Rename
-// TODO: Change this name. `ids` is not appropriate for now.
+type RenderTarget interface {
-type ids struct {
+	Texture() *Texture
-	currentRenderTarget *RenderTarget
+	Size() (width, height int)
+	Clear() error
+	Fill(clr color.Color) error
+	DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error
 }
 
-var idsInstance = &ids{}
+type renderTarget struct {
+	glRenderTarget *opengl.RenderTarget
+	texture        *Texture
+}
 
-func (i *ids) createRenderTarget(width, height int, filter int) (*RenderTarget, error) {
+func newRenderTarget(width, height int, filter int) (*renderTarget, error) {
 	glTexture, err := opengl.NewTexture(width, height, filter)
 	if err != nil {
 		return nil, err
 	}
 
-	// The current binded framebuffer can be changed.
-	i.currentRenderTarget = nil
 	glRenderTarget, err := opengl.NewRenderTargetFromTexture(glTexture)
 	if err != nil {
 		return nil, err
 	}
 
 	texture := &Texture{glTexture}
-	// TODO: Is |texture| necessary?
+	renderTarget := &renderTarget{glRenderTarget, texture}
-	renderTarget := &RenderTarget{glRenderTarget, texture}
-	i.fillRenderTarget(renderTarget, color.RGBA{0, 0, 0, 0})
-
 	return renderTarget, nil
 }
 
-func (i *ids) fillRenderTarget(renderTarget *RenderTarget, clr color.Color) error {
+func (r *renderTarget) Texture() *Texture {
-	if err := i.setViewportIfNeeded(renderTarget); err != nil {
+	return r.texture
+}
+
+func (r *renderTarget) Size() (width, height int) {
+	return r.glRenderTarget.Width(), r.glRenderTarget.Height()
+}
+
+func (r *renderTarget) Clear() error {
+	return r.Fill(color.RGBA{0, 0, 0, 0})
+}
+
+func (r *renderTarget) Fill(clr color.Color) error {
+	if err := r.glRenderTarget.SetAsViewport(); err != nil {
 		return err
 	}
 	const max = math.MaxUint16
-	r, g, b, a := clr.RGBA()
+	cr, cg, cb, ca := clr.RGBA()
-	gl.ClearColor(gl.GLclampf(float64(r)/max), gl.GLclampf(float64(g)/max), gl.GLclampf(float64(b)/max), gl.GLclampf(float64(a)/max))
+	rf := gl.GLclampf(float64(cr) / max)
+	gf := gl.GLclampf(float64(cg) / max)
+	bf := gl.GLclampf(float64(cb) / max)
+	af := gl.GLclampf(float64(ca) / max)
+	gl.ClearColor(rf, gf, bf, af)
 	gl.Clear(gl.COLOR_BUFFER_BIT)
 	return nil
 }
 
-func (i *ids) drawTexture(target *RenderTarget, texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error {
+func (r *renderTarget) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) error {
+	if err := r.glRenderTarget.SetAsViewport(); err != nil {
+		return err
+	}
 	glTexture := texture.glTexture
-	if err := i.setViewportIfNeeded(target); err != nil {
-		return err
-	}
-	projectionMatrix := target.glRenderTarget.ProjectionMatrix()
 	quads := textureQuads(parts, glTexture.Width(), glTexture.Height())
-	w, h := target.Size()
 	targetNativeTexture := gl.Texture(0)
-	if target.texture != nil {
+	if r.texture != nil {
-		targetNativeTexture = target.texture.glTexture.Native()
+		targetNativeTexture = r.texture.glTexture.Native()
 	}
+	w, h := r.Size()
+	projectionMatrix := r.glRenderTarget.ProjectionMatrix()
 	shader.DrawTexture(glTexture.Native(), targetNativeTexture, w, h, projectionMatrix, quads, &geo, &color)
 	return nil
 }
 
-func (i *ids) setViewportIfNeeded(renderTarget *RenderTarget) error {
-	if i.currentRenderTarget != renderTarget {
-		if err := renderTarget.glRenderTarget.SetAsViewport(); err != nil {
-			return err
-		}
-		i.currentRenderTarget = renderTarget
-	}
-	return nil
-}
-
 func u(x float64, width int) float32 {
 	return float32(x) / float32(internal.AdjustSizeForTexture(width))
 }
@@ -115,3 +122,41 @@ func textureQuads(parts []TexturePart, width, height int) []shader.TextureQuad {
 	}
 	return quads
 }
+
+type syncer interface {
+	Sync(func())
+}
+
+type syncRenderTarget struct {
+	syncer syncer
+	inner  RenderTarget
+}
+
+func (c *syncRenderTarget) Texture() *Texture {
+	return c.inner.Texture()
+}
+
+func (c *syncRenderTarget) Size() (width, height int) {
+	return c.inner.Size()
+}
+
+func (c *syncRenderTarget) Clear() (err error) {
+	c.syncer.Sync(func() {
+		err = c.inner.Clear()
+	})
+	return
+}
+
+func (c *syncRenderTarget) Fill(clr color.Color) (err error) {
+	c.syncer.Sync(func() {
+		err = c.inner.Fill(clr)
+	})
+	return
+}
+
+func (c *syncRenderTarget) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) (err error) {
+	c.syncer.Sync(func() {
+		err = c.inner.DrawTexture(texture, parts, geo, color)
+	})
+	return
+}

run.go

@@ -18,7 +18,7 @@ package ebiten
 
 // Run runs the game.
 // This function must be called from the main thread.
-func Run(f func(GraphicsContext) error, width, height, scale int, title string) error {
+func Run(f func(RenderTarget) error, width, height, scale int, title string) error {
 	err := startUI(width, height, scale, title)
 	if err != nil {
 		return err

syncgraphicscontext.go

@@ -1,65 +0,0 @@
-/*
-Copyright 2014 Hajime Hoshi
-
-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.
-*/
-
-package ebiten
-
-import (
-	"image/color"
-)
-
-type syncer interface {
-	Sync(f func())
-}
-
-type syncGraphicsContext struct {
-	syncer               syncer
-	innerGraphicsContext GraphicsContext
-}
-
-var _ GraphicsContext = new(syncGraphicsContext)
-
-func (c *syncGraphicsContext) Clear() (err error) {
-	c.syncer.Sync(func() {
-		err = c.innerGraphicsContext.Clear()
-	})
-	return
-}
-
-func (c *syncGraphicsContext) Fill(clr color.Color) (err error) {
-	c.syncer.Sync(func() {
-		err = c.innerGraphicsContext.Fill(clr)
-	})
-	return
-}
-
-func (c *syncGraphicsContext) DrawTexture(texture *Texture, parts []TexturePart, geo GeometryMatrix, color ColorMatrix) (err error) {
-	c.syncer.Sync(func() {
-		err = c.innerGraphicsContext.DrawTexture(texture, parts, geo, color)
-	})
-	return
-}
-
-func (c *syncGraphicsContext) PopRenderTarget() {
-	c.syncer.Sync(func() {
-		c.innerGraphicsContext.PopRenderTarget()
-	})
-}
-
-func (c *syncGraphicsContext) PushRenderTarget(renderTarget *RenderTarget) {
-	c.syncer.Sync(func() {
-		c.innerGraphicsContext.PushRenderTarget(renderTarget)
-	})
-}

ui.go

@@ -110,18 +110,22 @@ func (u *ui) Sync(f func()) {
 	u.use(f)
 }
 
-func (u *ui) draw(f func(GraphicsContext) error) (err error) {
+func (u *ui) draw(f func(RenderTarget) error) (err error) {
 	u.use(func() {
-		u.graphicsContext.preUpdate()
+		err = u.graphicsContext.preUpdate()
 	})
-	if err = f(&syncGraphicsContext{
+	if err != nil {
-		syncer:               u,
+		return
-		innerGraphicsContext: u.graphicsContext,
+	}
-	}); err != nil {
+	err = f(&syncRenderTarget{syncer: u, inner: u.graphicsContext.screen})
+	if err != nil {
 		return
 	}
 	u.use(func() {
-		u.graphicsContext.postUpdate()
+		err = u.graphicsContext.postUpdate()
+		if err != nil {
+			return
+		}
 		u.window.SwapBuffers()
 	})
 	return
@@ -140,13 +144,13 @@ func (u *ui) newTexture(img image.Image, filter int) (*Texture, error) {
 	return texture, err
 }
 
-func (u *ui) newRenderTarget(width, height int, filter int) (*RenderTarget, error) {
+func (u *ui) newRenderTarget(width, height int, filter int) (RenderTarget, error) {
-	var renderTarget *RenderTarget
+	var renderTarget RenderTarget
 	var err error
 	u.use(func() {
-		renderTarget, err = idsInstance.createRenderTarget(width, height, filter)
+		renderTarget, err = newRenderTarget(width, height, filter)
 	})
-	return renderTarget, err
+	return &syncRenderTarget{u, renderTarget}, err
 }
 
 func (u *ui) run() {