graphics: Call glBufferSubData for element array buffer every frame

This is a preparation for more flexible drawing commands.

internal/graphics/command.go

@@ -47,11 +47,27 @@ type commandQueue struct {
 	// nvertices must <= len(vertices).
 	// vertices is never shrunk since re-extending a vertices buffer is heavy.
 	nvertices int
+
+	indices []uint16
 }
 
 // theCommandQueue is the command queue for the current process.
 var theCommandQueue = &commandQueue{}
 
+func init() {
+	q := theCommandQueue
+	// Initialize indices for drawImageCommand.
+	q.indices = make([]uint16, 6*maxQuads)
+	for i := uint16(0); i < maxQuads; i++ {
+		q.indices[6*i+0] = 4*i + 0
+		q.indices[6*i+1] = 4*i + 1
+		q.indices[6*i+2] = 4*i + 2
+		q.indices[6*i+3] = 4*i + 1
+		q.indices[6*i+4] = 4*i + 2
+		q.indices[6*i+5] = 4*i + 3
+	}
+}
+
 // appendVertices appends vertices to the queue.
 func (q *commandQueue) appendVertices(vertices []float32) {
 	if len(q.vertices) < q.nvertices+len(vertices) {
@@ -140,7 +156,8 @@ func (q *commandQueue) Flush() error {
 			// Note that the vertices passed to BufferSubData is not under GC management
 			// in opengl package due to unsafe-way.
 			// See BufferSubData in context_mobile.go.
-			opengl.GetContext().BufferSubData(opengl.ArrayBuffer, q.vertices[lastN:n])
+			opengl.GetContext().ElementArrayBufferSubData(q.indices)
+			opengl.GetContext().ArrayBufferSubData(q.vertices[lastN:n])
 		}
 		// NOTE: WebGL doesn't seem to have gl.MAX_ELEMENTS_VERTICES or
 		// gl.MAX_ELEMENTS_INDICES so far.

internal/graphics/program.go

@@ -120,8 +120,6 @@ type openGLState struct {
 	lastColorMatrixTranslation []float32
 	lastSourceWidth            int
 	lastSourceHeight           int
-
-	indices []uint16
 }
 
 var (
@@ -229,19 +227,10 @@ func (s *openGLState) reset() error {
 
 	s.arrayBuffer = theArrayBufferLayout.newArrayBuffer()
 
-	s.indices = make([]uint16, 6*maxQuads)
-	for i := uint16(0); i < maxQuads; i++ {
-		s.indices[6*i+0] = 4*i + 0
-		s.indices[6*i+1] = 4*i + 1
-		s.indices[6*i+2] = 4*i + 2
-		s.indices[6*i+3] = 4*i + 1
-		s.indices[6*i+4] = 4*i + 2
-		s.indices[6*i+5] = 4*i + 3
-	}
 	// Note that the indices passed to NewElementArrayBuffer is not under GC management
 	// in opengl package due to unsafe-way.
 	// See NewElementArrayBuffer in context_mobile.go.
-	s.elementArrayBuffer = opengl.GetContext().NewElementArrayBuffer(s.indices)
+	s.elementArrayBuffer = opengl.GetContext().NewElementArrayBuffer(indicesNum * 2)
 
 	return nil
 }

internal/opengl/context_desktop.go

@@ -58,7 +58,6 @@ func init() {
 	ArrayBuffer = gl.ARRAY_BUFFER
 	ElementArrayBuffer = gl.ELEMENT_ARRAY_BUFFER
 	DynamicDraw = gl.DYNAMIC_DRAW
-	StaticDraw = gl.STATIC_DRAW
 	Triangles = gl.TRIANGLES
 	Lines = gl.LINES
 	Short = gl.SHORT
@@ -452,13 +451,13 @@ func (c *Context) NewArrayBuffer(size int) Buffer {
 	return buffer
 }
 
-func (c *Context) NewElementArrayBuffer(indices []uint16) Buffer {
+func (c *Context) NewElementArrayBuffer(size int) Buffer {
 	var buffer Buffer
 	_ = c.runOnContextThread(func() error {
 		var b uint32
 		gl.GenBuffers(1, &b)
 		gl.BindBuffer(uint32(ElementArrayBuffer), b)
-		gl.BufferData(uint32(ElementArrayBuffer), 2*len(indices), gl.Ptr(indices), uint32(StaticDraw))
+		gl.BufferData(uint32(ElementArrayBuffer), size, nil, uint32(DynamicDraw))
 		buffer = Buffer(b)
 		return nil
 	})
@@ -472,9 +471,16 @@ func (c *Context) BindBuffer(bufferType BufferType, b Buffer) {
 	})
 }
 
-func (c *Context) BufferSubData(bufferType BufferType, data []float32) {
+func (c *Context) ArrayBufferSubData(data []float32) {
 	_ = c.runOnContextThread(func() error {
-		gl.BufferSubData(uint32(bufferType), 0, len(data)*4, gl.Ptr(data))
+		gl.BufferSubData(uint32(ArrayBuffer), 0, len(data)*4, gl.Ptr(data))
+		return nil
+	})
+}
+
+func (c *Context) ElementArrayBufferSubData(data []uint16) {
+	_ = c.runOnContextThread(func() error {
+		gl.BufferSubData(uint32(ElementArrayBuffer), 0, len(data)*2, gl.Ptr(data))
 		return nil
 	})
 }

internal/opengl/context_js.go

@@ -55,7 +55,6 @@ func init() {
 	ArrayBuffer = BufferType(c.Get("ARRAY_BUFFER").Int())
 	ElementArrayBuffer = BufferType(c.Get("ELEMENT_ARRAY_BUFFER").Int())
 	DynamicDraw = BufferUsage(c.Get("DYNAMIC_DRAW").Int())
-	StaticDraw = BufferUsage(c.Get("STATIC_DRAW").Int())
 	Triangles = Mode(c.Get("TRIANGLES").Int())
 	Lines = Mode(c.Get("LINES").Int())
 	Short = DataType(c.Get("SHORT").Int())
@@ -358,11 +357,11 @@ func (c *Context) NewArrayBuffer(size int) Buffer {
 	return b
 }
 
-func (c *Context) NewElementArrayBuffer(indices []uint16) Buffer {
+func (c *Context) NewElementArrayBuffer(size int) Buffer {
 	gl := c.gl
 	b := gl.Call("createBuffer")
 	gl.Call("bindBuffer", int(ElementArrayBuffer), b)
-	gl.Call("bufferData", int(ElementArrayBuffer), indices, int(StaticDraw))
+	gl.Call("bufferData", int(ElementArrayBuffer), size, int(DynamicDraw))
 	return b
 }
 
@@ -371,9 +370,14 @@ func (c *Context) BindBuffer(bufferType BufferType, b Buffer) {
 	gl.Call("bindBuffer", int(bufferType), b)
 }
 
-func (c *Context) BufferSubData(bufferType BufferType, data []float32) {
+func (c *Context) ArrayBufferSubData(data []float32) {
 	gl := c.gl
-	gl.Call("bufferSubData", int(bufferType), 0, data)
+	gl.Call("bufferSubData", int(ArrayBuffer), 0, data)
+}
+
+func (c *Context) ElementArrayBufferSubData(data []uint16) {
+	gl := c.gl
+	gl.Call("bufferSubData", int(ElementArrayBuffer), 0, data)
 }
 
 func (c *Context) DeleteBuffer(b Buffer) {

internal/opengl/context_mobile.go

@@ -57,7 +57,6 @@ func init() {
 	ArrayBuffer = mgl.ARRAY_BUFFER
 	ElementArrayBuffer = mgl.ELEMENT_ARRAY_BUFFER
 	DynamicDraw = mgl.DYNAMIC_DRAW
-	StaticDraw = mgl.STATIC_DRAW
 	Triangles = mgl.TRIANGLES
 	Lines = mgl.LINES
 	Short = mgl.SHORT
@@ -353,6 +352,27 @@ func (c *Context) DisableVertexAttribArray(p Program, location string) {
 	gl.DisableVertexAttribArray(mgl.Attrib(l))
 }
 
+func (c *Context) NewArrayBuffer(size int) Buffer {
+	gl := c.gl
+	b := gl.CreateBuffer()
+	gl.BindBuffer(mgl.Enum(ArrayBuffer), b)
+	gl.BufferInit(mgl.Enum(ArrayBuffer), size, mgl.Enum(DynamicDraw))
+	return Buffer(b)
+}
+
+func (c *Context) NewElementArrayBuffer(size int) Buffer {
+	gl := c.gl
+	b := gl.CreateBuffer()
+	gl.BindBuffer(mgl.Enum(ElementArrayBuffer), b)
+	gl.BufferInit(mgl.Enum(ElementArrayBuffer), size, mgl.Enum(DynamicDraw))
+	return Buffer(b)
+}
+
+func (c *Context) BindBuffer(bufferType BufferType, b Buffer) {
+	gl := c.gl
+	gl.BindBuffer(mgl.Enum(bufferType), mgl.Buffer(b))
+}
+
 func uint16ToBytes(v []uint16) []byte {
 	u16h := (*reflect.SliceHeader)(unsafe.Pointer(&v))
 
@@ -364,27 +384,6 @@ func uint16ToBytes(v []uint16) []byte {
 	return b
 }
 
-func (c *Context) NewArrayBuffer(size int) Buffer {
-	gl := c.gl
-	b := gl.CreateBuffer()
-	gl.BindBuffer(mgl.Enum(ArrayBuffer), b)
-	gl.BufferInit(mgl.Enum(ArrayBuffer), size, mgl.Enum(DynamicDraw))
-	return Buffer(b)
-}
-
-func (c *Context) NewElementArrayBuffer(indices []uint16) Buffer {
-	gl := c.gl
-	b := gl.CreateBuffer()
-	gl.BindBuffer(mgl.Enum(ElementArrayBuffer), b)
-	gl.BufferData(mgl.Enum(ElementArrayBuffer), uint16ToBytes(indices), mgl.Enum(StaticDraw))
-	return Buffer(b)
-}
-
-func (c *Context) BindBuffer(bufferType BufferType, b Buffer) {
-	gl := c.gl
-	gl.BindBuffer(mgl.Enum(bufferType), mgl.Buffer(b))
-}
-
 func float32ToBytes(v []float32) []byte {
 	f32h := (*reflect.SliceHeader)(unsafe.Pointer(&v))
 
@@ -396,9 +395,14 @@ func float32ToBytes(v []float32) []byte {
 	return b
 }
 
-func (c *Context) BufferSubData(bufferType BufferType, data []float32) {
+func (c *Context) ArrayBufferSubData(data []float32) {
 	gl := c.gl
-	gl.BufferSubData(mgl.Enum(bufferType), 0, float32ToBytes(data))
+	gl.BufferSubData(mgl.Enum(ArrayBuffer), 0, float32ToBytes(data))
+}
+
+func (c *Context) ElementArrayBufferSubData(data []uint16) {
+	gl := c.gl
+	gl.BufferSubData(mgl.Enum(ElementArrayBuffer), 0, uint16ToBytes(data))
 }
 
 func (c *Context) DeleteBuffer(b Buffer) {