jsutil: Avoid creating Uint8Array at TemporaryUint8Array

Updates #1435

internal/graphicsdriver/opengl/context_js.go

@@ -483,16 +483,26 @@ func (c *context) bindElementArrayBuffer(b buffer) {
 
 func (c *context) arrayBufferSubData(data []float32) {
 	gl := c.gl
-	arr := jsutil.TemporaryUint8Array(len(data) * 4)
+	l := len(data) * 4
+	arr := jsutil.TemporaryUint8Array(l)
 	jsutil.CopySliceToJS(arr, data)
-	gl.Call("bufferSubData", gles.ARRAY_BUFFER, 0, arr)
+	if isWebGL2Available {
+		gl.Call("bufferSubData", gles.ARRAY_BUFFER, 0, arr, 0, l)
+	} else {
+		gl.Call("bufferSubData", gles.ARRAY_BUFFER, 0, arr.Call("subarray", 0, l))
+	}
 }
 
 func (c *context) elementArrayBufferSubData(data []uint16) {
 	gl := c.gl
-	arr := jsutil.TemporaryUint8Array(len(data) * 2)
+	l := len(data) * 2
+	arr := jsutil.TemporaryUint8Array(l)
 	jsutil.CopySliceToJS(arr, data)
-	gl.Call("bufferSubData", gles.ELEMENT_ARRAY_BUFFER, 0, arr)
+	if isWebGL2Available {
+		gl.Call("bufferSubData", gles.ELEMENT_ARRAY_BUFFER, 0, arr, 0, l)
+	} else {
+		gl.Call("bufferSubData", gles.ELEMENT_ARRAY_BUFFER, 0, arr.Call("subarray", 0, l))
+	}
 }
 
 func (c *context) deleteBuffer(b buffer) {
@@ -531,13 +541,20 @@ func (c *context) canUsePBO() bool {
 func (c *context) texSubImage2D(t textureNative, width, height int, args []*driver.ReplacePixelsArgs) {
 	c.bindTexture(t)
 	gl := c.gl
-	// void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
-	//                    GLsizei width, GLsizei height,
-	//                    GLenum format, GLenum type, ArrayBufferView? pixels);
 	for _, a := range args {
 		arr := jsutil.TemporaryUint8Array(len(a.Pixels))
 		jsutil.CopySliceToJS(arr, a.Pixels)
-		gl.Call("texSubImage2D", gles.TEXTURE_2D, 0, a.X, a.Y, a.Width, a.Height, gles.RGBA, gles.UNSIGNED_BYTE, arr)
+		if isWebGL2Available {
+			// void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
+			//                    GLsizei width, GLsizei height,
+			//                    GLenum format, GLenum type, ArrayBufferView pixels, srcOffset);
+			gl.Call("texSubImage2D", gles.TEXTURE_2D, 0, a.X, a.Y, a.Width, a.Height, gles.RGBA, gles.UNSIGNED_BYTE, arr, 0)
+		} else {
+			// void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
+			//                    GLsizei width, GLsizei height,
+			//                    GLenum format, GLenum type, ArrayBufferView? pixels);
+			gl.Call("texSubImage2D", gles.TEXTURE_2D, 0, a.X, a.Y, a.Width, a.Height, gles.RGBA, gles.UNSIGNED_BYTE, arr)
+		}
 	}
 }
 
@@ -551,6 +568,10 @@ func (c *context) newPixelBufferObject(width, height int) buffer {
 }
 
 func (c *context) replacePixelsWithPBO(buffer buffer, t textureNative, width, height int, args []*driver.ReplacePixelsArgs) {
+	if !isWebGL2Available {
+		panic("opengl: WebGL2 must be available when replacePixelsWithPBO is called")
+	}
+
 	c.bindTexture(t)
 	gl := c.gl
 	gl.Call("bindBuffer", gles.PIXEL_UNPACK_BUFFER, js.Value(buffer))
@@ -577,7 +598,11 @@ func (c *context) getBufferSubData(buffer buffer, width, height int) []byte {
 	gl.Call("bindBuffer", gles.PIXEL_UNPACK_BUFFER, buffer)
 	l := 4 * width * height
 	arr := jsutil.TemporaryUint8Array(l)
-	gl.Call("getBufferSubData", gles.PIXEL_UNPACK_BUFFER, 0, arr)
+	if isWebGL2Available {
+		gl.Call("getBufferSubData", gles.PIXEL_UNPACK_BUFFER, 0, arr, 0, l)
+	} else {
+		gl.Call("getBufferSubData", gles.PIXEL_UNPACK_BUFFER, 0, arr.Call("subarray", 0, l))
+	}
 	gl.Call("bindBuffer", gles.PIXEL_UNPACK_BUFFER, 0)
 	return jsutil.Uint8ArrayToSlice(arr, l)
 }

internal/jsutil/buf_js.go

@@ -23,12 +23,18 @@ import (
 // This enables to avoid unnecessary allocations of js.Value.
 var isTypedArrayWritable = js.Global().Get("go2cpp").Truthy()
 
-// temporaryArrayBuffer is a temporary buffer used at gl.readPixels or gl.texSubImage2D.
+var (
-// The read data is converted to Go's byte slice as soon as possible.
+	// temporaryArrayBuffer is a temporary buffer used at gl.readPixels or gl.texSubImage2D.
-// To avoid often allocating ArrayBuffer, reuse the buffer whenever possible.
+	// The read data is converted to Go's byte slice as soon as possible.
-var temporaryArrayBuffer = js.Global().Get("ArrayBuffer").New(16)
+	// To avoid often allocating ArrayBuffer, reuse the buffer whenever possible.
+	temporaryArrayBuffer = js.Global().Get("ArrayBuffer").New(16)
 
-var temporaryFloat32Array = js.Global().Get("Float32Array").New(temporaryArrayBuffer)
+	// temporaryUint8Array is a Uint8ArrayBuffer whose underlying buffer is always temporaryArrayBuffer.
+	temporaryUint8Array = js.Global().Get("Uint8Array").New(temporaryArrayBuffer)
+
+	// temporaryFloat32Array is a Float32ArrayBuffer whose underlying buffer is always temporaryArrayBuffer.
+	temporaryFloat32Array = js.Global().Get("Float32Array").New(temporaryArrayBuffer)
+)
 
 func ensureTemporaryArrayBufferSize(byteLength int) {
 	if bufl := temporaryArrayBuffer.Get("byteLength").Int(); bufl < byteLength {
@@ -39,20 +45,29 @@ func ensureTemporaryArrayBufferSize(byteLength int) {
 	}
 }
 
-func ensureTemporaryFloat32ArraySize(length int) {
+// TemporaryUint8Array returns a Uint8Array whose length is at least minLength.
-	ensureTemporaryArrayBufferSize(length * 4)
+// Be careful that the length can exceed the given minLength.
+func TemporaryUint8Array(minLength int) js.Value {
+	ensureTemporaryArrayBufferSize(minLength)
+	if temporaryUint8Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+		temporaryUint8Array = js.Global().Get("Uint8Array").New(temporaryArrayBuffer)
+	}
+	return temporaryUint8Array
+}
+
+// TemporaryFloat32Array returns a Float32Array whose length is at least minLength.
+// Be careful that the length can exceed the given minLength.
+func TemporaryFloat32Array(minLength int) js.Value {
+	ensureTemporaryArrayBufferSize(minLength * 4)
 	if temporaryFloat32Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
 		temporaryFloat32Array = js.Global().Get("Float32Array").New(temporaryArrayBuffer)
 	}
-}
+	return temporaryFloat32Array
-
-func TemporaryUint8Array(byteLength int) js.Value {
-	ensureTemporaryArrayBufferSize(byteLength)
-	return uint8Array(temporaryArrayBuffer, 0, byteLength)
 }
 
 var uint8ArrayObj js.Value
 
+// TODO: Remove this
 func uint8Array(buffer js.Value, byteOffset, byteLength int) js.Value {
 	if isTypedArrayWritable {
 		if Equal(uint8ArrayObj, js.Undefined()) {
@@ -65,10 +80,3 @@ func uint8Array(buffer js.Value, byteOffset, byteLength int) js.Value {
 	}
 	return js.Global().Get("Uint8Array").New(buffer, byteOffset, byteLength)
 }
-
-// TemporaryFloat32Array returns a Float32Array whose length is at least minLength.
-// Be careful that the length can exceed the given minLength.
-func TemporaryFloat32Array(minLength int) js.Value {
-	ensureTemporaryFloat32ArraySize(minLength * 4)
-	return temporaryFloat32Array
-}