graphicsdriver/opengl: Use PBO when retrieving pixels

internal/graphicsdriver/opengl/context_desktop.go

@@ -470,3 +470,11 @@ func (c *context) replacePixelsWithPBO(buffer buffer, t textureNative, width, he
 	gl.TexSubImage2D(gl.TEXTURE_2D, 0, 0, 0, int32(width), int32(height), gl.RGBA, gl.UNSIGNED_BYTE, nil)
 	gl.BindBuffer(gl.PIXEL_UNPACK_BUFFER, 0)
 }
+
+func (c *context) getBufferSubData(buffer buffer, width, height int) []byte {
+	gl.BindBuffer(gl.PIXEL_UNPACK_BUFFER, uint32(buffer))
+	pixels := make([]byte, 4*width*height)
+	gl.GetBufferSubData(gl.PIXEL_UNPACK_BUFFER, 0, 4*width*height, gl.Ptr(pixels))
+	gl.BindBuffer(gl.PIXEL_UNPACK_BUFFER, 0)
+	return pixels
+}

internal/graphicsdriver/opengl/context_js.go

@@ -565,3 +565,12 @@ func (c *context) replacePixelsWithPBO(buffer buffer, t textureNative, width, he
 	gl.Call("texSubImage2D", gles.TEXTURE_2D, 0, 0, 0, width, height, gles.RGBA, gles.UNSIGNED_BYTE, 0)
 	gl.Call("bindBuffer", int(pixelUnpackBuffer), nil)
 }
+
+func (c *context) getBufferSubData(buffer buffer, width, height int) []byte {
+	gl := c.gl
+	gl.Call("bindBuffer", int(pixelUnpackBuffer), buffer)
+	arr := jsutil.TemporaryUint8Array(4 * width * height)
+	gl.Call("getBufferSubData", int(pixelUnpackBuffer), 0, arr)
+	gl.Call("bindBuffer", int(pixelUnpackBuffer), 0)
+	return jsutil.Uint8ArrayToSlice(arr)
+}

internal/graphicsdriver/opengl/context_mobile.go

@@ -436,3 +436,9 @@ func (c *context) replacePixelsWithPBO(buffer buffer, t textureNative, width, he
 	c.ctx.TexSubImage2D(gles.TEXTURE_2D, 0, 0, 0, int32(width), int32(height), gles.RGBA, gles.UNSIGNED_BYTE, nil)
 	c.ctx.BindBuffer(gles.PIXEL_UNPACK_BUFFER, 0)
 }
+
+func (c *context) getBufferSubData(buffer buffer, width, height int) []byte {
+	// gl.GetBufferSubData doesn't exist on OpenGL ES 2 and 3.
+	// As PBO is not used in mobiles, leave this unimplemented so far.
+	panic("opengl: getBufferSubData is not implemented for mobiles")
+}

internal/graphicsdriver/opengl/gl/package_notwindows.go

@@ -122,6 +122,7 @@ package gl
 // typedef void  (APIENTRYP GPGENBUFFERS)(GLsizei  n, GLuint * buffers);
 // typedef void  (APIENTRYP GPGENFRAMEBUFFERSEXT)(GLsizei  n, GLuint * framebuffers);
 // typedef void  (APIENTRYP GPGENTEXTURES)(GLsizei  n, GLuint * textures);
+// typedef void  (APIENTRYP GPGETBUFFERSUBDATA)(GLenum  target, GLintptr  offset, GLsizeiptr  size, void * data);
 // typedef void  (APIENTRYP GPGETDOUBLEI_V)(GLenum  target, GLuint  index, GLdouble * data);
 // typedef void  (APIENTRYP GPGETDOUBLEI_VEXT)(GLenum  pname, GLuint  index, GLdouble * params);
 // typedef GLenum  (APIENTRYP GPGETERROR)();
@@ -246,6 +247,9 @@ package gl
 // static void  glowGenTextures(GPGENTEXTURES fnptr, GLsizei  n, GLuint * textures) {
 //   (*fnptr)(n, textures);
 // }
+// static void  glowGetBufferSubData(GPGETBUFFERSUBDATA fnptr, GLenum  target, GLintptr  offset, GLsizeiptr  size, void * data) {
+//   (*fnptr)(target, offset, size, data);
+// }
 // static void  glowGetDoublei_v(GPGETDOUBLEI_V fnptr, GLenum  target, GLuint  index, GLdouble * data) {
 //   (*fnptr)(target, index, data);
 // }
@@ -407,6 +411,7 @@ var (
 	gpGenBuffers                  C.GPGENBUFFERS
 	gpGenFramebuffersEXT          C.GPGENFRAMEBUFFERSEXT
 	gpGenTextures                 C.GPGENTEXTURES
+	gpGetBufferSubData            C.GPGETBUFFERSUBDATA
 	gpGetDoublei_v                C.GPGETDOUBLEI_V
 	gpGetDoublei_vEXT             C.GPGETDOUBLEI_VEXT
 	gpGetError                    C.GPGETERROR
@@ -569,6 +574,10 @@ func GenTextures(n int32, textures *uint32) {
 	C.glowGenTextures(gpGenTextures, (C.GLsizei)(n), (*C.GLuint)(unsafe.Pointer(textures)))
 }
 
+func GetBufferSubData(target uint32, offset int, size int, data unsafe.Pointer) {
+	C.glowGetBufferSubData(gpGetBufferSubData, (C.GLenum)(target), (C.GLintptr)(offset), (C.GLsizeiptr)(size), data)
+}
+
 func GetDoublei_v(target uint32, index uint32, data *float64) {
 	C.glowGetDoublei_v(gpGetDoublei_v, (C.GLenum)(target), (C.GLuint)(index), (*C.GLdouble)(unsafe.Pointer(data)))
 }
@@ -832,6 +841,10 @@ func InitWithProcAddrFunc(getProcAddr func(name string) unsafe.Pointer) error {
 	if gpGenTextures == nil {
 		return errors.New("glGenTextures")
 	}
+	gpGetBufferSubData = (C.GPGETBUFFERSUBDATA)(getProcAddr("glGetBufferSubData"))
+	if gpGetBufferSubData == nil {
+		return errors.New("glGetBufferSubData")
+	}
 	gpGetDoublei_v = (C.GPGETDOUBLEI_V)(getProcAddr("glGetDoublei_v"))
 	gpGetDoublei_vEXT = (C.GPGETDOUBLEI_VEXT)(getProcAddr("glGetDoublei_vEXT"))
 	gpGetError = (C.GPGETERROR)(getProcAddr("glGetError"))

internal/graphicsdriver/opengl/gl/package_windows.go

@@ -37,6 +37,7 @@ var (
 	gpGenBuffers                  uintptr
 	gpGenFramebuffersEXT          uintptr
 	gpGenTextures                 uintptr
+	gpGetBufferSubData            uintptr
 	gpGetDoublei_v                uintptr
 	gpGetDoublei_vEXT             uintptr
 	gpGetError                    uintptr
@@ -199,6 +200,10 @@ func GenTextures(n int32, textures *uint32) {
 	syscall.Syscall(gpGenTextures, 2, uintptr(n), uintptr(unsafe.Pointer(textures)), 0)
 }
 
+func GetBufferSubData(target uint32, offset int, size int, data unsafe.Pointer) {
+	syscall.Syscall6(gpGetBufferSubData, 4, uintptr(target), uintptr(offset), uintptr(size), uintptr(data), 0, 0)
+}
+
 func GetDoublei_v(target uint32, index uint32, data *float64) {
 	syscall.Syscall(gpGetDoublei_v, 3, uintptr(target), uintptr(index), uintptr(unsafe.Pointer(data)))
 }
@@ -462,6 +467,10 @@ func InitWithProcAddrFunc(getProcAddr func(name string) uintptr) error {
 	if gpGenTextures == 0 {
 		return errors.New("glGenTextures")
 	}
+	gpGetBufferSubData = getProcAddr("glGetBufferSubData")
+	if gpGetBufferSubData == 0 {
+		return errors.New("glGetBufferSubData")
+	}
 	gpGetDoublei_v = getProcAddr("glGetDoublei_v")
 	gpGetDoublei_vEXT = getProcAddr("glGetDoublei_vEXT")
 	gpGetError = getProcAddr("glGetError")

internal/graphicsdriver/opengl/graphics.go

@@ -152,6 +152,11 @@ func (g *Graphics) Draw(dst, src driver.ImageID, indexLen int, indexOffset int,
 	destination := g.images[dst]
 	source := g.images[src]
 
+	if !destination.pbo.equal(*new(buffer)) {
+		g.context.deleteBuffer(destination.pbo)
+		destination.pbo = *new(buffer)
+	}
+
 	g.drawCalled = true
 
 	if err := destination.setViewport(); err != nil {
@@ -294,6 +299,11 @@ func (g *Graphics) DrawShader(dst driver.ImageID, srcs [graphics.ShaderImageNum]
 	d := g.images[dst]
 	s := g.shaders[shader]
 
+	if !d.pbo.equal(*new(buffer)) {
+		g.context.deleteBuffer(d.pbo)
+		d.pbo = *new(buffer)
+	}
+
 	g.drawCalled = true
 
 	if err := d.setViewport(); err != nil {

internal/graphicsdriver/opengl/image.go

@@ -71,7 +71,16 @@ func (i *Image) Pixels() ([]byte, error) {
 	if err := i.ensureFramebuffer(); err != nil {
 		return nil, err
 	}
-	p := i.graphics.context.framebufferPixels(i.framebuffer, i.width, i.height)
+
+	// PBO is created only when PBO is enabled AND ReplacePixels is called.
+	// If PBO is enabled but the buffer doesn't exist, this means either ReplacePixels is not called or
+	// different draw calls than ReplacePixels were called.
+	if !i.graphics.context.canUsePBO() || i.pbo.equal(*new(buffer)) {
+		p := i.graphics.context.framebufferPixels(i.framebuffer, i.width, i.height)
+		return p, nil
+	}
+
+	p := i.graphics.context.getBufferSubData(i.pbo, i.width, i.height)
 	return p, nil
 }
 
@@ -123,12 +132,12 @@ func (i *Image) ReplacePixels(args []*driver.ReplacePixelsArgs) {
 		i.graphics.context.texSubImage2D(i.textureNative, w, h, args)
 		return
 	}
+
 	if i.pbo.equal(*new(buffer)) {
 		i.pbo = i.graphics.context.newPixelBufferObject(w, h)
 	}
 	if i.pbo.equal(*new(buffer)) {
 		panic("opengl: newPixelBufferObject failed")
 	}
-
 	i.graphics.context.replacePixelsWithPBO(i.pbo, i.textureNative, w, h, args)
 }