gpu/internal/opengl,internal/gl: avoid glBufferSubData after glBufferData

On my Fedora Intel GPU, issuing a glBufferSubData immediately after a
glBufferData with no data may leave the buffer cleared.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/internal/opengl/opengl.go

@@ -716,7 +716,7 @@ func (b *Backend) NewBuffer(typ driver.BufferBinding, size int) (driver.Buffer,
 		}
 		firstBinding := firstBufferType(typ)
 		b.glstate.bindBuffer(b.funcs, firstBinding, buf.obj)
-		b.funcs.BufferData(firstBinding, size, gl.DYNAMIC_DRAW)
+		b.funcs.BufferData(firstBinding, size, gl.DYNAMIC_DRAW, nil)
 	}
 	return buf, nil
 }
@@ -727,8 +727,7 @@ func (b *Backend) NewImmutableBuffer(typ driver.BufferBinding, data []byte) (dri
 	buf := &buffer{backend: b, obj: obj, typ: typ, size: len(data), hasBuffer: true}
 	firstBinding := firstBufferType(typ)
 	b.glstate.bindBuffer(b.funcs, firstBinding, buf.obj)
-	b.funcs.BufferData(firstBinding, len(data), gl.STATIC_DRAW)
-	buf.Upload(data)
+	b.funcs.BufferData(firstBinding, len(data), gl.STATIC_DRAW, data)
 	buf.immutable = true
 	if err := glErr(b.funcs); err != nil {
 		buf.Release()
@@ -1090,9 +1089,10 @@ func (b *buffer) Upload(data []byte) {
 			// the iOS GL implementation doesn't recognize when BufferSubData
 			// clears the entire buffer. Tell it and avoid GPU stalls.
 			// See also https://github.com/godotengine/godot/issues/23956.
-			b.backend.funcs.BufferData(firstBinding, b.size, gl.DYNAMIC_DRAW)
+			b.backend.funcs.BufferData(firstBinding, b.size, gl.DYNAMIC_DRAW, data)
+		} else {
+			b.backend.funcs.BufferSubData(firstBinding, 0, data)
 		}
-		b.backend.funcs.BufferSubData(firstBinding, 0, data)
 	}
 }
 

gpu/internal/opengl/srgb.go

@@ -72,8 +72,7 @@ func (s *SRGBFBO) Blit() {
 			-1, -1, 0, 0,
 			+1, -1, 1, 0,
 		})
-		s.c.BufferData(gl.ARRAY_BUFFER, len(coords), gl.STATIC_DRAW)
-		s.c.BufferSubData(gl.ARRAY_BUFFER, 0, coords)
+		s.c.BufferData(gl.ARRAY_BUFFER, len(coords), gl.STATIC_DRAW, coords)
 		s.blitted = true
 	}
 	s.state.useProgram(s.c, s.prog)

internal/gl/gl_js.go

@@ -104,8 +104,15 @@ func (f *Functions) BlendEquation(mode Enum) {
 func (f *Functions) BlendFuncSeparate(srcRGB, dstRGB, srcA, dstA Enum) {
 	f.Ctx.Call("blendFunc", int(srcRGB), int(dstRGB), int(srcA), int(dstA))
 }
-func (f *Functions) BufferData(target Enum, size int, usage Enum) {
-	f.Ctx.Call("bufferData", int(target), size, int(usage))
+func (f *Functions) BufferData(target Enum, size int, usage Enum, data []byte) {
+	if data == nil {
+		f.Ctx.Call("bufferData", int(target), size, int(usage))
+	} else {
+		if len(data) != size {
+			panic("size mismatch")
+		}
+		f.Ctx.Call("bufferData", int(target), f.byteArrayOf(data), int(usage))
+	}
 }
 func (f *Functions) BufferSubData(target Enum, offset int, src []byte) {
 	f.Ctx.Call("bufferSubData", int(target), offset, f.byteArrayOf(src))

internal/gl/gl_unix.go

@@ -782,8 +782,12 @@ func (f *Functions) BlitFramebuffer(sx0, sy0, sx1, sy1, dx0, dy0, dx1, dy1 int,
 	)
 }
 
-func (f *Functions) BufferData(target Enum, size int, usage Enum) {
-	C.glBufferData(&f.f, C.GLenum(target), C.GLsizeiptr(size), nil, C.GLenum(usage))
+func (f *Functions) BufferData(target Enum, size int, usage Enum, data []byte) {
+	var p unsafe.Pointer
+	if len(data) > 0 {
+		p = unsafe.Pointer(&data[0])
+	}
+	C.glBufferData(&f.f, C.GLenum(target), C.GLsizeiptr(size), p, C.GLenum(usage))
 }
 
 func (f *Functions) BufferSubData(target Enum, offset int, src []byte) {

internal/gl/gl_windows.go

@@ -159,8 +159,12 @@ func (c *Functions) BlendEquation(mode Enum) {
 func (c *Functions) BlendFuncSeparate(srcRGB, dstRGB, srcA, dstA Enum) {
 	syscall.Syscall6(_glBlendFuncSeparate.Addr(), 4, uintptr(srcRGB), uintptr(dstRGB), uintptr(srcA), uintptr(dstA), 0, 0)
 }
-func (c *Functions) BufferData(target Enum, size int, usage Enum) {
-	syscall.Syscall6(_glBufferData.Addr(), 4, uintptr(target), uintptr(size), 0, uintptr(usage), 0, 0)
+func (c *Functions) BufferData(target Enum, size int, usage Enum, data []byte) {
+	var p unsafe.Pointer
+	if len(data) > 0 {
+		p = unsafe.Pointer(&data[0])
+	}
+	syscall.Syscall6(_glBufferData.Addr(), 4, uintptr(target), uintptr(size), uintptr(p), uintptr(usage), 0, 0)
 }
 func (f *Functions) BufferSubData(target Enum, offset int, src []byte) {
 	if n := len(src); n > 0 {