graphicsdriver/metal: Give up reusing buffers

It was inevitable to rely on reference counts, which was too hacky.
Besides, reusing buffers doesn't improve performance.

internal/graphicsdriver/metal/buffer.go

@@ -1,108 +0,0 @@
-// Copyright 2019 The Ebiten Authors
-//
-// 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.
-
-// +build darwin
-
-package metal
-
-import (
-	"sort"
-	"unsafe"
-
-	"github.com/hajimehoshi/ebiten/internal/graphicsdriver/metal/mtl"
-)
-
-// #cgo LDFLAGS: -framework CoreFoundation
-//
-// #import <CoreFoundation/CoreFoundation.h>
-//
-// static int count(void* obj) {
-//   // TODO: Don't rely on the number of ref counts. CFGetRetainCount should be used only for debugging.
-//   // Note that checking whether MTLCommandBuffer's status is completed or not does not work, because the
-//   // CommandBuffer might still be used even in such situation.
-//   return CFGetRetainCount(obj);
-// }
-import "C"
-
-type buffer struct {
-	b   mtl.Buffer
-	len uintptr
-}
-
-func (b *buffer) used() bool {
-	// If the count is 2 or more, the buffer is actually retained outside.
-	// If the count is 1, the buffer is retained only by the buffer pool.
-	// The count cannot be 0 since the object is already freed in this case.
-	return C.count(b.b.Native()) > 1
-}
-
-var bufferPool = map[*buffer]struct{}{}
-
-func getBuffer(device mtl.Device, data unsafe.Pointer, lengthInBytes uintptr) *buffer {
-	for buf := range bufferPool {
-		if buf.used() {
-			continue
-		}
-		if buf.len < lengthInBytes {
-			continue
-		}
-		buf.b.CopyToContents(data, lengthInBytes)
-		buf.b.Retain()
-		return buf
-	}
-
-	gcBufferPool()
-
-	buf := &buffer{
-		b:   device.MakeBufferWithBytes(data, lengthInBytes, mtl.ResourceStorageModeManaged),
-		len: lengthInBytes,
-	}
-	buf.b.Retain()
-	bufferPool[buf] = struct{}{}
-	return buf
-}
-
-func putBuffer(buf *buffer) {
-	buf.b.Release()
-	// The buffer will be actually released after all the current command buffers are finished.
-	gcBufferPool()
-}
-
-func gcBufferPool() {
-	const threshold = 16
-
-	if len(bufferPool) < threshold {
-		return
-	}
-
-	toRemove := []*buffer{}
-	for buf := range bufferPool {
-		if buf.used() {
-			continue
-		}
-		toRemove = append(toRemove, buf)
-	}
-	sort.Slice(toRemove, func(a, b int) bool {
-		return toRemove[a].len < toRemove[b].len
-	})
-
-	l := len(toRemove)
-	if l > len(bufferPool)-threshold {
-		l = len(bufferPool) - threshold
-	}
-	for _, buf := range toRemove[:l] {
-		buf.b.Release()
-		delete(bufferPool, buf)
-	}
-}

internal/graphicsdriver/metal/driver.go

@@ -227,8 +227,8 @@ type Driver struct {
 
 	screenDrawable ca.MetalDrawable
 
-	vb *buffer
+	vb mtl.Buffer
-	ib *buffer
+	ib mtl.Buffer
 
 	src *Image
 	dst *Image
@@ -253,14 +253,14 @@ func (d *Driver) SetWindow(window uintptr) {
 
 func (d *Driver) SetVertices(vertices []float32, indices []uint16) {
 	mainthread.Run(func() error {
-		if d.vb != nil {
+		if d.vb != (mtl.Buffer{}) {
-			putBuffer(d.vb)
+			d.vb.Release()
 		}
-		if d.ib != nil {
+		if d.ib != (mtl.Buffer{}) {
-			putBuffer(d.ib)
+			d.ib.Release()
 		}
-		d.vb = getBuffer(d.device, unsafe.Pointer(&vertices[0]), unsafe.Sizeof(vertices[0])*uintptr(len(vertices)))
+		d.vb = d.device.MakeBufferWithBytes(unsafe.Pointer(&vertices[0]), unsafe.Sizeof(vertices[0])*uintptr(len(vertices)), mtl.ResourceStorageModeManaged)
-		d.ib = getBuffer(d.device, unsafe.Pointer(&indices[0]), unsafe.Sizeof(indices[0])*uintptr(len(indices)))
+		d.ib = d.device.MakeBufferWithBytes(unsafe.Pointer(&indices[0]), unsafe.Sizeof(indices[0])*uintptr(len(indices)), mtl.ResourceStorageModeManaged)
 		return nil
 	})
 }
@@ -538,7 +538,7 @@ func (d *Driver) Draw(indexLen int, indexOffset int, mode graphics.CompositeMode
 			rce.SetRenderPipelineState(d.rpss[mode])
 		}
 		rce.SetViewport(mtl.Viewport{0, 0, float64(w), float64(h), -1, 1})
-		rce.SetVertexBuffer(d.vb.b, 0, 0)
+		rce.SetVertexBuffer(d.vb, 0, 0)
 
 		viewportSize := [...]float32{float32(w), float32(h)}
 		rce.SetVertexBytes(unsafe.Pointer(&viewportSize[0]), unsafe.Sizeof(viewportSize), 1)
@@ -561,7 +561,7 @@ func (d *Driver) Draw(indexLen int, indexOffset int, mode graphics.CompositeMode
 		} else {
 			rce.SetFragmentTexture(mtl.Texture{}, 0)
 		}
-		rce.DrawIndexedPrimitives(mtl.PrimitiveTypeTriangle, indexLen, mtl.IndexTypeUInt16, d.ib.b, indexOffset*2)
+		rce.DrawIndexedPrimitives(mtl.PrimitiveTypeTriangle, indexLen, mtl.IndexTypeUInt16, d.ib, indexOffset*2)
 		rce.EndEncoding()
 
 		return nil