gpu,app/internal/wm: add Metal port

The OpenGL (ES) implementations on Apple platforms are deprecated and
don't support GPU compute programs. This change adds support for the
replacement, the Metal GPU API.

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

app/internal/wm/gl_ios.go

@@ -1,11 +1,13 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-//go:build darwin && ios
-// +build darwin,ios
+//go:build darwin && ios && nometal
+// +build darwin,ios,nometal
 
 package wm
 
 /*
+@import UIKit;
+
 #include <CoreFoundation/CoreFoundation.h>
 #include <OpenGLES/ES2/gl.h>
 #include <OpenGLES/ES2/glext.h>
@@ -15,6 +17,14 @@ __attribute__ ((visibility ("hidden"))) int gio_presentRenderbuffer(CFTypeRef ct
 __attribute__ ((visibility ("hidden"))) int gio_makeCurrent(CFTypeRef ctx);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createContext(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createGLLayer(void);
+
+static CFTypeRef getViewLayer(CFTypeRef viewRef) {
+	@autoreleasepool {
+		UIView *view = (__bridge UIView *)viewRef;
+		return CFBridgingRetain(view.layer);
+	}
+}
+
 */
 import "C"
 
@@ -36,12 +46,6 @@ type context struct {
 	colorBuffer gl.Renderbuffer
 }
 
-func init() {
-	layerFactory = func() uintptr {
-		return uintptr(C.gio_createGLLayer())
-	}
-}
-
 func newContext(w *window) (*context, error) {
 	ctx := C.gio_createContext()
 	if ctx == 0 {
@@ -55,7 +59,7 @@ func newContext(w *window) (*context, error) {
 	c := &context{
 		ctx:   ctx,
 		owner: w,
-		layer: C.CFTypeRef(w.contextLayer()),
+		layer: C.getViewLayer(w.contextView()),
 		c:     f,
 	}
 	return c, nil
@@ -116,7 +120,7 @@ func (c *context) Refresh() error {
 		c.frameBuffer = c.c.CreateFramebuffer()
 		c.colorBuffer = c.c.CreateRenderbuffer()
 	}
-	if !c.owner.isVisible() {
+	if !c.owner.visible {
 		// Make sure any in-flight GL commands are complete.
 		c.c.Finish()
 		return nil

app/internal/wm/gl_ios.m

@@ -1,12 +1,16 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// +build darwin,ios
+// +build darwin,ios,nometal
 
 @import UIKit;
 @import OpenGLES;
 
 #include "_cgo_export.h"
 
+Class gio_layerClass(void) {
+	return [CAEAGLLayer class];
+}
+
 int gio_renderbufferStorage(CFTypeRef ctxRef, CFTypeRef layerRef, GLenum buffer) {
 	EAGLContext *ctx = (__bridge EAGLContext *)ctxRef;
 	CAEAGLLayer *layer = (__bridge CAEAGLLayer *)layerRef;

app/internal/wm/gl_macos.go

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-//go:build darwin && !ios
-// +build darwin,!ios
+//go:build darwin && !ios && nometal
+// +build darwin,!ios,nometal
 
 package wm
 

app/internal/wm/gl_macos.m

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-// +build darwin,!ios
+// +build darwin,!ios,nometal
 
 @import AppKit;
 
@@ -8,6 +8,12 @@
 #include <OpenGL/OpenGL.h>
 #include "_cgo_export.h"
 
+CALayer *gio_layerFactory(void) {
+	@autoreleasepool {
+		return [CALayer layer];
+	}
+}
+
 CFTypeRef gio_createGLContext(void) {
 	@autoreleasepool {
 		NSOpenGLPixelFormatAttribute attr[] = {

app/internal/wm/metal_darwin.go

@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+//go:build !nometal
+// +build !nometal
+
+package wm
+
+import (
+	"errors"
+	"unsafe"
+
+	"gioui.org/gpu"
+)
+
+/*
+#cgo CFLAGS: -Werror -xobjective-c -fmodules -fobjc-arc
+
+@import Metal;
+@import QuartzCore.CAMetalLayer;
+
+#include <CoreFoundation/CoreFoundation.h>
+
+static CFTypeRef createMetalDevice(void) {
+	@autoreleasepool {
+		id<MTLDevice> dev = MTLCreateSystemDefaultDevice();
+		return CFBridgingRetain(dev);
+	}
+}
+
+static void setupLayer(CFTypeRef layerRef, CFTypeRef devRef) {
+	@autoreleasepool {
+		CAMetalLayer *layer = (__bridge CAMetalLayer *)layerRef;
+		id<MTLDevice> dev = (__bridge id<MTLDevice>)devRef;
+		layer.device = dev;
+		// Package gpu assumes an sRGB-encoded framebuffer.
+		layer.pixelFormat = MTLPixelFormatBGRA8Unorm_sRGB;
+		if (@available(iOS 11.0, *)) {
+			// Never let nextDrawable time out and return nil.
+			layer.allowsNextDrawableTimeout = NO;
+		}
+		if (@available(iOS 11.2, *)) {
+			// Minimize latency from input to window and save a bit of memory.
+			layer.maximumDrawableCount = 2;
+		}
+	}
+}
+
+static CFTypeRef nextDrawable(CFTypeRef layerRef) {
+	@autoreleasepool {
+		CAMetalLayer *layer = (__bridge CAMetalLayer *)layerRef;
+		return CFBridgingRetain([layer nextDrawable]);
+	}
+}
+
+static CFTypeRef drawableTexture(CFTypeRef drawableRef) {
+	@autoreleasepool {
+		id<CAMetalDrawable> drawable = (__bridge id<CAMetalDrawable>)drawableRef;
+		return CFBridgingRetain(drawable.texture);
+	}
+}
+
+static void presentDrawable(CFTypeRef queueRef, CFTypeRef drawableRef) {
+	@autoreleasepool {
+		id<MTLDrawable> drawable = (__bridge id<MTLDrawable>)drawableRef;
+		id<MTLCommandQueue> queue = (__bridge id<MTLCommandQueue>)queueRef;
+		id<MTLCommandBuffer> cmdBuffer = [queue commandBuffer];
+		[cmdBuffer presentDrawable:drawable];
+		[cmdBuffer commit];
+		[cmdBuffer waitUntilCompleted];
+	}
+}
+
+static CFTypeRef newCommandQueue(CFTypeRef devRef) {
+	@autoreleasepool {
+		id<MTLDevice> dev = (__bridge id<MTLDevice>)devRef;
+		return CFBridgingRetain([dev newCommandQueue]);
+	}
+}
+*/
+import "C"
+
+type mtlContext struct {
+	dev      C.CFTypeRef
+	view     C.CFTypeRef
+	layer    C.CFTypeRef
+	queue    C.CFTypeRef
+	drawable C.CFTypeRef
+	texture  C.CFTypeRef
+}
+
+func newMtlContext(w *window) (*mtlContext, error) {
+	dev := C.createMetalDevice()
+	if dev == 0 {
+		return nil, errors.New("metal: MTLCreateSystemDefaultDevice failed")
+	}
+	view := w.contextView()
+	layer := getMetalLayer(view)
+	if layer == 0 {
+		C.CFRelease(dev)
+		return nil, errors.New("metal: CAMetalLayer construction failed")
+	}
+	queue := C.newCommandQueue(dev)
+	if layer == 0 {
+		C.CFRelease(dev)
+		C.CFRelease(layer)
+		return nil, errors.New("metal: [MTLDevice newCommandQueue] failed")
+	}
+	C.setupLayer(layer, dev)
+	c := &mtlContext{
+		dev:   dev,
+		view:  view,
+		layer: layer,
+		queue: queue,
+	}
+	return c, nil
+}
+
+func (c *mtlContext) RenderTarget() gpu.RenderTarget {
+	if c.drawable != 0 || c.texture != 0 {
+		panic("a previous RenderTarget wasn't Presented")
+	}
+	c.drawable = C.nextDrawable(c.layer)
+	if c.drawable == 0 {
+		panic("metal: [CAMetalLayer nextDrawable] failed")
+	}
+	c.texture = C.drawableTexture(c.drawable)
+	if c.texture == 0 {
+		panic("metal: CADrawable.texture is nil")
+	}
+	return gpu.MetalRenderTarget{
+		Texture: unsafe.Pointer(c.texture),
+	}
+}
+
+func (c *mtlContext) API() gpu.API {
+	return gpu.Metal{
+		Device:      unsafe.Pointer(c.dev),
+		Queue:       unsafe.Pointer(c.queue),
+		PixelFormat: int(C.MTLPixelFormatBGRA8Unorm_sRGB),
+	}
+}
+
+func (c *mtlContext) Release() {
+	C.CFRelease(c.queue)
+	C.CFRelease(c.dev)
+	C.CFRelease(c.layer)
+	if c.drawable != 0 {
+		C.CFRelease(c.drawable)
+	}
+	if c.texture != 0 {
+		C.CFRelease(c.texture)
+	}
+	*c = mtlContext{}
+}
+
+func (c *mtlContext) Present() error {
+	C.CFRelease(c.texture)
+	c.texture = 0
+	C.presentDrawable(c.queue, c.drawable)
+	C.CFRelease(c.drawable)
+	c.drawable = 0
+	return nil
+}
+
+func (c *mtlContext) Lock() error {
+	return nil
+}
+
+func (c *mtlContext) Unlock() {}
+
+func (c *mtlContext) Refresh() error {
+	resizeDrawable(c.view, c.layer)
+	return nil
+}
+
+func (w *window) NewContext() (Context, error) {
+	return newMtlContext(w)
+}

app/internal/wm/metal_ios.go

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+//go:build !nometal
+// +build !nometal
+
+package wm
+
+/*
+#cgo CFLAGS: -Werror -xobjective-c -fmodules -fobjc-arc
+
+@import UIKit;
+
+@import QuartzCore.CAMetalLayer;
+
+#include <CoreFoundation/CoreFoundation.h>
+
+Class gio_layerClass(void) {
+	return [CAMetalLayer class];
+}
+
+static CFTypeRef getMetalLayer(CFTypeRef viewRef) {
+	@autoreleasepool {
+		UIView *view = (__bridge UIView *)viewRef;
+		return CFBridgingRetain(view.layer);
+	}
+}
+
+static void resizeDrawable(CFTypeRef viewRef, CFTypeRef layerRef) {
+	@autoreleasepool {
+		UIView *view = (__bridge UIView *)viewRef;
+		CAMetalLayer *layer = (__bridge CAMetalLayer *)layerRef;
+		layer.contentsScale = view.contentScaleFactor;
+		CGSize size = layer.bounds.size;
+		size.width *= layer.contentsScale;
+		size.height *= layer.contentsScale;
+		layer.drawableSize = size;
+	}
+}
+*/
+import "C"
+
+func getMetalLayer(view C.CFTypeRef) C.CFTypeRef {
+	return C.getMetalLayer(view)
+}
+
+func resizeDrawable(view, layer C.CFTypeRef) {
+	C.resizeDrawable(view, layer)
+}

app/internal/wm/metal_macos.go

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+//go:build darwin && !ios && !nometal
+// +build darwin,!ios,!nometal
+
+package wm
+
+/*
+#cgo CFLAGS: -Werror -xobjective-c -fmodules -fobjc-arc
+
+@import AppKit;
+
+@import QuartzCore.CAMetalLayer;
+
+#include <CoreFoundation/CoreFoundation.h>
+
+CALayer *gio_layerFactory(void) {
+	@autoreleasepool {
+		return [CAMetalLayer layer];
+	}
+}
+
+static CFTypeRef getMetalLayer(CFTypeRef viewRef) {
+	@autoreleasepool {
+		NSView *view = (__bridge NSView *)viewRef;
+		return CFBridgingRetain(view.layer);
+	}
+}
+
+static void resizeDrawable(CFTypeRef viewRef, CFTypeRef layerRef) {
+	@autoreleasepool {
+		NSView *view = (__bridge NSView *)viewRef;
+		CAMetalLayer *layer = (__bridge CAMetalLayer *)layerRef;
+		CGSize size = layer.bounds.size;
+		size.width *= layer.contentsScale;
+		size.height *= layer.contentsScale;
+		layer.drawableSize = size;
+	}
+}
+*/
+import "C"
+
+func getMetalLayer(view C.CFTypeRef) C.CFTypeRef {
+	return C.getMetalLayer(view)
+}
+
+func resizeDrawable(view, layer C.CFTypeRef) {
+	C.resizeDrawable(view, layer)
+}

app/internal/wm/os_ios.go

@@ -46,24 +46,6 @@ static void hideTextInput(CFTypeRef viewRef) {
 	[view resignFirstResponder];
 }
 
-static void addLayerToView(CFTypeRef viewRef, CFTypeRef layerRef) {
-	UIView *view = (__bridge UIView *)viewRef;
-	CALayer *layer = (__bridge CALayer *)layerRef;
-	[view.layer addSublayer:layer];
-}
-
-static void updateView(CFTypeRef viewRef, CFTypeRef layerRef) {
-	UIView *view = (__bridge UIView *)viewRef;
-	CAEAGLLayer *layer = (__bridge CAEAGLLayer *)layerRef;
-	layer.contentsScale = view.contentScaleFactor;
-	layer.bounds = view.bounds;
-}
-
-static void removeLayer(CFTypeRef layerRef) {
-	CALayer *layer = (__bridge CALayer *)layerRef;
-	[layer removeFromSuperlayer];
-}
-
 static struct drawParams viewDrawParams(CFTypeRef viewRef) {
 	UIView *v = (__bridge UIView *)viewRef;
 	struct drawParams params;
@@ -92,7 +74,6 @@ import (
 	"image"
 	"runtime"
 	"runtime/debug"
-	"sync/atomic"
 	"time"
 	"unicode/utf16"
 	"unsafe"
@@ -112,8 +93,7 @@ type window struct {
 	w           Callbacks
 	displayLink *displayLink
 
-	layer   C.CFTypeRef
-	visible atomic.Value
+	visible bool
 	cursor  pointer.CursorName
 
 	pointerMap []C.CFTypeRef
@@ -121,8 +101,6 @@ type window struct {
 
 var mainWindow = newWindowRendezvous()
 
-var layerFactory func() uintptr
-
 var views = make(map[C.CFTypeRef]*window)
 
 func init() {
@@ -145,9 +123,6 @@ func onCreate(view C.CFTypeRef) {
 	wopts := <-mainWindow.out
 	w.w = wopts.window
 	w.w.SetDriver(w)
-	w.visible.Store(false)
-	w.layer = C.CFTypeRef(layerFactory())
-	C.addLayerToView(view, w.layer)
 	views[view] = w
 	w.w.Event(system.StageEvent{Stage: system.StagePaused})
 }
@@ -163,9 +138,8 @@ func (w *window) draw(sync bool) {
 	if params.width == 0 || params.height == 0 {
 		return
 	}
-	wasVisible := w.isVisible()
-	w.visible.Store(true)
-	C.updateView(w.view, w.layer)
+	wasVisible := w.visible
+	w.visible = true
 	if !wasVisible {
 		w.w.Event(system.StageEvent{Stage: system.StageRunning})
 	}
@@ -195,7 +169,7 @@ func (w *window) draw(sync bool) {
 //export onStop
 func onStop(view C.CFTypeRef) {
 	w := views[view]
-	w.visible.Store(false)
+	w.visible = false
 	w.w.Event(system.StageEvent{Stage: system.StagePaused})
 }
 
@@ -205,9 +179,6 @@ func onDestroy(view C.CFTypeRef) {
 	delete(views, view)
 	w.w.Event(system.DestroyEvent{})
 	w.displayLink.Close()
-	C.removeLayer(w.layer)
-	C.CFRelease(w.layer)
-	w.layer = 0
 	w.view = 0
 }
 
@@ -341,12 +312,8 @@ func (w *window) lookupTouch(last bool, touch C.CFTypeRef) pointer.ID {
 	return pointer.ID(id)
 }
 
-func (w *window) contextLayer() uintptr {
-	return uintptr(w.layer)
-}
-
-func (w *window) isVisible() bool {
-	return w.visible.Load().(bool)
+func (w *window) contextView() C.CFTypeRef {
+	return w.view
 }
 
 func (w *window) ShowTextInput(show bool) {

app/internal/wm/os_ios.m

@@ -8,6 +8,8 @@
 #include "_cgo_export.h"
 #include "framework_ios.h"
 
+__attribute__ ((visibility ("hidden"))) Class gio_layerClass(void);
+
 @interface GioView: UIView <UIKeyInput>
 @end
 
@@ -125,6 +127,9 @@ NSArray<UIKeyCommand *> *_keyCommands;
 	gio_onFrameCallback((__bridge CFTypeRef)link);
 }
 
++ (Class)layerClass {
+    return gio_layerClass();
+}
 - (void)willMoveToWindow:(UIWindow *)newWindow {
 	if (self.window != nil) {
 		[[NSNotificationCenter defaultCenter] removeObserver:self
@@ -157,9 +162,6 @@ NSArray<UIKeyCommand *> *_keyCommands;
 	}
 }
 
-- (void)dealloc {
-}
-
 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
 	handleTouches(0, self, touches, event);
 }

app/internal/wm/os_macos.go

@@ -423,11 +423,9 @@ func gio_onClose(view C.CFTypeRef) {
 	deleteView(view)
 	w.w.Event(system.DestroyEvent{})
 	w.displayLink.Close()
-	w.displayLink = nil
 	C.CFRelease(w.view)
-	w.view = 0
 	C.CFRelease(w.window)
-	w.window = 0
+	*w = window{}
 }
 
 //export gio_onHide

app/internal/wm/os_macos.m

@@ -6,6 +6,8 @@
 
 #include "_cgo_export.h"
 
+__attribute__ ((visibility ("hidden"))) CALayer *gio_layerFactory(void);
+
 @interface GioAppDelegate : NSObject<NSApplicationDelegate>
 @end
 
@@ -54,13 +56,24 @@ static void handleMouse(NSView *view, NSEvent *event, int typ, CGFloat dx, CGFlo
 	gio_onMouse((__bridge CFTypeRef)view, typ, [NSEvent pressedMouseButtons], p.x, height - p.y, dx, dy, [event timestamp], [event modifierFlags]);
 }
 
-@interface GioView : NSView
+@interface GioView : NSView <CALayerDelegate>
 @end
 
 @implementation GioView
+// drawRect is called when OpenGL is used, displayLayer otherwise.
+// Don't know why.
 - (void)drawRect:(NSRect)r {
 	gio_onDraw((__bridge CFTypeRef)self);
 }
+- (void)displayLayer:(CALayer *)layer {
+	layer.contentsScale = self.window.backingScaleFactor;
+	gio_onDraw((__bridge CFTypeRef)self);
+}
+- (CALayer *)makeBackingLayer {
+	CALayer *layer = gio_layerFactory();
+	layer.delegate = self;
+	return layer;
+}
 - (void)mouseDown:(NSEvent *)event {
 	handleMouse(self, event, MOUSE_DOWN, 0, 0);
 }
@@ -221,6 +234,7 @@ CFTypeRef gio_createView(void) {
 		NSRect frame = NSMakeRect(0, 0, 0, 0);
 		GioView* view = [[GioView alloc] initWithFrame:frame];
 		[view setWantsLayer:YES];
+		view.layerContentsRedrawPolicy = NSViewLayerContentsRedrawDuringViewResize;
 		return CFBridgingRetain(view);
 	}
 }

go.mod

@@ -10,5 +10,5 @@ require (
 
 require (
 	gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2
-	gioui.org/shader v0.0.0-20210820085839-484f7c0305de
+	gioui.org/shader v0.0.0-20210821062758-133bba6632c7
 )

go.sum

@@ -4,8 +4,8 @@ dmitri.shuralyov.com/gpu/mtl v0.0.0-20201218220906-28db891af037/go.mod h1:H6x//7
 gioui.org/cpu v0.0.0-20210808092351-bfe733dd3334/go.mod h1:A8M0Cn5o+vY5LTMlnRoK3O5kG+rH0kWfJjeKd9QpBmQ=
 gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2 h1:AGDDxsJE1RpcXTAxPG2B4jrwVUJGFDjINIPi1jtO6pc=
 gioui.org/cpu v0.0.0-20210817075930-8d6a761490d2/go.mod h1:A8M0Cn5o+vY5LTMlnRoK3O5kG+rH0kWfJjeKd9QpBmQ=
-gioui.org/shader v0.0.0-20210820085839-484f7c0305de h1:fkcZh0i9T0SzMlqiDm2GBVqXZsbX6bevHcJHfR0llcg=
-gioui.org/shader v0.0.0-20210820085839-484f7c0305de/go.mod h1:mWdiME581d/kV7/iEhLmUgUK5iZ09XR5XpduXzbePVM=
+gioui.org/shader v0.0.0-20210821062758-133bba6632c7 h1:DzpPjbWzoI5cg+WBXWSF2007lzdViHKYZR5NUOKD55k=
+gioui.org/shader v0.0.0-20210821062758-133bba6632c7/go.mod h1:mWdiME581d/kV7/iEhLmUgUK5iZ09XR5XpduXzbePVM=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/Knetic/govaluate v3.0.1-0.20171022003610-9aa49832a739+incompatible/go.mod h1:r7JcOSlj0wfOMncg0iLm8Leh48TZaKVeNIfJntJ2wa0=

gpu/api.go

@@ -17,8 +17,14 @@ type OpenGLRenderTarget = driver.OpenGLRenderTarget
 // Direct3D11RenderTarget is a render target suitable for the Direct3D 11 backend.
 type Direct3D11RenderTarget = driver.Direct3D11RenderTarget
 
+// MetalRenderTarget is a render target suitable for the Metal backend.
+type MetalRenderTarget = driver.MetalRenderTarget
+
 // OpenGL denotes the OpenGL or OpenGL ES API.
 type OpenGL = driver.OpenGL
 
 // Direct3D11 denotes the Direct3D API.
 type Direct3D11 = driver.Direct3D11
+
+// Metal denotes the Apple Metal API.
+type Metal = driver.Metal

gpu/gpu.go

@@ -36,6 +36,7 @@ import (
 
 	// Register backends.
 	_ "gioui.org/gpu/internal/d3d11"
+	_ "gioui.org/gpu/internal/metal"
 	_ "gioui.org/gpu/internal/opengl"
 )
 
@@ -135,7 +136,7 @@ type imageOp struct {
 
 // shaderModuleVersion is the exact version of gioui.org/shader expected by
 // this package. Shader programs are not backwards or forwards compatible.
-const shaderModuleVersion = "v0.0.0-20210820085839-484f7c0305de"
+const shaderModuleVersion = "v0.0.0-20210821062758-133bba6632c7"
 
 func decodeStrokeOp(data []byte) clip.StrokeStyle {
 	_ = data[4]

gpu/headless/headless_darwin.go

@@ -3,46 +3,69 @@
 package headless
 
 import (
+	"errors"
+	"unsafe"
+
 	"gioui.org/gpu"
 	_ "gioui.org/internal/cocoainit"
 )
 
 /*
-#cgo CFLAGS: -DGL_SILENCE_DEPRECATION -Werror -Wno-deprecated-declarations -fmodules -fobjc-arc -x objective-c
+#cgo CFLAGS: -Werror -Wno-deprecated-declarations -fmodules -fobjc-arc -x objective-c
+#cgo LDFLAGS: -framework CoreGraphics
 
-#include <CoreFoundation/CoreFoundation.h>
+@import Metal;
 
-__attribute__ ((visibility ("hidden"))) CFTypeRef gio_headless_newContext(void);
-__attribute__ ((visibility ("hidden"))) void gio_headless_clearCurrentContext(CFTypeRef ctxRef);
-__attribute__ ((visibility ("hidden"))) void gio_headless_makeCurrentContext(CFTypeRef ctxRef);
+static CFTypeRef createDevice(void) {
+	@autoreleasepool {
+		id dev = MTLCreateSystemDefaultDevice();
+		return CFBridgingRetain(dev);
+	}
+}
+
+static CFTypeRef newCommandQueue(CFTypeRef devRef) {
+	@autoreleasepool {
+		id<MTLDevice> dev = (__bridge id<MTLDevice>)devRef;
+		return CFBridgingRetain([dev newCommandQueue]);
+	}
+}
 */
 import "C"
 
-type nsContext struct {
-	ctx C.CFTypeRef
+type mtlContext struct {
+	dev   C.CFTypeRef
+	queue C.CFTypeRef
 }
 
 func newContext() (context, error) {
-	ctx := C.gio_headless_newContext()
-	return &nsContext{ctx: ctx}, nil
+	dev := C.createDevice()
+	if dev == 0 {
+		return nil, errors.New("headless: failed to create Metal device")
+	}
+	queue := C.newCommandQueue(dev)
+	if queue == 0 {
+		C.CFRelease(dev)
+		return nil, errors.New("headless: failed to create MTLQueue")
+	}
+	return &mtlContext{dev: dev, queue: queue}, nil
 }
 
-func (c *nsContext) API() gpu.API {
-	return gpu.OpenGL{}
+func (c *mtlContext) API() gpu.API {
+	return gpu.Metal{
+		Device:      unsafe.Pointer(c.dev),
+		Queue:       unsafe.Pointer(c.queue),
+		PixelFormat: int(C.MTLPixelFormatRGBA8Unorm_sRGB),
+	}
 }
 
-func (c *nsContext) MakeCurrent() error {
-	C.gio_headless_makeCurrentContext(c.ctx)
+func (c *mtlContext) MakeCurrent() error {
 	return nil
 }
 
-func (c *nsContext) ReleaseCurrent() {
-	C.gio_headless_clearCurrentContext(c.ctx)
-}
+func (c *mtlContext) ReleaseCurrent() {}
 
-func (d *nsContext) Release() {
-	if d.ctx != 0 {
-		C.CFRelease(d.ctx)
-		d.ctx = 0
-	}
+func (d *mtlContext) Release() {
+	C.CFRelease(d.dev)
+	C.CFRelease(d.queue)
+	*d = mtlContext{}
 }

gpu/headless/headless_ios.m

@@ -1,25 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-// +build darwin,ios
-
-@import OpenGLES;
-
-#include <CoreFoundation/CoreFoundation.h>
-#include "_cgo_export.h"
-
-CFTypeRef gio_headless_newContext(void) {
-	EAGLContext *ctx = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
-	if (ctx == nil) {
-		return nil;
-	}
-	return CFBridgingRetain(ctx);
-}
-
-void gio_headless_clearCurrentContext(CFTypeRef ctxRef) {
-	[EAGLContext setCurrentContext:nil];
-}
-
-void gio_headless_makeCurrentContext(CFTypeRef ctxRef) {
-	EAGLContext *ctx = (__bridge EAGLContext *)ctxRef;
-	[EAGLContext setCurrentContext:ctx];
-}

gpu/headless/headless_macos.m

@@ -1,41 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-// +build darwin,!ios
-
-@import AppKit;
-@import OpenGL;
-@import OpenGL.GL;
-@import OpenGL.GL3;
-
-#include <CoreFoundation/CoreFoundation.h>
-#include "_cgo_export.h"
-
-CFTypeRef gio_headless_newContext(void) {
-	NSOpenGLPixelFormatAttribute attr[] = {
-		NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion3_2Core,
-		NSOpenGLPFAColorSize,     24,
-		NSOpenGLPFAAccelerated,
-		// Opt-in to automatic GPU switching. CGL-only property.
-		kCGLPFASupportsAutomaticGraphicsSwitching,
-		NSOpenGLPFAAllowOfflineRenderers,
-		0
-	};
-	NSOpenGLPixelFormat *pixFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attr];
-	if (pixFormat == nil) {
-		return NULL;
-	}
-	NSOpenGLContext *ctx = [[NSOpenGLContext alloc] initWithFormat:pixFormat shareContext:nil];
-	return CFBridgingRetain(ctx);
-}
-
-void gio_headless_clearCurrentContext(CFTypeRef ctxRef) {
-	NSOpenGLContext *ctx = (__bridge NSOpenGLContext *)ctxRef;
-	CGLUnlockContext([ctx CGLContextObj]);
-	[NSOpenGLContext clearCurrentContext];
-}
-
-void gio_headless_makeCurrentContext(CFTypeRef ctxRef) {
-	NSOpenGLContext *ctx = (__bridge NSOpenGLContext *)ctxRef;
-	[ctx makeCurrentContext];
-	CGLLockContext([ctx CGLContextObj]);
-}

gpu/internal/driver/api.go

@@ -26,6 +26,11 @@ type Direct3D11RenderTarget struct {
 	RenderTarget unsafe.Pointer
 }
 
+type MetalRenderTarget struct {
+	// Texture is a MTLTexture.
+	Texture unsafe.Pointer
+}
+
 type OpenGL struct {
 	// ES forces the use of ANGLE OpenGL ES libraries on macOS. It is
 	// ignored on all other platforms.
@@ -41,10 +46,20 @@ type Direct3D11 struct {
 	Device unsafe.Pointer
 }
 
+type Metal struct {
+	// Device is an MTLDevice.
+	Device unsafe.Pointer
+	// Queue is a MTLCommandQueue.
+	Queue unsafe.Pointer
+	// PixelFormat is the MTLPixelFormat of the default framebuffer.
+	PixelFormat int
+}
+
 // API specific device constructors.
 var (
 	NewOpenGLDevice     func(api OpenGL) (Device, error)
 	NewDirect3D11Device func(api Direct3D11) (Device, error)
+	NewMetalDevice      func(api Metal) (Device, error)
 )
 
 // NewDevice creates a new Device given the api.
@@ -62,11 +77,17 @@ func NewDevice(api API) (Device, error) {
 		if NewDirect3D11Device != nil {
 			return NewDirect3D11Device(api)
 		}
+	case Metal:
+		if NewMetalDevice != nil {
+			return NewMetalDevice(api)
+		}
 	}
 	return nil, fmt.Errorf("driver: no driver available for the API %T", api)
 }
 
 func (OpenGL) implementsAPI()                          {}
 func (Direct3D11) implementsAPI()                      {}
+func (Metal) implementsAPI()                           {}
 func (OpenGLRenderTarget) ImplementsRenderTarget()     {}
 func (Direct3D11RenderTarget) ImplementsRenderTarget() {}
+func (MetalRenderTarget) ImplementsRenderTarget()      {}

gpu/internal/metal/metal.go

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// This file exists so this package builds on non-Darwin platforms.
+
+package metal