[MONOMAC] Initial implementation of deferred rendering support

src/OSX/Avalonia.MonoMac/EmulatedFramebuffer.cs

@@ -2,17 +2,20 @@
 using Avalonia.Platform;
 using MonoMac.AppKit;
 using System.Runtime.InteropServices;
+using Avalonia.Threading;
 using MonoMac.CoreGraphics;
 
 namespace Avalonia.MonoMac
 {
     class EmulatedFramebuffer : ILockedFramebuffer
     {
+        private readonly TopLevelImpl.TopLevelView _view;
         private readonly CGSize _logicalSize;
-        public EmulatedFramebuffer(NSView view)
+
+        public EmulatedFramebuffer(TopLevelImpl.TopLevelView view, CGSize logicalSize, CGSize pixelSize)
         {
-            _logicalSize = view.Frame.Size;
-            var pixelSize = view.ConvertSizeToBacking(_logicalSize);
+            _view = view;
+            _logicalSize = logicalSize;
             Width = (int)pixelSize.Width;
             Height = (int)pixelSize.Height;
             RowBytes = Width * 4;
@@ -21,25 +24,78 @@ namespace Avalonia.MonoMac
             Address = Marshal.AllocHGlobal(Height * RowBytes);
         }
 
+        class DeferredRenderingHelper : IDisposable
+        {
+            private readonly NSView _view;
+            public void Dispose()
+            {
+                _view.NonUIUnlockFocus();
+            }
+
+            public DeferredRenderingHelper(NSView view)
+            {
+                _view = view;
+            }
+        }
+
+        DeferredRenderingHelper SetupWindowContext()
+        {
+            if (!_view.NonUILockFocusIfCanDraw())
+                return null;
+            return new DeferredRenderingHelper(_view);
+        }
+
         public void Dispose()
         {
             if (Address == IntPtr.Zero)
                 return;
             var nfo = (int) CGBitmapFlags.ByteOrder32Big | (int) CGImageAlphaInfo.PremultipliedLast;
 
-            using (var colorSpace = CGColorSpace.CreateDeviceRGB())
-            using (var bContext = new CGBitmapContext(Address, Width, Height, 8, Width * 4,
-                colorSpace, (CGImageAlphaInfo) nfo))
-            using (var image = bContext.ToImage())
-            using (var nscontext = NSGraphicsContext.CurrentContext)
-            using (var context = nscontext.GraphicsPort)
+            DeferredRenderingHelper deferred = null;
+            var isDeferred = !Dispatcher.UIThread.CheckAccess();
+            if (!isDeferred || (deferred = SetupWindowContext()) != null)
             {
-                context.SetFillColor(255, 255, 255, 255);
-                context.FillRect(new CGRect(default(CGPoint), _logicalSize));
-                context.DrawImage(new CGRect(default(CGPoint), _logicalSize), image);
+                CGImage image = null;
+                try
+                {
+                    lock (_view.SyncRoot)
+                    {
+                        using (deferred)
+                        using (var colorSpace = CGColorSpace.CreateDeviceRGB())
+                        using (var bContext = new CGBitmapContext(Address, Width, Height, 8, Width * 4,
+                            colorSpace, (CGImageAlphaInfo) nfo))
+                        {
+                            if (!isDeferred || deferred != null)
+                            {
+                                using (var nscontext = NSGraphicsContext.CurrentContext)
+                                using (var context = nscontext.GraphicsPort)
+                                {
+                                    image = bContext.ToImage();
+                                    context.SetFillColor(255, 255, 255, 255);
+                                    context.FillRect(new CGRect(default(CGPoint), _view.LogicalSize));
+                                    context.TranslateCTM(0, _view.LogicalSize.Height - _logicalSize.Height);
+                                    context.DrawImage(new CGRect(default(CGPoint), _logicalSize), image);
+                                    context.Flush();
+                                    nscontext.FlushGraphics();
+                                }
+                            }
+                        }
+                    }
+                }
+                finally
+                {
+                    if (image != null)
+                    {
+                        if (deferred == null)
+                            image.Dispose();
+                        else
+                            _view.SetBackBufferImage(new SavedImage(image, _logicalSize));
+                    }
+                }
             }
             Marshal.FreeHGlobal(Address);
             Address = IntPtr.Zero;
+
         }
 
         public IntPtr Address { get; private set; }
@@ -49,4 +105,22 @@ namespace Avalonia.MonoMac
         public Vector Dpi { get; }
         public PixelFormat Format { get; }
     }
+
+    class SavedImage : IDisposable
+    {
+        public CGImage Image { get; private set; }
+        public CGSize LogicalSize { get; }
+
+        public SavedImage(CGImage image, CGSize logicalSize)
+        {
+            Image = image;
+            LogicalSize = logicalSize;
+        }
+
+        public void Dispose()
+        {
+            Image?.Dispose();
+            Image = null;
+        }
+    }
 }

src/OSX/Avalonia.MonoMac/MonoMacPlatform.cs

@@ -1,10 +1,13 @@
 using System;
+using System.Threading;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
 using Avalonia.Platform;
 using Avalonia.Rendering;
 using MonoMac.AppKit;
+using MonoMac.Foundation;
+using MonoMac.ObjCRuntime;
 
 namespace Avalonia.MonoMac
 {
@@ -16,9 +19,11 @@ namespace Avalonia.MonoMac
         internal static NSApplication App;
         private static bool s_monoMacInitialized;
         private static bool s_showInDock = true;
+        private static IRenderLoop s_renderLoop;
 
         void DoInitialize()
         {
+            InitializeMonoMac();
             AvaloniaLocator.CurrentMutable
                 .Bind<IStandardCursorFactory>().ToTransient<CursorFactoryStub>()
                 .Bind<IPlatformIconLoader>().ToSingleton<IconLoader>()
@@ -27,9 +32,8 @@ namespace Avalonia.MonoMac
                 .Bind<IPlatformSettings>().ToConstant(this)
                 .Bind<IWindowingPlatform>().ToConstant(this)
                 .Bind<ISystemDialogImpl>().ToSingleton<SystemDialogsImpl>()
+                .Bind<IRenderLoop>().ToConstant(s_renderLoop)
                 .Bind<IPlatformThreadingInterface>().ToConstant(PlatformThreadingInterface.Instance);
-
-            InitializeMonoMac();
         }
 
         public static void Initialize()
@@ -39,13 +43,43 @@ namespace Avalonia.MonoMac
 
         }
 
+
+        /// <summary>
+        /// See "Using POSIX Threads in a Cocoa Application" section here:
+        /// https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/CreatingThreads.html#//apple_ref/doc/uid/20000738-125024
+        /// </summary>
+        class ThreadHelper : NSObject
+        {
+            private readonly AutoResetEvent _event = new AutoResetEvent(false);
+            [Export("doNothing")]
+            public void DoNothing()
+            {
+                _event.Set();
+            }
+
+            public static void InitializeCocoaThreadingLocks()
+            {
+                var helper = new ThreadHelper();
+                var thread = new NSThread(helper, Selector.FromHandle(Selector.GetHandle("doNothing")), new NSObject());
+                thread.Start();
+                helper._event.WaitOne();
+                helper._event.Dispose();
+                if (!NSThread.IsMultiThreaded)
+                {
+                    throw new Exception("Unable to initialize Cocoa threading");
+                }
+            }
+        }
+
         void InitializeMonoMac()
         {
             if(s_monoMacInitialized)
                 return;
             NSApplication.Init();
+            ThreadHelper.InitializeCocoaThreadingLocks();
             App = NSApplication.SharedApplication;
             UpdateActivationPolicy();
+            s_renderLoop = new RenderLoop(); //TODO: use CVDisplayLink
             s_monoMacInitialized = true;
         }
 
@@ -64,6 +98,7 @@ namespace Avalonia.MonoMac
             }
         }
 
+        public static bool UseDeferredRendering { get; set; } = true;
 
         public Size DoubleClickSize => new Size(4, 4);
         public TimeSpan DoubleClickTime => TimeSpan.FromSeconds(NSEvent.DoubleClickInterval);
@@ -87,8 +122,10 @@ namespace Avalonia
 {
     public static class MonoMacPlatformExtensions
     {
-        public static T UseMonoMac<T>(this T builder) where T : AppBuilderBase<T>, new()
+        public static T UseMonoMac<T>(this T builder, bool? useDeferredRendering = null) where T : AppBuilderBase<T>, new()
         {
+            if (useDeferredRendering.HasValue)
+                MonoMac.MonoMacPlatform.UseDeferredRendering = useDeferredRendering.Value;
             return builder.UseWindowingSubsystem(MonoMac.MonoMacPlatform.Initialize);
         }
     }

src/OSX/Avalonia.MonoMac/RenderLoop.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Avalonia.Platform;
+using Avalonia.Rendering;
+using MonoMac.Foundation;
+
+namespace Avalonia.MonoMac
+{
+    //TODO: Switch to using CVDisplayLink
+    public class RenderLoop : IRenderLoop
+    {
+        private readonly object _lock = new object();
+        private readonly IDisposable _timer;
+
+        public RenderLoop()
+        {
+            _timer = AvaloniaLocator.Current.GetService<IRuntimePlatform>().StartSystemTimer(new TimeSpan(0, 0, 0, 0, 1000 / 60),
+                () =>
+                {
+                    lock (_lock)
+                    {
+                        using (new NSAutoreleasePool())
+                        {
+                            Tick?.Invoke(this, EventArgs.Empty);
+                        }
+                    }
+                });
+        }
+
+        public event EventHandler<EventArgs> Tick;
+    }
+}

src/OSX/Avalonia.MonoMac/ThreadingUtils.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using MonoMac.AppKit;
+using MonoMac.ObjCRuntime;
+
+namespace Avalonia.MonoMac
+{
+    public static class ThreadingUtils
+    {
+        private static readonly IntPtr selUnlockFocusHandle = Selector.GetHandle("unlockFocus");
+        private static readonly IntPtr selLockFocusIfCanDrawHandle = Selector.GetHandle("lockFocusIfCanDraw");
+        private static readonly IntPtr selWindowHandle = Selector.GetHandle("window");
+        private static readonly IntPtr selCanDrawHandle = Selector.GetHandle("canDraw");
+
+        public static bool NonUILockFocusIfCanDraw(this NSView view)
+        {
+            return Messaging.bool_objc_msgSend(view.Handle, selLockFocusIfCanDrawHandle);
+        }
+
+        public static void NonUIUnlockFocus(this NSView view)
+        {
+            Messaging.void_objc_msgSend(view.Handle, selUnlockFocusHandle);
+        }
+
+        public static NSWindow NonUIGetWindow(this NSView view)
+        {
+            return (NSWindow) Runtime.GetNSObject(Messaging.IntPtr_objc_msgSendSuper(view.Handle, selWindowHandle));
+        }
+
+        public static bool BaseCanDraw(this NSView view)
+        {
+            return Messaging.bool_objc_msgSendSuper(view.SuperHandle, selCanDrawHandle);
+        }
+    }
+}

src/OSX/Avalonia.MonoMac/TopLevelImpl.cs

@@ -5,6 +5,7 @@ using Avalonia.Input.Raw;
 using Avalonia.Platform;
 using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Rendering;
+using Avalonia.Threading;
 using MonoMac.AppKit;
 
 using MonoMac.CoreGraphics;
@@ -37,6 +38,13 @@ namespace Avalonia.MonoMac
             private NSTrackingArea _area;
             private NSCursor _cursor;
 
+            public CGSize PixelSize { get; set; }
+
+            public CGSize LogicalSize { get; set; }
+
+            private SavedImage _backBuffer;
+            public object SyncRoot { get; } = new object();
+
             public TopLevelView(TopLevelImpl tl)
             {
                 _tl = tl;
@@ -44,17 +52,50 @@ namespace Avalonia.MonoMac
                 _keyboard = AvaloniaLocator.Current.GetService<IKeyboardDevice>();
             }
 
+            protected override void Dispose(bool disposing)
+            {
+                if (disposing)
+                    SetBackBufferImage(null);
+                base.Dispose(disposing);
+            }
+
             public override bool ConformsToProtocol(IntPtr protocol)
             {
                 var rv = base.ConformsToProtocol(protocol);
                 return rv;
             }
 
+            public override bool IsOpaque => false;
+
             public override void DrawRect(CGRect dirtyRect)
             {
+                lock (SyncRoot)
+                {
+                    if (_backBuffer != null)
+                    {
+                        using (var context = NSGraphicsContext.CurrentContext.GraphicsPort)
+                        {
+                            context.SetFillColor(255, 255, 255, 255);
+                            context.FillRect(new CGRect(default(CGPoint), LogicalSize));
+                            context.TranslateCTM(0, LogicalSize.Height - _backBuffer.LogicalSize.Height);
+                            context.DrawImage(new CGRect(default(CGPoint), _backBuffer.LogicalSize), _backBuffer.Image);
+                            context.Flush();
+                            NSGraphicsContext.CurrentContext.FlushGraphics();
+                        }
+                    }
+                }
                 _tl.Paint?.Invoke(dirtyRect.ToAvaloniaRect());
             }
 
+            public void SetBackBufferImage(SavedImage image)
+            {
+                lock (SyncRoot)
+                {
+                    _backBuffer?.Dispose();
+                    _backBuffer = image;
+                }
+            }
+            
             [Export("viewDidChangeBackingProperties:")]
             public void ViewDidChangeBackingProperties()
             {
@@ -78,7 +119,12 @@ namespace Avalonia.MonoMac
 
             public override void SetFrameSize(CGSize newSize)
             {
-                base.SetFrameSize(newSize);
+                lock (SyncRoot)
+                {
+                    base.SetFrameSize(newSize);
+                    LogicalSize = Frame.Size;
+                    PixelSize = ConvertSizeToBacking(LogicalSize);
+                }
 
                 if (_area != null)
                 {
@@ -348,9 +394,16 @@ namespace Avalonia.MonoMac
             View.Dispose();
         }
 
-        public IRenderer CreateRenderer(IRenderRoot root) => new ImmediateRenderer(root);
+        public IRenderer CreateRenderer(IRenderRoot root) =>
+            MonoMacPlatform.UseDeferredRendering
+                ? new DeferredRenderer(root, AvaloniaLocator.Current.GetService<IRenderLoop>())
+                : (IRenderer) new ImmediateRenderer(root);
 
-        public void Invalidate(Rect rect) => View.SetNeedsDisplayInRect(View.Frame);
+        public void Invalidate(Rect rect)
+        {
+            if (!MonoMacPlatform.UseDeferredRendering)
+                View.SetNeedsDisplayInRect(View.Frame);
+        }
 
         public abstract Point PointToClient(Point point);
 
@@ -360,6 +413,6 @@ namespace Avalonia.MonoMac
 
         public void SetInputRoot(IInputRoot inputRoot) => InputRoot = inputRoot;
 
-        public ILockedFramebuffer Lock() => new EmulatedFramebuffer(View);
+        public ILockedFramebuffer Lock() => new EmulatedFramebuffer(View, View.LogicalSize, View.PixelSize);
     }
 }