Merge pull request #11552 from AvaloniaUI/feature/media-context-4

Media system refactoring

src/Android/Avalonia.Android/AndroidPlatform.cs

@@ -52,11 +52,7 @@ namespace Avalonia.Android
                 EglPlatformGraphics.TryInitialize();
             }
             
-            Compositor = new Compositor(
-                AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(),
-                AvaloniaLocator.Current.GetService<IPlatformGraphics>());
-            
-
+            Compositor = new Compositor(AvaloniaLocator.Current.GetService<IPlatformGraphics>());
         }
     }
 

src/Avalonia.Base/Animation/Easings/IEasing.cs

@@ -1,8 +1,11 @@
+using Avalonia.Metadata;
+
 namespace Avalonia.Animation.Easings
 {
     /// <summary>
     /// Defines the interface for easing classes.
     /// </summary>
+    [NotClientImplementable]
     public interface IEasing
     {
         /// <summary>

src/Avalonia.Base/Layout/LayoutManager.cs

@@ -28,10 +28,12 @@ namespace Avalonia.Layout
         private bool _queued;
         private bool _running;
         private int _totalPassCount;
+        private Action _invokeOnRender;
 
         public LayoutManager(ILayoutRoot owner)
         {
             _owner = owner as Layoutable ?? throw new ArgumentNullException(nameof(owner));
+            _invokeOnRender = ExecuteQueuedLayoutPass;
         }
 
         public virtual event EventHandler? LayoutUpdated;
@@ -345,7 +347,7 @@ namespace Avalonia.Layout
             if (!_queued && !_running)
             {
                 _queued = true;
-                MediaContext.Instance.QueueLayoutPass(this);
+                MediaContext.Instance.BeginInvokeOnRender(_invokeOnRender);
             }
         }
 

src/Avalonia.Base/Media/MediaContext.Compositor.cs

@@ -40,28 +40,42 @@ partial class MediaContext
             _animationsAreWaitingForComposition = false;
 
             // Check if we have uncommited changes
-            if (_scheduleCommitOnLastCompositionBatchCompletion && _pendingCompositionBatches.Count > 0)
+            if (_scheduleCommitOnLastCompositionBatchCompletion)
             {
-                CommitCompositorsWithThrottling();
                 _scheduleCommitOnLastCompositionBatchCompletion = false;
+                if (!CommitCompositorsWithThrottling())
+                    ScheduleRenderForAnimationsIfNeeded();
+
             }
             // Check if there are active animations and schedule the next render
-            else if(_clock.HasSubscriptions) 
-                ScheduleRender(false);
+            else
+                ScheduleRenderForAnimationsIfNeeded();
         }
+    }
 
+    void ScheduleRenderForAnimationsIfNeeded()
+    {
+        if (_clock.HasSubscriptions) 
+            ScheduleRender(false);
     }
 
+    /// <summary>
+    /// Triggers a composition commit if any batches are waiting to be sent,
+    /// handles throttling
+    /// </summary>
+    /// <returns>true if there are pending commits in-flight and there will be a "all-done" callback later</returns>
     private bool CommitCompositorsWithThrottling()
     {
         // Check if we are still waiting for previous composition batches
         if (_pendingCompositionBatches.Count > 0)
         {
             _scheduleCommitOnLastCompositionBatchCompletion = true;
+            // Previous commit isn't handled yet
             return true;
         }
-
+        
         if (_requestedCommits.Count == 0)
+            // Nothing to do, and there are no pending commits
             return false;
         
         foreach (var c in _requestedCommits)

src/Avalonia.Base/Media/MediaContext.cs

@@ -16,6 +16,7 @@ internal partial class MediaContext : ICompositorScheduler
     private DispatcherOperation? _nextRenderOp;
     private DispatcherOperation? _inputMarkerOp;
     private TimeSpan _inputMarkerAddedAt;
+    private bool _isRendering;
     private bool _animationsAreWaitingForComposition;
     private const double MaxSecondsWithoutInput = 1;
     private readonly Action _render;
@@ -23,7 +24,17 @@ internal partial class MediaContext : ICompositorScheduler
     private readonly HashSet<Compositor> _requestedCommits = new();
     private readonly Dictionary<Compositor, Batch> _pendingCompositionBatches = new();
     private record  TopLevelInfo(Compositor Compositor, CompositingRenderer Renderer, ILayoutManager LayoutManager);
-    private readonly HashSet<LayoutManager> _queuedLayoutManagers = new();
+
+    private List<Action>? _invokeOnRenderCallbacks;
+    private readonly Stack<List<Action>> _invokeOnRenderCallbackListPool = new();
+
+    private DispatcherTimer _animationsTimer = new(DispatcherPriority.Render)
+    {
+        // Since this timer is used to drive animations that didn't contribute to the previous frame at all
+        // We can safely use 16ms interval until we fix our animation system to actually report the next expected 
+        // frame
+        Interval = TimeSpan.FromMilliseconds(16)
+    };
 
     private Dictionary<object, TopLevelInfo> _topLevels = new();
 
@@ -32,6 +43,11 @@ internal partial class MediaContext : ICompositorScheduler
         _render = Render;
         _inputMarkerHandler = InputMarkerHandler;
         _clock = new(this);
+        _animationsTimer.Tick += (_, _) =>
+        {
+            _animationsTimer.Stop();
+            ScheduleRender(false);
+        };
     }
     
     public static MediaContext Instance
@@ -95,11 +111,13 @@ internal partial class MediaContext : ICompositorScheduler
     {
         try
         {
+            _isRendering = true;
             RenderCore();
         }
         finally
         {
             _nextRenderOp = null;
+            _isRendering = false;
         }
     }
     
@@ -114,10 +132,7 @@ internal partial class MediaContext : ICompositorScheduler
         for (var c = 0; c < 10; c++)
         {
             _clock.HasNewSubscriptions = false;
-            //TODO: Integrate LayoutManager's attempt limit here
-            foreach (var layout in _queuedLayoutManagers.ToArray())
-                layout.ExecuteQueuedLayoutPass();
-            _queuedLayoutManagers.Clear();
+            FireInvokeOnRenderCallbacks();
             
             if (_clock.HasNewSubscriptions)
             {
@@ -127,14 +142,12 @@ internal partial class MediaContext : ICompositorScheduler
 
             break;
         }
-
-        // We are currently using compositor commit callbacks to drive animations
-        // Later we should use WPF's approach that asks the animation system for the next tick time
-        // and use some timer if the next animation frame is not needed to be sent to the compositor immediately
+        
         if (_requestedCommits.Count > 0 || _clock.HasSubscriptions)
         {
-            _animationsAreWaitingForComposition = true;
-            CommitCompositorsWithThrottling();
+            _animationsAreWaitingForComposition = CommitCompositorsWithThrottling();
+            if (!_animationsAreWaitingForComposition && _clock.HasSubscriptions) 
+                _animationsTimer.Start();
         }
     }
 
@@ -160,9 +173,55 @@ internal partial class MediaContext : ICompositorScheduler
         }
     }
 
-    public void QueueLayoutPass(LayoutManager layoutManager)
+    /// <summary>
+    /// Calls all _invokeOnRenderCallbacks until no more are added
+    /// </summary>
+    private void FireInvokeOnRenderCallbacks()
     {
-        _queuedLayoutManagers.Add(layoutManager);
-        ScheduleRender(true);
+        int callbackLoopCount = 0;
+        int count = _invokeOnRenderCallbacks?.Count ?? 0;
+
+        // This outer loop is to re-run layout in case the app causes a layout to get enqueued in response
+        // to a Loaded event. In this case we would like to re-run layout before we allow render.
+        do
+        {
+            while (count > 0)
+            {
+                callbackLoopCount++;
+                if (callbackLoopCount > 153)
+                    throw new InvalidOperationException("Infinite layout loop detected");
+
+                var callbacks = _invokeOnRenderCallbacks!;
+                _invokeOnRenderCallbacks = null;
+
+                for (int i = 0; i < count; i++) 
+                    callbacks[i].Invoke();
+                
+                callbacks.Clear();
+                _invokeOnRenderCallbackListPool.Push(callbacks);
+
+                count = _invokeOnRenderCallbacks?.Count ?? 0;
+            }
+
+            // TODO: port the rest of the Loaded logic later
+            // Fire all the pending Loaded events before Render happens
+            // but after the layout storm has subsided
+            // FireLoadedPendingCallbacks();
+
+            count =  _invokeOnRenderCallbacks?.Count ?? 0;
+        }
+        while (count > 0);
+    }
+    
+    public void BeginInvokeOnRender(Action callback)
+    {
+        if (_invokeOnRenderCallbacks == null)
+            _invokeOnRenderCallbacks =
+                _invokeOnRenderCallbackListPool.Count > 0 ? _invokeOnRenderCallbackListPool.Pop() : new();
+        
+        _invokeOnRenderCallbacks.Add(callback);
+
+        if (!_isRendering) 
+            ScheduleRender(true);
     }
 }

src/Avalonia.Base/Rendering/Composition/Compositor.cs

@@ -66,16 +66,14 @@ namespace Avalonia.Rendering.Composition
         /// Creates a new compositor on a specified render loop that would use a particular GPU
         /// </summary>
         [PrivateApi]
-        public Compositor(IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false) 
+        public Compositor(IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false)
             : this(RenderLoop.LocatorAutoInstance, gpu, useUiThreadForSynchronousCommits)
         {
-            
         }
-        
-        internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false) 
+
+        internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false)
             : this(loop, gpu, useUiThreadForSynchronousCommits, MediaContext.Instance, false)
         {
-            
         }
 
         internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu,

src/Avalonia.Base/Rendering/Composition/Drawing/RenderDataDrawingContext.cs

@@ -79,12 +79,19 @@ internal class RenderDataDrawingContext : DrawingContext
 
         if (!(parent.Node is T))
             throw new InvalidOperationException("Invalid Pop operation");
-        
-        foreach(var item in _currentItemList!)
-            parent.Node.Children.Add(item);
-        _currentItemList.Clear();
-        s_listPool.ReturnAndSetNull(ref _currentItemList);
+
+        var removeLastPush = true;
+        if (_currentItemList != null)
+        {
+            removeLastPush = _currentItemList.Count == 0;
+            foreach (var item in _currentItemList)
+                parent.Node.Children.Add(item);
+            _currentItemList.Clear();
+            s_listPool.ReturnAndSetNull(ref _currentItemList);
+        }
         _currentItemList = parent.Items;
+        if (removeLastPush)
+            _currentItemList.RemoveAt(_currentItemList.Count - 1);
     }
 
     void AddResource(object? resource)

src/Avalonia.Base/Rendering/Composition/Drawing/ServerResourceHelperExtensions.cs

@@ -50,7 +50,6 @@ static class ServerResourceHelperExtensions
             return immutable;
         if (transform is ICompositionRenderResource<ITransform> resource)
             resource.GetForCompositor(compositor);
-        ThrowNotCompatible(transform);
-        return null;
+        return new ImmutableTransform(transform.Value);
     }
 }

src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs

@@ -187,9 +187,7 @@ namespace Avalonia.Browser
 
         }
 
-        public Compositor Compositor { get; } = new(
-            AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(),
-            AvaloniaLocator.Current.GetRequiredService<IPlatformGraphics>());
+        public Compositor Compositor { get; } = new(AvaloniaLocator.Current.GetRequiredService<IPlatformGraphics>());
 
         public void Invalidate(Rect rect)
         {

src/iOS/Avalonia.iOS/Platform.cs

@@ -47,12 +47,8 @@ namespace Avalonia.iOS
                 .Bind<IDispatcherImpl>().ToConstant(DispatcherImpl.Instance)
                 .Bind<IKeyboardDevice>().ToConstant(keyboard);
 
-                Compositor = new Compositor(
-                    AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(),
-                    AvaloniaLocator.Current.GetService<IPlatformGraphics>());
+                Compositor = new Compositor(AvaloniaLocator.Current.GetService<IPlatformGraphics>());
         }
-
-
     }
 }
 

tests/Avalonia.Base.UnitTests/Rendering/SceneGraph/DrawOperationTests.cs

@@ -132,5 +132,18 @@ namespace Avalonia.Base.UnitTests.Rendering.SceneGraph
 
             Assert.True(ctx.Context.GetRenderResults()!.HitTest(new Point(25, 25)));
         }
+        
+        [Fact]
+        public void Empty_Push_Pop_Sequence_Produces_No_Results()
+        {
+            var ctx = new TestContext(_services);
+            using (ctx.Context.PushTransform(Matrix.CreateTranslation(20, 20)))
+            using (ctx.Context.PushOpacity(1, default))
+            {
+
+            }
+
+            Assert.Null(ctx.Context.GetRenderResults());
+        }
     }
 }