Make Android respect power saving/disabled animations

src/Controls/src/Core/AnimationExtensions.cs

@@ -26,6 +26,7 @@
 // THE SOFTWARE.
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using Microsoft.Maui.Animations;
 using Microsoft.Maui.Controls.Internals;
@@ -36,7 +37,14 @@ namespace Microsoft.Maui.Controls
 	/// <include file="../../docs/Microsoft.Maui.Controls/AnimationExtensions.xml" path="Type[@FullName='Microsoft.Maui.Controls.AnimationExtensions']/Docs/*" />
 	public static class AnimationExtensions
 	{
-		static readonly Dictionary<int, Animation> s_tweeners;
+		// We use a ConcurrentDictionary because Tweener relies on being able to remove
+		// animations from the AnimationManager within its finalizer (via the Remove extension
+		// method below). Since finalization occurs on a different thread, it risks crashes when
+		// the finalizer is running at the same time another animation is finsihing and removing
+		// itself from this dictionary. So until we can change that design, this dictionary must
+		// be thread-safe.
+		static readonly ConcurrentDictionary<int, Animation> s_tweeners;
+
 		static readonly Dictionary<AnimatableKey, Info> s_animations;
 		static readonly Dictionary<AnimatableKey, int> s_kinetics;
 		static int s_currentTweener = 1;
@@ -45,7 +53,7 @@ static AnimationExtensions()
 		{
 			s_animations = new Dictionary<AnimatableKey, Info>();
 			s_kinetics = new Dictionary<AnimatableKey, int>();
-			s_tweeners = new Dictionary<int, Animation>();
+			s_tweeners = new ConcurrentDictionary<int, Animation>();
 		}
 
 		public static int Add(this IAnimationManager animationManager, Action<double> step)
@@ -61,6 +69,7 @@ public static int Add(this IAnimationManager animationManager, Action<double> st
 			animation.Commit(animationManager);
 			return id;
 		}
+
 		public static int Insert(this IAnimationManager animationManager, Func<long, bool> step)
 		{
 			var id = s_currentTweener++;
@@ -74,11 +83,13 @@ public static int Insert(this IAnimationManager animationManager, Func<long, boo
 			animation.Commit(animationManager);
 			return id;
 		}
+
 		public static void Remove(this IAnimationManager animationManager, int tickerId)
 		{
-			var animation = s_tweeners[tickerId];
-			s_tweeners.Remove(tickerId);
-			animationManager.Remove(animation);
+			if (s_tweeners.TryRemove(tickerId, out Animation animation))
+			{
+				animationManager.Remove(animation);
+			}
 		}
 
 		/// <include file="../../docs/Microsoft.Maui.Controls/AnimationExtensions.xml" path="//Member[@MemberName='AbortAnimation']/Docs/*" />
@@ -213,14 +224,13 @@ static void AbortKinetic(AnimatableKey key)
 		{
 			if (s_kinetics.TryGetValue(key, out var ticker))
 			{
-				var animation = s_tweeners[ticker];
-				animation.AnimationManager?.Remove(ticker);
-				s_kinetics.Remove(key);
-			}
-			if (!s_kinetics.ContainsKey(key))
-			{
-				return;
+				if (s_tweeners.TryGetValue(ticker, out Animation animation))
+				{
+					animation.AnimationManager?.Remove(ticker);
+				}
 			}
+
+			s_kinetics.Remove(key);
 		}
 
 		static void AnimateInternal<T>(IAnimatable self, IAnimationManager animationManager, string name, Func<double, T> transform, Action<T> callback,
@@ -279,8 +289,11 @@ static void AnimateKineticInternal(IAnimatable self, IAnimationManager animation
 				if (!result)
 				{
 					finished?.Invoke();
+					if (s_kinetics.TryGetValue(key, out var ticker))
+					{
+						animationManager.Remove(ticker);
+					}
 					s_kinetics.Remove(key);
-					animationManager.Remove(tick);
 				}
 				return result;
 			});
@@ -292,21 +305,25 @@ static void AnimateKineticInternal(IAnimatable self, IAnimationManager animation
 		static void HandleTweenerFinished(object o, EventArgs args)
 		{
 			var tweener = o as Tweener;
-			Info info;
-			if (tweener != null && s_animations.TryGetValue(tweener.Handle, out info))
+
+			if (tweener != null && s_animations.TryGetValue(tweener.Handle, out Info info))
 			{
-				IAnimatable owner;
-				if (info.Owner.TryGetTarget(out owner))
-					owner.BatchBegin();
-				info.Callback(tweener.Value);
+				var tweenerValue = tweener.Value;
+				info.Owner.TryGetTarget(out IAnimatable owner);
+
+				owner?.BatchBegin();
+
+				info.Callback(tweenerValue);
 
 				var repeat = false;
 
 				// If the Ticker has been disabled (e.g., by power save mode), then don't repeat the animation
 				var animationsEnabled = info.AnimationManager.Ticker.SystemEnabled;
 
 				if (info.Repeat != null && animationsEnabled)
+				{
 					repeat = info.Repeat();
+				}
 
 				if (!repeat)
 				{
@@ -316,10 +333,9 @@ static void HandleTweenerFinished(object o, EventArgs args)
 					tweener.Stop();
 				}
 
-				info.Finished?.Invoke(tweener.Value, !animationsEnabled);
+				info.Finished?.Invoke(tweenerValue, !animationsEnabled);
 
-				if (info.Owner.TryGetTarget(out owner))
-					owner.BatchCommit();
+				owner?.BatchCommit();
 
 				if (repeat)
 				{
@@ -330,11 +346,7 @@ static void HandleTweenerFinished(object o, EventArgs args)
 
 		static void HandleTweenerUpdated(object o, EventArgs args)
 		{
-			var tweener = o as Tweener;
-			Info info;
-			IAnimatable owner;
-
-			if (tweener != null && s_animations.TryGetValue(tweener.Handle, out info) && info.Owner.TryGetTarget(out owner))
+			if (o is Tweener tweener && s_animations.TryGetValue(tweener.Handle, out Info info) && info.Owner.TryGetTarget(out IAnimatable owner))
 			{
 				owner.BatchBegin();
 				info.Callback(info.Easing.Ease(tweener.Value));

src/Controls/src/Core/Tweener.cs

@@ -27,7 +27,6 @@
 
 using System;
 using Microsoft.Maui.Animations;
-using Microsoft.Maui.Controls.Internals;
 
 namespace Microsoft.Maui.Controls
 {
@@ -39,28 +38,40 @@ public TweenerAnimation(Func<long, bool> step)
 		{
 			_step = step;
 		}
+
 		protected override void OnTick(double millisecondsSinceLastUpdate)
 		{
 			var running = _step.Invoke((long)millisecondsSinceLastUpdate);
 			HasFinished = !running;
 		}
 
+		internal override void ForceFinish()
+		{
+			if (HasFinished)
+			{
+				return;
+			}
+
+			HasFinished = true;
+
+			// The tweeners use long.MaxValue for in-band signaling that they should
+			// jump to the end of the animation 
+			_ = _step.Invoke(long.MaxValue);
+		}
 	}
 
 	internal class Tweener
 	{
-		IAnimationManager animationManager;
+		readonly IAnimationManager _animationManager;
 		long _lastMilliseconds;
-
-		int _timer;
+		int _animationManagerKey;
 		long _frames;
 
 		public Tweener(uint length, IAnimationManager animationManager)
 		{
 			Value = 0.0f;
 			Length = length;
-			this.animationManager = animationManager;
-			Rate = 1;
+			_animationManager = animationManager;
 			Loop = false;
 		}
 
@@ -69,119 +80,127 @@ public Tweener(uint length, uint rate, IAnimationManager animationManager)
 			Value = 0.0f;
 			Length = length;
 			Rate = rate;
-			this.animationManager = animationManager;
+			_animationManager = animationManager;
 			Loop = false;
 		}
 
 		public AnimatableKey Handle { get; set; }
 
 		public uint Length { get; }
 
-		public uint Rate { get; }
+		public uint Rate { get; } = 1;
 
 		public bool Loop { get; set; }
 
-		public double Value { get; private set; }
+		public double Value { get; set; }
 
 		public event EventHandler Finished;
+		public event EventHandler ValueUpdated;
 
 		public void Pause()
 		{
-			if (_timer != 0)
+			if (_animationManagerKey != 0)
 			{
-				animationManager.Remove(_timer);
-				_timer = 0;
+				_animationManager.Remove(_animationManagerKey);
+				_animationManagerKey = 0;
 			}
 		}
 
+		bool Step(long step) 
+		{
+			if (step == long.MaxValue)
+			{
+				// Signal that the Tweener is being force to move to the finished state, 
+				// usually because the underlying Ticker has been disabled by the system
+				FinishImmediately();
+				return false;
+			}
+			else
+			{
+				long ms = step + _lastMilliseconds;
+				Value = Math.Min(1.0f, ms / (double)Length);
+				_lastMilliseconds = ms;
+			}
+
+			long wantedFrames = (_lastMilliseconds / Rate) + 1;
+			if (wantedFrames > _frames || Value >= 1.0f)
+			{
+				ValueUpdated?.Invoke(this, EventArgs.Empty);
+			}
+
+			_frames = wantedFrames;
+
+			if (Value >= 1.0f)
+			{
+				if (Loop)
+				{
+					_lastMilliseconds = 0;
+					Value = 0.0f;
+					return true;
+				}
+
+				Finished?.Invoke(this, EventArgs.Empty);
+
+				Value = 0.0f;
+				_animationManagerKey = 0;
+				return false;
+			}
+
+			return true;
+		}
+
 		public void Start()
 		{
 			Pause();
 
 			_lastMilliseconds = 0;
 			_frames = 0;
 
-			if (!animationManager.Ticker.SystemEnabled)
+			if (!_animationManager.Ticker.SystemEnabled)
 			{
+				// The Ticker's disabled, probably because the system has animations disabled
+				// The Tweener should move immediately to the finished state and shut down
 				FinishImmediately();
 				return;
 			}
 
-			_timer = animationManager.Insert(step =>
-			{
-				if (step == long.MaxValue)
-				{
-					// We're being forced to finish
-					Value = 1.0;
-				}
-				else
-				{
-					long ms = step + _lastMilliseconds;
-
-					Value = Math.Min(1.0f, ms / (double)Length);
-
-					_lastMilliseconds = ms;
-				}
+			_animationManagerKey = _animationManager.Insert(Step);
 
-				long wantedFrames = (_lastMilliseconds / Rate) + 1;
-				if (wantedFrames > _frames || Value >= 1.0f)
-				{
-					ValueUpdated?.Invoke(this, EventArgs.Empty);
-				}
-				_frames = wantedFrames;
-
-				if (Value >= 1.0f)
-				{
-					if (Loop)
-					{
-						_lastMilliseconds = 0;
-						Value = 0.0f;
-						return true;
-					}
-
-					Finished?.Invoke(this, EventArgs.Empty);
-					Value = 0.0f;
-					_timer = 0;
-					return false;
-				}
-				return true;
-			});
-			if (!animationManager.Ticker.IsRunning)
-				animationManager.Ticker.Start();
+			if (!_animationManager.Ticker.IsRunning)
+				_animationManager.Ticker.Start();
 		}
 
 		void FinishImmediately()
 		{
 			Value = 1.0f;
+
 			ValueUpdated?.Invoke(this, EventArgs.Empty);
 			Finished?.Invoke(this, EventArgs.Empty);
+
 			Value = 0.0f;
-			_timer = 0;
+			_animationManagerKey = 0;
 		}
 
 		public void Stop()
 		{
 			Pause();
-			Value = 1.0f;
 			Finished?.Invoke(this, EventArgs.Empty);
 			Value = 0.0f;
 		}
 
-		public event EventHandler ValueUpdated;
-
 		~Tweener()
 		{
-			if (_timer != 0)
+			if (_animationManagerKey != 0)
 			{
 				try
 				{
-					animationManager.Remove(_timer);
+					_animationManager.Remove(_animationManagerKey);
 				}
 				catch (InvalidOperationException)
 				{
 				}
 			}
-			_timer = 0;
+			_animationManagerKey = 0;
 		}
 	}
 }