From 9debf63c71fc7b17e4c08b914fc977f67f0d5162 Mon Sep 17 00:00:00 2001
From: Nikita Tsukanov <keks9n@gmail.com>
Date: Mon, 29 May 2023 20:31:10 +0600
Subject: [PATCH] Fixed ToggleSwitch animation

---
 .../Media/MediaContext.Compositor.cs          | 13 ++++++++---
 src/Avalonia.Base/Media/MediaContext.cs       | 23 ++++++++++++++-----
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Base/Media/MediaContext.Compositor.cs b/src/Avalonia.Base/Media/MediaContext.Compositor.cs
index d9d3c915d4..6234f36a12 100644
--- a/src/Avalonia.Base/Media/MediaContext.Compositor.cs
+++ b/src/Avalonia.Base/Media/MediaContext.Compositor.cs
@@ -40,10 +40,10 @@ partial class MediaContext
             _animationsAreWaitingForComposition = false;
 
             // Check if we have uncommited changes
-            if (_scheduleCommitOnLastCompositionBatchCompletion && _pendingCompositionBatches.Count > 0)
+            if (_scheduleCommitOnLastCompositionBatchCompletion)
             {
-                CommitCompositorsWithThrottling();
                 _scheduleCommitOnLastCompositionBatchCompletion = false;
+                CommitCompositorsWithThrottling();
             }
             // Check if there are active animations and schedule the next render
             else if(_clock.HasSubscriptions) 
@@ -52,16 +52,23 @@ partial class MediaContext
 
     }
 
+    /// <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)
diff --git a/src/Avalonia.Base/Media/MediaContext.cs b/src/Avalonia.Base/Media/MediaContext.cs
index 023b2f728c..c261dd80b8 100644
--- a/src/Avalonia.Base/Media/MediaContext.cs
+++ b/src/Avalonia.Base/Media/MediaContext.cs
@@ -28,6 +28,14 @@ internal partial class MediaContext : ICompositorScheduler
     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();
 
     private MediaContext()
@@ -35,6 +43,11 @@ internal partial class MediaContext : ICompositorScheduler
         _render = Render;
         _inputMarkerHandler = InputMarkerHandler;
         _clock = new(this);
+        _animationsTimer.Tick += (_, _) =>
+        {
+            _animationsTimer.Stop();
+            ScheduleRender(false);
+        };
     }
     
     public static MediaContext Instance
@@ -129,14 +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();
         }
     }