agh

samples/Sandbox/App.axaml

@@ -3,6 +3,6 @@
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     x:Class="Sandbox.App">
     <Application.Styles>
-        <FluentTheme />
+        <SimpleTheme />
     </Application.Styles>
 </Application>

samples/Sandbox/MainWindow.axaml

@@ -1,4 +1,32 @@
 <Window xmlns="https://github.com/avaloniaui"
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         x:Class="Sandbox.MainWindow">
+  <StackPanel Orientation="Vertical" Spacing="4">
+    <TextBlock Classes="h2">A progress bar control</TextBlock>
+    <StackPanel Spacing="5">
+      <StackPanel Orientation="Horizontal" Spacing="5">
+        <TextBlock VerticalAlignment="Center">Maximum</TextBlock>
+        <NumericUpDown x:Name="maximum" Value="100" VerticalAlignment="Center"/>
+      </StackPanel>
+      <StackPanel Orientation="Horizontal" Spacing="5">
+        <TextBlock VerticalAlignment="Center">Minimum</TextBlock>
+        <NumericUpDown x:Name="minimum" Value="0" VerticalAlignment="Center"/>
+      </StackPanel>
+      <StackPanel Orientation="Horizontal" Spacing="5">
+        <TextBlock VerticalAlignment="Center">Progress Text Format</TextBlock>
+        <TextBox x:Name="stringFormat" Text="{}{0:0}%" VerticalAlignment="Center"/>
+      </StackPanel>
+      <CheckBox x:Name="showProgress" Margin="10,16,0,0" Content="Show Progress Text" />
+      <CheckBox x:Name="isIndeterminate" Margin="10,16,0,0" Content="Toggle Indeterminate" />
+      <CheckBox x:Name="isVisible" Margin="10,16,0,0" Content="Toggle Visibility" />
+      <StackPanel IsVisible="{Binding #isVisible.IsChecked}" Orientation="Horizontal" Margin="0,16,0,0" HorizontalAlignment="Center" Spacing="16">
+        <StackPanel Spacing="16">
+          <ProgressBar Height="200" IsIndeterminate="{Binding #isIndeterminate.IsChecked}" ShowProgressText="{Binding #showProgress.IsChecked}" Value="1.0" 
+                       Minimum="{Binding #minimum.Value}" Maximum="{Binding #maximum.Value}" ProgressTextFormat="{Binding #stringFormat.Text}"/>
+        </StackPanel>
+        </StackPanel> 
+ 
+    </StackPanel>
+  </StackPanel>
+
 </Window>

samples/Sandbox/Sandbox.csproj

@@ -2,9 +2,8 @@
 
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
-    <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
-    <IncludeAvaloniaGenerators>true</IncludeAvaloniaGenerators>
+    <TargetFramework>net8.0</TargetFramework>
+     <IncludeAvaloniaGenerators>true</IncludeAvaloniaGenerators>
 <!--    <AvaloniaXamlIlDebuggerLaunch>true</AvaloniaXamlIlDebuggerLaunch>-->
   </PropertyGroup>
 

src/Avalonia.Base/Animation/Animatable.cs

@@ -32,8 +32,7 @@ namespace Avalonia.Animation
         private Dictionary<ITransition, TransitionState>? _transitionState;
         private NotifyCollectionChangedEventHandler? _collectionChanged;
         
-        protected bool _animationsEnabled = true;
-        internal LightweightSubject<bool>? animationsStateSubject;
+        internal LightweightSubject<bool>? animationsGateSubject;
         
         private NotifyCollectionChangedEventHandler TransitionsCollectionChangedHandler => 
             _collectionChanged ??= TransitionsCollectionChanged;

src/Avalonia.Base/Animation/Animation.cs

@@ -277,7 +277,7 @@ namespace Avalonia.Animation
             var (animators, subscriptions) = InterpretKeyframes(control);
             
             var overrideSubject =  new LightweightSubject<bool>();
-            control.animationsStateSubject = overrideSubject;
+            control.animationsGateSubject = overrideSubject;
 
             if (animators.Count == 1)
             {

src/Avalonia.Base/Animation/Animators/Animator`1.cs

@@ -20,8 +20,11 @@ namespace Avalonia.Animation.Animators
         public virtual IDisposable? Apply(Animation animation, Animatable target, IClock? clock,
             IObservable<bool> match, IObservable<bool> state, Action? onComplete)
         {
-            var subject = new DisposeAnimationInstanceSubject<T>(this, animation, target, clock, state, onComplete);
-            return new CompositeDisposable(match.Subscribe(subject), subject);
+            var disposable = new CompositeDisposable();
+            var subject = new DisposeAnimationInstanceSubject<T>(this, animation, target, clock, onComplete, state, disposable);
+            disposable.Add(match.Subscribe(subject));
+            disposable.Add(subject);
+            return disposable;
         }
 
         protected T InterpolationHandler(double animationTime, T neutralValue)

src/Avalonia.Base/Animation/DisposeAnimationInstanceSubject.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Threading;
 using Avalonia.Animation.Animators;
+using Avalonia.Reactive;
 
 namespace Avalonia.Animation
 {
@@ -9,29 +11,32 @@ namespace Avalonia.Animation
     internal class DisposeAnimationInstanceSubject<T> : IObserver<bool>, IDisposable
     {
         private IDisposable? _lastInstance;
-        private bool _lastMatch;
+        private bool _lastMatch, _lastGate;
         private readonly Animator<T> _animator;
         private readonly Animation _animation;
         private readonly Animatable _control;
         private readonly Action? _onComplete;
         private readonly IClock? _clock;
+        private readonly object _lock = new object();
 
-        public DisposeAnimationInstanceSubject(Animator<T> animator,
-            Animation animation, Animatable control, IClock? clock, IObservable<bool> state, Action? onComplete)
+        public DisposeAnimationInstanceSubject(Animator<T> animator, 
+            Animation animation, Animatable control, IClock? clock, Action? onComplete, IObservable<bool> state, CompositeDisposable disposable)
         {
             this._animator = animator;
             this._animation = animation;
             this._control = control;
             this._onComplete = onComplete;
             this._clock = clock;
-
-            // TODO: this causes weird bugs.
-            state.Subscribe(this);
+            
+            disposable.Add(state.Subscribe(AnimationStateChange));
         }
         
         public void Dispose()
         {
-            _lastInstance?.Dispose();
+            lock (_lock)
+            {
+                _lastInstance?.Dispose();
+            }
         }
 
         public void OnCompleted()
@@ -40,27 +45,49 @@ namespace Avalonia.Animation
 
         public void OnError(Exception error)
         {
-            _lastInstance?.Dispose();
-            _lastInstance = null;
+            lock (_lock)
+            {
+                _lastInstance?.Dispose();
+                _lastInstance = null;
+            }
         }
 
-        public void OnNext(bool matchVal)
+        private void AnimationStateChange(bool gateState)
         {
-            if (matchVal != _lastMatch)
+            lock (_lock)
             {
-                _lastInstance?.Dispose();
+                if(Volatile.Read(ref _lastGate) == gateState) return;
+                Volatile.Write(ref _lastGate, gateState);
+                StateChange();
+            }
+        }
 
-                if (matchVal)
-                {
-                    _lastInstance = _animator.Run(_animation, _control, _clock, _onComplete);
-                }
-                else
-                {
-                    _lastInstance = null;
-                }
+        public void OnNext(bool matchVal)
+        {
+            lock (_lock)
+            {
+                if (Volatile.Read(ref _lastMatch) == matchVal) return;
+                Volatile.Write(ref _lastMatch, matchVal);
+                StateChange();
+            }
+        }
+        
+        void StateChange()
+        {
+            bool match = Volatile.Read(ref _lastMatch);
+            bool gate = Volatile.Read(ref _lastGate);
+            
+            _lastInstance?.Dispose();
 
-                _lastMatch = matchVal;
+            if (match & gate)
+            {
+                _lastInstance = _animator.Run(_animation, _control, _clock, _onComplete);
+            }
+            else
+            {
+                _lastInstance = null;
             }
         }
+        
     }
 }

src/Avalonia.Base/Visual.cs

@@ -104,6 +104,14 @@ namespace Avalonia
         /// </summary>
         public static readonly DirectProperty<Visual, Visual?> VisualParentProperty =
             AvaloniaProperty.RegisterDirect<Visual, Visual?>(nameof(VisualParent), o => o._visualParent);
+        
+        /// <summary>
+        /// Defines the <see cref="IsEffectivelyVisible"/> property.
+        /// </summary>
+        public static readonly DirectProperty<Visual, bool> IsEffectivelyVisibleProperty =
+            AvaloniaProperty.RegisterDirect<Visual, bool>(
+                nameof(IsEffectivelyVisible),
+                o => o._isEffectivelyVisible);
 
         /// <summary>
         /// Defines the <see cref="ZIndex"/> property.
@@ -121,7 +129,9 @@ namespace Avalonia
         private Visual? _visualParent;
         private bool _hasMirrorTransform;
         private TargetWeakEventSubscriber<Visual, EventArgs>? _affectsRenderWeakSubscriber;
-
+        private bool _isEffectivelyVisible = true;
+        
+        
         /// <summary>
         /// Initializes static members of the <see cref="Visual"/> class.
         /// </summary>
@@ -143,6 +153,7 @@ namespace Avalonia
         /// </summary>
         public Visual()
         {
+            SetAnimationGateState(false);
             // Disable transitions until we're added to the visual tree.
             DisableTransitions();
 
@@ -193,25 +204,7 @@ namespace Avalonia
         /// <summary>
         /// Gets a value indicating whether this control and all its parents are visible.
         /// </summary>
-        public bool IsEffectivelyVisible
-        {
-            get
-            {
-                Visual? node = this;
-
-                while (node != null)
-                {
-                    if (!node.IsVisible)
-                    {
-                        return false;
-                    }
-
-                    node = node.VisualParent;
-                }
-
-                return true;
-            }
-        }
+        public bool IsEffectivelyVisible { get; }
 
         /// <summary>
         /// Gets or sets a value indicating whether this control is visible.
@@ -496,7 +489,7 @@ namespace Avalonia
                 mutableTransform.Changed += RenderTransformChanged;
             }
 
-            EnableAnimations();
+            SetAnimationGateState(true);
             EnableTransitions();
             
             if (_visualRoot.Renderer is IRendererWithCompositor compositingRenderer)
@@ -540,7 +533,7 @@ namespace Avalonia
                 mutableTransform.Changed -= RenderTransformChanged;
             }
 
-            DisableAnimations();
+            SetAnimationGateState(false);
             DisableTransitions();
             OnDetachedFromVisualTree(e);
             DetachFromCompositor();
@@ -668,53 +661,33 @@ namespace Avalonia
         /// Called when the <see cref="IsVisible"/> property changes on any control.
         /// </summary>
         /// <param name="e">The event args.</param>
-        private static void IsVisibleChanged(AvaloniaPropertyChangedEventArgs e)
+        private void IsVisibleChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            if (e.Sender is not Visual visual) return;
-            
-            if (visual.IsEffectivelyVisible)
+            if (e.NewValue is bool newVisibility)
             {
-                visual.EnableAnimations();
-            }
-            else
-            {
-                visual.DisableAnimations();
-            }
+                CalculateEffectiveVisibility(newVisibility);
+            } 
         }
-        
-        internal void EnableAnimations()
+
+        private void SetAnimationGateState(bool gateState)
         {
-            if (!_animationsEnabled)
+            if (animationsGateSubject is { } animationsGate)
             {
-                _animationsEnabled = true;
-                
-                if (animationsStateSubject is { } ds)
-                {
-                    ds.OnNext(true);
-                }
-                
-                foreach (var child in this.GetVisualDescendants())
-                {
-                    child.EnableAnimations();
-                }
-            }
+                animationsGate.OnNext(gateState);
+            } 
         }
-
-        internal void DisableAnimations()
+        
+        internal void CalculateEffectiveVisibility(bool newVisibility)
         {
-            if (_animationsEnabled)
+            if(_isEffectivelyVisible == newVisibility) return;
+                
+            SetAndRaise(IsEffectivelyVisibleProperty, ref _isEffectivelyVisible, newVisibility);
+ 
+            SetAnimationGateState(newVisibility);
+            
+            foreach (var child in this.GetVisualDescendants())
             {
-                _animationsEnabled = false;
-
-                if (animationsStateSubject is { } ds)
-                {
-                    ds.OnNext(false);
-                }
-
-                foreach (var child in this.GetVisualDescendants())
-                {
-                    child.DisableAnimations();
-                }
+                child.CalculateEffectiveVisibility(newVisibility);
             }
         }