IsCheckedChanged fires before PropertyChanged

[ALDamico]

Describe the bug

ToggleButton's IsCheckedChanged event fires before PropertyChanged. This has the side effect of causing commands that fire on this event to use the incorrect boolean value.

To Reproduce

This repository contains a minimal example of this behavior

https://github.com/ALDamico/IsCheckedChangedBug

Expected behavior

I'd expect the IsCheckedChanged event to fire after PropertyChanged fires.

Avalonia version

11.2.3

OS

Windows

Additional context

Possible workaround

Trigger the command on PropertyChanged, if the ViewModel has few properties.

[robloo]

I don't think this is possible without something being wrong at a deeper level.

Avalonia/src/Avalonia.Controls/Primitives/ToggleButton.cs

Line 238 in 01a7c85

OnIsCheckedChanged(new RoutedEventArgs(IsCheckedChangedEvent));

IsCheckedChanged is fired FROM the property changed notification itself. The base OnPropertyChanged is called first as well.

In fact, within an event handler, it's designed to be able to read the current IsChecked property value.

[zii-dmg]

Tried in simple repro without tasks etc.

Something with animation?

Difference after Avalonia.Base.dll!Avalonia.AvaloniaObject.RaisePropertyChanged<bool?>(Avalonia.AvaloniaProperty<bool?> property, Avalonia.Data.Optional<bool?> oldValue, Avalonia.Data.BindingValue<bool?> newValue, Avalonia.Data.BindingPriority priority, bool isEffectiveValue).

First breakpoint IsCheckedChanged stacktrace:

AvaTest.dll!AvaTest.MainWindow.Btn_IsCheckedChanged(object sender, Avalonia.Interactivity.RoutedEventArgs e) Line 25	C#
Avalonia.Base.dll!Avalonia.Interactivity.Interactive.AddHandler.__InvokeAdapter|4_0<Avalonia.Interactivity.RoutedEventArgs>(System.Delegate baseHandler, object sender, Avalonia.Interactivity.RoutedEventArgs args)
Avalonia.Base.dll!Avalonia.Interactivity.Interactive.AddHandler.AnonymousMethod__4_1(System.Delegate baseHandler, object sender, Avalonia.Interactivity.RoutedEventArgs args)
Avalonia.Base.dll!Avalonia.Interactivity.EventRoute.RaiseEventImpl(Avalonia.Interactivity.RoutedEventArgs e)
Avalonia.Base.dll!Avalonia.Interactivity.Interactive.RaiseEvent(Avalonia.Interactivity.RoutedEventArgs e)
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.OnIsCheckedChanged(Avalonia.Interactivity.RoutedEventArgs e)
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.OnPropertyChanged(Avalonia.AvaloniaPropertyChangedEventArgs change)
Avalonia.Base.dll!Avalonia.AvaloniaObject.OnPropertyChangedCore(Avalonia.AvaloniaPropertyChangedEventArgs change)
Avalonia.Base.dll!Avalonia.Animation.Animatable.OnPropertyChangedCore(Avalonia.AvaloniaPropertyChangedEventArgs change)
Avalonia.Base.dll!Avalonia.AvaloniaObject.RaisePropertyChanged<bool?>(Avalonia.AvaloniaProperty<bool?> property, Avalonia.Data.Optional<bool?> oldValue, Avalonia.Data.BindingValue<bool?> newValue, Avalonia.Data.BindingPriority priority, bool isEffectiveValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.NotifyValueChanged(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? oldValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.SetAndRaiseCore(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? value, Avalonia.Data.BindingPriority priority, bool isOverriddenCurrentValue, bool isCoercedDefaultValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.SetCurrentValueAndRaise(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Base.dll!Avalonia.PropertyStore.ValueStore.SetCurrentValue<bool?>(Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Base.dll!Avalonia.AvaloniaObject.SetCurrentValue<bool?>(Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.Toggle()
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.OnClick()

Second got PropertyChanged:

AvaTest.dll!AvaTest.MainWindow.Btn_PropertyChanged(object sender, Avalonia.AvaloniaPropertyChangedEventArgs e) Line 20	C#
Avalonia.Base.dll!Avalonia.AvaloniaObject.RaisePropertyChanged<bool?>(Avalonia.AvaloniaProperty<bool?> property, Avalonia.Data.Optional<bool?> oldValue, Avalonia.Data.BindingValue<bool?> newValue, Avalonia.Data.BindingPriority priority, bool isEffectiveValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.NotifyValueChanged(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? oldValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.SetAndRaiseCore(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? value, Avalonia.Data.BindingPriority priority, bool isOverriddenCurrentValue, bool isCoercedDefaultValue)
Avalonia.Base.dll!Avalonia.PropertyStore.EffectiveValue<bool?>.SetCurrentValueAndRaise(Avalonia.PropertyStore.ValueStore owner, Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Base.dll!Avalonia.PropertyStore.ValueStore.SetCurrentValue<bool?>(Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Base.dll!Avalonia.AvaloniaObject.SetCurrentValue<bool?>(Avalonia.StyledProperty<bool?> property, bool? value)
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.Toggle()
Avalonia.Controls.dll!Avalonia.Controls.Primitives.ToggleButton.OnClick()

[robloo]

Or scheduling of the property change notification. Maybe the event is scheduled to fire after the internal override is called.

I know there is change notification grouping, etc. for performance.

The easiest would be simply to schedule OnIsCheckedChanged on the dispatcher too. But I think this is a general issue that should be addressed deeper in the framework.

[timunie]

Also DevTools could give a hint, see Events tab

[ALDamico]

Also DevTools could give a hint, see Events tab

I'm not terribly familiar with the devtools. What should I be looking out for, specifically?