/// <summary>
/// Indicates that a property change should cause <see cref="InvalidateVisual"/> to be
/// called.
/// </summary>
/// <typeparam name="T">The control which the property affects.</typeparam>
/// <param name="properties">The properties.</param>
/// <remarks>
/// This method should be called in a control's static constructor with each property
/// on the control which when changed should cause a redraw. This is similar to WPF's
/// FrameworkPropertyMetadata.AffectsRender flag.
/// </remarks>
protected static void AffectsRender <T>(params AvaloniaProperty[] properties)
where T : Visual
{
void Invalidate(AvaloniaPropertyChangedEventArgs e)
{
if (e.Sender is T sender)
{
if (e.OldValue is IAffectsRender oldValue)
{
WeakEventHandlerManager.Unsubscribe <EventArgs, T>(oldValue, nameof(oldValue.Invalidated), sender.AffectsRenderInvalidated);
}
if (e.NewValue is IAffectsRender newValue)
{
WeakEventHandlerManager.Subscribe <IAffectsRender, EventArgs, T>(newValue, nameof(newValue.Invalidated), sender.AffectsRenderInvalidated);
}
sender.InvalidateVisual();
}
}
foreach (var property in properties)
{
property.Changed.Subscribe(Invalidate);
}
}
protected override void UnsubscribeCore()
{
if (_reference.TryGetTarget(out var o) && o is INotifyPropertyChanged inpc)
{
WeakEventHandlerManager.Unsubscribe <PropertyChangedEventArgs, InpcPropertyAccessor>(
inpc,
nameof(INotifyPropertyChanged.PropertyChanged),
OnNotifyPropertyChanged);
}
}
protected override void UnsubscribeCore()
{
base.UnsubscribeCore();
if (_reference.TryGetTarget(out var o) && o is INotifyCollectionChanged incc)
{
WeakEventHandlerManager.Unsubscribe <NotifyCollectionChangedEventArgs, IndexerAccessor>(
incc,
nameof(INotifyCollectionChanged.CollectionChanged),
OnNotifyCollectionChanged);
}
}
public void EventShouldNotBeRaisedAfterUnsubscribe()
{
bool handled = false;
var subscriber = new Subscriber(() => handled = true);
var source = new EventSource();
WeakEventHandlerManager.Subscribe <EventSource, EventArgs, Subscriber>(source, "Event",
subscriber.OnEvent);
WeakEventHandlerManager.Unsubscribe <EventArgs, Subscriber>(source, "Event",
subscriber.OnEvent);
source.Fire();
Assert.False(handled);
}
static void InvalidateAndSubscribe(AvaloniaPropertyChangedEventArgs e)
{
if (e.Sender is T sender)
{
if (e.OldValue is IAffectsRender oldValue)
{
WeakEventHandlerManager.Unsubscribe <EventArgs, T>(oldValue, nameof(oldValue.Invalidated), sender.AffectsRenderInvalidated);
}
if (e.NewValue is IAffectsRender newValue)
{
WeakEventHandlerManager.Subscribe <IAffectsRender, EventArgs, T>(newValue, nameof(newValue.Invalidated), sender.AffectsRenderInvalidated);
}
sender.InvalidateVisual();
}
}