Snackbar.cs

using System.ComponentModel;
using System.Windows.Media.Animation;
using System.Windows.Threading;

namespace MaterialDesignThemes.Wpf;

public enum SnackbarActionButtonPlacementMode
{
    Auto,
    Inline,
    SeparateLine
}

/// <summary>
/// Implements a <see cref="Snackbar"/> inspired by the Material Design specs (https://material.google.com/components/snackbars-toasts.html).
/// </summary>
[ContentProperty(nameof(Message))]
public class Snackbar : Control
{
    private const string ActivateStoryboardName = "ActivateStoryboard";
    private const string DeactivateStoryboardName = "DeactivateStoryboard";

    private Action? _messageQueueRegistrationCleanUp;

    static Snackbar()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(Snackbar), new FrameworkPropertyMetadata(typeof(Snackbar)));
    }

    public static readonly DependencyProperty MessageProperty = DependencyProperty.Register(
        nameof(Message), typeof(SnackbarMessage), typeof(Snackbar), new PropertyMetadata(default(SnackbarMessage)));

    public SnackbarMessage? Message
    {
        get => (SnackbarMessage?)GetValue(MessageProperty);
        set => SetValue(MessageProperty, value);
    }

    public static readonly DependencyProperty MessageQueueProperty = DependencyProperty.Register(
        nameof(MessageQueue), typeof(SnackbarMessageQueue), typeof(Snackbar), new PropertyMetadata(default(SnackbarMessageQueue), MessageQueuePropertyChangedCallback),
        MessageQueueValidateValueCallback);

    private static void MessageQueuePropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        var snackbar = (Snackbar)dependencyObject;
        snackbar._messageQueueRegistrationCleanUp?.Invoke();
        var messageQueue = dependencyPropertyChangedEventArgs.NewValue as SnackbarMessageQueue;
        snackbar._messageQueueRegistrationCleanUp = messageQueue?.Pair(snackbar);
    }

    private static bool MessageQueueValidateValueCallback(object value)
    {
        if (value is null || ((SnackbarMessageQueue)value).Dispatcher == Dispatcher.CurrentDispatcher)
            return true;
        throw new ArgumentException("SnackbarMessageQueue must be created by the same thread.", nameof(value));
    }

    public SnackbarMessageQueue? MessageQueue
    {
        get => (SnackbarMessageQueue?)GetValue(MessageQueueProperty);
        set => SetValue(MessageQueueProperty, value);
    }

    public static readonly DependencyProperty IsActiveProperty = DependencyProperty.Register(
        nameof(IsActive), typeof(bool), typeof(Snackbar), new PropertyMetadata(default(bool), IsActivePropertyChangedCallback));

    public bool IsActive
    {
        get => (bool)GetValue(IsActiveProperty);
        set => SetValue(IsActiveProperty, value);
    }

    public event RoutedPropertyChangedEventHandler<bool> IsActiveChanged
    {
        add => AddHandler(IsActiveChangedEvent, value);
        remove => RemoveHandler(IsActiveChangedEvent, value);
    }

    public static readonly RoutedEvent IsActiveChangedEvent = EventManager.RegisterRoutedEvent(
        nameof(IsActiveChanged), RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<bool>), typeof(Snackbar));

    private static void OnIsActiveChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var instance = d as Snackbar;
        var args = new RoutedPropertyChangedEventArgs<bool>((bool)e.OldValue, (bool)e.NewValue)
        {
            RoutedEvent = IsActiveChangedEvent
        };
        instance?.RaiseEvent(args);
    }

    public static readonly RoutedEvent DeactivateStoryboardCompletedEvent = EventManager.RegisterRoutedEvent(
        nameof(DeactivateStoryboardCompleted), RoutingStrategy.Bubble, typeof(SnackbarMessageEventArgs), typeof(Snackbar));

    public event RoutedPropertyChangedEventHandler<SnackbarMessage> DeactivateStoryboardCompleted
    {
        add => AddHandler(DeactivateStoryboardCompletedEvent, value);
        remove => RemoveHandler(DeactivateStoryboardCompletedEvent, value);
    }

    private static void OnDeactivateStoryboardCompleted(IInputElement snackbar, SnackbarMessage message)
    {
        var args = new SnackbarMessageEventArgs(DeactivateStoryboardCompletedEvent, message);
        snackbar.RaiseEvent(args);
    }

    public TimeSpan ActivateStoryboardDuration { get; private set; }

    public TimeSpan DeactivateStoryboardDuration { get; private set; }

    public static readonly DependencyProperty ActionButtonStyleProperty = DependencyProperty.Register(
        nameof(ActionButtonStyle), typeof(Style), typeof(Snackbar), new PropertyMetadata(default(Style)));

    public Style? ActionButtonStyle
    {
        get => (Style?)GetValue(ActionButtonStyleProperty);
        set => SetValue(ActionButtonStyleProperty, value);
    }

    public override void OnApplyTemplate()
    {
        //we regards to notification of deactivate storyboard finishing,
        //we either build a storyboard in code and subscribe to completed event, 
        //or take the not 100% proof of the storyboard duration from the storyboard itself
        //...HOWEVER...we can both methods result can work under the same public API so 
        //we can flip the implementation if this version does not pan out

        //(currently we have no even on the activate animation; don't 
        // need it just now, but it would mirror the deactivate)

        ActivateStoryboardDuration = GetStoryboardResourceDuration(ActivateStoryboardName);
        DeactivateStoryboardDuration = GetStoryboardResourceDuration(DeactivateStoryboardName);

        base.OnApplyTemplate();
    }

    private TimeSpan GetStoryboardResourceDuration(string resourceName)
    {
        var storyboard = Template.Resources.Contains(resourceName)
            ? (Storyboard)Template.Resources[resourceName]
            : null;

        return storyboard != null && storyboard.Duration.HasTimeSpan
            ? storyboard.Duration.TimeSpan
            : new Func<TimeSpan>(() =>
            {
                System.Diagnostics.Debug.WriteLine(
                    $"Warning, no Duration was specified at root of storyboard '{resourceName}'.");
                return TimeSpan.Zero;
            })();
    }

    private static void IsActivePropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        OnIsActiveChanged(dependencyObject, dependencyPropertyChangedEventArgs);

        if ((bool)dependencyPropertyChangedEventArgs.NewValue) return;

        var snackbar = (Snackbar)dependencyObject;
        if (snackbar.Message is null) return;

        var dispatcherTimer = new DispatcherTimer
        {
            Tag = new Tuple<Snackbar, SnackbarMessage>(snackbar, snackbar.Message),
            Interval = snackbar.DeactivateStoryboardDuration
        };
        dispatcherTimer.Tick += DeactivateStoryboardDispatcherTimerOnTick;
        dispatcherTimer.Start();
    }

    private static void DeactivateStoryboardDispatcherTimerOnTick(object? sender, EventArgs eventArgs)
    {
        if (sender is DispatcherTimer dispatcherTimer)
        {
            dispatcherTimer.Stop();
            dispatcherTimer.Tick -= DeactivateStoryboardDispatcherTimerOnTick;
            var source = (Tuple<Snackbar, SnackbarMessage>)dispatcherTimer.Tag;
            OnDeactivateStoryboardCompleted(source.Item1, source.Item2);
        }
    }

    public static readonly DependencyProperty ActionButtonPlacementProperty = DependencyProperty.Register(
        nameof(ActionButtonPlacement), typeof(SnackbarActionButtonPlacementMode), typeof(Snackbar), new PropertyMetadata(SnackbarActionButtonPlacementMode.Auto));

    public SnackbarActionButtonPlacementMode ActionButtonPlacement
    {
        get => (SnackbarActionButtonPlacementMode)GetValue(ActionButtonPlacementProperty);
        set => SetValue(ActionButtonPlacementProperty, value);
    }

    public static readonly DependencyProperty CornerRadiusProperty = DependencyProperty.Register(
        nameof(CornerRadius), typeof(Thickness), typeof(Snackbar), new PropertyMetadata(new Thickness(0)));

    [Bindable(true)]
    [Category("Appearance")]
    public Thickness CornerRadius
    {
        get => (Thickness)GetValue(CornerRadiusProperty);
        set => SetValue(CornerRadiusProperty, value);
    }
}