QuickLook/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/Mediakit/DirectShow/Controls/MediaSeekingElement.cs

using System;
using System.Windows;
using WPFMediaKit.DirectShow.MediaPlayers;

namespace WPFMediaKit.DirectShow.Controls;

/// <summary>
/// The MediaSeekingElement adds media seeking functionality to
/// the MediaElementBase class.
/// </summary>
public abstract class MediaSeekingElement : MediaElementBase
{
    /// <summary>
    /// This flag is used to ignore PropertyChangedCallbacks
    /// for when a DependencyProperty is needs to be updated
    /// from the media player thread
    /// </summary>
    private bool m_ignorePropertyChangedCallback;

    #region MediaPosition

    public static readonly DependencyProperty MediaPositionProperty =
        DependencyProperty.Register("MediaPosition", typeof(long), typeof(MediaSeekingElement),
                                    new FrameworkPropertyMetadata((long)0,
                                                                  new PropertyChangedCallback(OnMediaPositionChanged)));

    public static readonly RoutedEvent MediaPositionChangedEvent = EventManager.RegisterRoutedEvent("MediaPositionChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(MediaSeekingElement));

    /// <summary>
    /// Is invoked whenever the current media position is changed.
    /// </summary>
    public event RoutedEventHandler MediaPositionChanged
    {
        add
        {
            this.AddHandler(MediaPositionChangedEvent, value);
        }
        remove
        {
            this.RemoveHandler(MediaPositionChangedEvent, value);
        }
    }

    /// <summary>
    /// Gets or sets the media position in units of CurrentPositionFormat
    /// </summary>
    public long MediaPosition
    {
        get { return (long)GetValue(MediaPositionProperty); }
        set { SetValue(MediaPositionProperty, value); }
    }

    private static void OnMediaPositionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((MediaSeekingElement)d).OnMediaPositionChanged(e);
    }

    protected virtual void OnMediaPositionChanged(DependencyPropertyChangedEventArgs e)
    {
        /* If the change came from within our class,
         * ignore this callback */
        if ((m_ignorePropertyChangedCallback))
        {
            m_ignorePropertyChangedCallback = false;
            return;
        }

        PlayerSetMediaPosition();
    }

    /// <summary>
    /// Used to set the MediaPosition without firing the
    /// PropertyChanged callback
    /// </summary>
    /// <param name="value">The value to set the MediaPosition to</param>
    protected void SetMediaPositionInternal(long value)
    {
        /* Flag that we want to ignore the next
         *PropertyChangedCallback
         * If the player is not currently paused!(otherwise it would only react every second seek) */
        m_ignorePropertyChangedCallback = this.PlayerState != PlayerState.Paused;

        MediaPosition = value;
        RaiseEvent(new RoutedEventArgs(MediaPositionChangedEvent, this));
    }

    private void PlayerSetMediaPosition()
    {
        var position = MediaPosition;
        if (MediaPlayerBase.Dispatcher.ShuttingOrShutDown)
            return;

        MediaPlayerBase.Dispatcher.BeginInvoke((Action)
                                              (() => MediaSeekingPlayer.MediaPosition = position));
    }

    #endregion MediaPosition

    #region MediaDuration

    private static readonly DependencyPropertyKey MediaDurationPropertyKey
       = DependencyProperty.RegisterReadOnly("MediaDuration", typeof(long), typeof(MediaSeekingElement),
                                             new FrameworkPropertyMetadata((long)0));

    public static readonly DependencyProperty MediaDurationProperty
        = MediaDurationPropertyKey.DependencyProperty;

    /// <summary>
    /// Gets the duration of the media in the units of CurrentPositionFormat
    /// </summary>
    public long MediaDuration
    {
        get { return (long)GetValue(MediaDurationProperty); }
    }

    /// <summary>
    /// Internal method to set the read-only MediaDuration
    /// </summary>
    protected void SetMediaDuration(long value)
    {
        SetValue(MediaDurationPropertyKey, value);
    }

    #endregion MediaDuration

    #region CurrentPositionFormat

    private static readonly DependencyPropertyKey CurrentPositionFormatPropertyKey
        = DependencyProperty.RegisterReadOnly("CurrentPositionFormat", typeof(MediaPositionFormat), typeof(MediaSeekingElement),
            new FrameworkPropertyMetadata(MediaPositionFormat.None));

    public static readonly DependencyProperty CurrentPositionFormatProperty
        = CurrentPositionFormatPropertyKey.DependencyProperty;

    /// <summary>
    /// The current position format that the media is currently using
    /// </summary>
    public MediaPositionFormat CurrentPositionFormat
    {
        get { return (MediaPositionFormat)GetValue(CurrentPositionFormatProperty); }
    }

    protected void SetCurrentPositionFormat(MediaPositionFormat value)
    {
        SetValue(CurrentPositionFormatPropertyKey, value);
    }

    #endregion CurrentPositionFormat

    #region PreferedPositionFormat

    public static readonly DependencyProperty PreferedPositionFormatProperty =
        DependencyProperty.Register("PreferedPositionFormat", typeof(MediaPositionFormat), typeof(MediaSeekingElement),
            new FrameworkPropertyMetadata(MediaPositionFormat.MediaTime,
                new PropertyChangedCallback(OnPreferedPositionFormatChanged)));

    /// <summary>
    /// The MediaPositionFormat that is prefered to be used
    /// </summary>
    public MediaPositionFormat PreferedPositionFormat
    {
        get { return (MediaPositionFormat)GetValue(PreferedPositionFormatProperty); }
        set { SetValue(PreferedPositionFormatProperty, value); }
    }

    private static void OnPreferedPositionFormatChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((MediaSeekingElement)d).OnPreferedPositionFormatChanged(e);
    }

    /// <summary>
    /// Executes when a the prefered position format has changed
    /// </summary>
    protected virtual void OnPreferedPositionFormatChanged(DependencyPropertyChangedEventArgs e)
    {
        if (HasInitialized)
            PlayerSetPreferedPositionFormat();
    }

    private void PlayerSetPreferedPositionFormat()
    {
        var format = PreferedPositionFormat;
        MediaPositionFormat currentFormat;
        long duration;

        /* We use BeginInvoke here to avoid what seems to be a deadlock */
        MediaSeekingPlayer.Dispatcher.BeginInvoke((Action)delegate
        {
            MediaSeekingPlayer.PreferedPositionFormat = format;
            currentFormat = MediaSeekingPlayer.CurrentPositionFormat;
            duration = MediaSeekingPlayer.Duration;

            Dispatcher.BeginInvoke((Action)delegate
            {
                SetCurrentPositionFormat(currentFormat);
                SetMediaDuration(duration);
            });
        });
    }

    #endregion PreferedPositionFormat

    #region SpeedRatio

    public static readonly DependencyProperty SpeedRatioProperty =
        DependencyProperty.Register("SpeedRatio", typeof(double), typeof(MediaSeekingElement),
            new FrameworkPropertyMetadata(1.0,
                new PropertyChangedCallback(OnSpeedRatioChanged)));

    /// <summary>
    /// Gets or sets the rate the media is played back
    /// </summary>
    public double SpeedRatio
    {
        get { return (double)GetValue(SpeedRatioProperty); }
        set { SetValue(SpeedRatioProperty, value); }
    }

    private static void OnSpeedRatioChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((MediaSeekingElement)d).OnSpeedRatioChanged(e);
    }

    protected virtual void OnSpeedRatioChanged(DependencyPropertyChangedEventArgs e)
    {
        if (HasInitialized)
            PlayerSetSpeedRatio();
    }

    private void PlayerSetSpeedRatio()
    {
        var speedRatio = SpeedRatio;

        MediaSeekingPlayer.Dispatcher.BeginInvoke((Action)delegate
        {
            MediaSeekingPlayer.SpeedRatio = speedRatio;
        });
    }

    #endregion SpeedRatio

    public override void EndInit()
    {
        PlayerSetMediaPosition();
        PlayerSetPreferedPositionFormat();
        PlayerSetSpeedRatio();
        base.EndInit();
    }

    /// <summary>
    /// Internal reference to the MediaSeekingPlayer
    /// </summary>
    protected MediaSeekingPlayer MediaSeekingPlayer
    {
        get { return MediaPlayerBase as MediaSeekingPlayer; }
    }

    /// <summary>
    /// Fires when a media operation has failed
    /// </summary>
    /// <param name="e">The failed arguments</param>
    protected override void OnMediaPlayerFailed(MediaFailedEventArgs e)
    {
        /* Reset some values on a failure of the media */
        Dispatcher.BeginInvoke((Action)delegate
        {
            SetMediaDuration(0);
            MediaPosition = 0;
        });

        base.OnMediaPlayerFailed(e);
    }

    /// <summary>
    /// Occurs when the media player is being initialized.  Here
    /// the method is overridden as to attach to media seeking
    /// related functionality
    /// </summary>
    protected override void InitializeMediaPlayer()
    {
        /* Let the base class have its way with it */
        base.InitializeMediaPlayer();

        if (MediaSeekingPlayer == null)
            throw new WPFMediaKitException("MediaSeekingPlayer is null or does not inherit MediaSeekingPlayer");

        /* Let us know when the media position has changed */
        MediaSeekingPlayer.MediaPositionChanged += OnMediaPlayerPositionChangedPrivate;
    }

    /// <summary>
    /// A private handler for the MediaPositionChanged event of the media player
    /// </summary>
    private void OnMediaPlayerPositionChangedPrivate(object sender, EventArgs e)
    {
        OnMediaPlayerPositionChanged();
    }

    /// <summary>
    /// Runs when the media player's position has changed
    /// </summary>
    protected virtual void OnMediaPlayerPositionChanged()
    {
        long position = MediaSeekingPlayer.MediaPosition;
        long duration = MediaSeekingPlayer.Duration;

        Dispatcher.BeginInvoke((Action)delegate
        {
            if (MediaDuration != duration)
                SetMediaDuration(duration);

            SetMediaPositionInternal(position);
        });
    }

    /// <summary>
    /// Runs when the MediaPlayer has successfully opened media
    /// </summary>
    protected override void OnMediaPlayerOpened()
    {
        MediaPositionFormat positionFormat = MediaSeekingPlayer.CurrentPositionFormat;
        long duration = MediaSeekingPlayer.Duration;

        Dispatcher.BeginInvoke((Action)delegate
        {
            /* Set our DP values */
            SetCurrentPositionFormat(positionFormat);
            SetMediaPositionInternal(0);
            SetMediaDuration(duration);
            double rate = SpeedRatio;
            double volume = Volume;
            MediaSeekingPlayer.Dispatcher.BeginInvoke((Action)delegate
            {
                MediaSeekingPlayer.SpeedRatio = rate;
                MediaPlayerBase.Volume = volume;
            });
        });

        base.OnMediaPlayerOpened();
    }
}