DirectVideo.cs

using System.Drawing;
using Gondwana.Rendering;
using Gondwana.Rendering.Backbuffers;
using Gondwana.Rendering.Views;
using Gondwana.Scenes;
using Gondwana.Video;
using SkiaSharp;
 
namespace Gondwana.Drawing.Direct;

public sealed class DirectVideo : DirectDrawingMovableBase
{
    private readonly IVideoPlayer _player;
    private readonly VideoFrameMailbox _mailbox = new();
    private SKBitmap? _frame;
    private bool _videoDisposed;
    private StretchMode _stretch = StretchMode.Fill;
 
    // ---- knobs ----

    public StretchMode Stretch
    {
        get => _stretch;
        set { if (_stretch != value) { _stretch = value; ForceRefresh(); } }
    }
 
    private double _playbackRate = 1.0;

    public double PlaybackRate
    {
        get => _playbackRate;
        set
        {
            _player.SetRate(value);
            _playbackRate = value;
        }
    }

    public bool Loop
    {
        get => _player.Loop;
        set => _player.Loop = value;
    }

    public DirectVideo(IVideoPlayer player, Uri source, RenderSurfaceHostBase renderSurfaceHost,
        SceneLayer sceneLayer, Rectangle worldBounds, string? name = null)
        : this(player, VideoSource.FromUri(source), renderSurfaceHost, sceneLayer, worldBounds, name) { }

    public DirectVideo(IVideoPlayer player, Uri source, RenderSurfaceHostBase renderSurfaceHost,
        View view, Rectangle screenBounds, string? name = null)
        : this(player, VideoSource.FromUri(source), renderSurfaceHost, view, screenBounds, name) { }

    public DirectVideo(Func<IVideoPlayer> playerFactory, Uri source, RenderSurfaceHostBase renderSurfaceHost,
        SceneLayer sceneLayer, Rectangle worldBounds, string? name = null)
        : this(playerFactory, VideoSource.FromUri(source), renderSurfaceHost, sceneLayer, worldBounds, name) { }

    public DirectVideo(Func<IVideoPlayer> playerFactory, Uri source, RenderSurfaceHostBase renderSurfaceHost,
        View view, Rectangle screenBounds, string? name = null)
        : this(playerFactory, VideoSource.FromUri(source), renderSurfaceHost, view, screenBounds, name) { }

    public DirectVideo(IVideoPlayer player, VideoSource source, RenderSurfaceHostBase renderSurfaceHost,
        SceneLayer sceneLayer, Rectangle worldBounds, string? name = null)
        : this(() => player, source, renderSurfaceHost, DirectDrawingMode.SceneLayer, sceneLayer, null, null, worldBounds, name) { }

    public DirectVideo(IVideoPlayer player, VideoSource source, RenderSurfaceHostBase renderSurfaceHost,
        View view, Rectangle screenBounds, string? name = null)
        : this(() => player, source, renderSurfaceHost, DirectDrawingMode.View, null, view, screenBounds, null, name) { }

    public DirectVideo(Func<IVideoPlayer> playerFactory, VideoSource source, RenderSurfaceHostBase renderSurfaceHost,
        SceneLayer sceneLayer, Rectangle worldBounds, string? name = null)
        : this(playerFactory, source, renderSurfaceHost, DirectDrawingMode.SceneLayer, sceneLayer, null, null, worldBounds, name) { }

    public DirectVideo(Func<IVideoPlayer> playerFactory, VideoSource source, RenderSurfaceHostBase renderSurfaceHost,
        View view, Rectangle screenBounds, string? name = null)
        : this(playerFactory, source, renderSurfaceHost, DirectDrawingMode.View, null, view, screenBounds, null, name) { }
 
    private DirectVideo(Func<IVideoPlayer> playerFactory, VideoSource source,
        RenderSurfaceHostBase renderSurfaceHost, DirectDrawingMode mode, SceneLayer? sceneLayer,
        View? view, Rectangle? screenBounds, Rectangle? worldBounds, string? name)
        : base(renderSurfaceHost, mode, sceneLayer, view, screenBounds, worldBounds, name)
    {
        try
        {
            ArgumentNullException.ThrowIfNull(playerFactory);
            ArgumentNullException.ThrowIfNull(source);
            _player = playerFactory() ?? throw new ArgumentException("The factory returned no video player.", nameof(playerFactory));
            HookPlayer();
            source.Open(_player);
            _player.Play();
        }
        catch
        {
            _mailbox.Dispose();
            if (_player is not null)
            {
                _player.FrameReady -= OnFrameReady;
                _player.StateChanged -= OnPlayerStateChanged;
                _player.Dispose();
            }
            base.Dispose(true); // Construction registered this drawing; undo on failure.
            throw;
        }
    }

    public void Open(VideoSource source)
    {
        ObjectDisposedException.ThrowIf(_videoDisposed, this);
        ArgumentNullException.ThrowIfNull(source);
        source.Open(_player);
        _mailbox.Consume(ref _frame); // Clear the prior source immediately on this engine thread.
        ForceRefresh();
        _player.Play();
    }

    public void Open(Uri source) => Open(VideoSource.FromUri(source));

    public VideoMetadata Metadata => _player.Metadata;

    public (int width, int height) NaturalSize => _player.NaturalSize;
    private void HookPlayer()
    {
        _player.FrameReady += OnFrameReady;
        _player.StateChanged += OnPlayerStateChanged;
    }

    protected override void OnDraw(BackbufferBase backbuffer, RectangleF destRectScreen)
    {
        var bmp = _frame;
        if (bmp is null) return;
 
        var canvas = backbuffer.Canvas;
        var dest = ComputeDestRect(destRectScreen, bmp.Width, bmp.Height, Stretch);
 
        // DirectDrawingBase.Draw applies opacity and fades once.
        canvas.Save();
        canvas.ClipRect(new SKRect(destRectScreen.Left, destRectScreen.Top, destRectScreen.Right, destRectScreen.Bottom));
        canvas.DrawBitmap(bmp, dest);
        canvas.Restore();
    }

    internal static SKRect ComputeDestRect(RectangleF bounds, int srcW, int srcH, StretchMode mode)
    {
        var b = bounds;
        var dst = new SKRect(b.Left, b.Top, b.Right, b.Bottom);
        if (mode == StretchMode.Fill || srcW <= 0 || srcH <= 0) return dst;
 
        float bw = b.Width, bh = b.Height;
        float arSrc = (float)srcW / srcH;
        float arDst = bw / bh;
 
        if (mode == StretchMode.None)
            return new SKRect(b.Left, b.Top, b.Left + srcW, b.Top + srcH);
 
        if (mode == StretchMode.Uniform)
        {
            if (arSrc > arDst)
            {
                float w = bw, h = w / arSrc, y = b.Top + (bh - h) / 2f;
                return new SKRect(b.Left, y, b.Left + w, y + h);
            }
            else
            {
                float h = bh, w = h * arSrc, x = b.Left + (bw - w) / 2f;
                return new SKRect(x, b.Top, x + w, b.Top + h);
            }
        }
 
        // UniformToFill
        if (arSrc < arDst)
        {
            float w = bw, h = w / arSrc, y = b.Top + (bh - h) / 2f;
            return new SKRect(b.Left, y, b.Left + w, y + h);
        }
        else
        {
            float h = bh, w = h * arSrc, x = b.Left + (bw - w) / 2f;
            return new SKRect(x, b.Top, x + w, b.Top + h);
        }
    }
 
    // The event pointer is valid only during the callback; copy before returning.
    private void OnFrameReady(object? sender, VideoFrameReadyEventArgs e) => _mailbox.Publish(e);
 
    private void OnPlayerStateChanged(object? sender, VideoStateChangedEventArgs e)
    {
        if (e.State is "MediaOpening" or "MediaOpened") _mailbox.Reset();
    }

    public override void Update(long tick)
    {
        if (_videoDisposed) return;
        if (_mailbox.Consume(ref _frame)) ForceRefresh();
        base.Update(tick);
    }
    // --- control surface (thin passthrough to player) ---

    public void Play() => _player.Play();

    public void Pause() => _player.Pause();

    public void Stop() => _player.Stop();

    public void Seek(TimeSpan position) => _player.Seek(position);
 
    // --- cleanup ---

    protected override void Dispose(bool disposing)
    {
        if (!disposing) { base.Dispose(false); return; }
        if (_videoDisposed) return;
        _videoDisposed = true;
        _mailbox.Dispose();
        _player.FrameReady -= OnFrameReady;
        _player.StateChanged -= OnPlayerStateChanged;
        try { _player.Dispose(); }
        finally
        {
            _frame?.Dispose();
            _frame = null;
            base.Dispose(true);
        }
    }
}