osu/osu.Game/Screens/OnlinePlay/Multiplayer/Spectate/CatchUpSyncManager.cs
2021-05-03 13:38:53 +09:00

151 lines
4.9 KiB
C#

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System.Collections.Generic;
using System.Linq;
using osu.Framework.Graphics;
using osu.Framework.Timing;
namespace osu.Game.Screens.OnlinePlay.Multiplayer.Spectate
{
/// <summary>
/// A <see cref="ISyncManager"/> which synchronises de-synced player clocks through catchup.
/// </summary>
public class CatchUpSyncManager : Component, ISyncManager
{
/// <summary>
/// The offset from the master clock to which player clocks should be synchronised to.
/// </summary>
public const double SYNC_TARGET = 16;
/// <summary>
/// The offset from the master clock at which player clocks begin resynchronising.
/// </summary>
public const double MAX_SYNC_OFFSET = 50;
/// <summary>
/// The maximum delay to start gameplay, if any (but not all) player clocks are ready.
/// </summary>
public const double MAXIMUM_START_DELAY = 15000;
/// <summary>
/// The master clock which is used to control the timing of all player clocks clocks.
/// </summary>
public IAdjustableClock MasterClock { get; }
/// <summary>
/// The player clocks.
/// </summary>
private readonly List<ISpectatorPlayerClock> playerClocks = new List<ISpectatorPlayerClock>();
private bool hasStarted;
private double? firstStartAttemptTime;
public CatchUpSyncManager(IAdjustableClock master)
{
MasterClock = master;
}
public void AddPlayerClock(ISpectatorPlayerClock clock) => playerClocks.Add(clock);
public void RemovePlayerClock(ISpectatorPlayerClock clock) => playerClocks.Remove(clock);
protected override void Update()
{
base.Update();
if (!attemptStart())
{
// Ensure all player clocks are stopped until the start succeeds.
foreach (var clock in playerClocks)
clock.Stop();
return;
}
updateCatchup();
updateMasterClock();
}
/// <summary>
/// Attempts to start playback. Waits for all player clocks to have available frames for up to <see cref="MAXIMUM_START_DELAY"/> milliseconds.
/// </summary>
/// <returns>Whether playback was started and syncing should occur.</returns>
private bool attemptStart()
{
if (hasStarted)
return true;
if (playerClocks.Count == 0)
return false;
int readyCount = playerClocks.Count(s => !s.WaitingOnFrames.Value);
if (readyCount == playerClocks.Count)
return hasStarted = true;
if (readyCount > 0)
{
firstStartAttemptTime ??= Time.Current;
if (Time.Current - firstStartAttemptTime > MAXIMUM_START_DELAY)
return hasStarted = true;
}
return false;
}
/// <summary>
/// Updates the catchup states of all player clocks clocks.
/// </summary>
private void updateCatchup()
{
for (int i = 0; i < playerClocks.Count; i++)
{
var clock = playerClocks[i];
double timeDelta = MasterClock.CurrentTime - clock.CurrentTime;
// Check that the player clock isn't too far ahead.
// This is a quiet case in which the catchup is done by the master clock, so IsCatchingUp is not set on the player clock.
if (timeDelta < -SYNC_TARGET)
{
clock.Stop();
continue;
}
// Make sure the player clock is running if it can.
if (!clock.WaitingOnFrames.Value)
clock.Start();
if (clock.IsCatchingUp)
{
// Stop the player clock from catching up if it's within the sync target.
if (timeDelta <= SYNC_TARGET)
clock.IsCatchingUp = false;
}
else
{
// Make the player clock start catching up if it's exceeded the maximum allowable sync offset.
if (timeDelta > MAX_SYNC_OFFSET)
clock.IsCatchingUp = true;
}
}
}
/// <summary>
/// Updates the master clock's running state.
/// </summary>
private void updateMasterClock()
{
bool anyInSync = playerClocks.Any(s => !s.IsCatchingUp);
if (MasterClock.IsRunning != anyInSync)
{
if (anyInSync)
MasterClock.Start();
else
MasterClock.Stop();
}
}
}
}