1
0
mirror of https://github.com/ppy/osu.git synced 2024-12-16 04:22:54 +08:00
osu-lazer/osu.Game/Rulesets/UI/Scrolling/Algorithms/SequentialScrollAlgorithm.cs
2019-01-24 17:43:03 +09:00

118 lines
5.2 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;
using System.Collections.Generic;
using osu.Game.Rulesets.Timing;
namespace osu.Game.Rulesets.UI.Scrolling.Algorithms
{
public class SequentialScrollAlgorithm : IScrollAlgorithm
{
private readonly Dictionary<double, double> positionCache;
private readonly IReadOnlyList<MultiplierControlPoint> controlPoints;
public SequentialScrollAlgorithm(IReadOnlyList<MultiplierControlPoint> controlPoints)
{
this.controlPoints = controlPoints;
positionCache = new Dictionary<double, double>();
}
public double GetDisplayStartTime(double time, double timeRange) => time - timeRange - 1000;
public float GetLength(double startTime, double endTime, double timeRange, float scrollLength)
{
var objectLength = relativePositionAtCached(endTime, timeRange) - relativePositionAtCached(startTime, timeRange);
return (float)(objectLength * scrollLength);
}
public float PositionAt(double time, double currentTime, double timeRange, float scrollLength)
{
// Caching is not used here as currentTime is unlikely to have been previously cached
double timelinePosition = relativePositionAt(currentTime, timeRange);
return (float)((relativePositionAtCached(time, timeRange) - timelinePosition) * scrollLength);
}
public double TimeAt(float position, double currentTime, double timeRange, float scrollLength)
{
// Convert the position to a length relative to time = 0
double length = position / scrollLength + relativePositionAt(currentTime, timeRange);
// We need to consider all timing points until the specified time and not just the currently-active one,
// since each timing point individually affects the positions of _all_ hitobjects after its start time
for (int i = 0; i < controlPoints.Count; i++)
{
var current = controlPoints[i];
var next = i < controlPoints.Count - 1 ? controlPoints[i + 1] : null;
// Duration of the current control point
var currentDuration = (next?.StartTime ?? double.PositiveInfinity) - current.StartTime;
// Figure out the length of control point
var currentLength = currentDuration / timeRange * current.Multiplier;
if (currentLength > length)
{
// The point is within this control point
return current.StartTime + length * timeRange / current.Multiplier;
}
length -= currentLength;
}
return 0; // Should never occur
}
private double relativePositionAtCached(double time, double timeRange)
{
if (!positionCache.TryGetValue(time, out double existing))
positionCache[time] = existing = relativePositionAt(time, timeRange);
return existing;
}
public void Reset() => positionCache.Clear();
/// <summary>
/// Finds the position which corresponds to a point in time.
/// This is a non-linear operation that depends on all the control points up to and including the one active at the time value.
/// </summary>
/// <param name="time">The time to find the position at.</param>
/// <param name="timeRange">The amount of time visualised by the scrolling area.</param>
/// <returns>A positive value indicating the position at <paramref name="time"/>.</returns>
private double relativePositionAt(double time, double timeRange)
{
if (controlPoints.Count == 0)
return time / timeRange;
double length = 0;
// We need to consider all timing points until the specified time and not just the currently-active one,
// since each timing point individually affects the positions of _all_ hitobjects after its start time
for (int i = 0; i < controlPoints.Count; i++)
{
var current = controlPoints[i];
var next = i < controlPoints.Count - 1 ? controlPoints[i + 1] : null;
// We don't need to consider any control points beyond the current time, since it will not yet
// affect any hitobjects
if (i > 0 && current.StartTime > time)
continue;
// Duration of the current control point
var currentDuration = (next?.StartTime ?? double.PositiveInfinity) - current.StartTime;
// We want to consider the minimal amount of time that this control point has affected,
// which may be either its duration, or the amount of time that has passed within it
var durationInCurrent = Math.Min(currentDuration, time - current.StartTime);
// Figure out how much of the time range the duration represents, and adjust it by the speed multiplier
length += durationInCurrent / timeRange * current.Multiplier;
}
return length;
}
}
}