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Some scrolling and performance improvements #28

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282 changes: 156 additions & 126 deletions scrollController/ScrollController.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,134 +2,164 @@
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace ScrollShared
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable")]
public class ScrollController
{
private const int Interval = 16;
private const int AccelerateThreshold = 2;
private const double Accelerator = 2.0;
private readonly double dpiRatio;

private readonly object locker = new object();
private readonly IPageScroller pageScroller;
private readonly ScrollingDirection direction;

private double totalDistance, remain;
private int totalRounds, round;

private Task workingThread = null;

public ScrollController(IPageScroller _pageScroller, ScrollingDirection _direction)
{
pageScroller = _pageScroller;
direction = _direction;

dpiRatio = SystemParameters.PrimaryScreenHeight / 720.0;
}

private int CalculateTotalRounds(double timeRatio, double requestDistance)
{
double distanceRatio = Math.Sqrt(Math.Abs(requestDistance / dpiRatio) / 720);
double maxTotalSteps = 10 + 25 * Math.Min(distanceRatio, 1.5);

return (int)(maxTotalSteps * timeRatio);
}

public void ScrollView(double distance, ScrollingSpeeds speedLever)
{
double intervalRatio = GetSpeedRatio(speedLever);

lock (locker)
{
if (Math.Sign(distance) != Math.Sign(remain))
{
remain = (int)distance;
}
else
{
remain += (int)(distance * (round < AccelerateThreshold ? 1 : Accelerator));
}

round = 0;
totalDistance = remain;
}

totalRounds = CalculateTotalRounds(intervalRatio, totalDistance);

if (workingThread == null)
{
workingThread = Task.Run(ScrollingThread);
}
}

private double GetSpeedRatio(ScrollingSpeeds speedLever)
{
var speedTable = new Dictionary<ScrollingSpeeds, double>()
{
{ScrollingSpeeds.Slow, 1.5},
{ScrollingSpeeds.Normal, 1.0},
{ScrollingSpeeds.Fast, 0.65}
};

return speedTable[speedLever];
}

private int CalculateScrollDistance()
{
double percent = (double)round / totalRounds;

var stepLength = 2 * totalDistance / totalRounds * (1 - percent);

int result = (int)Math.Round(stepLength);

return result;
}

public void StopScroll()
{
workingThread?.Wait(100);
CleanupScroll();
}

private void CleanupScroll()
{
lock (locker)
{
round = totalRounds;
totalDistance = remain = 0;

workingThread = null;
}
}

private async Task ScrollingThread()
{
while (round <= totalRounds)
{
var stepLength = CalculateScrollDistance();

if (stepLength == 0)
{
break;
}

lock (locker)
{
round += 1;
remain -= stepLength;
}

pageScroller.Scroll(direction, stepLength);

await Task.Delay(Interval);
}

CleanupScroll();
}
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable")]
public class ScrollController
{
private const long Interval = 33;
private const long MinInterval = 5;
private const int AccelerateThreshold = 2;
private const double Accelerator = 2.0;
private readonly double dpiRatio;

private readonly object locker = new object();
private readonly IPageScroller pageScroller;
private readonly ScrollingDirection direction;

private readonly Dictionary<ScrollingSpeeds, double> speedTable = new Dictionary<ScrollingSpeeds, double>()
{
{ScrollingSpeeds.Slow, 1.5},
{ScrollingSpeeds.Normal, 1.0},
{ScrollingSpeeds.Fast, 0.65}
};

private double totalDistance;
private double remain;
private int totalRounds;
private int round;

private AutoResetEvent stopScrollEvent = new AutoResetEvent(false);
private AutoResetEvent startScrollEvent = new AutoResetEvent(false);
private ManualResetEvent exitScrollThreadEvent = new ManualResetEvent(false);

private Thread workingThread;

public ScrollController(IPageScroller _pageScroller, ScrollingDirection _direction)
{
pageScroller = _pageScroller;
direction = _direction;
dpiRatio = SystemParameters.PrimaryScreenHeight / 720.0;
workingThread = new Thread(new ThreadStart(ScrollingThread));
workingThread.Start();
}

~ScrollController()
{
exitScrollThreadEvent.Set();
workingThread.Join();
}

private int CalculateTotalRounds(double timeRatio, double requestDistance)
{
double distanceRatio = Math.Sqrt(Math.Abs(requestDistance / dpiRatio) / 720);
double maxTotalSteps = 10 + 25 * Math.Min(distanceRatio, 1.5);

return (int)(maxTotalSteps * timeRatio);
}

public void ScrollView(double distance, ScrollingSpeeds speedLever)
{
double intervalRatio = GetSpeedRatio(speedLever);

lock (locker)
{
if (Math.Sign(distance) != Math.Sign(remain))
{
remain = (int)distance;
}
else
{
remain += (int)(distance * (round < AccelerateThreshold ? 1 : Accelerator));
}

round = 0;
totalDistance = remain;
}

totalRounds = CalculateTotalRounds(intervalRatio, totalDistance);

startScrollEvent.Set();
}

private double GetSpeedRatio(ScrollingSpeeds speedLever)
{
return speedTable[speedLever];
}

private int CalculateScrollDistance()
{
var percent = (double)round / totalRounds;
var stepLength = 2 * totalDistance / totalRounds * (1 - percent);
return (int)Math.Round(stepLength);
}

public void StopScroll()
{
stopScrollEvent.Set();
}

private void CleanupScroll()
{
lock (locker)
{
round = totalRounds;
totalDistance = remain = 0;
}
}

private void ScrollingThread()
{
var sleepWaitHandles = new WaitHandle[] { startScrollEvent, exitScrollThreadEvent };
var exitLoopWaitHandles = new WaitHandle[] { stopScrollEvent, exitScrollThreadEvent };
var stopWatch = new Stopwatch();
long remainingDelay;

// The first loop, sleep/run loop.
for (;;)
{
WaitHandle.WaitAny(sleepWaitHandles);
if (exitScrollThreadEvent.WaitOne(0))
{
return;
}

// The second loop, scrolling loop.
while (round <= totalRounds && WaitHandle.WaitAny(exitLoopWaitHandles, 0) == WaitHandle.WaitTimeout)
{
if (exitScrollThreadEvent.WaitOne(0))
{
return;
}

var stepLength = CalculateScrollDistance();

if (stepLength == 0)
{
break;
}

lock (locker)
{
++round;
remain -= stepLength;
}

stopWatch.Restart();

pageScroller.Scroll(direction, stepLength);

stopWatch.Stop();
remainingDelay = Math.Max(Interval - stopWatch.ElapsedMilliseconds, MinInterval);

// Delay.
WaitHandle.WaitAny(exitLoopWaitHandles, (int)remainingDelay);
}

CleanupScroll();
}
}
}
}