protected virtual void OnDisplayLinkLoop()
{
if (link == null || viewPort == null)
{
return;
}
var actualFrameDuration = link.TargetTimestamp - link.Timestamp;
var decelerationEllapsedTime = link.Timestamp - decelerationStartTime;
double frameOffsetX, frameOffsetY;
if (Math.Abs(decelerationVelocityX) > 0)
{
var framePositionX = decelerationVelocityX * decelerationEllapsedTime - decelerationX * Math.Pow(decelerationEllapsedTime, 2) / 2;
frameOffsetX = framePositionX - lastDecelerationFramePositionX;
lastDecelerationFramePositionX = framePositionX;
if (Math.Abs(decelerationVelocityX) - Math.Abs(decelerationX * decelerationEllapsedTime) <= 1)
{
decelerationVelocityX = 0;
}
}
else
{
frameOffsetX = 0;
}
if (Math.Abs(decelerationVelocityY) > 0)
{
var framePositionY = decelerationVelocityY * decelerationEllapsedTime - decelerationY * Math.Pow(decelerationEllapsedTime, 2) / 2;
frameOffsetY = framePositionY - lastDecelerationFramePositionY;
lastDecelerationFramePositionY = framePositionY;
if (Math.Abs(decelerationVelocityY) - Math.Abs(decelerationY * decelerationEllapsedTime) <= 1)
{
decelerationVelocityY = 0;
}
}
else
{
frameOffsetY = 0;
}
var movementVector = new CGPoint(frameOffsetX, frameOffsetY);
var success = viewPort.Offset(movementVector);
if (!success)
{
var movementDirections = GetVectorDirection(movementVector);
decelerationVelocityX = viewPort.CanMove(movementDirections & Direction.Horizontal) ? decelerationVelocityX : 0;
decelerationVelocityY = viewPort.CanMove(movementDirections & Direction.Vertical) ? decelerationVelocityY : 0;
}
if (decelerationEllapsedTime > 0.3f && Math.Abs(frameOffsetX) < 0.1 && Math.Abs(frameOffsetY) < 0.1)
{
StopDeceleration();
}
FireRedrawIsNeeded();
}
