/// <summary>
/// Calculates total and most recent change in scale
/// </summary>
/// <param name="previous"></param>
protected void CalculateScales(PinchEventArgs previous)
{
if (previous != null && Touches.Length > 1 && previous.Touches.Length > 1)
{
Distance = GetDistance(previous);
}
else if (Touches.Length > 1)
{
Distance = GetDistance();
}
else if (previous != null)
{
Distance = previous.Distance;
}
else
{
Distance = 0.0;
}
if (previous == null)
{
DeltaScale = 1.0;
TotalScale = 1.0;
return;
}
if (Touches.Length != previous.Touches.Length)
{
DeltaScale = 1.0;
TotalScale = previous.TotalScale;
return;
}
DeltaScale = Distance / previous.Distance;
TotalScale = previous.TotalScale * DeltaScale;
}
/// <summary>
/// Updates properties from the values from another instance
/// </summary>
/// <param name="source"></param>
public void ValueFrom(PinchEventArgs source)
{
base.ValueFrom(source);
Distance = source.Distance;
DeltaScale = source.DeltaScale;
TotalScale = source.TotalScale;
}
double GetDistance(PinchEventArgs previous)
{
var deltaX = (previous.Touches[1].X + Touches[1].X) / 2.0 - (previous.Touches[0].X + Touches[0].X) / 2.0;
var deltaY = (previous.Touches[1].Y + Touches[1].Y) / 2.0 - (previous.Touches[0].Y + Touches[0].Y) / 2.0;
var distance = Math.Sqrt(deltaX * deltaX + deltaY * deltaY);
return(distance);
}
/// <summary>
/// constructor
/// </summary>
/// <param name="source"></param>
/// <param name="newListener"></param>
public PinchEventArgs(PinchEventArgs source = null, Listener newListener = null) : base(source, newListener)
{
if (source != null)
{
Distance = source.Distance;
DeltaScale = source.DeltaScale;
TotalScale = source.TotalScale;
}
}
internal PinchEventArgs Diff(PinchEventArgs lastArgs)
{
return(new PinchEventArgs {
Cancelled = Cancelled,
Handled = Handled,
ViewPosition = ViewPosition,
Touches = Touches,
Listener = Listener,
Distance = Distance,
TotalScale = TotalScale,
DeltaScale = TotalScale / lastArgs.TotalScale
});
}