protected virtual void TouchGestureRecognizerOnPinch(object sender, PinchEventArgs args)
{
if (args.TouchActionType != TouchActionType.Moved)
{
return;
}
var previousPoint = args.PreviousPoint;
var newPoint = args.NewPoint;
var pivotPoint = args.PivotPoint;
var transformedPivotPoint = _skScene.GetCanvasPointFromViewPoint(pivotPoint);
SKPoint oldVector = previousPoint - pivotPoint;
SKPoint newVector = newPoint - pivotPoint;
if (TouchManipulationMode == TouchManipulationMode.ScaleRotate)
{
float angle = GetAngleBetweenVectors(oldVector, newVector);
_skScene.RotateByRadiansDelta(transformedPivotPoint, angle);
// Effectively rotate the old vector
float magnitudeRatio = oldVector.GetMagnitude() / newVector.GetMagnitude();
oldVector.X = magnitudeRatio * newVector.X;
oldVector.Y = magnitudeRatio * newVector.Y;
}
else if (TouchManipulationMode == TouchManipulationMode.IsotropicScale &&
EnableTwoFingersPanInIsotropicScaleMode)
{
float angle = GetAngleBetweenVectors(oldVector, newVector);
// Calculate the movement as a distance between old vector and a new vector
// but in orthogonal direction to the old vector.
float oldVectorOriginPoint = newVector.GetMagnitude() * (float)Math.Cos(angle);
float magnitudeRatio = oldVectorOriginPoint / oldVector.GetMagnitude();
SKPoint oldVectorOrigin = new SKPoint(oldVector.X * magnitudeRatio, oldVector.Y * magnitudeRatio);
SKPoint moveVector = newVector - oldVectorOrigin;
SKPoint dividedMoveVector = new SKPoint(moveVector.X * 0.5f, moveVector.Y * 0.5f);
_skScene.MoveByVector(dividedMoveVector);
}
var scale = newVector.GetMagnitude() / oldVector.GetMagnitude();
if (!float.IsNaN(scale) && !float.IsInfinity(scale))
{
_skScene.ZoomByScaleFactor(transformedPivotPoint, scale);
}
}
protected virtual void TouchGestureRecognizerOnPan(object sender, PanEventArgs args)
{
SKPoint resultVector = args.NewPoint - args.PreviousPoint;
_skScene.MoveByVector(resultVector);
}
