/// <summary>
/// Implementation of <see cref="FilterManipulation"/> that forces the rotation to be about
/// the center of the manipulation target.
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
public static void RotateAboutCenter(object sender, Manipulations.FilterManipulationEventArgs args)
{
var inputProcessor = sender as Manipulations.InputProcessor;
var target = inputProcessor.Target;
// Get the bounding box of the manipulation target, expressed in the coordinate system of its container
var rect = target.RenderTransform.TransformBounds(
new Windows.Foundation.Rect(0, 0, target.ActualWidth, target.ActualHeight));
args.Pivot = new Windows.Foundation.Point
{
X = rect.Left + (rect.Width / 2),
Y = rect.Top + (rect.Height / 2)
};
}
/// <summary>
/// Implementation of <see cref="FilterManipulation"/> that forces the center of mass of the
/// manipulation target to remain inside its container.
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
public static void ClampCenterOfMass(object sender, Manipulations.FilterManipulationEventArgs args)
{
var inputProcessor = sender as Manipulations.InputProcessor;
var target = inputProcessor.Target;
var container = inputProcessor.Reference;
// Get the bounding box and the center of mass of the manipulation target,
// expressed in the coordinate system of its container
var rect = target.RenderTransform.TransformBounds(
new Windows.Foundation.Rect(0, 0, target.ActualWidth, target.ActualHeight));
var centerOfMass = new Windows.Foundation.Point
{
X = rect.Left + (rect.Width / 2),
Y = rect.Top + (rect.Height / 2)
};
// Apply delta transform to the center of mass
var transform = new Windows.UI.Xaml.Media.CompositeTransform
{
CenterX = args.Pivot.X,
CenterY = args.Pivot.Y,
Rotation = args.Delta.Rotation,
ScaleX = args.Delta.Scale,
ScaleY = args.Delta.Scale,
TranslateX = args.Delta.Translation.X,
TranslateY = args.Delta.Translation.Y
};
var transformedCenterOfMass = transform.TransformPoint(centerOfMass);
// Reset the transformation if the transformed center of mass falls outside the container
if (transformedCenterOfMass.X < 0 || transformedCenterOfMass.X > container.ActualWidth ||
transformedCenterOfMass.Y < 0 || transformedCenterOfMass.Y > container.ActualHeight)
{
args.Delta = new Windows.UI.Input.ManipulationDelta
{
Rotation = 0F,
Scale = 1F,
Translation = new Windows.Foundation.Point(0, 0)
};
}
}
/// <summary>
/// Implementation of <see cref="FilterManipulation"/> that forces at least <see cref="ManipulationFilter.TargetMinSize"/>
/// pixels of the manipulation target to remain inside its container.
/// This filter also makes sure the manipulation target does not become too small or too big.
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
public static void Clamp(object sender, Manipulations.FilterManipulationEventArgs args)
{
var inputProcessor = sender as Manipulations.InputProcessor;
var target = inputProcessor.Target;
var container = inputProcessor.Reference;
// Get the bounding box of the manipulation target, expressed in the coordinate system of its container
var rect = target.RenderTransform.TransformBounds(
new Windows.Foundation.Rect(0, 0, target.ActualWidth, target.ActualHeight));
// Make sure the manipulation target does not go completely outside the boundaries of its container
var translate = new Windows.Foundation.Point
{
X = args.Delta.Translation.X,
Y = args.Delta.Translation.Y
};
if ((args.Delta.Translation.X > 0 && args.Delta.Translation.X > container.ActualWidth - rect.Left - ManipulationFilter.TargetMinInside) ||
(args.Delta.Translation.X < 0 && args.Delta.Translation.X < ManipulationFilter.TargetMinInside - rect.Right) ||
(args.Delta.Translation.Y > 0 && args.Delta.Translation.Y > container.ActualHeight - rect.Top - ManipulationFilter.TargetMinInside) ||
(args.Delta.Translation.Y < 0 && args.Delta.Translation.Y < ManipulationFilter.TargetMinInside - rect.Bottom))
{
translate.X = 0;
translate.Y = 0;
}
// Make sure the manipulation target does not become too small, or too big
float scale = args.Delta.Scale < 1F ?
(float)System.Math.Max(ManipulationFilter.TargetMinSize / System.Math.Min(rect.Width, rect.Height), args.Delta.Scale) :
(float)System.Math.Min(ManipulationFilter.TargetMaxSize / System.Math.Max(rect.Width, rect.Height), args.Delta.Scale);
args.Delta = new Windows.UI.Input.ManipulationDelta
{
Expansion = args.Delta.Expansion,
Rotation = args.Delta.Rotation,
Scale = scale,
Translation = translate
};
}