# ManipulationDeltaEventArgs.ReportBoundaryFeedback(ManipulationDelta) Method

## Definition

Specifies that the manipulation has gone beyond certain boundaries.

``public void ReportBoundaryFeedback (System.Windows.Input.ManipulationDelta unusedManipulation);``
Parameters
unusedManipulation
ManipulationDelta

The portion of the manipulation that represents moving beyond the boundary.

Exceptions

`unusedManipulation` is `null`.

## Examples

The following example shows an event handler for the ManipulationDelta event that calls the ReportBoundaryFeedback method when the user moves the element over the edge of its container. To test this example, follow the steps in Walkthrough: Creating Your First Touch Application and replace the code in step 5 with this code.

``````void Window_ManipulationDelta(object sender, ManipulationDeltaEventArgs e)
{

Rectangle rectToMove = e.OriginalSource as Rectangle;
Vector overshoot;

// When the element crosses the boundary of the window, check whether
// the manipulation is in inertia.  If it is, complete the manipulation.
// Otherwise, report the boundary feedback.
if (CalculateOvershoot(rectToMove, e.ManipulationContainer, out overshoot))
{
if (e.IsInertial)
{
e.Complete();
e.Handled = true;
return;
}
else
{
//Report that the element hit the boundary
e.ReportBoundaryFeedback(new ManipulationDelta(overshoot, 0, new Vector(), new Vector()));

}
}

// Move the element as usual.

// Get the Rectangle and its RenderTransform matrix.
Matrix rectsMatrix = ((MatrixTransform)rectToMove.RenderTransform).Matrix;

// Rotate the Rectangle.
rectsMatrix.RotateAt(e.DeltaManipulation.Rotation,
e.ManipulationOrigin.X,
e.ManipulationOrigin.Y);

// Resize the Rectangle.  Keep it square
// so use only the X value of Scale.
rectsMatrix.ScaleAt(e.DeltaManipulation.Scale.X,
e.DeltaManipulation.Scale.X,
e.ManipulationOrigin.X,
e.ManipulationOrigin.Y);

// Move the Rectangle.
rectsMatrix.Translate(e.DeltaManipulation.Translation.X,
e.DeltaManipulation.Translation.Y);

// Apply the changes to the Rectangle.
rectToMove.RenderTransform = new MatrixTransform(rectsMatrix);

e.Handled = true;
}

private bool CalculateOvershoot(UIElement element, IInputElement container, out Vector overshoot)
{
// Get axis aligned element bounds
var elementBounds = element.RenderTransform.TransformBounds(
VisualTreeHelper.GetDrawing(element).Bounds);

//double extraX = 0.0, extraY = 0.0;
overshoot = new Vector();

FrameworkElement parent = container as FrameworkElement;
if (parent == null)
{
return false;
}

// Calculate overshoot.
if (elementBounds.Left < 0)
overshoot.X = elementBounds.Left;
else if (elementBounds.Right > parent.ActualWidth)
overshoot.X = elementBounds.Right - parent.ActualWidth;

if (elementBounds.Top < 0)
overshoot.Y = elementBounds.Top;
else if (elementBounds.Bottom > parent.ActualHeight)
overshoot.Y = elementBounds.Bottom - parent.ActualHeight;

// Return false if Overshoot is empty; otherwsie, return true.
return !Vector.Equals(overshoot, new Vector());
}
``````
``````Private Sub Window_ManipulationDelta(ByVal sender As Object, ByVal e As ManipulationDeltaEventArgs)

Dim rectToMove As Rectangle = TryCast(e.OriginalSource, Rectangle)
Dim overshoot As Vector

' When the element crosses the boundary of the window, check whether
' the manipulation is in inertia. If it is, complete the manipulation.
' Otherwise, report the boundary feedback.
If CalculateOvershoot(rectToMove, e.ManipulationContainer, overshoot) Then
If e.IsInertial Then
e.Complete()
e.Handled = True
Exit Sub
Else
'Report that the element hit the boundary

e.ReportBoundaryFeedback(New ManipulationDelta(overshoot, 0, New Vector(), New Vector()))
End If
End If

' Move the element as usual.

' Get the Rectangle and its RenderTransform matrix.
Dim rectsMatrix As Matrix = DirectCast(rectToMove.RenderTransform, MatrixTransform).Matrix

' Rotate the Rectangle.
rectsMatrix.RotateAt(e.DeltaManipulation.Rotation, e.ManipulationOrigin.X, e.ManipulationOrigin.Y)

' Resize the Rectangle. Keep it square
' so use only the X value of Scale.
rectsMatrix.ScaleAt(e.DeltaManipulation.Scale.X, e.DeltaManipulation.Scale.X, e.ManipulationOrigin.X, e.ManipulationOrigin.Y)

' Move the Rectangle.
rectsMatrix.Translate(e.DeltaManipulation.Translation.X, e.DeltaManipulation.Translation.Y)

' Apply the changes to the Rectangle.
rectToMove.RenderTransform = New MatrixTransform(rectsMatrix)

e.Handled = True
End Sub

Private Function CalculateOvershoot(ByVal element As UIElement, ByVal container As IInputElement, ByRef overshoot As Vector) As Boolean
' Get axis aligned element bounds
Dim elementBounds = element.RenderTransform.TransformBounds(VisualTreeHelper.GetDrawing(element).Bounds)

'double extraX = 0.0, extraY = 0.0;
overshoot = New Vector()

Dim parent As FrameworkElement = TryCast(container, FrameworkElement)
If parent Is Nothing Then
Return False
End If

' Calculate overshoot.
If elementBounds.Left < 0 Then
overshoot.X = elementBounds.Left
ElseIf elementBounds.Right > parent.ActualWidth Then
overshoot.X = elementBounds.Right - parent.ActualWidth
End If

If elementBounds.Top < 0 Then
overshoot.Y = elementBounds.Top
ElseIf elementBounds.Bottom > parent.ActualHeight Then
overshoot.Y = elementBounds.Bottom - parent.ActualHeight
End If

' Return false if Overshoot is empty; otherwsie, return true.
Return Not Vector.Equals(overshoot, New Vector())
End Function
``````

## Remarks

Use the ReportBoundaryFeedback method to indicate that an element has moved beyond a certain boundary. For example, if a user moves an element outside of the bounds of a Window, you can call this method to report that to the window. When you call ReportBoundaryFeedback, the ManipulationBoundaryFeedback event occurs. By default, the Window subscribes to the ManipulationBoundaryFeedback event to provide visual feedback to the user that a boundary has been reached. You can subscribe to ManipulationBoundaryFeedback to implement custom behavior.