/// <summary>
/// Updates the X and Y properties based on the current rendered position of the associated element.
/// </summary>
private void UpdatePosition()
{
GeneralTransform elementToRoot = this.AssociatedObject.TransformToVisual(this.RootElement);
Point translation = MouseDragElementBehavior.GetTransformOffset(elementToRoot);
this.X = translation.X;
this.Y = translation.Y;
}
/// <summary>
/// Attempts to update the position of the associated element to the specified coordinates.
/// </summary>
/// <param name="point">The desired position of the element in root coordinates.</param>
private void UpdatePosition(Point point)
{
if (!this.settingPosition && this.AssociatedObject != null)
{
GeneralTransform elementToRoot = this.AssociatedObject.TransformToVisual(this.RootElement);
Point translation = MouseDragElementBehavior.GetTransformOffset(elementToRoot);
double xChange = double.IsNaN(point.X) ? 0 : point.X - translation.X;
double yChange = double.IsNaN(point.Y) ? 0 : point.Y - translation.Y;
this.ApplyTranslation(xChange, yChange);
}
}
/// <summary>
/// Applies a relative position translation to the associated element.
/// </summary>
/// <param name="x">The X component of the desired translation in root coordinates.</param>
/// <param name="y">The Y component of the desired translation in root coordinates.</param>
private void ApplyTranslation(double x, double y)
{
if (this.ParentElement != null)
{
GeneralTransform rootToParent = this.RootElement.TransformToVisual(this.ParentElement);
Point transformedPoint = MouseDragElementBehavior.TransformAsVector(rootToParent, x, y);
x = transformedPoint.X;
y = transformedPoint.Y;
if (this.ConstrainToParentBounds)
{
FrameworkElement parentElement = this.ParentElement;
Rect parentBounds = new Rect(0, 0, parentElement.ActualWidth, parentElement.ActualHeight);
GeneralTransform objectToParent = this.AssociatedObject.TransformToVisual(parentElement);
Rect objectBoundingBox = this.ElementBounds;
objectBoundingBox = objectToParent.TransformBounds(objectBoundingBox);
Rect endPosition = objectBoundingBox;
endPosition.X += x;
endPosition.Y += y;
if (!MouseDragElementBehavior.RectContainsRect(parentBounds, endPosition))
{
if (endPosition.X < parentBounds.Left)
{
double diff = endPosition.X - parentBounds.Left;
x -= diff;
}
else if (endPosition.Right > parentBounds.Right)
{
double diff = endPosition.Right - parentBounds.Right;
x -= diff;
}
if (endPosition.Y < parentBounds.Top)
{
double diff = endPosition.Y - parentBounds.Top;
y -= diff;
}
else if (endPosition.Bottom > parentBounds.Bottom)
{
double diff = endPosition.Bottom - parentBounds.Bottom;
y -= diff;
}
}
}
this.ApplyTranslationTransform(x, y);
}
}
private static void OnConstrainToParentBoundsChanged(object sender, DependencyPropertyChangedEventArgs args)
{
MouseDragElementBehavior b = (MouseDragElementBehavior)sender;
b.UpdatePosition(new Point(b.X, b.Y));
}
private static void OnYChanged(object sender, DependencyPropertyChangedEventArgs args)
{
MouseDragElementBehavior dragBehavior = (MouseDragElementBehavior)sender;
dragBehavior.UpdatePosition(new Point(dragBehavior.X, (double)args.NewValue));
}