private static void OnRequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
LoopPanel lp = sender as LoopPanel;
DependencyObject target = e.TargetObject as DependencyObject;
if (lp.BringChildrenIntoView && target != lp)
{
UIElement child = null;
while (target != null)
{
if ((target is UIElement) &&
lp.InternalChildren.Contains(target as UIElement))
{
child = target as UIElement;
break;
}
target = VisualTreeHelper.GetParent(target);
if (target == lp)
{
break;
}
}
if (child != null &&
lp.InternalChildren.Contains(child))
{
e.Handled = true;
// determine if the child needs to be brought into view
GeneralTransform childTransform = child.TransformToAncestor(lp);
Rect childRect = childTransform.TransformBounds(new Rect(new Point(0, 0), child.RenderSize));
Rect intersection = Rect.Intersect(new Rect(new Point(0, 0), lp.RenderSize), childRect);
// if the intersection is different than the child rect, it is either not visible
// or only partially visible, so adjust the Offset to bring it into view
if (!CalculateExtensions.AreVirtuallyEqual(childRect, intersection))
{
if (!intersection.IsEmpty)
{
// the child is already partially visible, so just scroll it into view
lp.Scroll((lp.Orientation == Orientation.Horizontal)
? (CalculateExtensions.AreVirtuallyEqual(childRect.X, intersection.X) ? childRect.Width - intersection.Width + Math.Min(0, lp.RenderSize.Width - childRect.Width) : childRect.X - intersection.X)
: (CalculateExtensions.AreVirtuallyEqual(childRect.Y, intersection.Y) ? childRect.Height - intersection.Height + Math.Min(0, lp.RenderSize.Height - childRect.Height) : childRect.Y - intersection.Y));
}
else
{
// the child is not visible at all
lp.Scroll((lp.Orientation == Orientation.Horizontal)
? (CalculateExtensions.StrictlyLessThan(childRect.Right, 0.0d) ? childRect.X : childRect.Right - lp.RenderSize.Width + Math.Min(0, lp.RenderSize.Width - childRect.Width))
: (CalculateExtensions.StrictlyLessThan(childRect.Bottom, 0.0d) ? childRect.Y : childRect.Bottom - lp.RenderSize.Height + Math.Min(0, lp.RenderSize.Height - childRect.Height)));
}
}
}
}
}
/// <summary>
/// Provides a helper method for scrolling the panel by viewport units rather than
/// adjusting the Offset property (which uses logical units)
/// </summary>
/// <param name="viewportUnits">The number of device independent pixels to scroll. A positive value
/// scrolls the Offset forward and a negative value scrolls it backward</param>
public void Scroll(double viewportUnits)
{
int childCount = this.InternalChildren.Count;
if (childCount == 0)
{
return;
}
// determine the new Offset value required to move the specified viewport units
double newOffset = this.Offset;
int childIndex = this.PivotalChildIndex;
bool isHorizontal = (this.Orientation == Orientation.Horizontal);
bool isForwardMovement = (viewportUnits > 0);
int directionalFactor = isForwardMovement ? 1 : -1;
double remainingExtent = Math.Abs(viewportUnits);
UIElement child = this.InternalChildren[childIndex];
double childExtent = isHorizontal ? child.DesiredSize.Width : child.DesiredSize.Height;
double fractionalOffset = (this.Offset > 0) ? this.Offset - Math.Truncate(this.Offset) : 1.0d - Math.Truncate(this.Offset) + this.Offset;
double childRemainingExtent = isForwardMovement ? childExtent - fractionalOffset * childExtent : fractionalOffset * childExtent;
if (CalculateExtensions.LessThanOrVirtuallyEqual(childRemainingExtent, remainingExtent))
{
newOffset = Math.Round(isForwardMovement ? newOffset + 1 - fractionalOffset : newOffset - fractionalOffset);
remainingExtent -= childRemainingExtent;
while (CalculateExtensions.StrictlyGreaterThan(remainingExtent, 0.0d))
{
childIndex = isForwardMovement ? (childIndex + 1) % childCount : (childIndex == 0 ? childCount - 1 : childIndex - 1);
child = this.InternalChildren[childIndex];
childExtent = isHorizontal ? child.DesiredSize.Width : child.DesiredSize.Height;
if (CalculateExtensions.LessThanOrVirtuallyEqual(childExtent, remainingExtent))
{
newOffset += 1.0d * directionalFactor;
remainingExtent -= childExtent;
}
else
{
newOffset += remainingExtent * directionalFactor / childExtent;
remainingExtent = 0.0d;
}
}
}
else
{
newOffset += remainingExtent * directionalFactor / childExtent;
remainingExtent = 0.0d;
}
this.Offset = newOffset;
}
public static bool AreVirtuallyEqual(Point p1, Point p2)
{
return(CalculateExtensions.AreVirtuallyEqual(p1.X, p2.X) && CalculateExtensions.AreVirtuallyEqual(p1.Y, p2.Y));
}
public static bool AreVirtuallyEqual(Rect r1, Rect r2)
{
return(CalculateExtensions.AreVirtuallyEqual(r1.TopLeft, r2.TopLeft) && CalculateExtensions.AreVirtuallyEqual(r1.BottomRight, r2.BottomRight));
}
