/// <summary>
/// Checks if the manipulation should cause a tilt, and if so starts the
/// tilt effect.
/// </summary>
/// <param name="source">The source of the manipulation (the tilt
/// container, eg entire page).</param>
/// <param name="e">The args from the ManipulationStarted event.</param>
static void TryStartTiltEffect(FrameworkElement source, ManipulationStartedEventArgs e)
{
#if WP7
ContentPresenter lastContentPresenter = null;
#endif
foreach (FrameworkElement ancestor in (e.OriginalSource as FrameworkElement).GetVisualAncestors())
{
#if WP7
var contentPresenter = ancestor as ContentPresenter;
if (contentPresenter != null)
{
lastContentPresenter = contentPresenter;
}
#endif
foreach (Type t in TiltableItems)
{
if (t.IsAssignableFrom(ancestor.GetType()))
{
FrameworkElement elementSuppressingTilt = null;
// Look up the tree to find either an explicit DO or DO NOT suppress.
if (ancestor.ReadLocalValue(SuppressTiltProperty) is bool)
{
elementSuppressingTilt = ancestor;
}
else
{
elementSuppressingTilt = ancestor.GetVisualAncestors().FirstOrDefault(x => x.ReadLocalValue(SuppressTiltProperty) is bool);
}
if (elementSuppressingTilt != null && (bool)elementSuppressingTilt.ReadLocalValue(SuppressTiltProperty) == true)
{
continue;
}
else
{
#if WP7
// Check whether the first child of a ListBoxItem's ContentPresenter has SuppressTilt set to true
if (t == typeof(ListBoxItem) && lastContentPresenter != null)
{
var childElement = lastContentPresenter.GetVisualChildren().FirstOrDefault() as FrameworkElement;
if (childElement != null)
{
object suppressTilt = childElement.ReadLocalValue(SuppressTiltProperty);
if (suppressTilt is bool && (bool)suppressTilt == true)
{
return;
}
}
}
#endif
#if WP8
if (t == typeof(LongListSelector))
{
StartTiltEffectOnLLS((LongListSelector)ancestor, e);
}
else
{
#endif
// Use first child of the control, so that we can add transforms and not
// impact any transforms on the control itself.
FrameworkElement element = VisualTreeHelper.GetChild(ancestor, 0) as FrameworkElement;
FrameworkElement container = e.ManipulationContainer as FrameworkElement;
if (element == null || container == null)
{
return;
}
// Touch point relative to the element being tilted.
Point tiltTouchPoint = container.TransformToVisual(element).Transform(e.ManipulationOrigin);
// Center of the element being tilted.
Point elementCenter = new Point(element.ActualWidth / 2, element.ActualHeight / 2);
// Camera adjustment.
Point centerToCenterDelta = GetCenterToCenterDelta(element, source);
BeginTiltEffect(element, tiltTouchPoint, elementCenter, centerToCenterDelta);
#if WP8
}
#endif
return;
}
}
}
}
}