/// <summary>
/// Adds a subscription to the element manipulation API of a <see cref="UIElement"/> to then
/// be able to notify an observer of any gesture detected.
/// </summary>
/// <param name="observer">Observer associated to a gesture surface, to process any gesture detected.</param>
/// <param name="gestureSurface">Surface associated with the observer in which the gesture will take place.</param>
internal void AddObserver(IGestureRecognitionObserver observer, UIElement gestureSurface)
{
// Register the surface first, using the fact the observer registry (_observersOfElement) doesn't have a reference
// to the surface.
RegisterGestureSurface(gestureSurface);
// Then you register the observer.
var observers = GetObserversFor(gestureSurface);
observers = IncludeObserver(observers, observer);
_observersOfElement[gestureSurface] = observers;
}
/// <summary>
/// Adds a subscription to the element manipulation API of a <see cref="UIElement"/> to then
/// be able to notify an observer of any gesture detected.
/// </summary>
/// <param name="observer">Observer associated to a gesture surface, to process any gesture detected.</param>
/// <param name="gestureSurface">Surface associated with the observer in which the gesture will take place.</param>
internal void AddObserver(IGestureRecognitionObserver observer, UIElement gestureSurface)
{
// Register the surface first, using the fact the observer registry (_observersOfElement) doesn't have a reference
// to the surface.
RegisterGestureSurface(gestureSurface);
// Then you register the observer.
var observers = GetObserversFor(gestureSurface);
observers = IncludeObserver(observers, observer);
_observersOfElement[gestureSurface] = observers;
}
/// <summary>
/// Drops the subscription to the gesture surface and its associated observer.
/// </summary>
/// <param name="observer">Observer associated to a gesture surface, to process any gesture detected.</param>
/// <param name="gestureSurface">Surface associated with the observer in which the gesture will take place.</param>
internal void RemoveObserver(IGestureRecognitionObserver observer, UIElement gestureSurface)
{
// Removing the observer from the subscriptions
var observers = GetObserversFor(gestureSurface);
observers.RemoveWhere(o => o == observer);
_observersOfElement[gestureSurface] = observers;
// If there is nobody observing the element, let's drop it.
if (!_observersOfElement[gestureSurface].Any())
{
// clearing the subscriptions
gestureSurface.ManipulationStarting -= HandleManipulationStarting;
gestureSurface.ManipulationCompleted -= HandleManipulationCompleted;
gestureSurface.ManipulationDelta -= HandleManipulationDelta;
// removing everything else.
_observersOfElement.Remove(gestureSurface);
}
}
/// <summary>
/// Drops the subscription to the gesture surface and its associated observer.
/// </summary>
/// <param name="observer">Observer associated to a gesture surface, to process any gesture detected.</param>
/// <param name="gestureSurface">Surface associated with the observer in which the gesture will take place.</param>
internal void RemoveObserver(IGestureRecognitionObserver observer, UIElement gestureSurface)
{
// Removing the observer from the subscriptions
var observers = GetObserversFor(gestureSurface);
observers.RemoveWhere(o => o == observer);
_observersOfElement[gestureSurface] = observers;
// If there is nobody observing the element, let's drop it.
if (!_observersOfElement[gestureSurface].Any())
{
// clearing the subscriptions
gestureSurface.ManipulationStarting -= HandleManipulationStarting;
gestureSurface.ManipulationCompleted -= HandleManipulationCompleted;
gestureSurface.ManipulationDelta -= HandleManipulationDelta;
// removing everything else.
_observersOfElement.Remove(gestureSurface);
}
}
private static HashSet<IGestureRecognitionObserver> IncludeObserver(HashSet<IGestureRecognitionObserver> observers, IGestureRecognitionObserver observer)
{
observers.Add(observer);
return observers;
}
private static HashSet <IGestureRecognitionObserver> IncludeObserver(HashSet <IGestureRecognitionObserver> observers, IGestureRecognitionObserver observer)
{
observers.Add(observer);
return(observers);
}