private void ThrowEnterAndLeaveTouchEvents(UIElement currentElement, UIElement previousElement, TouchEventArgs touchEvent)
{
var commonElement = FindCommonParent(currentElement, previousElement);
// raise leave events to the hierarchy: previousElt -> commonElementParent
var previousElementParent = previousElement;
while (previousElementParent != commonElement && previousElementParent != null)
{
if (previousElementParent.IsHierarchyEnabled && previousElementParent.IsTouched)
{
touchEvent.Handled = false; // reset 'handled' because it corresponds to another event
previousElementParent.RaiseTouchLeaveEvent(touchEvent);
}
previousElementParent = previousElementParent.VisualParent;
}
// raise enter events to the hierarchy: newElt -> commonElementParent
var newElementParent = currentElement;
while (newElementParent != commonElement && newElementParent != null)
{
if (newElementParent.IsHierarchyEnabled && !newElementParent.IsTouched)
{
touchEvent.Handled = false; // reset 'handled' because it corresponds to another event
newElementParent.RaiseTouchEnterEvent(touchEvent);
}
newElementParent = newElementParent.VisualParent;
}
}
private void UpdateTouchEvents(UIComponentProcessor.UIComponentState state, GameTime gameTime)
{
var rootElement = state.UIComponent.RootElement;
var intersectionPoint = Vector3.Zero;
var lastTouchPosition = new Vector2(float.NegativeInfinity);
// analyze pointer event input and trigger UI touch events depending on hit Tests
foreach (var pointerEvent in compactedPointerEvents)
{
// performance optimization: skip all the events that started outside of the UI
var lastTouchedElement = state.LastTouchedElement;
if (lastTouchedElement == null && pointerEvent.State != PointerState.Down)
continue;
var time = gameTime.Total;
var currentTouchPosition = pointerEvent.Position;
var currentTouchedElement = lastTouchedElement;
// re-calculate the element under cursor if click position changed.
if (lastTouchPosition != currentTouchPosition)
currentTouchedElement = GetElementAtScreenPosition(rootElement, pointerEvent.Position, ref intersectionPoint);
if (pointerEvent.State == PointerState.Down || pointerEvent.State == PointerState.Up)
state.LastIntersectionPoint = intersectionPoint;
var touchEvent = new TouchEventArgs
{
Action = TouchAction.Down,
Timestamp = time,
ScreenPosition = currentTouchPosition,
ScreenTranslation = pointerEvent.DeltaPosition,
WorldPosition = intersectionPoint,
WorldTranslation = intersectionPoint - state.LastIntersectionPoint
};
switch (pointerEvent.State)
{
case PointerState.Down:
touchEvent.Action = TouchAction.Down;
if (currentTouchedElement != null)
currentTouchedElement.RaiseTouchDownEvent(touchEvent);
break;
case PointerState.Up:
touchEvent.Action = TouchAction.Up;
// generate enter/leave events if we passed from an element to another without move events
if (currentTouchedElement != lastTouchedElement)
ThrowEnterAndLeaveTouchEvents(currentTouchedElement, lastTouchedElement, touchEvent);
// trigger the up event
if (currentTouchedElement != null)
currentTouchedElement.RaiseTouchUpEvent(touchEvent);
break;
case PointerState.Move:
touchEvent.Action = TouchAction.Move;
// first notify the move event (even if the touched element changed in between it is still coherent in one of its parents)
if (currentTouchedElement != null)
currentTouchedElement.RaiseTouchMoveEvent(touchEvent);
// then generate enter/leave events if we passed from an element to another
if (currentTouchedElement != lastTouchedElement)
ThrowEnterAndLeaveTouchEvents(currentTouchedElement, lastTouchedElement, touchEvent);
break;
case PointerState.Out:
case PointerState.Cancel:
touchEvent.Action = TouchAction.Move;
// generate enter/leave events if we passed from an element to another without move events
if (currentTouchedElement != lastTouchedElement)
ThrowEnterAndLeaveTouchEvents(currentTouchedElement, lastTouchedElement, touchEvent);
// then raise leave event to all the hierarchy of the previously selected element.
var element = currentTouchedElement;
while (element != null)
{
if (element.IsTouched)
element.RaiseTouchLeaveEvent(touchEvent);
element = element.VisualParent;
}
break;
default:
throw new ArgumentOutOfRangeException();
}
lastTouchPosition = currentTouchPosition;
state.LastTouchedElement = currentTouchedElement;
state.LastIntersectionPoint = intersectionPoint;
}
}