/// <summary>
/// Implements copy functionalty for GetAsFrozenCore and GetCurrentValueAsFrozenCore
/// Timeline does not need to override CloneCore and CloneCurrentValueCore.
/// </summary>
/// <param name="sourceTimeline"></param>
private void CopyCommon(Timeline sourceTimeline)
{
// When creating a frozen copy of a Timeline we want to copy the
// event handlers. This is for two reasons
//
// 1.) Internally when creating a clock tree we use
// a frozen copy of the timing tree. If that frozen
// copy does not preserve the event handlers then
// any callbacks registered on the Timelines will be lost.
//
// 2.) GetAsFrozen and GetCurrentValueAsFrozen don't always clone.
// If any object in the tree is frozen it'll simply return it.
// If we did not copy the event handlers GetAsFrozen
// would return different results depending on whether a
// Timeline was frozen before the call.
//
//
// The other two clone methods make unfrozen clones, so it's consisent
// to not copy the event handlers for those methods. Cloning an object
// is basically the only way to get a 'fresh' copy without event handlers
// attached. If someone wants a frozen clone they probably want an exact
// copy of the original.
EventHandlersStore sourceStore = EventHandlersStoreField.GetValue(sourceTimeline);
if (sourceStore != null)
{
Debug.Assert(sourceStore.Count > 0);
EventHandlersStoreField.SetValue(this, new EventHandlersStore(sourceStore));
}
}
/// <summary>
/// Adds a delegate to the list of event handlers on this object.
/// </summary>
/// <param name="key">
/// A unique identifier for the event handler.
/// </param>
/// <param name="handler">The delegate to add.</param>
private void AddEventHandler(EventPrivateKey key, Delegate handler)
{
WritePreamble();
EventHandlersStore store = EventHandlersStoreField.GetValue(this);
if (store == null)
{
store = new EventHandlersStore();
EventHandlersStoreField.SetValue(this, store);
}
store.Add(key, handler);
WritePostscript();
}
/// <summary>
/// Removes a delegate from the list of event handlers on this object.
/// </summary>
/// <param name="key">
/// A unique identifier for the event handler.
/// </param>
/// <param name="handler">The delegate to remove.</param>
private void RemoveEventHandler(EventPrivateKey key, Delegate handler)
{
WritePreamble();
EventHandlersStore store = EventHandlersStoreField.GetValue(this);
if (store != null)
{
store.Remove(key, handler);
if (store.Count == 0)
{
// last event handler was removed -- throw away underlying EventHandlersStore
EventHandlersStoreField.ClearValue(this);
}
WritePostscript();
}
}