/// <summary>
/// Returns the value unchanged, but subscribes to its events if it is itself
/// a ChangeableState. Designed to be used with read-only properties with
/// pre-initialized values.
/// </summary>
/// <typeparam name="T">The type of the value.</typeparam>
/// <param name="property">The name of the property the value will be assigned to.</param>
/// <param name="value">The value to subscribe to, if it is a ChangeableState.</param>
/// <returns></returns>
protected T Subscribe <T>(string property, T value)
{
if (value is ChangeableState newSubstate)
{
PropertyChangeEventHandler newHandler = (object sender, PropertyChangeEventArgs e) =>
{
this.OnPropertyChanged(property + "." + e.PropertyName, e.NewValue);
};
_substates[property] = new SubstateListener(newSubstate, newHandler);
newSubstate.PropertyChanged += newHandler;
}
return(value);
}
private void OnPropertyChanged(string propertyName, object newValue)
{
bool lockTaken = false;
bool iAmEntrant = false;
try
{
Monitor.Enter(_stateLock, ref lockTaken);
if (reentrant)
{
return; // prevent re-entry from substate update => prevents infinite loops
}
reentrant = iAmEntrant = true;
bool shouldUpdateSubstate = newValue is ChangeableState && ShouldUpdatePropertyAsSubstate(propertyName);
if (_substates.ContainsKey(propertyName)) // discard old substate regardless
{
SubstateListener substate = _substates[propertyName];
substate.State.PropertyChanged -= substate.Handler;
_substates.Remove(propertyName);
}
if (_pausedStateDirtySet != null) // paused?
{
_pausedStateDirtySet[propertyName] = newValue;
return;
}
if (shouldUpdateSubstate)
{
ChangeableState newSubstate = (ChangeableState)newValue;
PropertyChangeEventHandler newHandler = (object sender, PropertyChangeEventArgs e) =>
{
this.OnPropertyChanged(propertyName + "." + e.PropertyName, e.NewValue);
};
_substates[propertyName] = new SubstateListener(newSubstate, newHandler);
newSubstate.PropertyChanged += newHandler;
}
PropertyChanged?.Invoke(this, new PropertyChangeEventArgs(propertyName, newValue));
}
finally
{
reentrant &= !iAmEntrant;
if (lockTaken)
{
Monitor.Exit(_stateLock);
}
}
}