internal void AssignEventHandlerId(ref RenderTreeFrame frame)
{
var id = ++_lastEventHandlerId;
_eventHandlersById.Add(id, (UIEventHandler)frame.AttributeValue);
frame = frame.WithAttributeEventHandlerId(id);
}
internal void AssignEventHandlerId(ref RenderTreeFrame frame)
{
var id = ++_lastEventHandlerId;
// The attribute value might be a more specialized type like UIKeyboardEventHandler.
// In that case, it won't be a UIEventHandler, and it will go down the MulticastDelegate
// code path (MulticastDelegate is any delegate).
//
// In order to dispatch the event, we need a UIEventHandler, so we're going weakly
// typed here. The user will get a cast exception if they map the wrong type of
// delegate to the event.
if (frame.AttributeValue is UIEventHandler wrapper)
{
_eventHandlersById.Add(id, wrapper);
}
else if (frame.AttributeValue is MulticastDelegate @delegate)
{
// IMPORTANT: we're creating an additional delegate when necessary. This is
// going to get cached in _eventHandlersById, but the render tree diff
// will operate on 'AttributeValue' which means that we'll only create a new
// wrapper delegate when the underlying delegate changes.
//
// TLDR: If the component uses a method group or a non-capturing lambda
// we don't allocate much.
_eventHandlersById.Add(id, (UIEventArgs e) => @delegate.DynamicInvoke(e));
}
frame = frame.WithAttributeEventHandlerId(id);
}
internal void AssignEventHandlerId(ref RenderTreeFrame frame)
{
var id = ++_lastEventHandlerId;
if (frame.AttributeValue is MulticastDelegate @delegate)
{
_eventBindings.Add(id, new EventHandlerInvoker(@delegate));
}
frame = frame.WithAttributeEventHandlerId(id);
}