def register_listener(self, listener, event_types='all'):
"""
Add a listener to this event_dispatcher.
Any object with an ``on_event`` method can be added as a listener. This
method should accept BearEvent as a single argument and return either
nothing, or a single BearEvent, or a list of BearEvents.
To choose event types to subscribe to, ``event_types`` kwarg can be
set to a string or an iterable of strings. If an iterable, its elements
should be event types the listener subscribes to.
If a string, the following rules apply:
1. If a string equals 'all', the listener is subscribed to all currently
registered event types.
2. Elif a string starts with '*', the listener is subscribed to all
currently registered event types for whose type ``event_types[1:]`` is a
substring (regardless of its position). For example, '*ecs' subscribes
to all ECS events, like 'ecs_add', 'ecs_move', 'ecs_remove' and so on;
'*move' would subscribe only to 'ecs_move' and 'ecs_remove'.
3. Else a string is interpreted as a single event type.
Whether in list or string, unregistered event types raise
BearLoopException.
:param listener: a listener to add.
:param event_types: event types to which it wants to subscribe
"""
if not hasattr(listener, 'on_event'):
raise BearLoopException('Cannot add an object without on_event' +
' method as a listener')
if isinstance(event_types, str):
if event_types == 'all':
# Subscribing to all events
types = self.listeners.keys()
elif event_types[0] == '*':
# Subscribing to a group of events
types = []
mask = event_types[1:]
for event_type in self.listeners:
if mask in event_type:
types.append(event_type)
else:
# Subscribing to a single event type
types = [event_types]
else:
# Subscribing to a list of event types
types = event_types
for event_type in types:
try:
self.listeners[event_type].append(listener)
except KeyError:
# The incorrect list elements or single value processed here
raise BearLoopException('Unknown event class {}'.format(
event_type))
def add_event(self, event):
"""
Add a BearEvent to the queue.
:param event:
:return:
"""
if not isinstance(event, BearEvent):
raise BearLoopException('Only BearEvents can be added to queue')
if event.event_type not in self.event_types:
raise BearLoopException('Incorrect event type \"{}\"'.format(
event.event_type))
self.deque.append(event)
def unregister_listener(self, listener, event_types='all'):
"""
Unsubscribe a listener from all or some of its event types.
:param listener: listener to unsubscribe
:param event_types: a list of event types to unsubscribe from or 'all'. Defaults to 'all'
"""
if event_types == 'all':
event_types = self.listeners.keys()
for event_type in event_types:
if listener in self.listeners[event_type]:
try:
self.listeners[event_type].remove(listener)
except KeyError:
raise BearLoopException(f'Attempting to unsubscribe from nonexistent event type {event_type}')
def dispatch_events(self):
"""
Dispatch all the events to their listeners.
Whatever they return is added to the queue.
"""""
while len(self.deque) > 0:
e = self.deque.popleft()
for listener in self.listeners[e.event_type]:
r = listener.on_event(e)
if r:
if isinstance(r, BearEvent):
self.add_event(r)
elif isinstance(r, list):
for event in r:
self.add_event(event)
else:
raise BearLoopException('on_event returns something ' +
'other than BearEvent')
def fps(self, value):
if not isinstance(value, int):
raise BearLoopException('Only int acceptable as FPS')
self.frame_time = 1/value