OpenSlides/openslides/utils/projector.py

75 lines
2.4 KiB
Python
Raw Normal View History

from django.dispatch import Signal
from .dispatch import SignalConnectMetaClass
class ProjectorElement(object, metaclass=SignalConnectMetaClass):
"""
Base class for an element on the projector.
Every app which wants to add projector elements has to create classes
subclassing from this base class with different names. The name attribute
has to be set. The metaclass (SignalConnectMetaClass) does the rest of the
magic.
"""
signal = Signal()
name = None
def __init__(self, **kwargs):
"""
Initializes the projector element instance. This is done when the
signal is sent.
Because of Django's signal API, we have to take wildcard keyword
arguments. But they are not used here.
"""
pass
@classmethod
def get_dispatch_uid(cls):
"""
Returns the classname as a unique string for each class. Returns None
for the base class so it will not be connected to the signal.
"""
if not cls.__name__ == 'ProjectorElement':
return cls.__name__
def check_and_update_data(self, projector_object, config_entry):
"""
Checks projector element data via self.check_data() and updates
them via self.update_data(). The projector object and the config
entry have to be given.
"""
self.projector_object = projector_object
self.config_entry = config_entry
assert self.config_entry.get('name') == self.name, (
'To get data of a projector element, the correct config entry has to be given.')
self.check_data()
return self.update_data() or {}
def check_data(self):
"""
Method can be overridden to validate projector element data. This
may raise ProjectorException in case of an error.
Default: Does nothing.
"""
pass
def update_data(self):
"""
Method can be overridden to update the projector element data
output. This should return a dictonary. Use this for server
calculated data which have to be forwared to the client.
Default: Does nothing.
"""
pass
def get_requirements(self, config_entry):
"""
Returns an iterable of instances that are required for this projector
element. The config_entry has to be given.
"""
return ()