Source code for pyface.timer.i_timer

# (C) Copyright 2005-2022 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
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"""
Interfaces and base classes for cross-toolkit timers

This module defines interfaces for toolkit event-loop based timers.  It also
provides a base implementation that can be easily specialized for a particular
back-end, and mixins that provide additional capabilities.
"""
from abc import abstractmethod
import time

from traits.api import (
    ABCHasTraits,
    Bool,
    Callable,
    Dict,
    Event,
    Float,
    HasTraits,
    Int,
    Interface,
    Property,
    Range,
    Tuple,
    provides,
    Union,
)

perf_counter = time.perf_counter


[docs]class ITimer(Interface): """ Interface for timer classes. This is a base interface which doesn't specify any particular notification mechanism. """ # ITimer interface ------------------------------------------------------- #: The interval at which to call the callback in seconds. interval = Range(low=0.0) #: The number of times to repeat the callback, or None if no limit. repeat = Union(None, Int) #: The maximum length of time to run in seconds, or None if no limit. expire = Union(None, Float) #: Whether or not the timer is currently running. active = Bool() # ------------------------------------------------------------------------- # ITimer interface # -------------------------------------------------------------------------
[docs] @classmethod def timer(cls, **traits): """ Convenience method that creates and starts a timer. """ pass
[docs] @classmethod def single_shot(cls, **traits): """ Convenience method that creates and starts a single-shot timer. """ pass
[docs] def start(self): """ Start the timer. """ pass
[docs] def stop(self): """ Stop the timer. """ pass
[docs] def perform(self): """ The method that will be called by the timer. """ pass
[docs]class IEventTimer(ITimer): """ Interface for timers which fire a trait event periodically. """ # IEventTimer interface -------------------------------------------------- #: A traits Event to fire when the callback happens. timeout = Event()
[docs]class ICallbackTimer(ITimer): """ Interface for timers which call a callback periodically. """ # ICallbackTimer interface ----------------------------------------------- #: The callback to make, or None if no callback. callback = Callable #: Positional arguments to give the callback. args = Tuple() #: Keyword arguments to give the callback. kwargs = Dict()
[docs]@provides(ITimer) class BaseTimer(ABCHasTraits): """ Base class for timer classes. This class has a class variable which tracks active timers to prevent failures caused by garbage collection. A timer is added to this tracker when it is started if the repeat value is not None. """ # BaseTimer interface ---------------------------------------------------- #: Class variable tracking all active timers. _active_timers = set() # ITimer interface ------------------------------------------------------- #: The interval at which to call the callback in seconds. interval = Range(low=0.0, value=0.05) #: The number of times to repeat the callback, or None if no limit. repeat = Union(None, Int) #: The maximum length of time to run in seconds, or None if no limit. expire = Union(None, Float) #: Property that controls the state of the timer. active = Property(Bool, observe="_active") # Private interface ------------------------------------------------------ #: Whether or not the timer is currently running. _active = Bool() #: The most recent start time. _start_time = Float() # ------------------------------------------------------------------------- # ITimer interface # -------------------------------------------------------------------------
[docs] @classmethod def timer(cls, **traits): """ Convenience method that creates and starts a timer. """ timer = cls(**traits) timer.start() return timer
[docs] @classmethod def single_shot(cls, **traits): timer = cls(repeat=1, **traits) timer.start() return timer
[docs] def start(self): """ Start the timer. """ if not self._active: if self.repeat is not None: self._active_timers.add(self) if self.expire is not None: self._start_time = perf_counter() self._active = True self._start()
[docs] def stop(self): """ Stop the timer. """ if self._active: self._active_timers.discard(self) self._stop() self._active = False
[docs] def perform(self): """ Perform the callback. The timer will stop if repeats is not None and less than 1, or if the `_perform` method raises StopIteration. """ if self.expire is not None: if perf_counter() - self._start_time > self.expire: self.stop() return if self.repeat is not None: self.repeat -= 1 try: self._perform() except StopIteration: self.stop() except: self.stop() raise else: if self.repeat is not None and self.repeat <= 0: self.stop() self.repeat = 0
# BaseTimer Protected methods def _start(self): """ Start the toolkit timer. Subclasses should overrided this method. """ raise NotImplementedError() def _stop(self): """ Stop the toolkit timer. Subclasses should overrided this method. """ raise NotImplementedError() @abstractmethod def _perform(self): """ perform the appropriate action. Subclasses should overrided this method. """ raise NotImplementedError() # ------------------------------------------------------------------------- # Private interface # ------------------------------------------------------------------------- # Trait property handlers ------------------------------------------------ def _get_active(self): return self._active def _set_active(self, value): if value: self.start() else: self.stop()
[docs]@provides(IEventTimer) class MEventTimer(HasTraits): """ Mixin for event timer classes. Other code can listen to the `timeout` event using standard traits listeners. """ # IEventTimer interface -------------------------------------------------- #: A traits Event to fire when the callback happens. timeout = Event() # ------------------------------------------------------------------------- # ITimer interface # ------------------------------------------------------------------------- # ITimer Protected methods ----------------------------------------------- def _perform(self): """ Fire the event. """ self.timeout = True
[docs]@provides(ITimer) class MCallbackTimer(HasTraits): """ Mixin for callback timer classes. """ # ICallbackTimer interface ----------------------------------------------- #: The callback to make. callback = Callable #: Positional arguments to give the callback. args = Tuple() #: Keyword arguments to give the callback. kwargs = Dict() # ------------------------------------------------------------------------- # ITimer interface # ------------------------------------------------------------------------- # ITimer Protected methods ----------------------------------------------- def _perform(self): """ Perform the callback. """ self.callback(*self.args, **self.kwargs)