"""Precise framerate calculation function scheduling. The :py:mod:`~pyglet.clock` module allows you to schedule functions to run periodically, or for one-shot future execution. pyglet's default event loop (:py:func:`~pyglet.app.run`) keeps an internal instance of a :py:class:`~pyglet.clock.Clock`, which is ticked automatically. .. note:: Some internal modules will schedule items on the clock. If you are using a custom event loop, always remember to `tick` the clock! Scheduling ========== You can schedule a function to be called every time the clock is ticked:: def callback(dt): print(f"{dt} seconds since last callback") clock.schedule(callback) The `schedule_interval` method causes a function to be called every "n" seconds:: clock.schedule_interval(callback, 0.5) # called twice a second The `schedule_once` method causes a function to be called once "n" seconds in the future:: clock.schedule_once(callback, 5) # called in 5 seconds All the `schedule` methods will pass on any additional args or keyword args you specify to the callback function:: def move(dt, velocity, sprite): sprite.position += dt * velocity clock.schedule(move, velocity=5.0, sprite=alien) You can cancel a function scheduled with any of these methods using `unschedule`:: clock.unschedule(move) Using multiple clocks ===================== The clock functions are all relayed to an instance of :py:class:`~pyglet.clock.Clock` which is initialised with the module. You can get this instance to use directly:: clk = pyglet.clock.get_default() You can also replace the default clock with your own: myclk = pyglet.clock.Clock() pyglet.clock.set_default(myclk) Each clock maintains its own set of scheduled functions and frequency measurement. Each clock must be "ticked" separately. Multiple and derived clocks potentially allow you to separate "game-time" and "wall-time", or to synchronise your clock to an audio or video stream instead of the system clock. """ from __future__ import annotations import time as _time from typing import Any, Callable from heapq import heappop as _heappop from heapq import heappush as _heappush from heapq import heappushpop as _heappushpop from operator import attrgetter as _attrgetter from collections import deque as _deque class _ScheduledItem: __slots__ = ['func', 'args', 'kwargs'] def __init__(self, func: Callable, args: Any, kwargs: Any) -> None: self.func = func self.args = args self.kwargs = kwargs class _ScheduledIntervalItem: __slots__ = ['func', 'interval', 'last_ts', 'next_ts', 'args', 'kwargs'] def __init__(self, func: Callable, interval: float, last_ts: float, next_ts: float, args: Any, kwargs: Any) -> None: self.func = func self.interval = interval self.last_ts = last_ts self.next_ts = next_ts self.args = args self.kwargs = kwargs def __lt__(self, other: _ScheduledIntervalItem) -> bool: return self.next_ts < other.next_ts class Clock: # List of functions to call every tick. _schedule_items: list # List of schedule interval items kept in sort order. _schedule_interval_items: list # If True, a sleep(0) is inserted on every tick. _force_sleep: bool = False def __init__(self, time_function: Callable = _time.perf_counter) -> None: """Initialise a Clock, with optional custom time function. You can provide a custom time function to return the elapsed time of the application, in seconds. Defaults to ``time.perf_counter``, but can be replaced to allow for easy time dilation effects or game pausing. """ self.time = time_function self.last_ts = None self.next_ts = self.time() # Used by self.get_frequency to show update frequency self.times: _deque = _deque() self.cumulative_time = 0.0 self.window_size = 60 self._schedule_items = [] self._schedule_interval_items = [] self._current_interval_item = None @staticmethod def sleep(microseconds: float) -> None: _time.sleep(microseconds * 1e-6) def update_time(self) -> float: """Get the elapsed time since the last call to `update_time`. This updates the clock's internal measure of time and returns the difference (in seconds) since the last time it was called. The first call of this method always returns 0. """ ts = self.time() if self.last_ts is None: delta_t = 0.0 else: delta_t = ts - self.last_ts self.times.appendleft(delta_t) if len(self.times) > self.window_size: self.cumulative_time -= self.times.pop() self.cumulative_time += delta_t self.last_ts = ts return delta_t def call_scheduled_functions(self, dt: float) -> bool: """Call scheduled functions that elapsed on the last `update_time`. This method is called automatically when the clock is ticked (see :py:meth:`~pyglet.clock.tick`), so you need not call it yourself in most cases. Args: dt: The elapsed time since the last update to pass to each scheduled function. This is *not* used to calculate which functions have elapsed. Returns: ``True`` if any functions were called, else ``False``. """ now = self.last_ts or self.time() result = False # flag indicates if any function was called # handle items scheduled for every tick if self._schedule_items: result = True # duplicate list in case event unschedules itself for item in list(self._schedule_items): item.func(dt, *item.args, **item.kwargs) # check the next scheduled item that is not called each tick # if it is scheduled in the future, then exit interval_items = self._schedule_interval_items try: if interval_items[0].next_ts > now: return result except IndexError: # The interval_items list is empty return result # NOTE: there is no special handling required to manage things # that are scheduled during this loop, due to the heap self._current_interval_item = item = None get_soft_next_ts = self._get_soft_next_ts while interval_items: # the scheduler will hold onto a reference to an item in # case it needs to be rescheduled. it is more efficient # to push and pop the heap at once rather than two operations if item is None: item = _heappop(interval_items) else: item = _heappushpop(interval_items, item) # a scheduled function may try to unschedule itself, # so we need to keep a reference to the current # item no longer on heap to be able to check self._current_interval_item = item # if next item is scheduled in the future then break if item.next_ts > now: break # execute the callback item.func(now - item.last_ts, *item.args, **item.kwargs) if item.interval: # Try to keep timing regular, even if overslept this time; # but don't schedule in the past (which could lead to # infinitely-worsening error). item.next_ts = item.last_ts + item.interval item.last_ts = now # test the schedule for the next execution if item.next_ts <= now: # the scheduled time of this item has already # passed, so it must be rescheduled if now - item.next_ts < 0.05: # missed execution time by 'reasonable' amount, so # reschedule at normal interval item.next_ts = now + item.interval else: # missed by significant amount, now many events have # likely missed execution. do a soft re-schedule to # avoid lumping many events together. # in this case, the next dt will not be accurate item.next_ts = get_soft_next_ts(now, item.interval) item.last_ts = item.next_ts - item.interval else: # not an interval, so this item will not be rescheduled self._current_interval_item = item = None if item is not None: _heappush(interval_items, item) return True def tick(self, poll: bool = False) -> float: """Signify that one frame has passed. This will call any scheduled functions that have elapsed, and returns the number of seconds since the last time this method has been called. The first time this method is called, 0 is returned. Args: poll: If True, the function will call any scheduled functions but will not sleep or busy-wait for any reason. Recommended for advanced applications managing their own sleep timers only. """ if not poll and self._force_sleep: self.sleep(0) delta_t = self.update_time() self.call_scheduled_functions(delta_t) return delta_t def get_sleep_time(self, sleep_idle: bool) -> float | None: """Get the time until the next item is scheduled, if any. Applications can choose to continue receiving updates at the maximum framerate during idle time (when no functions are scheduled), or they can sleep through their idle time and allow the CPU to switch to other processes or run in low-power mode. If ``sleep_idle`` is ``True`` the latter behaviour is selected, and ``None`` will be returned if there are no scheduled items. Otherwise, if ``sleep_idle`` is ``False``, or if any scheduled items exist, a value of 0 is returned. Args: sleep_idle: If True, the application intends to sleep through its idle time; otherwise it will continue ticking at the maximum frame rate allowed. """ if self._schedule_items or not sleep_idle: return 0.0 if self._schedule_interval_items: return max(self._schedule_interval_items[0].next_ts - self.time(), 0.0) return None def get_frequency(self) -> float: """Get the average clock update frequency of recent history. The result is the average of a sliding window of the last "n" updates, where "n" is some number designed to cover approximately 1 second. This is the clock frequence, **not** the Window redraw rate (fps). """ if not self.cumulative_time: return 0 return len(self.times) / self.cumulative_time def _get_nearest_ts(self) -> float: """Get the nearest timestamp. Schedule from now, unless now is sufficiently close to last_ts, in which case use last_ts. This clusters together scheduled items that probably want to be scheduled together. """ last_ts = self.last_ts or self.next_ts ts = self.time() if ts - last_ts > 0.2: return ts return last_ts def _get_soft_next_ts(self, last_ts: float, interval: float) -> float: def taken(ts: float, e: float) -> bool: """Check if `ts` has already got an item scheduled nearby.""" # TODO this function is slow and called very often. # Optimise it, maybe? for item in self._schedule_interval_items: if abs(item.next_ts - ts) <= e: return True elif item.next_ts > ts + e: return False return False # sorted list is required to produce expected results # taken() will iterate through the heap, expecting it to be sorted # and will not always catch the smallest value, so sort here. # do not remove the sort key...it is faster than relaying comparisons # NOTE: do not rewrite as popping from heap, as that is super slow! self._schedule_interval_items.sort(key=_attrgetter('next_ts')) # Binary division over interval: # # 0 interval # |--------------------------| # 5 3 6 2 7 4 8 1 Order of search # # i.e., first scheduled at interval, # then at interval/2 # then at interval/4 # then at interval*3/4 # then at ... # # Schedule is hopefully then evenly distributed for any interval, # and any number of scheduled functions. next_ts = last_ts + interval if not taken(next_ts, interval / 4): return next_ts dt = interval divs = 1 while True: next_ts = last_ts for _ in range(divs - 1): next_ts += dt if not taken(next_ts, dt / 4): return next_ts dt /= 2 divs *= 2 # Avoid infinite loop in pathological case if divs > 16: return next_ts def schedule(self, func: Callable, *args: Any, **kwargs: Any) -> None: """Schedule a function to be called every tick. The scheduled function should have a prototype that includes ``dt`` as the first argument, which gives the elapsed time in seconds since the last clock tick. Any additional args or kwargs given to this method are passed on to the callback:: def callback(dt, *args, **kwargs): pass .. note:: Functions scheduled using this method will be called every tick by the default pyglet event loop, which can lead to high CPU usage. It is usually better to use :py:meth:`~pyglet.clock.schedule_interval` unless this is desired. """ item = _ScheduledItem(func, args, kwargs) self._schedule_items.append(item) def schedule_once(self, func: Callable, delay: float, *args: Any, **kwargs: Any) -> None: """Schedule a function to be called once after ``delay`` seconds. The callback function prototype is the same as for :py:meth:`~pyglet.clock.Clock.schedule`. """ last_ts = self._get_nearest_ts() next_ts = last_ts + delay item = _ScheduledIntervalItem(func, 0, last_ts, next_ts, args, kwargs) _heappush(self._schedule_interval_items, item) def schedule_interval(self, func: Callable, interval: float, *args: Any, **kwargs: Any) -> None: """Schedule a function to be called every ``interval`` seconds. To schedule a function to be called at 60Hz (60fps), you would use ``1/60`` for the interval, and so on. If pyglet is unable to call the function on time, the schedule will be skipped (not accumulated). This can occur if the main thread is overloaded, or other hard blocking calls taking place. The callback function prototype is the same as for :py:meth:`~pyglet.clock.Clock.schedule`. .. note:: Specifying an interval of ``0`` will prevent the function from being called again. If you want to schedule a function to be called as often as possible, see :py:meth:`~pyglet.clock.Clock.schedule`. """ last_ts = self._get_nearest_ts() next_ts = last_ts + interval item = _ScheduledIntervalItem(func, interval, last_ts, next_ts, args, kwargs) _heappush(self._schedule_interval_items, item) def schedule_interval_for_duration(self, func: Callable, interval: float, duration: float, *args: Any, **kwargs: Any) -> None: """Temporarily schedule a function to be called every ``interval`` seconds. This method will schedule a function to be called every ``interval`` seconds (see :py:meth:`~pyglet.clock.Clock.schedule_interval`), but will automatically unschedule it after ``duration`` seconds. The callback function prototype is the same as for :py:meth:`~pyglet.clock.Clock.schedule`. :Args: func: The function to call when the timer lapses. interval: The number of seconds to wait between each call. duration: The number of seconds for which the function is scheduled. """ # NOTE: unschedule wrapper that takes `dt` argument def _unschedule(_dt: float, _func: Callable) -> None: self.unschedule(_func) self.schedule_interval(func, interval, *args, **kwargs) self.schedule_once(_unschedule, duration, func) def schedule_interval_soft(self, func: Callable, interval: float, *args: Any, **kwargs: Any) -> None: """Schedule a function to be called approximately every ``interval`` seconds. This method is similar to :py:meth:`~pyglet.clock.Clock.schedule_interval`, except that the clock will move the interval out of phase with other scheduled functions in order to distribute CPU load more evenly. This is useful for functions that need to be called regularly, but not relative to the initial start time. :py:mod:`pyglet.media` does this for scheduling audio buffer updates, which need to occur regularly -- if all audio updates are scheduled at the same time (for example, mixing several tracks of a music score, or playing multiple videos back simultaneously), the resulting load on the CPU is excessive for those intervals but idle outside. Using the soft interval scheduling, the load is more evenly distributed. Soft interval scheduling can also be used as an easy way to schedule graphics animations out of phase; for example, multiple flags waving in the wind. """ next_ts = self._get_soft_next_ts(self._get_nearest_ts(), interval) last_ts = next_ts - interval item = _ScheduledIntervalItem(func, interval, last_ts, next_ts, args, kwargs) _heappush(self._schedule_interval_items, item) def unschedule(self, func: Callable) -> None: """Remove a function from the schedule. If the function appears in the schedule more than once, all occurrences are removed. If the function was not scheduled, no error is raised. """ # clever remove item without disturbing the heap: # 1. set function to an empty lambda -- original function is not called # 2. set interval to 0 -- item will be removed from heap eventually valid_items = {item for item in self._schedule_interval_items if item.func == func} if self._current_interval_item and self._current_interval_item.func == func: valid_items.add(self._current_interval_item) for item in valid_items: item.interval = 0 item.func = lambda x, *args, **kwargs: x self._schedule_items = [i for i in self._schedule_items if i.func != func] # Default clock. _default = Clock() def set_default(default: Clock) -> None: """Set the default clock to use for all module-level functions. By default, an instance of :py:class:`~pyglet.clock.Clock` is used. """ global _default _default = default def get_default() -> Clock: """Get the pyglet default Clock. Return the :py:class:`~pyglet.clock.Clock` instance that is used by all module-level clock functions. """ return _default def tick(poll: bool = False) -> float: """:see: :py:meth:`~pyglet.clock.Clock.tick`.""" return _default.tick(poll) def get_sleep_time(sleep_idle: bool) -> float | None: """:see: :py:meth:`~pyglet.clock.Clock.get_sleep_time`.""" return _default.get_sleep_time(sleep_idle) def get_frequency() -> float: """:see: :py:meth:`~pyglet.clock.Clock.get_frequency`.""" return _default.get_frequency() def schedule(func: Callable, *args: Any, **kwargs: Any) -> None: """:see: :py:meth:`~pyglet.clock.Clock.schedule`.""" _default.schedule(func, *args, **kwargs) def schedule_interval(func: Callable, interval: float, *args: Any, **kwargs: Any) -> None: """:see: :py:meth:`~pyglet.clock.Clock.schedule_interval`.""" _default.schedule_interval(func, interval, *args, **kwargs) def schedule_interval_for_duration(func: Callable, interval: float, duration: float, *args, **kwargs) -> None: """:see: :py:meth:`~pyglet.clock.Clock.schedule_interval_for_duration`.""" _default.schedule_interval_for_duration(func, interval, duration, *args, **kwargs) def schedule_interval_soft(func: Callable, interval: float, *args, **kwargs) -> None: """:see: :py:meth:`~pyglet.clock.Clock.schedule_interval_soft`.""" _default.schedule_interval_soft(func, interval, *args, **kwargs) def schedule_once(func: Callable, delay: float, *args, **kwargs) -> None: """:see: :py:meth:`~pyglet.clock.Clock.schedule_once`.""" _default.schedule_once(func, delay, *args, **kwargs) def unschedule(func: Callable) -> None: """:see: :py:meth:`~pyglet.clock.Clock.unschedule`.""" _default.unschedule(func)