Experimental new version of the window which provides a fixed update. (#1944)

* Started working on Clock and Timer classes

* Mostly finished clock and timer

* Created the updated window class

The fixed update implementation is created, but classes to access the clocks and other variables is still necessary.

* Tired best to fix linting.

Can't fix a few issues due to it being an experimental view/window.

* Add __init__.py for clock in experimental

* Top-level docstring and experimental.clock.clock_window.Window docstring fixes

* Add fixed update None return annotations

* Fix missing annotation on TextureAnimationSprite._animation

* Use nasty typing tricks to make mypy pass

* Fix no newline to make ruff pass

---------

Co-authored-by: pushfoo <36696816+pushfoo@users.noreply.github.com>

Author: DragonMoffon

arcade/experimental/clock/__init__.py

@@ -0,0 +1,21 @@
+"""Experimental fixed update support.
+
+.. warning:: The classes in this module have incomplete typing!
+
+             Using them in your projects may make your IDE or type checker
+             complain. Pull requests welcome.
+
+See the following pull request for more information:
+`https://github.com/pythonarcade/arcade/pull/1944`_
+"""
+from arcade.experimental.clock.timer import Timer
+from arcade.experimental.clock.clock import Clock
+from arcade.experimental.clock.clock_window import View, Window
+
+
+__all__ = [
+    "Timer",
+    "Clock",
+    "View",
+    "Window"
+]

arcade/experimental/clock/clock.py

@@ -0,0 +1,142 @@
+from typing import Optional, Set
+from arcade.experimental.clock.timer import Timer
+
+
+class Clock:
+    """
+    A clock for managing elapsed time, delta time, and timers
+
+    A clock has a tick method that can either be called directly
+    or is called by its parent clock. If a clock has a parent
+    DO NOT CALL its tick method.
+
+    A clock can have any number of child timers or clocks.
+    The children and timers are stored in unordered sets, therefore
+    the properties which return them make no promises on the order.
+
+    The tick speed of a clock is how fast time elapses for it.
+
+    When a clock calls tick on its children it passes its modified delta_time
+
+    Arcade's clocks are synchronous. No matter how long an update takes
+    all queries to a clock's elapsed time will be the same. This ensures
+    that two objects who have the same lifespan and are created at the
+    same time will die on the same frame in the future.
+    """
+
+    def __init__(self, *,
+                 tick_speed: float = 1.0,
+                 initial_elapsed_time: float = 0.0,
+                 initial_tick_count: int = 0,
+                 frozen: bool = False,
+                 parent: Optional["Clock"] = None
+                 ):
+        self.tick_speed: float = tick_speed
+        self._frozen: bool = frozen
+
+        self._elapsed_time: float = initial_elapsed_time
+        self._tick_count: int = initial_tick_count
+
+        self._parent: Optional[Clock] = parent
+
+        self._children: Set[Clock] = set()
+        self._timers: Set[Timer] = set()
+
+        self._delta_time_raw: float = 0.0
+
+    def tick(self, delta_time: float):
+        self._tick_count += 1
+        if self._frozen:
+            return
+        self._delta_time_raw = delta_time
+
+        self._elapsed_time = self._delta_time_raw * self.tick_speed
+
+        for child in tuple(self._children):
+            child.tick(self._delta_time_raw * self.tick_speed)
+
+        for timer in tuple(self._timers):
+            if timer.complete:
+                timer.kill()
+            timer.check()
+
+    #def create_new_child(self, *,
+    #                     tick_speed: float = 1.0,
+    #                     inherit_elapsed: bool = False,
+    #                     inherit_count: bool = False,
+    #                     lifespan: float = 0.0
+    #                    ) -> "Clock":
+    #    pass
+
+    #def create_new_timer(self, duration: float, callback: Callable,
+    #                     *args,
+    #                     **kwargs
+    #                     ) -> Timer:
+    #    pass
+
+    def add_clock(self, new_child: "Clock"):
+        pass
+
+    def add_timer(self, new_timer: Timer):
+        pass
+
+    def free(self):
+        if self._parent:
+            self._parent.pop_child(self)
+
+    def time_since(self, start: float):
+        return self._elapsed_time - start
+
+    @property
+    def delta_time(self):
+        return self._delta_time_raw * self._tick_speed
+
+    @property
+    def delta_time_raw(self):
+        return self._delta_time_raw
+
+    @property
+    def elapsed(self):
+        return self._elapsed_time
+
+    @property
+    def frozen(self):
+        return self._frozen
+
+    def freeze(self):
+        self._frozen = True
+
+    def unfreeze(self):
+        self._frozen = False
+
+    def toggle_frozen(self) -> bool:
+        self._frozen = bool(1 - self._frozen)
+        return self._frozen
+
+    @property
+    def children(self):
+        return tuple(self._children)
+
+    def pop_child(self, child: "Clock"):
+        pass
+
+    @property
+    def timers(self):
+        return tuple(self._timers)
+
+    def pop_timer(self, timer: Timer):
+        """
+        Popping a timer allows you to remove a timer from a clock without destroying the timer.
+        """
+        pass
+
+    @property
+    def parent(self):
+        return self._parent
+
+    def transfer_parent(self, new_parent):
+        pass
+
+    @property
+    def tick_count(self):
+        return self._tick_count