Merge #316

316: Move things, break loops r=pathunstrom a=astronouth7303

Grab a u-haul! 🚚 

Generally moving things and reducing imports to improve the import loop situation

* Break up "the machinery implementing a thing" and "a pile of things that use the thing"
* Prefer module imports to individual imports, so any unavoidable loops don't wreck everything.

Depends on #306 because I didn't feel like dealing with the merge conflict.

No docs changes because this doesn't touch anything publicly documented.

Co-authored-by: Jamie Bliss <jamie@ivyleav.es>

ppb/assets.py

@@ -7,7 +7,7 @@
 import threading
 
 import ppb.vfs as vfs
-from ppb.systems import System
+from ppb.systemslib import System
 
 __all__ = 'Asset', 'AssetLoadingSystem',
 

ppb/camera.py

@@ -1,7 +1,7 @@
 from typing import Sequence
 from numbers import Number
 
-from ppb import Vector
+from ppb_vector import Vector
 from ppb.sprites import BaseSprite
 from ppb.flags import DoNotRender
 

ppb/engine.py

@@ -11,10 +11,8 @@
 from typing import Union
 
 import ppb.events as events
-from ppb.events import StartScene
-from ppb.events import EventMixin
-from ppb.events import Quit
-from ppb.systems import PygameEventPoller
+from ppb.eventlib import EventMixin
+from ppb.systems import EventPoller
 from ppb.systems import Renderer
 from ppb.systems import Updater
 from ppb.assets import AssetLoadingSystem
@@ -27,7 +25,7 @@
 class GameEngine(EventMixin, LoggingMixin):
 
     def __init__(self, first_scene: Type, *,
-                 basic_systems=(Renderer, Updater, PygameEventPoller, AssetLoadingSystem),
+                 basic_systems=(Renderer, Updater, EventPoller, AssetLoadingSystem),
                  systems=(), scene_kwargs=None, **kwargs):
 
         super(GameEngine, self).__init__()
@@ -135,7 +133,7 @@ def publish(self):
             for game_object in scene:
                 game_object.__event__(event, self.signal)
 
-    def on_start_scene(self, event: StartScene, signal: Callable[[Any], None]):
+    def on_start_scene(self, event: events.StartScene, signal: Callable[[Any], None]):
         """
         Start a new scene. The current scene pauses.
         """
@@ -159,7 +157,7 @@ def on_replace_scene(self, event: events.ReplaceScene, signal):
         self.stop_scene()
         self.start_scene(event.new_scene, event.kwargs)
 
-    def on_quit(self, quit_event: Quit, signal: Callable[[Any], None]):
+    def on_quit(self, quit_event: events.Quit, signal: Callable[[Any], None]):
         self.running = False
 
     def pause_scene(self):

ppb/eventlib.py

@@ -0,0 +1,67 @@
+"""
+The event machinery
+"""
+
+import logging
+import re
+
+__all__ = (
+    'EventMixin', 'BadEventHandlerException',
+)
+
+boundaries_finder = re.compile('(.)([A-Z][a-z]+)')
+boundaries_finder_2 = re.compile('([a-z0-9])([A-Z])')
+
+
+def camel_to_snake(txt):
+    s1 = boundaries_finder.sub(r'\1_\2', txt)
+    return boundaries_finder_2.sub(r'\1_\2', s1).lower()
+
+
+class BadEventHandlerException(TypeError):
+
+    def __init__(self, instance, method, event):
+        object_type = type(instance)
+        event_type = type(event)
+        o_name = object_type.__name__
+        e_name = event_type.__name__
+        article = ['a', 'an'][int(e_name.lower()[0] in "aeiou")]
+
+        message = f"""
+{o_name}.{method}() signature incorrect, it should accept {article} {e_name} object and a signal function.
+
+{e_name} is a dataclass that represents an event. Its attributes 
+tell you about the event.
+
+The signal function is a function you can call that accepts an event instance
+as its only parameter. Call it to add an event to the queue. You don't have to
+use it, but it is a mandatory argument provided by ppb.
+
+It should look like this:
+
+def {method}({e_name.lower()}_event: {e_name}, signal_function):
+    (Your code goes here.)
+"""
+        super().__init__(message)
+
+
+class EventMixin:
+    def __event__(self, bag, fire_event):
+        elog = logging.getLogger('game.events')
+
+        name = camel_to_snake(type(bag).__name__)
+        meth_name = 'on_' + name
+        meth = getattr(self, meth_name, None)
+        if callable(meth):
+            try:
+                elog.debug(f"Calling handler {meth} for {name}")
+                meth(bag, fire_event)
+            except TypeError as ex:
+                from inspect import signature
+                sig = signature(meth)
+                try:
+                    sig.bind(bag, fire_event)
+                except TypeError:
+                    raise BadEventHandlerException(self, meth_name, bag) from ex
+                else:
+                    raise

ppb/events.py

@@ -1,6 +1,7 @@
+"""
+A big pile of the events defined in PPB.
+"""
 from dataclasses import dataclass
-import logging
-import re
 from typing import Any
 from typing import Collection
 from typing import Dict
@@ -11,7 +12,6 @@
 
 __all__ = (
     'StartScene',
-    'EventMixin',
     'PreRender',
     'Quit',
     'Render',
@@ -24,63 +24,6 @@
     'Update',
 )
 
-boundaries_finder = re.compile('(.)([A-Z][a-z]+)')
-boundaries_finder_2 = re.compile('([a-z0-9])([A-Z])')
-
-def camel_to_snake(txt):
-    s1 = boundaries_finder.sub(r'\1_\2', txt)
-    return boundaries_finder_2.sub(r'\1_\2', s1).lower()
-
-
-class BadEventHandlerException(TypeError):
-
-    def __init__(self, instance, method, event):
-        object_type = type(instance)
-        event_type = type(event)
-        o_name = object_type.__name__
-        e_name = event_type.__name__
-        article = ['a', 'an'][int(e_name.lower()[0] in "aeiou")]
-
-        message = f"""
-{o_name}.{method}() signature incorrect, it should accept {article} {e_name} object and a signal function.
-
-{e_name} is a dataclass that represents an event. Its attributes 
-tell you about the event.
-
-The signal function is a function you can call that accepts an event instance
-as its only parameter. Call it to add an event to the queue. You don't have to
-use it, but it is a mandatory argument provided by ppb.
-
-It should look like this:
-
-def {method}({e_name.lower()}_event: {e_name}, signal_function):
-    (Your code goes here.)
-"""
-        super().__init__(message)
-
-
-class EventMixin:
-    def __event__(self, bag, fire_event):
-        elog = logging.getLogger('game.events')
-
-        name = camel_to_snake(type(bag).__name__)
-        meth_name = 'on_' + name
-        meth = getattr(self, meth_name, None)
-        if callable(meth):
-            try:
-                elog.debug(f"Calling handler {meth} for {name}")
-                meth(bag, fire_event)
-            except TypeError as ex:
-                from inspect import signature
-                sig = signature(meth)
-                try:
-                    sig.bind(bag, fire_event)
-                except TypeError:
-                    raise BadEventHandlerException(self, meth_name, bag) from ex
-                else:
-                    raise
-
-
 # Remember to define scene at the end so the pargs version of __init__() still works
 
 from ppb.scenes import BaseScene

ppb/features/twophase.py

@@ -2,8 +2,8 @@
 A system for two phase updates: Update, and Commit.
 """
 from dataclasses import dataclass
-from ppb.systems import System
-from ppb.events import EventMixin
+from ppb.systemslib import System
+from ppb.eventlib import EventMixin
 
 __all__ = 'Commit',
 

ppb/scenes.py

@@ -9,7 +9,7 @@
 from typing import Type
 
 from ppb.camera import Camera
-from ppb.events import EventMixin
+from ppb.eventlib import EventMixin
 
 
 class GameObjectCollection(Collection):

ppb/sprites.py

@@ -4,7 +4,7 @@
 
 import ppb
 from ppb import Vector
-from ppb.events import EventMixin
+from ppb.eventlib import EventMixin
 from ppb.utils import FauxFloat
 
 import ppb_vector