A basic scenes manager for Pyglet

scenes_manager.py

from typing import Any, Type

import pyglet


class Scene:
    """Base class for a scene."""
    
    def __init__(self, window: pyglet.window.Window, state: Any = None) -> None:
        self.window = window
        self.state = state
    
    def draw(self) -> None:
        """Draws the scene.

        This method is called on every frame similar to `pyglet.window.Window.draw()`
        and is used to draw the scene.
        """

    def on_load(self) -> None:
        """Hook for when scene is loaded.
        
        This method is called when a scene is initially loaded
        and could be overridden for any kind of preprocessing.
        """

    def on_unload(self) -> None:
        """Hook for when scene is unloaded.
        
        This method is called when a scene is unloaded (i.e. another
        scene is loaded) and could be overridden for any kind of
        preprocessing.
        """
 

class ScenesManager:
    """Scenes manager managing transitions between scenes.
    
    Parameters
    ----------
    window: pyglet.window.Window
        The pyglet window instance.
    """
    
    def __init__(self, window: pyglet.window.Window) -> None:
        self._window = window
        self._current_scene = None

    def get_current_scene(self) -> Scene:
        """Gets current scene.
        
        Raises ValueError if no scene is set.
        """
        if self._current_scene is None:
            raise ValueError("no scene set")

        return self._current_scene            

    def load(self, scene: Type[Scene], state: Any = None) -> None:
        """Loads a scene.
        
        The previous scene is unloaded and its `Scene.on_unload` hook
        is called and the scene being loaded is setup and its `Scene.on_load`
        hook is called.
        
        Parameters
        ----------
        scene: Type[Scene]
            The scene class to load.
        """
        if self._current_scene:
            self._current_scene.on_unload()

        self._current_scene = scene(self._window, state)
        self._current_scene.on_load()
    
    def draw(self, clear_window: bool = True) -> None:
        """Calls the draw method of the current scene.
        
        This also clears the window before drawing the scene
        unless `clear_window` is set to `False`.
        
        If no scene is set, this method does nothing.
        """
        if self._current_scene is None:
            return
        if clear_window:
            self._window.clear()
        
        self._current_scene.draw()