1. Installation 1. Установка

Install both the PySDL3 bindings and the Box2D library for Python via pip:

Установите привязки PySDL3 и библиотеку Box2D для Python через pip:

2. Project Structure 2. Структура проекта

Create a folder named pysdl3-box2d with the following hierarchy:

Создайте папку с именем pysdl3-box2d со следующей иерархией:

pysdl3-box2d/
├── main.py
└── debug_drawer.py

3. Source Code (Callback System) 3. Исходный код (Система Callbacks)

PySDL3 relies on the SDL3 callback-based architecture. Ensure environment variables are set before importing sdl3. Copy this code into main.py:

PySDL3 опирается на архитектуру обратных вызовов (callbacks) SDL3. Убедитесь, что переменные среды установлены до импорта sdl3. Скопируйте этот код в файл main.py:

import ctypes
import math
import os

# 1. Set environment variables BEFORE importing sdl3
os.environ["SDL_MAIN_USE_CALLBACKS"] = "1"
os.environ["SDL_RENDER_DRIVER"] = "opengl"

import sdl3
from Box2D import (b2_dynamicBody, b2BodyDef, b2CircleShape, b2FixtureDef,
                    b2PolygonShape, b2Vec2, b2World)
from debug_drawer import DebugDrawer

renderer = ctypes.POINTER(sdl3.SDL_Renderer)()
window = ctypes.POINTER(sdl3.SDL_Window)()

world = b2World(gravity=b2Vec2(0, 9.8))
ppm = 30 # pixels per meter

@sdl3.SDL_AppInit_func
def SDL_AppInit(appstate, argc, argv):
    if not sdl3.SDL_Init(sdl3.SDL_INIT_VIDEO):
        return sdl3.SDL_APP_FAILURE
    if not sdl3.SDL_CreateWindowAndRenderer("Draw Box2D colliders".encode(), 500, 300, 0, window, renderer):
        return sdl3.SDL_APP_FAILURE

    sdl3.SDL_SetRenderVSync(renderer, 1)

    debugDrawer = DebugDrawer(renderer, ppm)
    debugDrawer.flags = { "drawShapes": True }
    world.renderer = debugDrawer

    # Example: Create a ground body
    groundBody = world.CreateBody(b2BodyDef(position=(250/ppm, 270/ppm)))
    groundBody.CreateFixture(shape=b2PolygonShape(box=(400/2/ppm, 40/2/ppm)), density=0)

    return sdl3.SDL_APP_CONTINUE

@sdl3.SDL_AppEvent_func
def SDL_AppEvent(appstate, event):
    if sdl3.SDL_DEREFERENCE(event).type == sdl3.SDL_EVENT_QUIT:
        return sdl3.SDL_APP_SUCCESS
    return sdl3.SDL_APP_CONTINUE

@sdl3.SDL_AppIterate_func
def SDL_AppIterate(appstate):
    sdl3.SDL_SetRenderDrawColor(renderer, 50, 50, 50, sdl3.SDL_ALPHA_OPAQUE)
    sdl3.SDL_RenderClear(renderer)

    world.Step(0.016, 3, 2)
    world.DrawDebugData()

    sdl3.SDL_RenderPresent(renderer)
    return sdl3.SDL_APP_CONTINUE

@sdl3.SDL_AppQuit_func
def SDL_AppQuit(appstate, result):
    sdl3.SDL_DestroyRenderer(renderer)
    sdl3.SDL_DestroyWindow(window)

4. Running the Application 4. Запуск приложения

Run the script via your terminal:

Запустите скрипт через терминал:

python main.py