315. Contador de FPS en main

Añade un contador de FPS periódico y sencillo a main.py.

Lección 315 de 356 · tests/chapter_10_performance/test_315_main_fps_counter.py

Archivo a actualizar

main.py

Por qué existe este paso

Antes de optimizar el renderizado con pygame o la velocidad del emulador, el ejecutor manual debería mostrar una señal sencilla de FPS de extremo a extremo en el terminal.

El contador de FPS debería medir la ruta completa del fotograma manual

Console.step_until_next_frame()
Console.render_framebuffer()
draw_framebuffer(...)
pygame.display.flip()

Ejemplo de implementación sugerida

import time

FPS_REPORT_INTERVAL_SECONDS = 1.0

...

running = True
last_fps_report_time = time.perf_counter()
frames_since_last_report = 0

while running:
    ...

    executed = console.step_until_next_frame()
    framebuffer = console.render_framebuffer()
    draw_framebuffer(window, framebuffer, SCALE)
    pygame.display.flip()

    frames_since_last_report += 1
    now = time.perf_counter()
    elapsed = now - last_fps_report_time

    if elapsed >= FPS_REPORT_INTERVAL_SECONDS:
        fps = frames_since_last_report / elapsed
        print(f"fps={fps:.1f}")
        frames_since_last_report = 0
        last_fps_report_time = now

Importante

Esto es intencionadamente sencillo. No separa el tiempo de emulación del tiempo de renderizado. Solo ofrece una señal visible en el terminal antes del trabajo de optimización.

¿Por qué tests de forma del código fuente? main.py abre pygame y ejecuta un bucle manual. Los tests automatizados no deben llamar a main(), abrir una ventana ni requerir una ROM comercial.

Fuera de alcance

optimizar el dibujado con pygame
ritmo de fotogramas / límite de velocidad
perfilar subsistemas individuales
lanzar PyPy
llamar a main() desde pytest

Ejecutar esta lección

uv run pytest tests/chapter_10_performance/test_315_main_fps_counter.py -v

Implementación de ejemplo

Ejemplo de implementación sugerida

import time

FPS_REPORT_INTERVAL_SECONDS = 1.0

...

running = True
last_fps_report_time = time.perf_counter()
frames_since_last_report = 0

while running:
    ...

    executed = console.step_until_next_frame()
    framebuffer = console.render_framebuffer()
    draw_framebuffer(window, framebuffer, SCALE)
    pygame.display.flip()

    frames_since_last_report += 1
    now = time.perf_counter()
    elapsed = now - last_fps_report_time

    if elapsed >= FPS_REPORT_INTERVAL_SECONDS:
        fps = frames_since_last_report / elapsed
        print(f"fps={fps:.1f}")
        frames_since_last_report = 0
        last_fps_report_time = now

Ver código del testtest_315_main_fps_counter.py

import inspect

import main


def test_main_imports_time_for_fps_measurement():
    """
    Objective:
    FPS reporting should use a monotonic high-resolution timer from the standard
    library.
    """
    source = inspect.getsource(main)

    assert "import time" in source


def test_main_defines_one_second_fps_report_interval():
    """
    Objective:
    The first FPS counter should be intentionally simple and report about once per
    second.
    """
    assert hasattr(main, "FPS_REPORT_INTERVAL_SECONDS")
    assert main.FPS_REPORT_INTERVAL_SECONDS == 1.0


def test_main_initializes_fps_counter_state_before_loop():
    """
    Objective:
    main.py should track when the previous report happened and how many frames have
    completed since then.
    """
    source = inspect.getsource(main.main)

    assert "last_fps_report_time = time.perf_counter()" in source
    assert "frames_since_last_report = 0" in source


def test_main_counts_frames_after_display_flip():
    """
    Objective:
    The FPS counter should measure the full manual frame path, including pygame
    drawing and display flip.
    """
    source = inspect.getsource(main.main)

    flip_index = source.index("pygame.display.flip()")
    count_index = source.index("frames_since_last_report += 1")

    assert flip_index < count_index


def test_main_prints_fps_when_one_second_interval_elapsed():
    """
    Objective:
    main.py should compute frames / elapsed time and print a small terminal signal.
    """
    source = inspect.getsource(main.main)

    assert "elapsed = now - last_fps_report_time" in source
    assert "elapsed >= FPS_REPORT_INTERVAL_SECONDS" in source
    assert "fps = frames_since_last_report / elapsed" in source
    assert "fps=" in source


def test_main_resets_fps_counter_after_report():
    """
    Objective:
    After printing a report, the next one-second window should start fresh.
    """
    source = inspect.getsource(main.main)

    assert "frames_since_last_report = 0" in source
    assert "last_fps_report_time = now" in source


def test_fps_counter_stays_in_manual_frontend_not_emulator_core():
    """
    Objective:
    FPS reporting is manual/frontend observability. The emulator core should not
    import time for display reporting.
    """
    core_files = [
        "emulator/console.py",
        "emulator/cpu/cpu.py",
        "emulator/ppu/ppu.py",
        "emulator/rendering/frame_compositor.py",
    ]

    for file_path in core_files:
        source = open(file_path, encoding="utf-8").read()
        assert "import time" not in source

Funciones de test (7)

test_main_imports_time_for_fps_measurement
test_main_defines_one_second_fps_report_interval
test_main_initializes_fps_counter_state_before_loop
test_main_counts_frames_after_display_flip
test_main_prints_fps_when_one_second_interval_elapsed
test_main_resets_fps_counter_after_report
test_fps_counter_stays_in_manual_frontend_not_emulator_core