Why Is My PyGame Display Blank?

PyGame - Void Display Mystery

When creating a visual application using PyGame, you may encounter instances where nothing is rendered on the screen despite drawing commands. To resolve this, it's crucial to understand the concept of display updates.

In PyGame, you draw on a Surface object associated with the display. However, these changes only become visible after updating the display using functions like pygame.display.update() or pygame.display.flip().

While pygame.display.flip() updates the entire display, pygame.display.update() can target specific areas.

To ensure the smooth operation of a PyGame application, a typical loop involves:

1. Event Handling: Get user input using pygame.event.get() or pygame.event.pump().
2. Game State and Object Updates: Adjust game states and object positions based on input and time.
3. Display Clearing: Clear the previous frame's contents using DISPLAY.fill(0).
4. Scene Rendering: Draw all necessary objects onto the canvas.
5. Display Update: Update the visible display using pygame.display.update() or pygame.display.flip().
6. Frame Rate Control: Limit the frames per second to avoid excessive CPU usage using pygame.time.Clock().

An example of a corrected PyGame loop:

import pygame
from pygame.locals import *
pygame.init()

DISPLAY = pygame.display.set_mode((800,800))
pygame.display.set_caption("thing")
clock = pygame.time.Clock()

run = True
while run:
    # Handle events
    for event in pygame.event.get():
        if event.type == QUIT:
            run = False

    # Clear display
    DISPLAY.fill(0)

    # Draw scene
    pygame.draw.rect(DISPLAY, (200, 200, 200), pygame.Rect(0, 400, 800, 400))

    # Update display
    pygame.display.flip()

    # Limit frames per second
    clock.tick(60)

pygame.quit()
exit()

This should resolve the issue of an empty screen and ensure proper rendering in PyGame.

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