Pygame. How do I resize a surface and keep all objects within proportionate to the new window size?

Question

If I set a pygame window to resizable and then click and drag on the border of the window the window will get larger but nothing blit onto the surface will get larger with i

Answer 1

Don't draw on the screen directly, but on another surface. Then scale that other surface to size of the screen and blit it on the screen.

Here's a simple example:

import pygame
from pygame.locals import *

def main():
    pygame.init()
    screen = pygame.display.set_mode((200, 200),HWSURFACE|DOUBLEBUF|RESIZABLE)
    fake_screen = screen.copy()
    pic = pygame.surface.Surface((50, 50))
    pic.fill((255, 100, 200))

    while True:
        for event in pygame.event.get():
            if event.type == QUIT: 
                pygame.display.quit()
            elif event.type == VIDEORESIZE:
                screen = pygame.display.set_mode(event.size, HWSURFACE|DOUBLEBUF|RESIZABLE)

        fake_screen.fill('black')
        fake_screen.blit(pic, (100, 100))
        screen.blit(pygame.transform.scale(fake_screen, screen.get_rect().size), (0, 0))
        pygame.display.flip()
    
main()