Pygame Surface updates non-sequentially

Question

I am attempting to implement a simple Pygame script that is supposed to:

First, check for when the user presses the Space key;
On Space keypress, display some text; then
Pauses for 2 seconds and then update the screen to its original state.

Note that all of the above events must occur sequentially, and cannot be out of order.

I am encountering problems where the program first pauses, then displays the text only appears for a split second (or not at all) before the screen updates to its original state.

The program seems to have skipped over step 2 and proceeded with the pause in step 3 before displaying text. My code is as follows:

import pygame
import sys
from pygame.locals import *

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)

pygame.init()
wS = pygame.display.set_mode((500, 500), 0, 32)


# Method works as intended by itself
def create_text(x, y, phrase, color):
    """
    Create and displays text onto the globally-defined `wS` Surface
    (params in docstring omitted)
    """
    # Assume that the font file exists and is successfully found
    font_obj = pygame.font.Font("./roboto_mono.ttf", 32)
    text_surface_obj = font_obj.render(phrase, True, color)
    text_rect_obj = text_surface_obj.get_rect()
    text_rect_obj.center = (x, y)
    wS.blit(text_surface_obj, text_rect_obj)


while True:
    wS.fill(BLACK)
    for event in pygame.event.get():
        if event.type == KEYDOWN and event.key == K_SPACE:

            # Snippet containing unexpected behavior
            create_text(250, 250, "Hello world!", WHITE)
            pygame.display.update()
            pygame.time.delay(2000)
            # Snippet end

        if event.type == QUIT:
            pygame.quit()
            sys.exit(0)
    pygame.display.update()

Thanks in advance!

Try to remove the two lines under pygame.time.delay(2000). It looks like they're unnecessary and could cause the problem. — skrx
@skrx Once I've removed the two lines below the delay() method call, I do see the Hello World! text getting blitted; however, it only gets displayed for an instant (one frame?) as opposed to the intended 2 seconds. — Jerrybibo
That's odd. The execution of the program should be stopped after the delay call. BTW, I had trouble to reproduce the bug in the first place. I think I saw it once for a very short time but couldn't reproduce it again. Perhaps it would be better to restructure the program and use one of these timers. — skrx

Unknown Unknown · Accepted Answer · 2018-07-16T22:01:17

For some reason the program worked for me with the only thing I changed was the font. This is the same as what @Omega0x013 is doing, but you have an unlimited framerate. It works because FPS.tick() returns the amount of time since it was last called, if you don't specify a frame rate, it does not hold the program.

import pygame
import sys
from pygame.locals import *
displayText = False
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)

pygame.init()
wS = pygame.display.set_mode((500, 500), 0, 32)


# Method works as intended by itself
def create_text(x, y, phrase, color):
    """
    Create and displays text onto the globally-defined `wS` Surface
    (params in docstring omitted)
    """
    # Assume that the font file exists and is successfully found

    font_obj = pygame.font.Font(None,30)
    text_surface_obj = font_obj.render(phrase, True, color)
    text_rect_obj = text_surface_obj.get_rect()
    text_rect_obj.center = (x, y)
    wS.blit(text_surface_obj, text_rect_obj)

FPS = pygame.time.Clock()
while True:
    wS.fill(BLACK)
    for event in pygame.event.get():
        if event.type == KEYDOWN and event.key == K_SPACE:
            totalTime = 0
            FPS.tick()
            displayText = True

        if event.type == QUIT:
            pygame.quit()
            sys.exit(0)
    if displayText:
        totalTime += FPS.tick()
        create_text(250, 250, "Hello world!", WHITE)
        if totalTime >= 2000:
            displayText = False
    pygame.display.update()

Pygame Surface updates non-sequentially

2 Answers