Pygame won't render rect at mouse position?

Question

I wrote this simple code, to spawn a rect at the mouse position when the mouse button is clicked. But it wont render the rect for some reason. It prints "mouse" when clicked, but no rect!

import pygame
from pygame.locals import *


WHITE = (255,255,255)

while True:

    pygame.init()

    DISPLAY = pygame.display.set_mode((400,400))

    for event in pygame.event.get():

        if event.type == QUIT:
            pygame.quit()
        
        if event.type == KEYDOWN and event.key == K_ESCAPE:
            pygame.quit()

        if event.type == MOUSEBUTTONDOWN:
            pygame.draw.rect(DISPLAY,WHITE,(pygame.mouse.get_pos()[0],pygame.mouse.get_pos()[1],20,20))
            print('mouse')

 

    pygame.display.update()

Any kind of help is much appreciated!

Answer 1

You must initialize pygame (pygame.init()) and create the display surface (pygame.display.set_mode()) before the application loop.

import pygame
from pygame.locals import *

pygame.init()
DISPLAY = pygame.display.set_mode((400,400))
WHITE = (255,255,255)

run = True
while run:
    for event in pygame.event.get():
        if event.type == QUIT:
            run = False
        if event.type == KEYDOWN and event.key == K_ESCAPE:
            run = False

        if event.type == MOUSEBUTTONDOWN:
            print('mouse')
            pygame.draw.rect(DISPLAY, WHITE, (*event.pos, 20, 20))
        
    pygame.display.update()

pygame.quit()
exit()

---

However, the typical PyGame application loop has to:

• handle the events by calling either pygame.event.pump() or pygame.event.get().
• update the game states and positions of objects dependent on the input events and time (respectively frames)
• clear the entire display or draw the background
• draw the entire scene (blit all the objects)
• update the display by calling either pygame.display.update() or pygame.display.flip()
• limit the frames per second to limit CPU usage with pygame.time.Clock.tick

Redraw the scene is every frame. The event occurs just once when the mouse button is clicked. Add the mouse click positions to a list and draw the rectangles in the application loop, at the positions stored in the list:

import pygame
from pygame.locals import *

pygame.init()
DISPLAY = pygame.display.set_mode((400,400))
WHITE = (255,255,255)
clock = pygame.time.Clock()
pos_list = []

run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == QUIT:
            run = False
        if event.type == KEYDOWN and event.key == K_ESCAPE:
            run = False

        if event.type == MOUSEBUTTONDOWN:
            print('mouse')
            pos_list.append(event.pos)

    DISPLAY.fill(0)
    for pos in pos_list:
        pygame.draw.rect(DISPLAY, WHITE, (*pos, 20, 20))
    pygame.display.update()

pygame.quit()
exit()

Answer 2

The problem is that you initialize the window in the while loop.

You have to do it like this:

import pygame
from pygame.locals import *


WHITE = (255,255,255)
pygame.init()
DISPLAY = pygame.display.set_mode((400,400))

while True:

    for event in pygame.event.get():

        if event.type == QUIT:
            pygame.quit()
        
        if event.type == KEYDOWN and event.key == K_ESCAPE:
            pygame.quit()

        if event.type == MOUSEBUTTONDOWN:
            pygame.draw.rect(DISPLAY,WHITE,(pygame.mouse.get_pos()[0],pygame.mouse.get_pos()[1],20,20))
            print('mouse')

 

    pygame.display.update()

Answer 3

You actually do render the rectangle! The problem is that you re-initialize the window so fast that you do not see it in your while loop

This code will work:

import pygame
from pygame.locals import *


WHITE = (255, 255, 255)

pygame.init()
DISPLAY = pygame.display.set_mode((400, 400))

while True:

    for event in pygame.event.get():

        if event.type == QUIT:
            pygame.quit()

        if event.type == KEYDOWN and event.key == K_ESCAPE:
            pygame.quit()

        if event.type == MOUSEBUTTONDOWN:
            pygame.draw.rect(DISPLAY, WHITE, (pygame.mouse.get_pos()[
                             0], pygame.mouse.get_pos()[1], 20, 20))
            print('mouse')

    pygame.display.update()