How to stop cursor lag in Pygame? - pygame

Question

I have created a shooting game using Pygame in which one's cursor turns into a cross-hair and moves around shooting static images. However, the lag on the cross-hair is simply unbearable as the image is continually redrawn and a new background imposed over it every clock tick.
My code is as below:
import pygame, sys, random
class Crosshair(pygame.sprite.Sprite):
def __init__(self):
super().__init__()
self.image = pygame.image.load("ch.png").convert_alpha()
self.rect = self.image.get_rect()
self.gunshot = pygame.mixer.Sound("gs.wav")
def shoot(self):
self.gunshot.play()
pygame.sprite.spritecollide(crosshair, target_group, True)
def update(self):
self.rect.center = pygame.mouse.get_pos()
class Target(pygame.sprite.Sprite):
def __init__(self, pos_x, pos_y):
super().__init__()
self.image = pygame.image.load("al.png").convert_alpha()
self.rect = self.image.get_rect()
self.rect.center = [pos_x, pos_y]
pygame.init()
clock = pygame.time.Clock()
screen_width = 1920
screen_height = 1080
screen = pygame.display.set_mode((screen_width, screen_height))
background = pygame.image.load("hoc.png").convert_alpha()
pygame.mouse.set_visible(False)
crosshair = Crosshair()
crosshair_group = pygame.sprite.Group()
crosshair_group.add(crosshair)
target_group = pygame.sprite.Group()
for target in range(20):
new_target = Target(random.randrange(0, screen_width), random.randrange(0, screen_height))
target_group.add(new_target)
Running = True
while Running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
sys.exit()
if event.type == pygame.MOUSEBUTTONDOWN:
crosshair.shoot()
pygame.display.flip()
screen.blit(background, (0, 0))
target_group.draw(screen)
crosshair_group.draw(screen)
crosshair_group.update()
clock.tick(60)
Is there any way to make the cross-hair motion smoother? Most of the code is taken almost directly from a Youtube tutorial, but for some reason I am experiencing this problem when others are not.

Answer 1

It is a matter of indentation. You must update and draw the scene in the application loop rather than the event loop. The application loop is executed once per frame, but the event loop is only executed when an event occurse. Actually the call of clock.tick(60) slows down your application after each event instead of each frame:
while Running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
sys.exit()
if event.type == pygame.MOUSEBUTTONDOWN:
crosshair.shoot()
# INDENTATION
#<--|
pygame.display.flip()
screen.blit(background, (0, 0))
target_group.draw(screen)
crosshair_group.draw(screen)
crosshair_group.update()
clock.tick(60)