Cells Are Skipped When I Move The Mouse Quickly

Here is a python script that creates a pygame window and fills in the cell that is clicked on. import pygame from math import floor, sqrt from sys import exit as _exit cellsize =

Solution 1:

Implement a function, that returns the index of a cell at a certain position:

defcellAtPos(pos):
    c = (floor(pos[0] / cellsize[0]), floor(pos[1] / cellsize[1]))
    return c[1] * mapSize[0] + c[0]

Store the mouse buttons and position in ever frame:

mousePreviousFrame = mouse
mousePosPreviousFrame = mousepos

With the mouse button is pressed and was pressed in the previous frame, calculate the vector the mouse moved:

if mouse[0] and mousePreviousFrame[0]:
    direction = (mousepos[0] - mousePosPreviousFrame[0], mousepos[1] - mousePosPreviousFrame[1])

Fill the cells along the vector in a loop:

mag = hypot(*direction)
if mag != 0:
    normdir = (direction[0] / mag, direction[1] / mag)
    for i inrange(int(mag)):
        current = mousePosPreviousFrame[0] + normdir[0] * i,  mousePosPreviousFrame[1] + normdir[1] * i 
        cells[cellAtPos(current)] = True

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Minimal example

import pygame
from math import floor, sqrt, hypot
from sys import exit as _exit

cellsize = (5, 5)
mapSize = (int(600 / cellsize[0]), int(600 / cellsize[1]))
cells = [Falsefor i inrange(mapSize[0] * mapSize[1])]

defcellAtPos(pos):
    c = (floor(pos[0] / cellsize[0]), floor(pos[1] / cellsize[1]))
    return c[1] * mapSize[0] + c[0]

pygame.init()
window = pygame.display.set_mode((600, 600))
mousePreviousFrame = pygame.mouse.get_pos()

run = Truewhile run:
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.QUIT:
            run = False
  
    mouse = pygame.mouse.get_pressed()
    mousepos = pygame.mouse.get_pos()
    if mouse[0]:
        cells[cellAtPos(mousepos)] = Trueif mouse[0] and mousePreviousFrame[0]:
        direction = (mousepos[0] - mousePosPreviousFrame[0], mousepos[1] - mousePosPreviousFrame[1])
        mag = hypot(*direction)
        if mag != 0:
            normdir = (direction[0] / mag, direction[1] / mag)
            for i inrange(int(mag)):
                current = mousePosPreviousFrame[0] + normdir[0] * i,  mousePosPreviousFrame[1] + normdir[1] * i 
                cells[cellAtPos(current)] = True
    mousePreviousFrame = mouse
    mousePosPreviousFrame = mousepos

    #draw
    window.fill((255, 255, 255))
    for x inrange(mapSize[0]):
        for y inrange(mapSize[1]):
            if (cells[y * mapSize[0] + x]):
                pygame.draw.rect(window, (0, 0, 0), (x * cellsize[0], y * cellsize[1], cellsize[0], cellsize[1]))

    pygame.display.flip()

pygame.quit()
_exit()