Question

My goal is to make a module that will make a grid on a pygame canvas and allow you to highlight boxes by their x and y coords.

Here is a simple example usage.

from grid import Grid

g = Grid(100, 100, 10) # width and height in cells, cell width in pixels
g.highlightBox(2, 2, (0, 255, 0)) # cell x and y, rgb color tuple
g.clearGrid()

Here is the code I have so far. The problem is, I need to have an event loop to keep the window open and make the close button functional, but I also need to allow the other functions to draw to the screen.

import pygame
import sys

class Grid:
    colors = {"blue":(0, 0, 255), "red":(255, 0, 0), "green":(0, 255, 0), "black":(0, 0, 0), "white":(255, 255, 255)}

    def __init__(self, width, height, cellSize, borderWidth=1):
        self.cellSize = cellSize
        self.borderWidth = borderWidth
        self.width = width * (cellSize + borderWidth)
        self.height = height * (cellSize + borderWidth)
        self.screen = pygame.display.set_mode((self.width, self.height))

        running = True
        while running:
            event = pygame.event.poll()
            if event.type == pygame.QUIT:
                running = False

    def clearGrid(self):
        pass

    def highlightBox(self, x, y, color):
        xx = x * (self.cellSize + self.borderWidth)
        yy = y * (self.cellSize + self.borderWidth)
        pygame.draw.rect(self.screen, color, (xx, yy, self.cellSize, self.cellSize), 0)

When I run the first sample, the code will be stuck in the loop, not allowing me to run the highlightBox function until the loop is done(the exit button is pressed).

Answer 1

I got a working version with the multiprocessing library and pipes. It seems kinda unpythonic but it will work for this project.

import pygame
import sys
from multiprocessing import Process, Pipe

class Grid:
    colors = {"blue":(0, 0, 255), "red":(255, 0, 0), "green":(0, 255, 0), "black":(0, 0, 0), "white":(255, 255, 255)}

    def __init__(self, width, height, cellSize, borderWidth=1):
        self.cellSize = cellSize
        self.borderWidth = borderWidth
        self.width = width * (cellSize + borderWidth)
        self.height = height * (cellSize + borderWidth)

        #pygame.draw.rect(self.screen, todo[1], (todo[2], todo[3], todo[4], todo[5]), 0)
        self.parent_conn, self.child_conn = Pipe()
        self.p = Process(target=self.mainLoop, args=(self.child_conn, self.width, self.height,))
        self.p.start()

    def close():
        self.p.join()

    def clearGrid(self):
        pass

    def highlightBox(self, x, y, color):
        xx = x * (self.cellSize + self.borderWidth)
        yy = y * (self.cellSize + self.borderWidth)
        self.parent_conn.send(["box", color, xx, yy, self.cellSize, self.cellSize])

    def mainLoop(self, conn, width, height):
        #make window
        screen = pygame.display.set_mode((self.width, self.height))

        running = True
        while running:
            # is there data to read
            if conn.poll():
                #read all data
                todo = conn.recv()
                print("Recived " + str(todo))

            #do the drawing
            if todo[0] == "box":
                print("drawing box")
                pygame.draw.rect(screen, todo[1], (todo[2], todo[3], todo[4], todo[5]), 0) #color, x, y, width, height
                todo = ["none"]

            #draw to screen
            pygame.display.flip()

            #get events
            event = pygame.event.poll()
            if event.type == pygame.QUIT:
                running = False