First game with graphics, part 3

After an unplanned abscence, finally I'll show you how to control an image on screen with the mouse.

This example is actually very similar to the last one. I added a generous amount of whitespace in order to clearly read each function and each class.

import pygame


#These two constants refer to the ball's initial position
# and radius. The radius will be useful to position the center
# of the ball on the tip of the mouse pointer. I'll expand on
# this later.

STARTING_POINT = (340,250)
BALL_RADIUS = 12


class Ball:


    def __init__(self,imageFile,position_arg):

        self.image = pygame.image.load(imageFile)
        pygame.Surface.convert(self.image)
        self.position = position_arg


# The ball class no longer needs a "move" function,
# since the ball will only change position according to
# the mouse position.


    def set_position(self,position_arg):

        self.position = position_arg



class AssetManager:

    def load_ball(self,imageFile,position):
        return Ball(imageFile,position)




class InputManager:


    def check_events(self):

        for event in pygame.event.get():

            if event.type == pygame.QUIT:

                game.running = False




    def process_input(self,ball):

        mouse = pygame.mouse.get_pressed()

# This variable, mousePos, could just be the tuple returned by pygame.mouse.get_pos(), which is the position of the mouse pointer in the 'x' and 'y' axis, respectively. If we passed pygame.mouse.get_pos() directly to ball.set_position(), then we'd move the ball by its top-left corner, which looks kind of weird. To move the ball by its center, we just substract the ball's radius to both positions.

        mousePos = ( (pygame.mouse.get_pos()[0] - BALL_RADIUS) , (pygame.mouse.get_pos()[1] - BALL_RADIUS) )


        if mouse[0]:
          
            ball.set_position(mousePos)    




class Game:



    def __init__(self,resolution,caption):


        self.screen = pygame.display.set_mode(resolution)
        pygame.display.set_caption(caption)
        self.clock = pygame.time.Clock()
        self.running = True
        self.gray = (220,220,220)



    def draw_screen(self,ball):

        self.screen.fill(self.gray)
        self.screen.blit(ball.image,ball.position)
        pygame.display.flip()



    def main_loop(self,framerate,assets):

        ball = assets.load_ball('ball2.png',STARTING_POINT)

        while self.running:

            self.clock.tick(framerate)
            input_manager.check_events()
            input_manager.process_input(ball)

            self.draw_screen(ball)

        pygame.quit()



assets = AssetManager()
input_manager = InputManager()
game = Game((800,600),"Game")
game.main_loop(60,assets)

In the next post, I'll describe the actual idea for the game, and I'll add some functionality.

Until then, take care!