Develop Reference

what does draw.lines return?

from what I understand draw.lines joins each coordinate that is passed to it, so if we have [A, B, C]
will draw a line from coordinate A to coordinate B and from B to C and if closed is True it draws a line from coordinate A to coordinate C therefore it will always join the first coordinate with the last one its right?
what i don't understand is what the rect variable returns..
I think that every time I add a new coordinate it returns (starting_point, rectangle_size) where starting point is the first coordinate and the rectangle size is calculated by the distance of the first coordinate with the last one then draw the rectangle with draw.rect
but the reasoning I don't think is right because if I add a coordinate of this type to the list the rectangle remains unchanged
CODE:
"""Place a polygone line with the clicks of the mouse."""
import pygame
from pygame.locals import *
RED = (255, 0, 0)
GREEN = (0, 255, 0)
GRAY = (150, 150, 150)
pygame.init()
screen = pygame.display.set_mode((640, 240))
drawing = False
points = []
running = True
while running:
for event in pygame.event.get():
if event.type == MOUSEBUTTONDOWN:
points.append(event.pos)
drawing = True
elif event.type == MOUSEBUTTONUP:
drawing = False
elif event.type == MOUSEMOTION and drawing:
points[-1] = event.pos
screen.fill(GRAY)
if len(points)>1:
rect = pygame.draw.lines(screen, RED, True, points, 3)
pygame.draw.rect(screen, GREEN, rect, 1)
pygame.display.update()
pygame.quit()

pygame.draw.lines() returns a pygame.Rect object that encloses all the points of the line:
a rect bounding the changed pixels, if nothing is drawn the bounding rect's position will be the position of the first point in the points parameter (float values will be truncated) and its width and height will be 0
The rectangle does not start at any particular point on the line, but is just large enough to enclose all the points along the line.
It returns the same as:
list_x, list_y = zip(*points)
min_x, max_x = min(list_x), max(list_x)
min_y, max_y = min(list_y), max(list_y)
rect = pygame.Rect(min_x, min_y, max_x-min_x, max_y-min_y)

According to the docs:
Returns:
a rect bounding the changed pixels, if nothing is drawn the bounding rect's position will be the position of the first point in the points parameter (float values will be truncated) and its width and height will be 0

this is the reasoning I made:
import pygame
def minore(lista_coordinate, asse):
dimensione = lista_coordinate[0][asse]
for coordinata in lista_coordinate:
if coordinata[asse] < dimensione:
dimensione = coordinata[asse]
return dimensione
def maggiore(lista_coordinate, asse):
dimensione = lista_coordinate[0][asse]
for coordinata in lista_coordinate:
if coordinata[asse] > dimensione:
dimensione = coordinata[asse]
return dimensione
pygame.init()
schermo = pygame.display.set_mode((500, 400))
punti = [(100, 100), (200, 100), (200, 50), (150, 80)]
larghezza_minore = minore(punti, 0)
larghezza_maggiore = maggiore(punti, 0)
larghezza_rettangolo = larghezza_maggiore - larghezza_minore
altezza_minore = minore(punti, 1)
altezza_maggiore = maggiore(punti, 1)
altezza_rettangolo = altezza_maggiore - altezza_minore
dimensioni_rettangolo = (larghezza_rettangolo, altezza_rettangolo)
inizio = (larghezza_minore, altezza_minore)
pygame.draw.lines(schermo, (255, 0, 0), True, punti, 3)
pygame.draw.rect(schermo, (0, 255, 0), (inizio, dimensioni_rettangolo), 1)
pygame.display.update()

pyglet drawing primitive GL_POINT. A buffer issue?

Beginner in pyglet. I have an issue when drawing GL_POINT using pyglet.graphicss.draw(). I want this GL_POINT to be drawn after another on the next pixel buffer, but it seems the function does not keep the last GL_POINT to be drawn on the next pixel buffer.
import pyglet
from pyglet.gl import *
from pyglet.window import key # for key input, on_key_press
window = pyglet.window.Window(800, 600) # create a window object with the resolution of 800x600
window.set_caption('window title')
glClear(GL_COLOR_BUFFER_BIT)
#window.event
def on_key_press(symbol, modifiers): # keyboard input handler
if symbol == key.L: # Drawing a center point
print("DRAWING TEST A POINT (400, 300)")
pyglet.graphics.draw(
1, pyglet.gl.GL_POINTS,
('v2i', (400, 300))
)
elif symbol == key.K: # Drawing a bit further 100 more horizontally from center point
print("DRAWING TEST A POINT (500, 300)")
pyglet.graphics.draw(
1, pyglet.gl.GL_POINTS,
('v2i', (500, 300))
)
pyglet.app.run()
Pressing L would draw a center point.
Then pressing K would draw 100 more horizontally from the center point with the last center point gone.
Where is the bug? is there something wrong with my code? if not,
my guess would be, does pyglet.graphicss.draw() function actually redraw one after another primitive shape? How do I code to draw one after another?

The issue is caused by Double buffering. You can solve the issue by drawing the point to both buffers. Draw the point twice and swap the OpenGL front and back buffers in between by (flip).
pyglet.graphics.draw(
1, pyglet.gl.GL_POINTS,
('v2i', (400, 300))
)
window.flip()
pyglet.graphics.draw(
1, pyglet.gl.GL_POINTS,
('v2i', (400, 300))
)
But I recommend to add the points to a list and to draw the list. e.g.:
import pyglet
from pyglet.gl import *
from pyglet.window import key # for key input, on_key_press
points = []
window = pyglet.window.Window(800, 600) # create a window object with the resolution of 800x600
window.set_caption('window title')
glClear(GL_COLOR_BUFFER_BIT)
#window.event
def on_key_press(symbol, modifiers): # keyboard input handler
global points
if symbol == key.L: # Drawing a center point
print("DRAWING TEST A POINT (400, 300)")
points += [400, 300]
elif symbol == key.K: # Drawing a bit further 100 more horizontally from center point
print("DRAWING TEST A POINT (500, 300)")
points += [500, 300]
pyglet.graphics.draw(len(points) // 2, pyglet.gl.GL_POINTS, ('v2i', points))
pyglet.app.run()

Switching the displayed surface in PyGame allows the user to scroll off the borders of the surface

I am creating a randomly generated map in with PyGame. However, I've run into an issue, where, if the user scrolls away from the top-left corner of the map and changes the PyGame surface that's displayed, an issue happens.
The problem is, PyGame still starts them on the upper-left of the surface, and will then allow them to scroll off the edges of the surface because the list that keeps track of that, camera_pos, now has incorrect values.
All of the surfaces are the same dimensions and I want to make it so the user is in the same position when they change the displayed surface. However, I'm not sure how to set the position of the user's view when pygame switches surfaces.
How can I switch the position of the user's view back to what it used to be when the surface is switched?
I have made a MCV Example below I hope will help. Instead of displaying maps, it just draws a border around a solid color. I apologize for how long it is. I'm not sure how to make it much shorter.
In this example, scrolling is done with the arrow keys. You can press r, g, or b on the keyboard to display the different colored surfaces.
import pygame
import numpy as np
import sys
def scroll_y(display_surface, offset):
"""
Handles vertical scrolling.
:param display_surface: A pyGame surface object.
:param offset: The speed of the scroll
"""
width, height = display_surface.get_size()
map_copy = display_surface.copy()
display_surface.blit(map_copy, (0, offset))
# handle scrolling down
if offset < 0:
display_surface.blit(map_copy,
(0, height + offset),
(0, 0, width, -offset))
# handle scrolling up
else:
display_surface.blit(map_copy,
(0, 0),
(0, height - offset, width, offset))
def scroll_x(display_surface, offset):
"""
Handles horizontal scrolling.
:param display_surface: A pyGame surface object.
:param offset: The speed of the scroll
"""
width, height = display_surface.get_size()
map_copy = display_surface.copy()
display_surface.blit(map_copy, (offset, 0))
# handle scrolling right
if offset < 0:
display_surface.blit(map_copy,
(width + offset, 0),
(0, 0, -offset, height))
# handle scrolling left
else:
display_surface.blit(map_copy,
(0, 0),
(width - offset, 0, offset, height))
def main():
"""
This function displays the three surfaces.
Press r to show the red surface (which is displayed by default).
Press g to show the green surface.
Press b to show the blue surface.
"""
pygame.init()
window = pygame.display.set_mode((1600, 900))
red_surface = pygame.Surface([3200, 1800]).convert(window)
green_surface = pygame.Surface([3200, 1800]).convert(window)
blue_surface = pygame.Surface([3200, 1800]).convert(window)
red_surface.fill((255, 145, 145))
green_surface.fill((145, 255, 145))
blue_surface.fill((145, 145, 255))
# draw thick black lines on surface borders
pygame.draw.rect(red_surface, (0, 0, 0), (0, 0, 3200, 1800), 40)
pygame.draw.rect(green_surface, (0, 0, 0), (0, 0, 3200, 1800), 40)
pygame.draw.rect(blue_surface, (0, 0, 0), (0, 0, 3200, 1800), 40)
display_surface = red_surface.copy()
camera_pos = np.array([0, 0])
while True: # <-- the pyGame loop
event = pygame.event.poll()
pressed = pygame.key.get_pressed()
# handle closing the window
if event.type == pygame.QUIT:
break
window.blit(display_surface, (0, 0))
# handle switching display modes
if pressed[pygame.K_g]:
display_surface = green_surface
elif pressed[pygame.K_b]:
display_surface = blue_surface
elif pressed[pygame.K_r]:
display_surface = red_surface
# handle scrolling, make sure you can't scroll past the borders
if pressed[pygame.K_UP] and camera_pos[1] > 0:
scroll_y(display_surface, 5)
camera_pos[1] -= 5
elif pressed[pygame.K_DOWN] and camera_pos[1] < (1800 / 2):
scroll_y(display_surface, -5)
camera_pos[1] += 5
elif pressed[pygame.K_LEFT] and camera_pos[0] > 0:
scroll_x(display_surface, 5)
camera_pos[0] -= 5
elif pressed[pygame.K_RIGHT] and camera_pos[0] < (3200 / 2):
scroll_x(display_surface, -5)
camera_pos[0] += 5
# updates what the window displays
pygame.display.update()
pygame.quit()
sys.exit(0)
if __name__ == "__main__":
# runs the pyGame loop
main()

Here's what I think is a fairly elegant solution that doesn't require the two scrolling functions, scroll_x() and scroll_y() you have. Because it was so fast not using them, the main loop was detecting the same scrolling key as being pressed multiple times — necessitating the addition of a pygame.time.Clock to slow the frame-rate down to something reasonable.
Instead of scrolling the display surfaces themselves via those scrolling functions, as your code was doing, this version just updates the current "camera" position, then blits the corresponding region of the current display_surface to the window whenever it's modified. The camera's position is constrained by making sure its x and y components stay within some boundary limit constants — MINX,MINY and MAXX,MAXY — which get computed based the values of some other previously defined constants.
The use of symbolic constants rather than hardcoding literal values multiple places in the code is considered a very good programming practice because it makes changing them easier, since doing so only requires a source code change to be done one place.
import pygame
import sys
def main():
"""
This function displays the three surfaces.
Press r to show the red surface (which is displayed by default).
Press g to show the green surface.
Press b to show the blue surface.
"""
FPS = 60 # Frames per second
SURF_WIDTH, SURF_HEIGHT = 3200, 1800
WIN_WIDTH, WIN_HEIGHT = 1600, 900
DX, DY = 5, 5 # Scroll amounts.
MINX, MAXX = DX, SURF_WIDTH - WIN_WIDTH + DX - 1
MINY, MAXY = DY, SURF_HEIGHT - WIN_HEIGHT + DY - 1
pygame.init()
pygame.font.init()
fonts = pygame.font.get_fonts()
clock = pygame.time.Clock()
window = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))
red_surface = pygame.Surface([SURF_WIDTH, SURF_HEIGHT]).convert(window)
green_surface = pygame.Surface([SURF_WIDTH, SURF_HEIGHT]).convert(window)
blue_surface = pygame.Surface([SURF_WIDTH, SURF_HEIGHT]).convert(window)
red_surface.fill((255, 145, 145))
green_surface.fill((145, 255, 145))
blue_surface.fill((145, 145, 255))
# Draw thick black lines on surface borders
pygame.draw.rect(red_surface, (0, 0, 0), (0, 0, SURF_WIDTH, SURF_HEIGHT), 40)
pygame.draw.rect(green_surface, (0, 0, 0), (0, 0, SURF_WIDTH, SURF_HEIGHT), 40)
pygame.draw.rect(blue_surface, (0, 0, 0), (0, 0, SURF_WIDTH, SURF_HEIGHT), 40)
# Draw label on each of the surfaces for testing. (ADDED)
font = pygame.font.SysFont(None, 35)
rtext = font.render('red surface', True, (255, 0, 0))
textpos = rtext.get_rect(centerx=300, centery=200) # Reused.
red_surface.blit(rtext, textpos)
rtext = font.render('green surface', True, (0, 192, 0))
green_surface.blit(rtext, textpos)
rtext = font.render('blue surface', True, (0, 0, 255))
blue_surface.blit(rtext, textpos)
display_surface = red_surface
camera_pos = pygame.math.Vector2(0, 0)
update_surface = True
while True: # Game loop
if update_surface:
window.blit(display_surface, (0, 0), (camera_pos[0], camera_pos[1],
WIN_WIDTH, WIN_HEIGHT))
update_surface = False
event = pygame.event.poll()
pressed = pygame.key.get_pressed()
# Close window?
if event.type == pygame.QUIT or pressed[pygame.K_ESCAPE]:
break
# Switch display surface?
if pressed[pygame.K_g]:
display_surface = green_surface
update_surface = True
elif pressed[pygame.K_b]:
display_surface = blue_surface
update_surface = True
elif pressed[pygame.K_r]:
display_surface = red_surface
update_surface = True
# Constrain scrolling to within borders
if pressed[pygame.K_LEFT] and camera_pos[0] >= MINX:
camera_pos[0] -= DX
update_surface = True
elif pressed[pygame.K_RIGHT] and camera_pos[0] <= MAXX:
camera_pos[0] += DX
update_surface = True
elif pressed[pygame.K_UP] and camera_pos[1] >= MINY:
camera_pos[1] -= DY
update_surface = True
elif pressed[pygame.K_DOWN] and camera_pos[1] <= MAXY:
camera_pos[1] += DY
update_surface = True
# updates what the window displays
pygame.display.update()
clock.tick(FPS)
pygame.quit()
sys.exit(0)
if __name__ == "__main__":
main() # runs the pyGame loop

Increase the size of an image during a collision with pygame?

I have a program with a player (who is an image) and a rectangle and I want that when the player has a collision with the rectangle, the size of the image increase.
For now, I have this code :
import pygame
from random import randint
WIDTH, HEIGHT = 800, 800
FPS = 60
pygame.init()
win = pygame.display.set_mode((WIDTH, HEIGHT))
fenetre_rect = pygame.Rect(0, 0, WIDTH, HEIGHT)
pygame.display.set_caption("Hagar.io")
clock = pygame.time.Clock()
bg = pygame.image.load("bg.png").convert()
bg_surface = bg.get_rect(center=(WIDTH / 2, HEIGHT / 2))
bg_x = bg_surface.x
bg_y = bg_surface.y
x_max = WIDTH / 2
y_max = HEIGHT / 2
# player
player = pygame.transform.scale(pygame.image.load("player.png").convert_alpha(), (i, i))
player_rect = player.get_rect(center=(x_max, y_max))
# cell
rect_surface = pygame.Rect(300, 500, 20, 20)
# Game loop
running = True
while running:
dt = clock.tick(FPS) / 1000
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
if player_rect.colliderect(rect_surface):
print("collide")
bg_surface.x = bg_x
bg_surface.y = bg_y
# draw on screen
win.blit(bg, bg_surface)
pygame.draw.rect(win, (255, 0, 0), rect_surface)
win.blit(player, player_rect)
pygame.display.flip()
pygame.quit()
I have try to add in the "colliderect" condition but it does not work :
player_rect.width += 1
player_rect.height += 1
Thanks for your help !

This line
player = pygame.transform.scale(pygame.image.load("player.png").convert_alpha(), (i, i))
is using the variable i but it is not defined in your code. I'm not sure where it is defined, but it is key to what you want. I will try to answer without this information anyway:
Thing is, enlarging the rect won't do anything, because a rect is just coordinates. You have to scale the actual image, and pygame.transform.scale does exactly that.
You can keep the image in a separate variable player_img:
player_img = pygame.image.load("player.png").convert_alpha()
player = pygame.transform.scale(player_img, (i, i))
Then when you want to scale it differently, just call .scale() again:
double_size_player = pygame.transform.scale(player_img, (i*2, i*2))
That still leaves us to the mistery of your undefined i variable, but I think you get the gist of it. Remeber that you have to extract a new rect from the scaled image because it will be bigger.

PySDL2 drawing order

The code below draws a black background, a white box and text. However it seems that the drawing order is not determined and I sometimes have the text or the rectangle covered by the background rectangle. I'm trying to understand what the appropriate way to manage this is?
import sdl2.ext
import sdl2.sdlttf
from sdl2 import SDL_Color, SDL_Init
WHITE = SDL_Color(255, 255, 255)
class Entity(sdl2.ext.Entity):
def __init__(self, world, sprite, posx=0, posy=0):
self.sprite = sprite
self.sprite.position = posx, posy
sdl2.ext.init()
window = sdl2.ext.Window("PySDL2", size=(320, 240))
window.show()
world = sdl2.ext.World()
texture_renderer = sdl2.ext.Renderer(window)
spriterenderer = sdl2.ext.TextureSpriteRenderSystem(texture_renderer)
factory = sdl2.ext.SpriteFactory(sdl2.ext.TEXTURE, renderer=texture_renderer)
world.add_system(spriterenderer)
sdl2.sdlttf.TTF_Init()
font = sdl2.sdlttf.TTF_OpenFont('resources/Helvetica.dfont',32)
text_surface = sdl2.sdlttf.TTF_RenderText_Blended(font, 'test', WHITE).contents
sdl2.sdlttf.TTF_CloseFont(font)
bg = factory.from_color(sdl2.ext.Color(0, 0, 0), size = (320,240))
Entity(world, bg, 0, 0)
c = factory.from_color(sdl2.ext.Color(255, 255, 255), size = (50,50))
Entity(world, c, 100, 100)
text_sprite = factory.from_surface(text_surface)
text_entity = Entity(world, text_sprite, 50, 50)
def run():
running = True
while running:
events = sdl2.ext.get_events()
for event in events:
if event.type == sdl2.SDL_QUIT:
running = False
break
world.process()
run()
sdl2.ext.quit()

The default implementation of the TextureSpriteRenderSystem uses the depth attribute of Sprite object to determine the drawing order. If all sprites feature the same depth, the drawing order of them is undetermined, which results in your unwanted behaviour.
A Sprite with a depth value of 0 will be drawn below (or prior to) a Sprite with a higher depth value, e.g. 10. The default depth for each Sprite being created is 0. You could set your background's and rectangle's depth to a negative value in order to enforce the drawing order:
bg = factory.from_color(sdl2.ext.Color(0, 0, 0), size = (320,240))
bg.depth = -99 # always below everything
Entity(world, bg, 0, 0)
c = factory.from_color(sdl2.ext.Color(255, 255, 255), size = (50,50))
c.depth = -1
Entity(world, c, 100, 100)
You can read more about it in the PySDL2 sprite documentation.