CODEWITHSUNDEEP
python-3.xpygamepygame-surface
Forsaken_Knight77
Forsaken_Knight77

Reputation: 596

How do I get the Mouse Position on a Pygame Scaled Surface?

The game I'm making blits everything onto a pygame.surface which is then scaled to the size of the user's display, maintaining aspect ratio, before the surface is then blitted to the main screen. The problem I'm having now, is that when I query the mouse position (because I want to do a hover effect on certain sprites), it's way off where the sprite is but the x and y match the sprite's coords. Is this because I've scaled the surface? And if so, is there a built-in Pygame method for assigning the mouse to different surfaces? Or will I have to write an algorithm to convert the coords?

Upvotes: 4

Views: 2546

Answers (1)

sloth
sloth

Reputation: 101122

You can just "scale" the mouse position, too, by the factor you scaled your source surface

Here's a simple example

import string
import pygame as pg

pg.init()
screen = pg.display.set_mode((640, 480))
screen_rect = screen.get_rect()
clock = pg.time.Clock()

# the surface we draw our stuff on
some_surface = pg.Surface((320, 240))
some_surface_rect = some_surface.get_rect()

# just something we want to check for mouse hovering
click_me = pg.Surface((100, 100))
click_me_rect = click_me.get_rect(center=(100, 100))

hover = False
done = False
while not done:
    for event in pg.event.get():
        if event.type == pg.QUIT or event.type == pg.KEYDOWN and event.key == pg.K_ESCAPE:
            done = True

    # draw some stuff on our surface
    some_surface.fill(pg.Color('gray12'))
    click_me.fill(pg.Color('dodgerblue') if not hover else pg.Color('red'))
    some_surface.blit(click_me, click_me_rect)
    # scale it
    scaled_surface = pg.transform.scale(some_surface, screen_rect.size)
    # draw it on the window
    screen.blit(scaled_surface, (0, 0))

    pos = list(pg.mouse.get_pos())
    # take the mouse position and scale it, too
    ratio_x = (screen_rect.width / some_surface_rect.width)
    ratio_y = (screen_rect.height / some_surface_rect.height)
    scaled_pos = (pos[0] / ratio_x, pos[1] / ratio_y)

    # use collidepoint as usual
    hover = click_me_rect.collidepoint(scaled_pos)

    pg.display.flip()
    clock.tick(60)

pg.quit()

enter image description here

Of course this only works because scaled_surface is blitted at (0, 0) of the screen. If you would blit it elsewhere, you would have to translate the mouse position accordingly.

Upvotes: 5

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