Example Usage (Pygame)

This library allows you to make tweens and compose them with other tweens that can be used a variety of cases. For instance, you can move objects, change their color, etc. The library operates on fields of objects. Let us see what that means with an example in Pygame-ce (although the example can be adapted to other game libraries).

import transytion as ty
from dataclasses import dataclass
from transytion.ease_funcs import bounce
import pygame


pygame.init()
screen = pygame.display.set_mode((1280, 720))
clock = pygame.time.Clock()
running = True
dt = 0

@dataclass
class Ball:
    x: float
    y: float
    r: float

ball = Ball(screen.get_width() / 2.0, 0.0 - 40, 40)

# 1 second qudratic fall to center of screen.
fall = ty.Tween(1.0, # Duration of tween is 1 seconds.
                ball, # What object to mess with.
                {"y" : screen.get_height() / 2}, # Animate what to where.
                ease_func=quad) # How to animate it (defaults to linear)

ty.default_manager.add(fall) # Start the tween.

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    ty.default_manager.update(dt)

    screen.fill((0,0,0))
    pygame.draw.circle(screen, "red", (ball.x, ball.y), ball.r)

    pygame.display.flip()
    dt = clock.tick(60) / 1000

pygame.quit()

This is a modification of the first example presented here. It is recommended you become familiar with that example, and then continue with this example. If you run the example, you should see:

What is going on?

@dataclass
class Ball:
    x: float
    y: float
    r: float

This is used to keep track of the location (and radius) of the ball on the screen. Tweens operate on attributes of objects, so by making a Ball object we may tween the y (x, or even r) attributes.

# 1 second qudratic fall to center of screen.
fall = ty.Tween(1.0, # Duration of tween is 1 seconds.
                ball, # What object to mess with.
                {"y" : screen.get_height() / 2}, # Animate what to where.
                ease_func=quad) # How to animate it (defaults to linear)

This constructs our tween. It should be pointed out, by itself, the Tween object does not do anything until we tell it to run.

ty.default_manager.add(fall) # Start the tween.

Once the tween is added to a TweenManager object, (such as ty.default_manager) the tween begins execution. You can make as many manager objects as you want, but you need at least one, and it is perfectly reasonable to use just one. That is why transytion includes a default_manager for ease of use.

Lastly, the TweenManager needs the time to update each tween it is managing. This is done by going to your game loop and adding the line

ty.default_manager.update(dt)