Easing Functions¶

Easing functions control the acceleration curve of animations, making them feel more natural and dynamic.

What is Easing?¶

An easing function takes a progress value t (0.0 to 1.0) and returns a modified value. This controls how the animation progresses over time:

Linear: Constant speed (no easing)
Ease-in: Starts slow, accelerates
Ease-out: Starts fast, decelerates
Ease-in-out: Starts slow, speeds up, then slows down

Using Easing Functions¶

By Name¶

Pass the function name as a string:

wa.move(win, 500, 100, duration=1.0, ease="ease_out_cubic")
wa.fade(win, 0.5, duration=0.5, ease="ease_in_out_quad")

By Function¶

Import and pass the function directly:

from window_art import ease_out_cubic

wa.move(win, 500, 100, duration=1.0, ease=ease_out_cubic)

Custom Easing¶

Create your own easing function:

def my_ease(t: float) -> float:
    # Must take t in [0, 1] and return value in approximately [0, 1]
    return t * t * t

wa.move(win, 500, 100, duration=1.0, ease=my_ease)

Available Easing Functions¶

Linear¶

Name	Description
`linear`	Constant speed, no easing

Quadratic (Power of 2)¶

Name	Description
`ease_in_quad`	Accelerating from zero
`ease_out_quad`	Decelerating to zero
`ease_in_out_quad`	Accelerate then decelerate

Aliases: ease_in, ease_out, ease_in_out

Cubic (Power of 3)¶

Name	Description
`ease_in_cubic`	Stronger acceleration
`ease_out_cubic`	Stronger deceleration
`ease_in_out_cubic`	Smooth S-curve

Quartic (Power of 4)¶

Name	Description
`ease_in_quart`	Even stronger acceleration
`ease_out_quart`	Even stronger deceleration
`ease_in_out_quart`	Pronounced S-curve

Quintic (Power of 5)¶

Name	Description
`ease_in_quint`	Strong acceleration
`ease_out_quint`	Strong deceleration
`ease_in_out_quint`	Strong S-curve

Sine¶

Name	Description
`ease_in_sine`	Gentle sinusoidal acceleration
`ease_out_sine`	Gentle sinusoidal deceleration
`ease_in_out_sine`	Gentle S-curve

Exponential¶

Name	Description
`ease_in_expo`	Exponential acceleration
`ease_out_expo`	Exponential deceleration
`ease_in_out_expo`	Exponential S-curve

Circular¶

Name	Description
`ease_in_circ`	Circular curve acceleration
`ease_out_circ`	Circular curve deceleration
`ease_in_out_circ`	Circular S-curve

Back (Overshoot)¶

Overshoots the target slightly, then settles.

Name	Description
`ease_in_back`	Pulls back before accelerating
`ease_out_back`	Overshoots then settles
`ease_in_out_back`	Both effects combined

Elastic¶

Spring-like oscillation.

Name	Description
`ease_in_elastic`	Elastic wind-up
`ease_out_elastic`	Elastic snap and wobble
`ease_in_out_elastic`	Both effects combined

Bounce¶

Ball-bouncing effect.

Name	Description
`ease_in_bounce`	Reverse bounce at start
`ease_out_bounce`	Bounces at the end
`ease_in_out_bounce`	Both effects combined

Visual Reference¶

Here's how each easing family looks:

Linear:        ────────────────  (constant slope)

Ease-in:       ___________╱      (slow start)

Ease-out:      ╱───────────      (slow end)

Ease-in-out:   ____╱────────     (slow start and end)

Bounce:        ╱╲╱╲╱─────────    (bouncing effect)

Elastic:       ⌇⌇╱───────────    (spring oscillation)

Back:          ╲_╱───────────    (overshoot)

Choosing an Easing Function¶

For UI Elements¶

Appearing: ease_out_cubic or ease_out_quad
Disappearing: ease_in_cubic or ease_in_quad
Moving: ease_in_out_cubic

For Playful Effects¶

Bouncy: ease_out_bounce
Springy: ease_out_elastic
Snappy: ease_out_back

For Subtle Motion¶

Gentle: ease_in_out_sine
Smooth: ease_in_out_quad

For Dramatic Effect¶

Explosive: ease_out_expo
Powerful: ease_out_quint

Example: Comparing Easing Functions¶

import window_art as wa

easings = [
    "linear",
    "ease_out_quad",
    "ease_out_cubic",
    "ease_out_bounce",
    "ease_out_elastic",
]

with wa.run():
    windows = []
    for i, ease_name in enumerate(easings):
        win = wa.window(100, 100 + i * 60, 50, 50, color="coral")
        windows.append((win, ease_name))

    wa.wait(0.5)

    # Move each window with different easing
    for win, ease_name in windows:
        wa.move(win, 600, win.y, duration=1.5, ease=ease_name)

    wa.wait(1)

Programmatic Access¶

Get Easing by Name¶

from window_art import get_easing

ease_func = get_easing("ease_out_bounce")
value = ease_func(0.5)  # Get value at t=0.5

List All Easing Functions¶

from window_art.easing import EASING_FUNCTIONS

for name in EASING_FUNCTIONS:
    print(name)

Mathematical Formulas¶

For reference, here are the formulas for the basic easing families:

Quadratic¶

def ease_in_quad(t):
    return t * t

def ease_out_quad(t):
    return 1 - (1 - t) * (1 - t)

def ease_in_out_quad(t):
    if t < 0.5:
        return 2 * t * t
    return 1 - (-2 * t + 2) ** 2 / 2

Cubic¶

def ease_in_cubic(t):
    return t * t * t

def ease_out_cubic(t):
    return 1 - (1 - t) ** 3

def ease_in_out_cubic(t):
    if t < 0.5:
        return 4 * t * t * t
    return 1 - (-2 * t + 2) ** 3 / 2