test-kivy-app/kivy_venv/lib/python3.11/site-packages/kivymd/animation.py

"""
Animation
=========

.. versionadded:: 2.0.0

Adds new transitions to the :class:`~kivy.animation.AnimationTransition` class:
- "easing_standard"
- "easing_decelerated"
- "easing_accelerated"
- "easing_linear"


.. code-block:: python


    from kivy.lang import Builder
    from kivy.animation import Animation
    from kivy.uix.boxlayout import BoxLayout
    from kivy.clock import Clock
    from kivy.metrics import dp
    from kivy.properties import ListProperty

    from kivymd.app import MDApp


    class AnimBox(BoxLayout):
        obj_pos = ListProperty([0, 0])


    UI = '''
    <AnimBox>:
        transition:"in_out_bounce"
        size_hint_y:None
        height:dp(100)
        obj_pos:[dp(40), self.pos[-1] + dp(40)]
        canvas:
            Color:
                rgba:app.theme_cls.primaryContainerColor
            Rectangle:
                size:[self.size[0], dp(5)]
                pos:self.pos[0], self.pos[-1] + dp(50)
            Color:
                rgba:app.theme_cls.primaryColor
            Rectangle:
                size:[dp(30)] * 2
                pos:root.obj_pos
        MDLabel:
            adaptive_height:True
            text:root.transition
            padding:[dp(10), 0]
            halign:"center"

    MDGridLayout:
        orientation:"lr-tb"
        cols:1
        md_bg_color:app.theme_cls.backgroundColor
        spacing:dp(10)
    '''


    class MotionApp(MDApp):

        def build(self):
            return Builder.load_string(UI)

        def on_start(self):
            for transition in [
                "easing_linear",
                "easing_accelerated",
                "easing_decelerated",
                "easing_standard",
                "in_out_cubic"
            ]: # Add more here for comparison
                print(transition)
                widget = AnimBox()
                widget.transition = transition
                self.root.add_widget(widget)
            Clock.schedule_once(self.run_animation, 1)

        _inverse = True
        def run_animation(self, dt):
            x = (self.root.children[0].width - dp(30)) if self._inverse else 0
            for widget in self.root.children:
                Animation(
                    obj_pos=[x, widget.obj_pos[-1]], t=widget.transition, d=3
                ).start(widget)
            self._inverse = not self._inverse
            Clock.schedule_once(self.run_animation, 3.1)
    
    MotionApp().run()

.. image:: https://github.com/kivymd/KivyMD/assets/68729523/21c847b0-284a-4796-b704-e4a2531fbb1b 
    :align: center
"""

import math
import sys
import kivy.animation

float_epsilon = 8.3446500e-7

if sys.version_info < (3, 11):
    cbrt = lambda number: (abs(number) ** (1/3)) * (-1 if number < 0 else 1)
else:
    cbrt = math.cbrt

class CubicBezier:
    """Ported from Android source code"""

    p0 = 0
    p1 = 0
    p2 = 0
    p3 = 0

    def __init__(self, *args):
        self.p0, self.p1, self.p2, self.p3 = args

    def evaluate_cubic(self, p1, p2, t):
        a = 1.0 / 3.0 + (p1 - p2)
        b = p2 - 2.0 * p1
        c = p1
        return 3.0 * ((a * t + b) * t + c) * t

    def clamp_range(self, r):
        if r < 0.0:
            if -float_epsilon <= r < 0.0:
                return 0.0
            else:
                return math.nan
        elif r > 1.0:
            if 1.0 <= r <= 1.0 + float_epsilon:
                return 1.0
            else:
                return math.nan
        else:
            return r

    def close_to(self, x, y):
        return abs(x - y) < float_epsilon

    def find_first_cubic_root(self, p0, p1, p2, p3):
        a = 3.0 * (p0 - 2.0 * p1 + p2)
        b = 3.0 * (p1 - p0)
        c = p0
        d = -p0 + 3.0 * (p1 - p2) + p3
        if self.close_to(d, 0.0):
            if self.close_to(a, 0.0):
                if self.close_to(b, 0.0):
                    return math.nan
                return self.clamp_range(-c / b)
            else:
                q = math.sqrt(b * b - 4.0 * a * c)
                a2 = 2.0 * a
                root = self.clamp_range((q - b) / a2)
                if not math.isnan(root):
                    return root
                return self.clamp_range((-b - q) / a2)
        a /= d
        b /= d
        c /= d
        o3 = (3.0 * b - a * a) / 9.0
        q2 = (2.0 * a * a * a - 9.0 * a * b + 27.0 * c) / 54.0
        discriminant = q2 * q2 + o3 * o3 * o3
        a3 = a / 3.0

        if discriminant < 0.0:
            mp33 = -(o3 * o3 * o3)
            r = math.sqrt(mp33)
            t = -q2 / r
            cos_phi = max(-1.0, min(t, 1.0))
            phi = math.acos(cos_phi)
            t1 = 2.0 * cbrt(r)
            root = self.clamp_range(t1 * math.cos(phi / 3.0) - a3)
            if not math.isnan(root):
                return root
            root = self.clamp_range(
                t1 * math.cos((phi + 2.0 * math.pi) / 3.0) - a3
            )
            if not math.isnan(root):
                return root
            return self.clamp_range(
                t1 * math.cos((phi + 4.0 * math.pi) / 3.0) - a3
            )

        elif self.close_to(discriminant, 0.0):
            u1 = -cbrt(q2)
            root = self.clamp_range(2.0 * u1 - a3)
            if not math.isnan(root):
                return root
            return self.clamp_range(-u1 - a3)

        sd = math.sqrt(discriminant)
        u1 = cbrt(-q2 + sd)
        v1 = cbrt(q2 + sd)
        return self.clamp_range(u1 - v1 - a3)

    def t(self, value: float):
        return self.evaluate_cubic(
            self.p1,
            self.p3,
            self.find_first_cubic_root(
                -value,
                self.p0 - value,
                self.p2 - value,
                1.0 - value,
            ),
        )


class MDAnimationTransition(kivy.animation.AnimationTransition):
    """KivyMD's equivalent of kivy's `AnimationTransition`"""
    
    easing_standard = CubicBezier(0.4, 0.0, 0.2, 1.0).t
    easing_decelerated = CubicBezier(0.0, 0.0, 0.2, 1.0).t
    easing_accelerated = CubicBezier(0.4, 0.0, 1.0, 1.0).t
    easing_linear = CubicBezier(0.0, 0.0, 1.0, 1.0).t

# TODO: add `easing_emphasized` here
# it's defination is
# path(M 0,0 C 0.05, 0, 0.133333, 0.06, 0.166666, 0.4 C 0.208333, 0.82, 0.25, 1, 1, 1)

# Monkey patch kivy's animation module
kivy.animation.AnimationTransition = MDAnimationTransition