test-kivy-app/kivy_venv/lib/python3.11/site-packages/kivy/effects/dampedscroll.py

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2024-09-15 12:12:16 +00:00
'''
Damped scroll effect
====================
.. versionadded:: 1.7.0
This damped scroll effect will use the
:attr:`~kivy.effects.scroll.ScrollEffect.overscroll` to calculate the scroll
value, and slows going back to the upper or lower limit.
'''
__all__ = ('DampedScrollEffect',)
from kivy.effects.scroll import ScrollEffect
from kivy.properties import NumericProperty, BooleanProperty
from kivy.metrics import sp
class DampedScrollEffect(ScrollEffect):
'''DampedScrollEffect class. See the module documentation for more
information.
'''
edge_damping = NumericProperty(0.25)
'''Edge damping.
:attr:`edge_damping` is a :class:`~kivy.properties.NumericProperty` and
defaults to 0.25
'''
spring_constant = NumericProperty(2.0)
'''Spring constant.
:attr:`spring_constant` is a :class:`~kivy.properties.NumericProperty` and
defaults to 2.0
'''
min_overscroll = NumericProperty(.5)
'''An overscroll less than this amount will be normalized to 0.
.. versionadded:: 1.8.0
:attr:`min_overscroll` is a :class:`~kivy.properties.NumericProperty` and
defaults to .5.
'''
round_value = BooleanProperty(True)
'''If True, when the motion stops, :attr:`value` is rounded to the nearest
integer.
.. versionadded:: 1.8.0
:attr:`round_value` is a :class:`~kivy.properties.BooleanProperty` and
defaults to True.
'''
def update_velocity(self, dt):
if abs(self.velocity) <= self.min_velocity and self.overscroll == 0:
self.velocity = 0
# why does this need to be rounded? For now refactored it.
if self.round_value:
self.value = round(self.value)
return
total_force = self.velocity * self.friction * dt / self.std_dt
if abs(self.overscroll) > self.min_overscroll:
total_force += self.velocity * self.edge_damping
total_force += self.overscroll * self.spring_constant
else:
self.overscroll = 0
stop_overscroll = ''
if not self.is_manual:
if self.overscroll > 0 and self.velocity < 0:
stop_overscroll = 'max'
elif self.overscroll < 0 and self.velocity > 0:
stop_overscroll = 'min'
self.velocity = self.velocity - total_force
if not self.is_manual:
self.apply_distance(self.velocity * dt)
if stop_overscroll == 'min' and self.value > self.min:
self.value = self.min
self.velocity = 0
return
if stop_overscroll == 'max' and self.value < self.max:
self.value = self.max
self.velocity = 0
return
self.trigger_velocity_update()
def on_value(self, *args):
scroll_min = self.min
scroll_max = self.max
if scroll_min > scroll_max:
scroll_min, scroll_max = scroll_max, scroll_min
if self.value < scroll_min:
self.overscroll = self.value - scroll_min
elif self.value > scroll_max:
self.overscroll = self.value - scroll_max
else:
self.overscroll = 0
self.scroll = self.value
def on_overscroll(self, *args):
self.trigger_velocity_update()
def apply_distance(self, distance):
os = abs(self.overscroll)
if os:
distance /= 1. + os / sp(200.)
super(DampedScrollEffect, self).apply_distance(distance)