Sideband_CE/sbapp/kivymd/effects/fadingedge/fadingedge.py

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2022-07-07 22:16:10 +02:00
"""
Effects/FadingEdgeEffect
========================
.. versionadded:: 1.0.0
The `FadingEdgeEffect` class implements a fade effect for `KivyMD` widgets:
.. code-block:: python
from kivy.lang import Builder
from kivy.uix.scrollview import ScrollView
from kivymd.app import MDApp
from kivymd.effects.fadingedge.fadingedge import FadingEdgeEffect
from kivymd.uix.list import OneLineListItem
KV = '''
MDScreen:
FadeScrollView:
fade_height: self.height / 2
fade_color: root.md_bg_color
MDList:
id: container
'''
class FadeScrollView(FadingEdgeEffect, ScrollView):
pass
class Test(MDApp):
def build(self):
return Builder.load_string(KV)
def on_start(self):
for i in range(20):
self.root.ids.container.add_widget(
OneLineListItem(text=f"Single-line item {i}")
)
Test().run()
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/fading-edge-effect-white.gif
:align: center
.. note:: Use the same color value for the fade_color parameter as for the
parent widget.
"""
from typing import Union
from kivy.clock import Clock
from kivy.graphics.context_instructions import Color
from kivy.graphics.vertex_instructions import Rectangle
from kivy.metrics import dp
from kivy.properties import BooleanProperty, ColorProperty, NumericProperty
from kivymd.theming import ThemableBehavior
__all_ = ("FadingEdgeEffect",)
class FadingEdgeEffect(ThemableBehavior):
"""
The class implements the fade effect.
.. versionadded:: 1.0.0
"""
fade_color = ColorProperty(None)
"""
Fade color.
:attr:`fade_color` is an :class:`~kivy.properties.ColorProperty`
and defaults to `None`.
"""
fade_height = NumericProperty(0)
"""
Fade height.
:attr:`fade_height` is an :class:`~kivy.properties.ColorProperty`
and defaults to `0`.
"""
edge_top = BooleanProperty(True)
"""
Display fade edge top.
:attr:`edge_top` is an :class:`~kivy.properties.BooleanProperty`
and defaults to `True`.
"""
edge_bottom = BooleanProperty(True)
"""
Display fade edge bottom.
:attr:`edge_bottom` is an :class:`~kivy.properties.BooleanProperty`
and defaults to `True`.
"""
_height_segment = 10
def __init__(self, **kwargs):
super().__init__(**kwargs)
Clock.schedule_once(self.set_fade)
# TODO: Perhaps it would be better if we used a Shader for the fade effect.
# But, I think the canvas instructions shouldn't affect performance
def set_fade(self, interval: Union[int, float]) -> None:
"""Draws a bottom and top fade border on the canvas."""
fade_color = (
self.theme_cls.primary_color
if not self.fade_color
else self.fade_color
)
height_segment = (
self.fade_height if self.fade_height else dp(100)
) // self._height_segment
alpha = 1.1
with self.canvas:
for i in range(self._height_segment):
alpha -= 0.1
Color(rgba=(fade_color[:-1] + [round(alpha, 1)]))
rectangle_top = (
Rectangle(
pos=(self.x, self.height - (i * height_segment)),
size=(self.width, height_segment),
)
if self.edge_top
else None
)
rectangle_bottom = (
Rectangle(
pos=(self.x, i * height_segment),
size=(self.width, height_segment),
)
if self.edge_bottom
else None
)
# How I hate lambda functions because of their length :(
# But I dont want to call the arguments by short,
# incomprehensible names 'a', 'b', 'c'.
self.bind(
pos=lambda instance_fadind_edge_effect, window_size, rectangle_top=rectangle_top, rectangle_bottom=rectangle_bottom, index=i: self.update_canvas(
instance_fadind_edge_effect,
window_size,
rectangle_top,
rectangle_bottom,
index,
),
size=lambda instance_fadind_edge_effect, window_size, rectangle_top=rectangle_top, rectangle_bottom=rectangle_bottom, index=i: self.update_canvas(
instance_fadind_edge_effect,
window_size,
rectangle_top,
rectangle_bottom,
index,
),
)
def update_canvas(
self,
instance_fadind_edge_effect,
size: list[int, int],
rectangle_top: Rectangle,
rectangle_bottom: Rectangle,
index: int,
) -> None:
"""
Updates the position and size of the fade border on the canvas.
Called when the application screen is resized.
"""
height_segment = (
self.fade_height if self.fade_height else dp(100)
) // self._height_segment
if rectangle_top:
rectangle_top.pos = (
instance_fadind_edge_effect.x,
size[1]
- (index * height_segment - instance_fadind_edge_effect.y),
)
rectangle_top.size = (size[0], height_segment)
if rectangle_bottom:
rectangle_bottom.pos = (
instance_fadind_edge_effect.x,
index * height_segment + instance_fadind_edge_effect.y,
)
rectangle_bottom.size = (size[0], height_segment)