#!python
import kivy

kivy.require("1.5.1")
from kivy.uix.gridlayout import GridLayout  # noqa: E402
from kivy.uix.slider import Slider  # noqa: E402
from functools import partial  # noqa: E402


class DraggableScrollbar(GridLayout):
    slider = None

    def __init__(self, recycleView, **kwargs):

        # call the constructor of parent
        # if they are any graphics object, they will be added on our new canvas
        super(DraggableScrollbar, self).__init__(**kwargs)
        self.cols = 2
        self.orientation = "lr-bt"

        # the last child of layout1 and this will act as the draggable scrollbar
        self.slider = Slider(
            min=0,
            max=1,
            value=25,
            orientation="vertical",
            step=0.01,
            size_hint=(0.03, 0.95),
        )

        recycleView.bind(scroll_y=partial(self.slider_change))

        # what this does is, whenever the slider is dragged, it scrolls the previously added scrollview by the same amount the slider is dragged
        self.slider.bind(value=partial(self.scroll_change, recycleView))

        self.add_widget(recycleView)
        self.add_widget(self.slider)

    def scroll_change(self, recycleView, instance, value):
        recycleView.scroll_y = value

    def slider_change(self, instance, value):
        if value >= 0:
            # this to avoid 'maximum recursion depth exceeded' error
            self.slider.value = value