(Kivy) magnet + drag_n_drop = awesome

main.py

'''
https://youtu.be/fP0Pxy_3cSI
'''
from kivy.app import runTouchApp
from kivy.lang import Builder
from kivy.uix.label import Label
import rich_drag_n_drop


KV_CODE = '''
BoxLayout:
    RichDraggableGridLayout:
        id: left
        drag_classes: ['test', ]
        cols: 4
    Widget:
        size_hint_x: None
        width: 1
        canvas:
            Color:
                rgb: .5, 0, 1
            Rectangle:
                pos: self.pos
                size: self.size
    RichDraggableBoxLayout:
        id: right
        size_hint_x: .3
        orientation: 'vertical'
        drag_classes: ['test', ]
'''


root = Builder.load_string(KV_CODE)
left = root.ids.left
for i in range (10):
    left.add_widget(
        Label(text=str(i), font_size='80'),
        drag_cls='test')
right = root.ids.right
for text in 'ABCDE':
    right.add_widget(
        Label(text=text, font_size='80'),
        drag_cls='test')

runTouchApp(root)
print('left:', [c.text for c in left.children_without_case])
print('right:', [c.text for c in right.children_without_case])

rich_drag_n_drop.py

'''
Installation
============

python -m pip install kivy_garden.drag_n_drop --extra-index-url https://kivy-garden.github.io/simple/
garden install magnet
'''

__all__ = (
    'RichDraggableLayoutBehavior', 'RichDraggableGridLayout',
    'RichDraggableBoxLayout',
)

from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.garden.magnet import Magnet
from kivy_garden.drag_n_drop import (
    DraggableController, DraggableLayoutBehavior, DraggableObjectBehavior,
    SpacerWidget,
)


class DraggableMagnet(DraggableObjectBehavior, Magnet):
    def initiate_drag(self):
        self.parent.remove_widget(self)


class RichDraggableLayoutBehavior(DraggableLayoutBehavior):

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        magnet = Magnet(duration=.2)
        magnet.add_widget(SpacerWidget())
        self.spacer_widget = magnet
        self.drag_controller = DraggableController()

    def add_widget(self, widget, index=0, *, drag_cls=''):
        if isinstance(widget, Magnet):
            super().add_widget(widget, index=index)
        else:
            magnet = DraggableMagnet(
                drag_cls=drag_cls,
                duration=.5,
                drag_controller=self.drag_controller
            )
            magnet.add_widget(widget)
            super().add_widget(magnet, index=index)

    def remove_widget(self, widget):
        if isinstance(widget, Magnet):
            super().remove_widget(widget)
        else:
            for c in self.children:
                if c.children[0] == widget:
                    c.remove_widget(widget)
                    super().remove_widget(c)

    def handle_drag_release(self, index, drag_widget):
        c = drag_widget.children[0]
        s = self.spacer_widget
        c.pos, c.size = s.pos, s.size
        self.add_widget(drag_widget, index)

    @property
    def children_without_case(self):
        return (magnet.children[0] for magnet in self.children)


class RichDraggableGridLayout(RichDraggableLayoutBehavior, GridLayout):
    def compare_pos_to_widget(self, widget, pos):
        x, y = pos
        if y > widget.top:
            return 'before'
        elif y < widget.y:
            return 'after'
        elif x > widget.right:
            return 'after'
        elif x < widget.x:
            return 'before'
        else:
            spacer = self.spacer_widget
            if widget.parent is spacer.parent:
                children = widget.parent.children
                if children.index(spacer) > children.index(widget):
                    return 'after'
        return 'before'


class RichDraggableBoxLayout(RichDraggableLayoutBehavior, BoxLayout):
    def compare_pos_to_widget(self, widget, pos):
        if self.orientation == 'vertical':
            return 'before' if pos[1] >= widget.center_y else 'after'
        return 'before' if pos[0] < widget.center_x else 'after'