Imitating 'async_bind'

async_bind.py

# imitating 'async_bind'


from kivy.config import Config
Config.set('input', 'mouse', 'mouse,disable_multitouch')
import kivy
kivy.require('2.0.0')
import trio
from kivy.app import App
from kivy.uix.widget import Widget


async def async_bind(ed, name, *, filter=None):
    def _callback(*args):
        nonlocal parameter
        if (filter is not None) and not filter(*args):
            return
        parameter = args
        event.set()

    parameter = None
    bind_id = ed.fbind(name, _callback)
    assert bind_id > 0  # check if binding succeeded
    try:
        while True:
            event = trio.Event()
            await event.wait()
            yield parameter
    finally:
        ed.unbind_uid(name, bind_id)


class Paint(Widget):
    def on_touch_down(self, touch):
        if not self.collide_point(*touch.opos):
            return
        nursery = App.get_running_app().nursery
        nursery.start_soon(self.draw_polyline, touch)

    async def draw_polyline(self, touch):
        from kivy.graphics import Line
        def hide_touch(*args):
            return True
        try:
            self.bind(
                on_touch_down=hide_touch,
                on_touch_move=hide_touch,
                on_touch_up=hide_touch,
            )
            to_widget = self.to_widget
            line = Line(
                width=2,
                points=[*to_widget(*touch.opos), *to_widget(*touch.pos)]
            )
            self.canvas.add(line)
            async for widet, touch in async_bind(self, 'on_touch_down'):
                if touch.button == 'left':
                    p = line.points
                    p.extend(to_widget(*touch.opos))
                    line.points = p
                elif touch.button == 'right':
                    break
        finally:
            self.unbind(
                on_touch_down=hide_touch,
                on_touch_move=hide_touch,
                on_touch_up=hide_touch,
            )



class SampleApp(App):
    nursery = None

    def build(self):
        return Paint()

    async def root_task(self):
        async with trio.open_nursery() as nursery:
            self.nursery = nursery
            async def app_task():
                await self.async_run(async_lib='trio')
                nursery.cancel_scope.cancel()
            nursery.start_soon(app_task)
    

trio.run(SampleApp().root_task)