Three Dollar Quill

"""Adapter widget to run the Trio and pyglet event loops together.

I tried and failed to come up with a Three Little Pigs joke.
"""

import pyglet.app
import pyglet.event
import pyglet.window
import trio.lowlevel


class TrioLoop(pyglet.event.EventDispatcher):
    """Custom widget for running a Trio event loop concurrently with pyglet."""

    started = False

    def start_trio(self, trio_main):
        """Queue the Trio mainloop to run when the app starts.

        This function should be called once, before pyglet.app.run().
        """
        if self.started:
            raise RuntimeError
        self.started = True
        pyglet.app.platform_event_loop.post_event(self, "on_trio_start", trio_main)

    def _schedule_callback(self, callback):
        """Schedule the guest loop callback in pyglet's event loop."""
        pyglet.app.platform_event_loop.post_event(self, "on_trio_callback", callback)

    def _done_callback(self, outcome):
        """Schedule the done callback in pyglet's event loop."""
        pyglet.app.platform_event_loop.post_event(self, "on_trio_done", outcome)

    def on_trio_start(self, trio_main):
        """Handle the on_trio_start event. Start Trio in guest mode."""
        trio.lowlevel.start_guest_run(
            trio_main,
            run_sync_soon_threadsafe=self._schedule_callback,
            done_callback=self._done_callback,
        )

    def on_trio_callback(self, callback):
        """Handle the on_trio_callback event."""
        callback()

    def on_trio_done(self, outcome):
        """Handle the on_trio_done event. Stop the event loop.

        This function should, but does not yet, do something with the "outcome"
        parameter.
        """
        pyglet.app.event_loop.exit()


TrioLoop.register_event_type("on_trio_start")
TrioLoop.register_event_type("on_trio_callback")
TrioLoop.register_event_type("on_trio_done")


async def mainloop():
    """Run a combination of the Trio and pyglet tutorials.

    This code isn't really useful on its own, but functions as a
    proof-of-concept and manual test.
    """
    for _ in range(5):
        window = pyglet.window.Window()
        label = pyglet.text.Label(
            "Hello from Trio",
            font_name="Times New Roman",
            font_size=36,
            x=window.width // 2,
            y=window.height // 2,
            anchor_x="center",
            anchor_y="center",
        )

        @window.event
        def on_draw():
            window.clear()
            label.draw()

        await trio.sleep(1)


if __name__ == "__main__":
    trio_loop = TrioLoop()
    trio_loop.start_trio(mainloop)
    pyglet.app.run()