Merge branch 'win-sleep-bug' of github.com:textualize/textual into wi…

…n-sleep-bug

src/textual/_time.py

@@ -1,5 +1,5 @@
-import platform
 import asyncio
+import platform
 from asyncio import sleep as asyncio_sleep
 from time import monotonic, perf_counter
 

src/textual/_win_sleep.py

@@ -4,6 +4,8 @@
 This should only be imported on Windows.
 """
 
+from __future__ import annotations
+
 import asyncio
 from time import sleep as time_sleep
 from typing import Coroutine
@@ -31,16 +33,25 @@ async def time_sleep_coro(secs: float):
     print("Exception found")
 
     def sleep(secs: float) -> Coroutine[None, None, None]:
+        """Wrapper around `time.sleep` to match the signature of the main case below."""
         return time_sleep_coro(secs)
 
 else:
 
+    async def no_sleep_coro():
+        """Creates a coroutine that does nothing for when no sleep is needed."""
+        pass
+
     def sleep(secs: float) -> Coroutine[None, None, None]:
         """A replacement sleep for Windows.
 
         Note that unlike `time.sleep` this *may* sleep for slightly less than the
         specified time. This is generally not an issue for Textual's use case.
 
+        In order to create a timer that _can_ be cancelled on Windows, we need to
+        create a timer and a separate event, and then we wait for either of the two
+        things. When Textual wants to quit, we set the cancel event.
+
         Args:
             secs: Seconds to sleep for.
         """
@@ -49,7 +60,7 @@ def sleep(secs: float) -> Coroutine[None, None, None]:
         sleep_for = max(0, secs - 0.001)
         if sleep_for < 0.0005:
             # Less than 0.5ms and its not worth doing the sleep
-            return time_sleep_coro(0)
+            return no_sleep_coro()
 
         timer = kernel32.CreateWaitableTimerExW(
             None,
@@ -77,6 +88,7 @@ def sleep(secs: float) -> Coroutine[None, None, None]:
             return time_sleep_coro(sleep_for)
 
         def cancel_inner():
+            """Sets the cancel event so we know we can stop waiting for the timer."""
             kernel32.SetEvent(cancel_event)
 
         async def cancel():

tests/test_win_sleep.py

@@ -4,7 +4,6 @@
 
 import pytest
 
-from textual._win_sleep import sleep
 from textual.app import App
 
 pytestmark = pytest.mark.skipif(