Originally, black_bindings found each contiguous "//|" block and sent
it to black independently. This was slower than it needed to be.
Instead, swap the comment prefix: when running black, take off
"//|" prefixes and put "##|" prefixes on all un-prefixed lines.
Then, after black is run, do the opposite operation
This more than doubles the overall speed of "pre-commit run --all",
from 3m20s to 55s CPU time on my local machine (32.5s to under 10s
"elapsed" time)
It also causes a small amount of churn in the bindings, because
black now sees enough context to know whether one 'def' follows another
or ends the 'def's in a 'class'. In the latter case, it adds an extra
newline, which becomes a "//|" line.
I'm less sure why a trailing comma was omitted before down in
rp2pio/StateMachine.c but let's roll with it.
This allows a small wrapper class to be written
```py
class AsyncEventQueue:
def __init__(self, events):
self._events = events
async def __await__(self):
yield asyncio.core._io_queue.queue_read(self._events)
return self._events.get()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
pass
```
and used to just "await" the next event:
```py
async def key_task():
print("waiting for keypresses")
with keypad.KeyMatrix([board.D4], [board.D5]) as keys, AsyncEventQueue(keys.events) as ev:
while True:
print(await ev)
```
Because checking the empty status of the EventQueue does not enter
CircuitPython bytecode, it's assumed (but not measured) that this is
more efficient than an equivalent loop with an `await async.sleep(0)`
yield and introduces less latency than any non-zero sleep value.
