Feature or enhancement
Proposal:
This is a niche use case in the spirit of #110771 that has arisen in recent development of Toga.
GUI toolkits all have event loops, and it is highly desirable to be able to use Python asyncio calls in a GUI app. To this end, it necessary to make Python's asyncio event loop co-exist with the GUI's event loop and any platform specific issues.
On the Windows platform, a desirable property is to be able to listen for and process IOCP events independently. This can allow GUI-asyncio event loops to be reactive and avoid the need to polling.
The proposed change in asyncio.IocpProactor is to decompose asyncio.IocpProactor._poll() as follows:
def _process_completion_status(self, status):
err, transferred, key, address = status
try:
f, ov, obj, callback = self._cache.pop(address)
except KeyError:
if self._loop.get_debug():
self._loop.call_exception_handler({
'message': ('GetQueuedCompletionStatus() returned an '
'unexpected event'),
'status': ('err=%s transferred=%s key=%#x address=%#x'
% (err, transferred, key, address)),
})
# key is either zero, or it is used to return a pipe
# handle which should be closed to avoid a leak.
if key not in (0, _overlapped.INVALID_HANDLE_VALUE):
_winapi.CloseHandle(key)
return
if obj in self._stopped_serving:
f.cancel()
# Don't call the callback if _register() already read the result or
# if the overlapped has been cancelled
elif not f.done():
try:
value = callback(transferred, key, ov)
except OSError as e:
f.set_exception(e)
self._results.append(f)
else:
f.set_result(value)
self._results.append(f)
finally:
f = None
def _poll(self, timeout=None):
if timeout is None:
ms = INFINITE
elif timeout < 0:
raise ValueError("negative timeout")
else:
# GetQueuedCompletionStatus() has a resolution of 1 millisecond,
# round away from zero to wait *at least* timeout seconds.
ms = math.ceil(timeout * 1e3)
if ms >= INFINITE:
raise ValueError("timeout too big")
while True:
status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
if status is None:
break
ms = 0
self._process_completion_status(status)
# Remove unregistered futures
for ov in self._unregistered:
self._cache.pop(ov.address, None)
self._unregistered.clear()Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
No response
Linked PRs
Feature or enhancement
Proposal:
This is a niche use case in the spirit of #110771 that has arisen in recent development of Toga.
GUI toolkits all have event loops, and it is highly desirable to be able to use Python
asynciocalls in a GUI app. To this end, it necessary to make Python's asyncio event loop co-exist with the GUI's event loop and any platform specific issues.On the Windows platform, a desirable property is to be able to listen for and process IOCP events independently. This can allow GUI-asyncio event loops to be reactive and avoid the need to polling.
The proposed change in
asyncio.IocpProactoris to decomposeasyncio.IocpProactor._poll()as follows:Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
No response
Linked PRs