win_event_device_watcher wait before notify - #12207
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Events on removal arrive rapidly and so calling the callback for each is
redundant but also wrong:
In testing, disconnection happened in two stages, triggering two events:
OLD group, before disconnection:
\\?\usb#vid_8086&pid_0b3a&mi_00#6&1e67ef5f&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
FIRST event after disconnection, NEW group:
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
OLD-NEW = removed
NEW-OLD = added
And operator-() is subtract_sets():
for each item on LEFT side:
add to result if none on RIGHT side is a superset of LEFT
In this case:
NEW is subset of OLD -> OLD is superset of NEW
OLD-NEW = 1 device removed
NEW-OLD = 0 device added
SECOND event after disconnection, OLD=previous NEW:
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
In this case:
NEW=empty
OLD-NEW = 1 device removed (again!?)
NEW-OLD = 0 device added
Solution is fairly simple, and was already done in udev device-watcher:
wait a short while and only notify of changes after a brief time elapses
post-event. Any new event refreshes the timer.
Nir-Az
reviewed
Sep 19, 2023
| break; | ||
| auto data = reinterpret_cast<extra_data*>(GetWindowLongPtr(hWnd, GWLP_USERDATA)); | ||
| auto next = data->_last; | ||
| std::wstring temp = reinterpret_cast<DEV_BROADCAST_DEVICEINTERFACE*>(lParam)->dbcc_name; |
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Any idea what was the reason for all of this code?
And why it is not needed anymore?
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I can't very well comment about the first.
But it's not needed any more because we just get everything again fresh (after a delay), just as if we did query_devices. This is how udev does it, too.
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Probably they were trying to save time...
Nir-Az
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Sep 19, 2023
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Overall, it looks like a great enhancement.
Just wondering about the code removal, too bad they didn't wrote comments because I have no idea what they did there.
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Events on removal arrive rapidly and so calling the callback for each is redundant but also wrong:
In testing, disconnection happened in two stages, triggering two events:
OLD group, before disconnection:
\\?\usb#vid_8086&pid_0b3a&mi_00#6&1e67ef5f&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
FIRST event after disconnection, NEW group:
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
OLD-NEW = removed
NEW-OLD = added
And operator-() is subtract_sets():
for each item on LEFT side:
add to result if none on RIGHT side is a superset of LEFT
In this case:
NEW is subset of OLD -> OLD is superset of NEW
OLD-NEW = 1 device removed
NEW-OLD = 0 device added
SECOND event after disconnection, OLD=previous new:
\\?\usb#vid_8086&pid_0b3a&mi_03#6&1e67ef5f&0&0003#{e5323777-f976-4f5b-9b55-b94699c46e44}\global
In this case:
NEW=empty
OLD-NEW = 1 device removed (again!?)
NEW-OLD = 0 device added
Solution is fairly simple, and was already done in udev device-watcher: wait a short while and only notify of changes after a brief time elapses post-event. Any new event refreshes the timer.