MSDN says the low-order bit is the only one that's reliable and also that code shouldn't use HIWORD/LOWORD to extract these bits

https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getasynckeystate

ANGLE is doing both using macros and checking the hi-order bit.

@ https://cs.chromium.org/chromium/src/third_party/angle/util/windows/win32/Win32Window.cpp?q=GetAsyncKeyState&sq=package:chromium&dr=C
 

MSDN says the hi-order bit is the only one that's reliable and that HIWORD shouldn't be used to extract this bit:

https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getasynckeystate

ANGLE is using HIWORD

@ https://cs.chromium.org/chromium/src/third_party/angle/util/windows/win32/Win32Window.cpp?q=GetAsyncKeyState&sq=package:chromium&dr=C