If you want to recognize a Smartphone's Action key, and preserve this fact
even if someday the Action key might be mapped to a different VK code than a
PC's Enter key, then you want to use VK_TACTION in your program.
I think that in principle the VK_T**** definitions had the same idea. For a
PC's keyboard there are no VK_*** definitions for keys that have digits 0 to
9 on them, and programs should use values '0' through '9' or 0x30 through
0x39. For Smartphones and Pocket PCs, the VK_T*** definitions are oddly
coded in Unicode. In my experience characters might be encoded in either
ANSI code pages or Unicode, but those were character values not VK codes.
This is the only place where VK codes are coded in Unicode. My programs use
values 0x30 through 0x39.
winuserm.h shows that VK_TACTION is mapped to VK_RETURN at the present time.
winuser.h shows that VK_RETURN is mapped to 0x0D at the present time.
In principle I agree (though for this I would probably write VK_TACTION).
However, the relationship among Windows CE, OEM keyboard drivers, the SIP
panel, and applications is so messed up that I don't know any really
reliable solution. For example when I tried to process WM_KEYDOWN, I was
always getting VK_PROCESSKEY instead of the actual key. Reading MSDN, I
found alternative code that was asserted to work, but it really provided a
second copy of the VK_PROCESSKEY constant instead of the actual key.
Microsoft posted some code that was asserted to work, using undocumented
features of a partly documented function, but it really provided a third
copy of the VK_PROCESSKEY constant instead of the actual key.
I ended up doing lots of experiments, some hits and misses on VK codes, and
mostly hits on WM_CHAR messages. If a VK code turns out to be equal to a
value that can be delivered by a WM_CHAR message as a character, then it's
ambiguous, we can't really figure out which key was pressed. I had to avoid
processing most WM_KEYDOWN messages except for a few VK codes that I hoped
would be accurate, and process WM_CHAR messages for most keys.