For example, in user32.dll is the function
RegisterUserAPIHooks. That is
totally undocumented.
However, it is one of the many undocumented functions that only exist to
allow components of windows to talk to each other (in this case it exists
only to allow uxtheme/comctl32 to hook user32 and do
non-client-area themeing).
The question is, do we implement such functions?
Well... If it is exported by the DLL then it should be exported. But if it
is undocumented I don't think it should be implemented until an application
is found which uses it. Not having a RegisterUserAPIHooks implementation
doesn't make ReactOS run less windows programs. I would suggest something
like introducing a "UNDOCUMENTED;" macro (like the UNIMPLEMENTED; macro) to
track down used undocumented functions...
Sebastiaan