Delphi correct signature for LowLevelKeyboardProc()

Question

I´m writing a global keyboard hook in Delphi 2007 and Windows 10. I´ve found different signatures for a Delphi LowLevelKeyboardProc callback. Someones like this and windows documentation (https://docs.microsoft.com/es-es/previous-versions/windows/desktop/legacy/ms644985(v=vs.85))
LowLevelKeyboardProc() never is executed
prompt that lparam is a pointer to a TKBDLLHOOKSTRUCT record.
Other ones however (http://www.delphifaq.com/faq/delphi_windows_API/f512.shtml and https://www.swissdelphicenter.ch/en/showcode.php?id=1722), show

function KeyHookFunc(Code, VirtualKey, KeyStroke: Integer): LRESULT; stdcall;

completely ignoring the TKBDLLHOOKSTRUCT record pointer.
Which one is correct?
I'm guessing the first one is the correct one but I need to be sure. I´ve been using such signature but when I call another Function in the same unit (and DLL) passing lParam it causes Access Violation when accessing it. All functions and procedures within the DLL use stdcall

The MS link is correct. It's difficult to say why your code isn't working, because we can't see your code from here. The Delphi definition can be found in Windows.pas: TFNHookProc = function (code: Integer; wparam: WPARAM; lparam: LPARAM): LRESULT stdcall; — Ken White

Sertac Akyuz Sertac Akyuz · Accepted Answer · 2019-12-26T18:53:35

All of the callback declarations are correct, although the latter two links do not give examples of LowLevelKeyboardProc but KeyboardProc. IOW, they are not low level keyboard hooks.

Note the latter two wouldn't work in 64 bits due to Integer usage instead of WPARAM, LPARAM and LRESULT.

Delphi correct signature for LowLevelKeyboardProc()

1 Answers