Windows Global Keyboard Hook - Delphi

Question

I've created a GLOBAL keyboard hook DLL, using source code found on the internet. For the best part it works brilliant, except when it comes to browsers.

It picks up every key in the browser except, it seems, when the browser gets focus, it looses the first key that is pressed. Tested this in IE and Firefox and it seems to be the same for both.

For instance, if I open IE and start typing www. , I only get back ww. If the browser window stays in focus no further keys are lost. As soon as the browser looses focus and regains focus, the first key is again missing.

Could it be because of using only WH_KEYDOWN instead of WH_KEYPRESS / WH_KEYUP ? Can anyone shed some light on this please?

Thank you

PS: The hook function itself is below: The DLL is sent a memo box and app handle to wich the DLL will send messages as well as a usermessage.

    function KeyHookFunc(Code, VirtualKey, KeyStroke: Integer): LRESULT; stdcall; 
var
  KeyState1: TKeyBoardState; 
  AryChar: array[0..1] of Char; 
  Count: Integer; 
begin 
  Result := 0; 
  if Code = HC_NOREMOVE then Exit;

  Result := CallNextHookEx(hKeyHook, Code, VirtualKey, KeyStroke); 
  {I moved the CallNextHookEx up here but if you want to block 
   or change any keys then move it back down} 
  if Code < 0 then 
    Exit; 
  if Code = HC_ACTION then 
  begin 
    if ((KeyStroke and (1 shl 30)) <> 0) then 
      if not IsWindow(hMemo) then
      begin 
       {I moved the OpenFileMapping up here so it would not be opened 
        unless the app the DLL is attatched to gets some Key messages} 
        hMemFile  := OpenFileMapping(FILE_MAP_WRITE, False, 'NetParentMAP');//Global7v9k
        PHookRec1 := MapViewOfFile(hMemFile, FILE_MAP_WRITE, 0, 0, 0); 
        if PHookRec1 <> nil then 
        begin 
          hMemo := PHookRec1.MemoHnd; 
          hApp  := PHookRec1.AppHnd; 
        end; 
      end;
    if ((KeyStroke AND (1 shl 31))  = 0) then //if ((KeyStroke and (1 shl 30)) <> 0) then
    begin 
      GetKeyboardState(KeyState1); 
      Count := ToAscii(VirtualKey, KeyStroke, KeyState1, AryChar, 0); 
      if Count = 1 then
      begin
        SendMessage(hMemo, WM_CHAR, Ord(AryChar[0]), 0); 
        {I included 2 ways to get the Charaters, a Memo Hnadle and 
         a WM_USER+1678 message to the program} 
        PostMessage(hApp, WM_USER + 1678, Ord(AryChar[0]), 0);
      end;
    end; 
  end; 
end; 

Answer 1

You are not assigning your hMemo and hApp values early enough. You are waiting until a notification with a "previous state" flag of 1, which indicates a key has been held down for at least 1 repeat count, or is being released, whichever occurs first. Thus, hMemo and hApp are not available yet when your hook detects its first key down notification. That is why you miss characters. Try this instead:

function KeyHookFunc(Code, VirtualKey, KeyStroke: Integer): LRESULT; stdcall;
var
  KeyState1: TKeyBoardState;
  AryChar: array[0..1] of Char;
  Count: Integer;
begin
  Result := CallNextHookEx(hKeyHook, Code, VirtualKey, KeyStroke);
  if Code <> HC_ACTION then Exit;

  { a key notification had occured, prepare the HWNDs
  before checking the actual key state }
  if (hMemo = 0) or (hApp = 0) then
  begin
    if hMemFile = 0 then
    begin
      hMemFile := OpenFileMapping(FILE_MAP_WRITE, False, 'NetParentMAP');
      if hMemFile = 0 then Exit;
    end;
    if PHookRec1 = nil then
    begin
      PHookRec1 := MapViewOfFile(hMemFile, FILE_MAP_WRITE, 0, 0, 0);
      if PHookRec1 = nil then Exit;
    end;
    hMemo := PHookRec1.MemoHnd;
    hApp  := PHookRec1.AppHnd;
    if (hMemo = 0) and (hApp = 0) then Exit;
  end;

  if ((KeyStroke and (1 shl 31)) = 0) then // a key is down
  begin
    GetKeyboardState(KeyState1);
    Count := ToAscii(VirtualKey, KeyStroke, KeyState1, AryChar, 0);
    if Count = 1 then
    begin
      if hMemo <> 0 then SendMessage(hMemo, WM_CHAR, Ord(AryChar[0]), 0);
      if hApp <> 0 then PostMessage(hApp, WM_USER + 1678, Ord(AryChar[0]), 0);
    end;
  end;
end;