Understanding how to use Windows Hooks

Question

Im trying to use SetWindowsHookEx to Hook Mouse in some process. Im using Delphi 7. Code (DLL):

function MouseProc(code: integer; wParam: WPARAM; lParam: LPARAM)
  : LongInt; stdcall;
var
  AppWnd: HWND;
begin
  Result := 0;
  if (code < 0) then
    Result := CallNextHookEx(HookHandle, code, wParam, lParam)
  else begin
    AppWnd := FindWindowW('ichookapplication', nil);
    SendMessage(AppWnd, MW_MOUSEHOOKED,  wParam, GetCurrentProcessId);
    Result := CallNextHookEx(HookHandle, code, wParam, lParam);
  end;
end;

procedure HookThreadId(theadId: Cardinal) export; stdcall;
var
  e: DWORD;
begin
  HookHandle := SetWindowsHookEx(WH_MOUSE, @MouseProc, 0, theadId);
  if (HookHandle = 0) then
  begin
    e := GetLastError;
    MessageBox(0, 'error', PAnsiChar(IntToStr(e)), MB_OK);
  end;
end;

MW_MOUSEHOOKED is WM_USER + 101;

application:

//loading code
if (dll = 0) then
  begin
    dll := LoadLibrary('mhook.dll');
    @Hook := nil;
    @SetThreadHook := nil;
  end;
  if (dll > HINSTANCE_ERROR) then
  begin
    pH := GetProcAddress(dll, 'Hook');
    @Hook := pH;
    pSth := GetProcAddress(dll, 'HookThreadId');
    @SetThreadHook := pSth;
  end;

// attach code
h := FindWindow(nil, 'Form1');
  terminalProc := GetWindowThreadProcessId(h, nil);
  if (terminalProc = 0) then
  begin
      ShowMessage(IntToStr(GetLastError));
     Exit;
  end;


SetThreadHook(terminalProc);

So. SetWindowsHookEx returns 1428 error: Cannot set nonlocal hook without a module handle. But as i know if im using dll hmodule is not needed... How i whant it will work: Every mouse event will passing to my app (window class is 'ichookapplication') using WM_DATA (wParam is event data, lParam is ProcessId)

Thanks!

Answer 1

WH_MOUSE is a global hook. The DLL will be injected into hooked processes. You do need to supply a module handle. The name associated with error code 1428 is pretty clear, ERROR_HOOK_NEEDS_HMOD. It's not as though it's difficult to provide a module handle. Pass HInstance.

If you don't want to inject, then you'll need to use WH_MOUSE_LL instead of WH_MOUSE.