Create Tranzparent Menu

var
  Form1: TForm1;
  hHookID: HHOOK;
  
//

function MakeWndTrans(Wnd: HWND; nAlpha: Integer = 10): Boolean;
type
  TSetLayeredWindowAttributes = function(hwnd: HWND; crKey: COLORREF; bAlpha: Byte;
    dwFlags: Longint): Longint; stdcall;
const
  // Use crKey as the transparency color.
  LWA_COLORKEY = 1;
  // Use bAlpha to determine the opacity of the layered window..
  LWA_ALPHA = 2;
  WS_EX_LAYERED = $80000;
var
  hUser32: HMODULE;
  SetLayeredWindowAttributes: TSetLayeredWindowAttributes;
  i : Integer;
begin
  Result := False;
  // Here we import the function from USER32.DLL
  hUser32 := GetModuleHandle('USER32.DLL');
  if hUser32 <> 0 then
  begin
    @SetLayeredWindowAttributes := GetProcAddress(hUser32,'SetLayeredWindowAttributes');
    // If the import did not succeed, make sure your app can handle it!
    if @SetLayeredWindowAttributes <> nil then
    begin
      // Check the current state of the dialog, and then add the WS_EX_LAYERED attribute
      SetWindowLong(Wnd, GWL_EXSTYLE, GetWindowLong(Wnd, GWL_EXSTYLE) or WS_EX_LAYERED);
      // The SetLayeredWindowAttributes function sets the opacity and

      // Transparency color key of a layered window
      SetLayeredWindowAttributes(Wnd, 0, Trunc((255 / 100) * (100 - nAlpha)), LWA_ALPHA);
      Result := True;
    end;
  end;
end;

// hook procedure
function HookCallWndProc(nCode: Integer; wParam, lParam: Longint): Longint; stdcall;
const
 MENU_CLASS = '#32768';
 N_ALPHA = 60;
var
  cwps: TCWPStruct;
  lRet: THandle;
  szClass: array[0..8] of char;
begin
  if (nCode = HC_ACTION) then
  begin
    CopyMemory(@cwps, Pointer(lParam), SizeOf(CWPSTRUCT));
    case cwps.message of
      WM_CREATE:
        begin
          GetClassName(cwps.hwnd, szClass, Length(szClass)-1);
          // Window name for menu is #32768
          if (lstrcmpi(szClass, MENU_CLASS) = 0) then
          begin
            MakeWndTrans(cwps.hwnd, N_ALPHA {Alphablending});
          end;
        end;
    end;
  end;
  // Call the next hook in the chain
  Result := CallNextHookEx(WH_CALLWNDPROC, nCode, wParam, lParam);
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  tpid: DWORD;
begin
  // Retrieve the identifier of the thread that created the specified window
  tpid := GetWindowThreadProcessId(Handle, nil);
  // The SetWindowsHookEx function installs an application-defined
  // hook procedure into a hook chain
  hHookID := SetWindowsHookEx(WH_CALLWNDPROC, HookCallWndProc, 0, tpid);
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  if (hHookID <> 0) then
    // Removes the hook procedure
    UnhookWindowsHookEx(hHookID);
end;