program nonVCL;

{$APPTYPE CONSOLE}

uses
  SysUtils, Windows, Messages;

var
  MyNoVCLClass: TWndClassEx;

function WndProc(hWnd: HWND; uMsg: UINT; wParam: WPARAM;
  lParam: LPARAM): LRESULT; stdcall;
begin
  Result := 0;
  case uMsg of
    WM_ERASEBKGND:
    begin
      DefWindowProc(hWnd, uMsg, wParam, lParam);
      //DC in wParam
      MoveToEx(wParam, 10, 10, nil);
      LineTo(wParam, 180, 180);
      Result:= 1;
    end;
    WM_CREATE:
    begin
      CreateWindow('Edit', 'AEdit', WS_VISIBLE or WS_CHILD,
        80, 80, 100, 30, hWnd, 0, HInstance, nil);
      CreateWindow('Button', 'AButton', WS_VISIBLE or WS_CHILD,
        0, 0, 100, 30, hWnd, 0, HInstance, nil);
    end;
    WM_DESTROY:
    begin
      PostQuitMessage(0);
    end;
    else
      Result:= DefWindowProc(hWnd, uMsg, wParam, lParam);
  end;
end;

procedure InitWindowClass;
begin
  MyNoVCLClass.style := 0;
  MyNoVCLClass.cbSize := SizeOf(TWndClassEx);
  MyNoVCLClass.lpfnWndProc:= @WndProc;
  MyNoVCLClass.cbClsExtra:= 0;
  MyNoVCLClass.cbWndExtra:= 0;
  MyNoVCLClass.hInstance:= HInstance;
  MyNoVCLClass.hIcon:= 0;
  MyNoVCLClass.hCursor:= LoadCursor(0, IDC_ARROW);
  MyNoVCLClass.hbrBackground:= COLOR_WINDOW;
  MyNoVCLClass.lpszMenuName:= nil;
  MyNoVCLClass.lpszClassName:= 'MyTest';
  MyNoVCLClass.hIconSm:= 0;

  RegisterClassEx(MyNoVCLClass);
end;

var
  MSG: TMSG;
  TempError: Cardinal;
begin
  InitWindowClass;
  WriteLn(IntToStr(GetLastError)); //2

  CreateWindowEx(WS_EX_WINDOWEDGE or WS_EX_CONTROLPARENT or WS_EX_APPWINDOW,
    'MyTest', 'Caption',
    WS_OVERLAPPEDWINDOW or WS_VISIBLE,
    200, 200, 250, 200,
    0, 0, hInstance, nil);

  WriteLn(IntToStr(GetLastError)); //0
  while (GetMessage(MSG, 0, 0, 0)) do //verzichte auf Überprüfung auf -1, da hier unnötig
  begin
    TranslateMessage(MSG); //nötig für Texteingaben
    DispatchMessage(MSG);

    TempError:= GetLastError;
    if(TempError <> 0) then
      WriteLn(IntToStr(TempError));
  end;
  UnregisterClass(MyNoVCLClass.lpszClassName, HInstance);
end.