在另一个子窗口的顶部绘制一个子窗口

我在win32应用程序中有不同的屏幕服务于不同的目的，每个屏幕都有不同的背景。主窗口有自己的静态背景。我正在使用以下代码在自定义窗口上绘制屏幕背景。

panelBackground = LoadBitmap ( hInstance, MAKEINTRESOURCE ( bitmap ) );
WNDCLASSEX wincl;
wincl.hInstance         = hInstance;
wincl.lpszClassName     = "jPanel";
wincl.lpfnWndProc       = WndProc;
wincl.style             = CS_BYTEALIGNWINDOW;// | CS_HREDRAW | CS_VREDRAW;
wincl.cbSize            = sizeof (WNDCLASSEX);
wincl.hIcon             = 0;
wincl.hIconSm           = 0;
wincl.hCursor           = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName      = NULL;
wincl.cbClsExtra        = 0;
wincl.cbWndExtra        = 4;
wincl.hbrBackground     = ( HBRUSH ) GetStockObject( BLACK_BRUSH );
RegisterClassEx (&wincl);
hwnd = CreateWindowEx ( 0, "jPanel", txt.c_str(), WS_CLIPSIBLINGS | WS_CHILD, x, y, width, height, parent, 0, hInstance, 0) ;
SetWindowLong( hwnd , 0 , ( LONG ) this ) ;
SetWindowPos ( hwnd , HWND_BOTTOM, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE ) ;

然后在WndProc中:

view::jPanel* panel = ( view::jPanel* ) GetWindowLong( hwnd , 0 ) ;
case WM_PAINT:
  {
     if ( ! panel )
        return 0 ;
     HDC hdc ;
     PAINTSTRUCT ps ;
     RECT rect ;
     GetClientRect( hwnd , &rect ) ;
      hdc = BeginPaint( hwnd , &ps ) ;

         HDC dcSkin = CreateCompatibleDC ( hdc );                               // memory dc for skin
         HDC hMemDc = CreateCompatibleDC ( hdc );                               // memory dc for painting

         HBITMAP hmemBmp = CreateCompatibleBitmap ( hdc, rect.right - rect.left, rect.bottom - rect.top  );     // Create bitmap to draw on

         HBITMAP hOldMemBmp = (HBITMAP)SelectObject ( hMemDc, hmemBmp );        // select memory bitmap in memory dc
         HBITMAP hOldSkinBmp = (HBITMAP)SelectObject ( dcSkin, panel->panelBackground );    //select skin bitmap in skin memory dc

            BitBlt ( hMemDc, 0, 0, rect.right - rect.left, rect.bottom - rect.top, dcSkin, 0, 0, SRCCOPY );     // Paint Skin on Memory DC
            BitBlt ( hdc, 0, 0, rect.right - rect.left, rect.bottom - rect.top, hMemDc, 0, 0, SRCCOPY );            // Paint Skin on Window DC

         //<<<... DeleteDC will leak memory if it holds a resource, so lets select the old bitmap back in the memory DCs
         SelectObject ( hMemDc, hOldMemBmp );                                   // select old bitmaps back to their respective DCs before deleting
         SelectObject ( dcSkin, hOldSkinBmp );                                  // select old bitmaps back to their respective DCs before deleting

         DeleteObject ( hOldSkinBmp );
         DeleteObject ( hOldMemBmp );
         DeleteObject(  hmemBmp );
         DeleteDC ( hMemDc );
         DeleteDC ( dcSkin );

      EndPaint( hwnd , &ps ) ;
  }
  break ;

问题:属于该屏幕的子窗口(按钮，编辑控件)不显示，我猜它们在屏幕背景窗口下面。用WS_EX_TOPMOST样式将控件向上移动z-order不起作用，也不能用SetWindowPos (hwnd, HWND_BOTTOM, 0,0,0,0, SWP_NOSIZE | SWP_NOMOVE)在z-order的底部移动屏幕背景窗口;作品。

和yes按钮是BS_BITMAP样式的