win32 - how avoid flickers with transparent controls?

[joaquim]

1 - for avoid flickers, we use: WS_CLIPCHILDREN on parent window style.
2 - for be transparent we do:

case WM_ERASEBKGND:
            case WM_CTLCOLORBTN:
            case WM_CTLCOLORSTATIC:
            {
                return (LRESULT)GetStockObject(NULL_BRUSH);
            }
            break;

and now we can use the WM_PAINT for draw what we need.
use:

RECT d;
                GetClientRect(hwnd,&d);
                RedrawWindow(hwnd,&d,nullptr,RDW_UPDATENOW | RDW_INVALIDATE);

for repaint the control.
now see the transparent flicker-free control.
(if i draw a filled rectangle, the control backcolor is showed )
so how can i redraw the control without that problem?(see the image... 1 image above another)

[joaquim]

how can i clear the control, when i use the WS_CLIPCHILDREN style?