LRESULT Ctrl::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
//...
	HWND hwnd = GetHWND();
	switch(message) {
//...
	case WM_PAINT:
		ASSERT(hwnd);
		if(IsVisible() && hwnd) {
			PAINTSTRUCT ps;
			SyncScroll();
			HDC dc = BeginPaint(hwnd, &ps);
			fullrefresh = false;
			SystemDraw draw(dc);
//...
			UpdateArea(draw, Rect(ps.rcPaint));
//...
			EndPaint(hwnd, &ps);
		}
		return 0L;