Создание перекрывающего дочернего окна

#include "stdafx.h"
#include <windows.h>
#include <windowsx.h>
 
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
 
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpszCmdLine, int nCmdShow)
{
    WNDCLASS wc;
    memset(&wc, 0, sizeof(wc));
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hbrBackground = GetStockBrush(WHITE_BRUSH);
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = TEXT("MyWinClass");
    RegisterClass(&wc);
 
    HWND hWnd = CreateWindow(wc.lpszClassName, TEXT("My window title"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 460, 350, NULL, NULL, hInstance, NULL);
    if (!hWnd)
        return -1;
 
    CreateWindow(TEXT("BUTTON"), TEXT("clip (1)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | WS_CLIPSIBLINGS, 100, 50, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("clip (2)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | WS_CLIPSIBLINGS, 100, 75, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("clip (3)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | WS_CLIPSIBLINGS, 150, 50, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("clip (4)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON | WS_CLIPSIBLINGS, 150, 75, 100, 50, hWnd, NULL, hInstance, NULL);
 
    CreateWindow(TEXT("BUTTON"), TEXT("usual (1)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 100, 150, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("usual (2)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 100, 175, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("usual (3)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 150, 150, 100, 50, hWnd, NULL, hInstance, NULL);
    CreateWindow(TEXT("BUTTON"), TEXT("usual (4)"), WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 150, 175, 100, 50, hWnd, NULL, hInstance, NULL);
 
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);
 
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
 
    return (int)msg.wParam;
}
 
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
        case WM_LBUTTONDOWN:
            InvalidateRect(hWnd, 0, FALSE);
            return 0;
 
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
 
        case WM_PAINT:
        {
            RECT rc;
            GetClientRect(hWnd, &rc);
            PAINTSTRUCT ps;
            HDC dc = BeginPaint(hWnd, &ps);
            WCHAR text[1024] = { 0 };
            wcscat(text, TEXT("Z-order:\n"));
            HWND temp = GetWindow(hWnd, GW_CHILD);
            for (int i=0; i<10 && temp; i++)
            {
                size_t len = wcslen(text);
                GetWindowText(temp, text + len, 1024 - len);
                wcscat(text, TEXT("\n"));
                temp = GetWindow(temp, GW_HWNDNEXT);
            }
            DrawText(dc, text, -1, &rc, 0);
            EndPaint(hWnd, &ps);
            return 0;
        }
    }
 
    return DefWindowProc(hWnd, message, wParam, lParam);
}