跟建立普通的win32視窗一樣，執行緒中的視窗也需要註冊和視窗處理過程

// Test_WM_CLOSE.cpp : Defines the entry point for the application.
//

#include "framework.h"
#include "Test_WM_CLOSE.h"
#include <thread>

#define MAX_LOADSTRING 100

// Global Variables:
HINSTANCE hInst;                                // current instance
WCHAR szTitle[MAX_LOADSTRING];                  //
 
 The title bar text
WCHAR szWindowClass[MAX_LOADSTRING];            // the main window class name
HWND hWnd;
HWND g_hWnd;
HWND button;
// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, 
 
int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK WndProc1(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam);
void CreateWndInThread(int nWidth, int nHeight);


int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPWSTR    lpCmdLine,
                     _In_ 
 
int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: Place code here.

    // Initialize global strings
    LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadStringW(hInstance, IDC_TESTWMCLOSE, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    // Perform application initialization:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTWMCLOSE));

    MSG msg;

    // Main message loop:
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return (int) msg.wParam;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEXW wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_TESTWMCLOSE));
    wcex.hCursor        = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName   = MAKEINTRESOURCEW(IDC_TESTWMCLOSE);
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

    return RegisterClassExW(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   hInst = hInstance; // Store instance handle in our global variable

   hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE: Processes messages for the main window.
//
//  WM_COMMAND  - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY  - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
    {
        std::thread t(CreateWndInThread, 960, 480);
        t.detach();
    }
    break;
    case WM_COMMAND:
        {
            int wmId = LOWORD(wParam);
            // Parse the menu selections:
            switch (wmId)
            {
            case IDM_ABOUT:
                DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                break;
            case IDM_EXIT:
                DestroyWindow(hWnd);
                break;
            default:
                return DefWindowProc(hWnd, message, wParam, lParam);
            }
        }
        break;
    case WM_LBUTTONDOWN:
    {
        SendMessage(g_hWnd, WM_CLOSE, 0, 0);
    }
    break;
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            // TODO: Add any drawing code that uses hdc here...
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    UNREFERENCED_PARAMETER(lParam);
    switch (message)
    {
    case WM_INITDIALOG:
        return (INT_PTR)TRUE;

    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
        {
            EndDialog(hDlg, LOWORD(wParam));
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

LRESULT CALLBACK WndProc1(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
{
    switch (wMsg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, wMsg, wParam, lParam);
    }
}

void CreateWndInThread(int nWidth, int nHeight)
{
    WNDCLASSEXA wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = WndProc1;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = GetModuleHandle(nullptr);
    wcex.hIcon = 0;
    wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wcex.lpszMenuName = NULL;

    char cName[MAX_PATH] = { 0 };
    GetModuleFileNameA(wcex.hInstance, cName, sizeof(cName));
    char* szApp = strrchr(cName, '\\') + 1;
    strchr(szApp, '.')[0] = '\0';

    wcex.lpszClassName = szApp;
    wcex.hIconSm = 0;
    RegisterClassExA(&wcex);

    g_hWnd = CreateWindowA(szApp, nullptr, WS_POPUP | WS_CLIPCHILDREN | WS_CLIPSIBLINGS, 0, 0, nWidth, nHeight, NULL, NULL, wcex.hInstance, 0);
    button = CreateWindowA("BUTTON", "click", WS_VISIBLE | WS_CHILD, 100, 100, 100, 100, g_hWnd, NULL, wcex.hInstance, 0);
    ShowWindow(g_hWnd, SW_SHOW);
    UpdateWindow(g_hWnd);

    MSG msg;
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}

Note: 我在子執行緒的視窗中又建立了一個按鈕控制元件，如果想要在主執行緒中關閉按鈕視窗，比如在WM_LBUTTONDOWN事件中，我們想點選滑鼠左鍵後，按鈕控制元件被關閉。那麼我們需要傳送WM_CLOSE訊息，因為DestroyWindow無法跨執行緒關閉視窗。

 case WM_LBUTTONDOWN:
    {
        SendMessage(g_hWnd, WM_CLOSE, 0, 0);
    }

std::thread :表示一個執行執行緒。執行緒允許多個功能併發執行。 (C++11起）

detch:允許執行緒獨立於執行緒控制代碼執行