在开发“518抽奖软件”的时候，需要用到窗口化、全屏化、移到扩展屏的功能。 网上找的代码都不够全面，有时候会被任务栏挡住。所以自己写了一个代码，下面的代码是商业产品上正式使用的代码，比一般网上随便写的代码好的多，各种情况测试都通过。

窗口创建阶段的源码

     
    if (m_wndPos.wndMode == WNDMODE_WINDOW)
        m_hMain = CreateWindow(WNDCLASS_NAME, g_title, WS_POPUP, m_wndPos.x, m_wndPos.y, m_wndPos.w, m_wndPos.h, NULL, NULL, m_hInst, NULL);
    else 
        m_hMain = CreateWindow(WNDCLASS_NAME, g_title, WS_POPUP, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN), NULL, NULL, m_hInst, NULL);

    ShowWindow (m_hMain, SW_SHOW);
    UpdateWindow (m_hMain);
    SetWindowPos(m_hMain, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);

窗口消息里的源码

     case WM_ACTIVATEAPP:
        if ((BOOL)wParam) {
            SetWindowPos(hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE);
        }
        else {
            SetWindowPos(hWnd, HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE | SWP_NOACTIVATE);
            PostMessage(hWnd, WM_APP_BRINGTOTOP, 0, 0);
        }
        break;
    case WM_APP_BRINGTOTOP:
        BringWindowToTop(GetForegroundWindow());
        break;
    case WM_SHOWWINDOW:
        if (!(BOOL)wParam) return DefWindowProc(hWnd, message, wParam, lParam);
        else SetWindowPos(hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE);
        break;
    case WM_LBUTTONDOWN:
        BringWindowToTop(g_app.m_hMain);
        break;

窗口化、全屏化、扩展屏切换的源码

     wndPos_t& wp = g_app.m_wndPos;
    int cx = GetSystemMetrics(SM_CXSCREEN);
    int cy = GetSystemMetrics(SM_CYSCREEN);

    if (wmId == IDM_window)
    {
        if (wp.wndMode == WNDMODE_EXSCRN) SetCursorPos(cx - 1, cy - 1); //鼠标移回主窗口

        wp.wndMode = WNDMODE_WINDOW;
        MoveWindow(g_app.m_hMain, wp.x, wp.y, wp.w, wp.h, TRUE);

        Sleep(16);
        BringWindowToTop(g_app.m_hMain);
    }
    else if (wmId == IDM_fuscrn)
    {
        if (wp.wndMode == WNDMODE_EXSCRN) SetCursorPos(cx - 1, cy - 1); //鼠标移到扩展屏

        wp.wndMode = WINMODE_FUSCRN;
        MoveWindow(g_app.m_hMain, 0, 0, cx, cy, TRUE);
    }
    else if (wmId == IDM_exscrn)
    {
        RECT rc;
        if (!g_app.get_exscrn(rc)) MessageBox(g_app.m_hMain, L"无扩展屏", g_title, MB_OK | MB_ICONWARNING);
        else
        {
            wp.wndMode = WNDMODE_EXSCRN;
            MoveWindow(g_app.m_hMain, rc.left, rc.top, rc.right - rc.left, rc.bottom - rc.top, TRUE);
            SetCursorPos(rc.right - 1, rc.bottom - 1);
        }
    }

获得第二屏（扩展屏）位置的源码

     BOOL Tapp::get_exscrn(RECT& rcExscrn)
    {
        RECT rc = { 0 };
        EnumDisplayMonitors(NULL, NULL, Callback_enumMonitors, (LPARAM)&rc);
        if (rc.left == 0 && rc.top == 0 && rc.right == 0 && rc.bottom == 0) return FALSE;
        rcExscrn = rc;
        return TRUE;
    }
    static BOOL CALLBACK Callback_enumMonitors(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData)
    {
        RECT* rc = (RECT*)dwData;
    
        MONITORINFO mi = { 0 };
        mi.cbSize = sizeof(MONITORINFO);
        GetMonitorInfo(hMonitor, &mi);
        if (mi.dwFlags != MONITORINFOF_PRIMARY)
        {
            *rc = mi.rcMonitor;
            return FALSE;
        }
        return TRUE;
    }