Windows API Programming-----Disable task switching in Windows NT environments

Function prototypes:BOOL WINAPI systemparametersinfo (  _in_    uint  uiaction,  _in_    uint  Uiparam,  _ Inout_ PVOID pvparam,  _in_    UINT  fwinini); Function MSDN Link: https://msdn.microsoft.com/en-us/library/ms724947 (v=vs.85). aspx

usage: UINT npreviousstate; // Disable task switching SystemParametersInfo (Spi_setscreensaverrunning,true,&npreviousstate,0)// Allow task switching SystemParametersInfo (Spi_setscreensaverrunning,false,&npreviousstate,0);

code example:

//DisableChangeTask.cpp: Defines the entry point for the application. //#include"stdafx.h"#include"DisableChangeTask.h"#defineMax_loadstring 100typedefstruct_dlong{LONG WParam; LONG LParam;} Dlong;//Global Variables:HINSTANCE HInst;//Current InstanceWCHAR sztitle[max_loadstring];//title bar TextWCHAR szwindowclass[max_loadstring];//main window class name//The forward declaration of the function contained 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);//MyFunction, that is, using this function to process messagesBOOL CALLBACK Enumwindowsproc (HWND hwnd, LPARAM LPARAM);intapientry wWinMain (_in_ hinstance hinstance, _in_opt_ hinstance hprevinstance, _in_ lpwstr lpCmdLine, _in_intncmdshow)    {Unreferenced_parameter (hprevinstance);    Unreferenced_parameter (lpCmdLine); if(lpCmdLine! =NULL) {        if(Lstrlen (lpCmdLine) >=1) {MessageBox (NULL, lpCmdLine, TEXT ("The cmdline"), MB_OK); }    }    //TODO: Place the code here. //Initializing global StringsLoadstringw (hinstance, Ids_app_title, SzTitle, max_loadstring);    Loadstringw (HInstance, Idc_disablechangetask, Szwindowclass, max_loadstring);    MyRegisterClass (HINSTANCE); //To perform an application initialization:    if(!InitInstance (HINSTANCE, nCmdShow)) {        returnFALSE; } haccel hacceltable=loadaccelerators (hinstance, Makeintresource (Idc_disablechangetask));    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_disablechangetask)); Wcex.hcursor=loadcursor (nullptr, Idc_arrow); Wcex.hbrbackground= (Hbrush) (color_window+1); Wcex.lpszmenuname=Makeintresourcew (Idc_disablechangetask); Wcex.lpszclassname=Szwindowclass; WCEX.HICONSM=LoadIcon (Wcex.hinstance, Makeintresource (Idi_small)); returnREGISTERCLASSEXW (&Wcex);}////function: InitInstance (hinstance, int)////Purpose: Save the instance handle and create the main window////notes:////in this function, we save the instance handle in the global variable and//Create and display the main program window. //BOOL InitInstance (HInstance hinstance,intncmdshow) {HInst= HInstance;//storing an instance handle in a global variableHWND hwnd=Createwindoww (Szwindowclass, SzTitle, Ws_overlappedwindow, Cw_usedefault,0, Cw_usedefault,0, nullptr, nullptr, hinstance, nullptr); if(!hWnd) {      returnFALSE; }/********************************my code goes here***************************/BOOL old;   Dlong Dlong; Dlong.wparam=(WPARAM) hWnd; Dlong.lparam=(LPARAM) FALSE; EnumWindows (Enumwindowsproc, (LONG)&Dlong); //using the screen saver to trick the operating system against Alt+tab/escSystemParametersInfo (spi_screensaverrunning, TRUE, &old,0);/********************************my code goes up there***********************/ShowWindow (hWnd, ncmdshow);   UpdateWindow (HWND); returnTRUE;}////functions: WndProc (HWND, UINT, WPARAM, LPARAM)////Purpose: Processes the message of the main window. ////wm_command-Processing Application Menu//WM_PAINT-Draw the main window//Wm_destroy-Sends an exit message and returns////LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM WPARAM, LPARAM LPARAM) {Switch(message) {/*****************my code goes below***************/     CaseWm_syscommand:if(WParam = = sc_minimize)return 0; returnDefWindowProc (hWnd, message, WParam, LParam);  Break; /*****************my code goes above***************/     Casewm_command: {intWmid =LoWord (WParam); //Analysis Menu Selection:            Switch(wmid) { CaseIdm_about:dialogbox (HInst, Makeintresource (Idd_aboutbox), hWnd, about);  Break;  CaseIdm_exit:destroywindow (HWND);  Break; default:                returnDefWindowProc (hWnd, message, WParam, LParam); }        }         Break;  Casewm_paint: {paintstruct ps; HDC HDC= BeginPaint (HWnd, &PS); //TODO: Add any drawing code here that uses HDC ...EndPaint (HWnd, &PS); }         Break;  CaseWm_destroy:/******* allows the task to switch ******** when exiting the current window*/Dlong Dlong;        BOOL old; Dlong.lparam=(LPARAM) TRUE; Dlong.wparam=(WPARAM) hWnd; EnumWindows (Enumwindowsproc, (LONG)&Old ); SystemParametersInfo (spi_screensaverrunning, FALSE,&old,0); /******* allows the task to switch ******** when exiting the current window*/PostQuitMessage (0);  Break; default:        returnDefWindowProc (hWnd, message, WParam, LParam); }    return 0;}//The message handler for the About box. int_ptr CALLBACK About (HWND hdlg, UINT message, WPARAM WPARAM, LPARAM LPARAM) {unreferenced_parameter (LPARAM); Switch(message) { CaseWm_initdialog:return(INT_PTR) TRUE;  CaseWm_command:if(LoWord (wParam) = = IDOK | | LoWord (wParam) = =IDCANCEL)            {EndDialog (hdlg, LoWord (WParam)); return(INT_PTR) TRUE; }         Break; }    return(INT_PTR) FALSE;} BOOL CALLBACK Enumwindowsproc (HWND hwnd, LPARAM LPARAM) {Dlong*pdlong = (dlong*) LParam; BOOL benable= (BOOL) pdlong->LParam; if(hwnd! = (HWND) pdlong->WParam)    EnableWindow (hwnd, benable); returnTRUE;}

Run Result: If you do not close the running interface, you cannot switch to another task:

Windows API Programming-----Disable task switching in Windows NT environments