block keyboard.ahk

#Requires AutoHotkey v2.0
#SingleInstance
#UseHook

; V2 rewrite and simplification by author: nopeless @ github.com
;
; Originally written by Lexikos (404)
;  http://www.autohotkey.com/forum/post-147849.html#147849
; Modifications by Trevor Bekolay for the How-To Geek
;  http://www.howtogeek.com/ 

#<!l:: {
    KeyWait "LWin"
    KeyWait "LAlt"
    KeyWait "l"
    MsgBox("Windows+Alt+L to unlock (Click OK to start blocking)")
    BlockKeyboard(true)
}

BlockKeyboard(block) {
    Static hHook := 0, cb := ""

    If (!cb)
        cb := CallbackCreate(BlockKeyboard_HookProc)

    If (block && !hHook) {
        hHook := DllCall("SetWindowsHookEx"
            , "int", 13
            , "ptr", cb
            , "ptr", 0
            , "uint", 0)
    }

    If (!block && hHook) {
        DllCall("UnhookWindowsHookEx", "ptr", hHook)
        hHook := 0
    }
}

BlockKeyboard_HookProc(nCode, wParam, lParam)
{
    Static winPressed := 0, altPressed := 0
    
    if (NumGet(lParam, 8, "UInt") & 0x80) {
        winPressed := 0
        altPressed := 0
        return 1
    }
    
    key := NumGet(lParam, 4, "UInt")
    
    if (key = 91) {
        winPressed := 1
        return 1
    }
    
    if (key = 56) {
        altPressed := 1
        return 1
    }

    if (winPressed && altPressed && key = 38)
    {
        BlockKeyboard(false)
        winPressed := 0
        altPressed := 0
    }
    
    return 1
}

BlockKeyboard(block) {
    Static kHook := 0, mHook := 0, cb := ""

    If (!cb)
        cb := CallbackCreate(BlockKeyboard_HookProc)

    If (block && !kHook && !mHook) {
        kHook := DllCall("SetWindowsHookEx"
            , "int", 13
            , "ptr", cb
            , "ptr", 0
            , "uint", 0)
        mHook := DllCall("SetWindowsHookEx"
            , "int", 14
            , "ptr", cb
            , "ptr", 0
            , "uint", 0)
    }

    If (!block && kHook) {
        DllCall("UnhookWindowsHookEx", "ptr", kHook)
        kHook := 0
    }
    
    If (!block && mHook) {
        DllCall("UnhookWindowsHookEx", "ptr", mHook)
        mHook := 0
    }
}

Replace BlockKeyboard with this to also block mouse inputs