The BlockInput function blocks keyboard and mouse input events from reaching applications.
Syntax
BOOL BlockInput( BOOL fBlockIt );
Parameters
fBlockIt [in] Specifies the function's purpose. If this parameter is TRUE, keyboard and mouse input events are blocked. If this parameter is FALSE, keyboard and mouse events are unblocked. Note that only the thread that blocked input can successfully unblock input.
Return Value
If the function succeeds, the return value is nonzero.If input is already blocked, the return value is zero. To get extended error information, call GetLastError.
If the function succeeds, the return value is nonzero.
If input is already blocked, the return value is zero. To get extended error information, call GetLastError.
Remarks
When input is blocked, real physical input from the mouse or keyboard will not affect the input queue's synchronous key state (reported by GetKeyState and GetKeyboardState), nor will it affect the asynchronous key state (reported by GetAsyncKeyState). However, the thread that is blocking input can affect both of these key states by calling SendInput. No other thread can do this.The system will unblock input in the following cases: The thread that blocked input unexpectedly exits without calling BlockInput with fBlock set to FALSE. In this case, the system cleans up properly and re-enables input. Windows 95/98/Me: The system displays the Close Program/Fault dialog box. This can occur if the thread faults or if the user presses CTRL+ALT+DEL. Windows 2000/XP: The user presses CTRL+ALT+DEL or the system invokes the Hard System Error modal message box (for example, when a program faults or a device fails).
When input is blocked, real physical input from the mouse or keyboard will not affect the input queue's synchronous key state (reported by GetKeyState and GetKeyboardState), nor will it affect the asynchronous key state (reported by GetAsyncKeyState). However, the thread that is blocking input can affect both of these key states by calling SendInput. No other thread can do this.
The system will unblock input in the following cases:
Function Information
Minimum DLL Versionuser32.dllHeaderDeclared in winable.hImport libraryUser32.libMinimum operating systems Windows 98, Windows 2000
See Also
Keyboard Input, GetAsyncKeyState, GetKeyboardState, GetKeyState, SendInput
<DllImport("user32.dll", CharSet:=CharSet.Auto, ExactSpelling:=True)> _Public Shared Function BlockInput(<[In], MarshalAs(UnmanagedType.Bool)> ByVal fBlockIt As Boolean) As <MarshalAs(UnmanagedType.Bool)> Boolean End Function
[return: MarshalAs(UnmanagedType.Bool)] [DllImport("user32.dll", CharSet=CharSet.Auto, ExactSpelling=true)] public static extern bool BlockInput([In, MarshalAs(UnmanagedType.Bool)] bool fBlockIt);