Installs or uninstalls the keyboard hook.
InstallKeybdHook Install, Force
Omit this parameter or pass true (any non-zero, non-blank value) to require that the hook be installed. Pass false to remove any requirement previously set by this function and potentially uninstall the hook.
If Force is true and Install is omitted or true, the hook is uninstalled and reinstalled. This has the effect of giving it precedence over any hooks previously installed by other processes. If the system has stopped calling the hook due to an unresponsive program, reinstalling the hook might get it working again.
If Force is true and Install is false, the hook is uninstalled even if needed for some other purpose. If a hotkey, hotstring or InputHook requires the hook, it will stop working until the hook is reinstalled. The hook may be reinstalled explicitly by calling this function, or automatically as a side-effect of enabling or disabling a hotkey or calling some other function which requires the hook.
If Force is false, an internal variable is updated to indicate whether the hook is required by the script, but there might be no immediate change if the hook is required for some other purpose.
The keyboard hook monitors keystrokes for the purpose of activating hotstrings and any keyboard hotkeys not supported by RegisterHotkey (which is a function built into the operating system). It also supports a few other features such as the InputHook function.
AutoHotkey does not install the keyboard and mouse hooks unconditionally because together they consume at least 500 KB of memory. Therefore, the keyboard hook is normally installed only when the script contains one of the following: 1) hotstrings; 2) one or more hotkeys that require the keyboard hook (most do not); 3) SetCaps/Scroll/NumLock AlwaysOn/AlwaysOff; 4) active Input hooks.
By contrast, the InstallKeybdHook function can be used to unconditionally install the keyboard hook, which has benefits including:
!LButton::) can suppress the window menu more efficiently, by sending only one menu mask key when the Alt key is released, instead of sending one each time the button is clicked.
Keyboard hotkeys which do not require the hook will use the reg method even if the InstallKeybdHook function is used. By contrast, applying the #UseHook directive or the $ prefix to a keyboard hotkey forces it to require the hook, which causes the hook to be installed if the hotkey is enabled.
You can determine whether a script is using the hook via the KeyHistory function or menu item. You can determine which hotkeys are using the hook via the ListHotkeys function or menu item.
InstallMouseHook, #UseHook, Hotkey, InputHook, KeyHistory, Hotstrings, GetKeyState, KeyWait