A script for enabling/disabling keyboard input in GameMaker.

keyboard_enabled.gml

gml_pragma("global", @'
        global.keyboard_mapping = undefined;');
/// @desc Disables/enables the keyboard.
/// @param enable {Bool} Whether to enable the keyboard.
/// @author Kat @katsaii
if (argument0) {
    // revert remaps
    if (global.keyboard_mapping != undefined) {
        var maps = global.keyboard_mapping;
        var key = ds_map_find_first(maps);
        repeat (ds_map_size(maps)) {
            keyboard_set_map(key, maps[? key]);
            // goto next key
            key = ds_map_find_next(maps, key);
        }
        ds_map_destroy(maps);
        global.keyboard_mapping = undefined;
    }
} else {
    // unmap keyboard keys
    if (global.keyboard_mapping == undefined) {
        var maps = ds_map_create();
        for (var key = 0; key < 255; key++) {
            switch (key) {
            case vk_anykey:
            case vk_nokey:
                // blacklisted keys
                continue;
            }
            maps[? key] = keyboard_get_map(key);
            keyboard_clear(key);
            keyboard_set_map(key, vk_nokey);
        }
        global.keyboard_mapping = maps;
    }
}

keyboard_is_enabled.gml

/// @desc Returns whether the keyboard is enabled.
/// @author Kat @katsaii
return global.keyboard_mapping == undefined;