GML Script. Knows what OS you are using, and if you are using a gamepad or keyboard/mouse. Use bootstrap after input_change(). Bootstrapper ensures that a gamepad is connected before allowing the user to swap over to gamepad input from Keyboard/mouse.

input_change

///PC users or PS4 Input
if os_type == os_windows || os_ps4 || os_xboxone
{
    if gamepad_button_check_any(global.gpDevice)
    {
        global.KBMuser = false;
    }
    if keyboard_check(vk_anykey) || mouse_check_button(mb_any)
    {
        global.KBMuser = true;
    }
    
    global.dp_up = vk_up;
    global.dp_down = vk_down;
    global.dp_left = vk_left;
    global.dp_right = vk_right;
    global.confirm = ord("Z");
    global.cancel = ord("X");
    global.button3 = ord("C");
    global.button4 = ord("V");
    global.start = vk_enter;
    global.select = gp_select;
    global.mouse = true;
    if gamepad_is_connected(0) || gamepad_is_connected(4)
    {
        global.gpadConnected = true;
    }
    
    if global.gpadConnected == true && global.KBMuser = false
    {
        global.dp_up = gp_padu;
        global.dp_down = gp_padd;
        global.dp_left = gp_padl;
        global.dp_right = gp_padr;
        global.confirm = gp_face1;
        global.cancel = gp_face2;
        global.button3 = gp_face3;
        global.button4 = gp_face4;
        global.triggerr = gp_shoulderr;
        global.bumperr = gp_shoulderrb;
        global.triggerl = gp_shoulderl;
        global.bumperl = gp_shoulderlb;
        global.start = gp_start;
        global.select = gp_select;
        global.mouse = false;
    }
}

///PS Vita Input
if os_type == os_psvita
{
    global.dp_up = gp_padu;
    global.dp_down = gp_padd;
    global.dp_left = gp_padl;
    global.dp_right = gp_padr;
    global.confirm = gp_face1;
    global.cancel = gp_face2;
    global.button3 = gp_face3;
    global.button4 = gp_face4;
    global.triggerr = gp_shoulderr;
    global.bumperr = gp_shoulderrb;
    global.triggerl = gp_shoulderl;
    global.bumperl = gp_shoulderlb;
    global.start = gp_start;
    global.select = gp_select;
    global.mouse = false;
}

///Japanese PlayStation
if (os_type == os_ps4 || os_psvita) && global.language == "ja"
{
    global.confirm = gp_face2;
    global.cancel = gp_face1;
}

///Ouya Input
if os_type == os_android
{
    if global.os_ouya == true
    {
        global.dp_up = "BUTTON_DPAD_UP";
        global.dp_down = "BUTTON_DPAD_DOWN";
        global.dp_left = "BUTTON_DPAD_LEFT";
        global.dp_right = "BUTTON_DPAD_RIGHT";
        global.confirm = "BUTTON_O";
        global.cancel = "BUTTON_A";
        global.button3 = "BUTTON_U";
        global.button4 = "BUTTON_Y";
        global.triggerr = gp_shoulderr; //
        global.bumperr = "BUTTON_R1";
        global.triggerl = gp_shoulderl; //
        global.bumperl = "BUTTON_L1";
        global.start = "BUTTON_R3";
        global.select = "BUTTON_L3";
        global.mouse = true;
    }
}

input_gamepad_bootstrap

///gamepad_bootstrap(device number)
var device = argument0;

if gamepad_is_connected(device)
{
    global.gpadConnected = true;
}
else
{
    global.gpadConnected = false;
}