Macro buttons 

macro_rules! buttons {
    (@inner $chain:tt , $($tail:tt)*) => { ... };
    (@inner $chain:tt !$button:tt $($tail:tt)*) => { ... };
    (@inner $chain:tt $button:tt $($tail:tt)*) => { ... };
    (@inner $chain:tt) => { ... };
    ($($args:tt)*) => { ... };
}

Passing multiple buttons as an argument for functions.

This macro produces a value of type [ButtonArg].

Syntax

This macro receives variant names of Button separated by commas,

buttons!(A, B, Esc, F12);

Or number letarals corresponding to numeric keys.

buttons!(0, 1, 2);

Variables can be used by enclosing them in square brackets.

let a = Button::A;
buttons!([a], B, C);

The prefix ! means that this key is released.

let b = Button::B;
buttons!(!A, ![b], !0);

Nested buttons!(..) will be flattened.

let arg = buttons!(A, B, C);
assert_eq!(
    buttons!([arg], D, E),
    buttons!(A, B, C, D, E),
);

The prefix ! of nested buttons!(..) will affect each button.

let arg = buttons!(A, B, C);
assert_eq!(
    buttons!(![arg], D, E),
    buttons!(!A, !B, !C, D, E),
);