Implement the length() methods for requests and replies with the macro.

[Antikyth]

The procedural macro that generates X messages in X11 needs to implement the length() method on its messages. This method needs to count up the byte size all the items in the message definition (fields, unused bytes, and field lengths).

[Antikyth]

The derive macro for cornflakes::ByteSize will probably be useful reference.

[Antikyth]

Examples

The code needs to generate the implementation for length() so that can sum the byte sizes, like in this example. The cornflakes::ByteSize trait is how you can get the byte size for any type that is (de)serialized:

pub trait ByteSize {
    fn byte_size(&self) -> usize;
}

And here is an actual example of one of the tests written to ensure that this is implemented correctly:

#[test]
fn reparent_window_length_is_correct() {
    // header (total: 4 bytes):
    // - major opcode (the request's "ID"): u8, 1 byte
    // - empty (for this request)
    // - length of the request: u16, 2 bytes (that's what we're calculating)
    let reparent_window = ReparentWindow {
        target: Window::new(0), // 4 bytes (`u32` wrapper)
        new_parent: Window::new(0), // 4 bytes (`u32` wrapper)
        new_x: 0, // 2 bytes (`u16`)
        new_y: 0, // 2 bytes (`u16`)
    };

    // total is 4 + 4 + 2 + 2 + (header: 4) = 16

    // length of a message is in multiples of 4 bytes, so the length should be 16 / 4 = 4
    assert_eq!(reparent_window.length(), 4);
}

[Antikyth]

This is complete.