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//! Bearing: the injected direction that [`Direction::With`](crate::Direction) and
//! [`Direction::Against`](crate::Direction) are measured against (§3.12).
use std::time::Duration;
use crate::protocol::opcode::{BEARING_PER_AXIS, BEARING_VECTOR};
/// How the box reads whether native motion runs with or against injected motion.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
pub enum BearingMode {
/// Each axis compares its sign against its bearing (the default).
#[default]
PerAxis,
/// The native delta is projected onto the injected XY vector. Only the part along the injection
/// is weighed; the part across it is relayed unscaled. Smoother on diagonals, but X and Y are not
/// independent.
///
/// One relative scale governs both axes: the lower of X's and Y's. Setting only X's scale weighs
/// Y's motion too. `RESP(LOCKS)` reports that scale on both relative entries.
///
/// The projection moves motion between the axes. Each axis's absolute scale then applies to what
/// the projection left on that axis, not to the sign the report carried (an absolute scale governs
/// what is emitted). So a block also covers motion the projection moved onto the axis.
Vector,
}
impl BearingMode {
/// Wire `mode` byte.
pub fn as_u8(self) -> u8 {
match self {
BearingMode::PerAxis => BEARING_PER_AXIS,
BearingMode::Vector => BEARING_VECTOR,
}
}
/// Decodes a wire `mode` byte; `None` if unknown.
pub fn from_u8(v: u8) -> Option<BearingMode> {
Some(match v {
BEARING_PER_AXIS => BearingMode::PerAxis,
BEARING_VECTOR => BearingMode::Vector,
_ => return None,
})
}
}
/// Configured bearing (`RESP(OPTIONS, BEARING)`, §4.14).
///
/// [`Default`] is the boot state, so a `MockBox` replies as hardware does:
/// [`BEARING_WINDOW_DEFAULT`](crate::BEARING_WINDOW_DEFAULT) in [`BearingMode::PerAxis`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Bearing {
/// How long the last injected delta's direction stays the reference for
/// [`Direction::With`](crate::Direction) and [`Direction::Against`](crate::Direction). `None` =
/// off: the relative directions are inert whatever their scale. Whole milliseconds on the wire,
/// so it reads back rounded.
pub window: Option<Duration>,
/// Whether the bearing is read per axis or as one vector.
pub mode: BearingMode,
}
impl Default for Bearing {
fn default() -> Bearing {
Bearing {
window: Some(crate::BEARING_WINDOW_DEFAULT),
mode: BearingMode::PerAxis,
}
}
}
impl Bearing {
/// `[what][id][window u16 LE][mode]` (§4.14).
pub(crate) fn from_payload(p: &[u8]) -> Option<Bearing> {
if p.len() < 5 {
return None;
}
let ms = u16::from_le_bytes([p[2], p[3]]);
Some(Bearing {
window: (ms != 0).then(|| Duration::from_millis(ms as u64)),
mode: BearingMode::from_u8(p[4])?,
})
}
/// Whether the bearing window is on; with it off the relative directions do nothing.
pub fn is_live(&self) -> bool {
self.window.is_some()
}
}