class_name HudInstrument
extends Control

# Shared base for the HUD's procedural instruments (heading tape, attitude
# indicator, gauges): the exponential-smoothing weight calc and the
# angle-aware lerp helper they all use. Each instrument still owns its own
# _process (smoothing 1-2 distinct fields) and _draw (entirely bespoke).

const SMOOTHING := 12.0
# _draw does real work (text shaping, building point arrays); nobody can
# perceive an instrument repainting faster than this, so redraws are paced
# to it independently of the render frame rate — value smoothing itself
# still runs every _process call, only the (expensive) repaint is throttled.
const REDRAW_INTERVAL := 1.0 / 60.0

var _time_since_redraw := 0.0


static func lerp_angle_deg(from: float, to: float, weight: float) -> float:
	return rad_to_deg(lerp_angle(deg_to_rad(from), deg_to_rad(to), weight))


# Shortest signed distance from `from` to `to` in degrees, wrapped to
# [-180, 180]. Use this (never a plain subtraction) to decide whether an
# angle that wraps around (heading, roll) has moved enough to redraw —
# a naive delta gives a false-large jump at the 0/360 boundary.
static func angle_delta_deg(from: float, to: float) -> float:
	return wrapf(to - from, -180.0, 180.0)


func _smoothing_weight(delta: float) -> float:
	return 1.0 - exp(-SMOOTHING * delta)  # frame-rate independent


# Call instead of queue_redraw() directly once a subclass's _process has
# decided the smoothed value moved enough to warrant a repaint.
func _throttled_redraw(delta: float) -> void:
	_time_since_redraw += delta
	if _time_since_redraw >= REDRAW_INTERVAL:
		_time_since_redraw = 0.0
		queue_redraw()