Struct BudgetController 

pub struct BudgetController { /* private fields */ }

Adaptive budget controller combining PID regulation with e-process gating.

Architecture

frame_time ─┬─► PID Controller ─► control signal u_t
            │                              │
            └─► E-Process ──────► gate ────┤
                                           ▼
                                   Decision Logic
                                   ┌───────────────┐
                                   │ u_t > thresh   │──► DEGRADE (if e-process permits)
                                   │ u_t < -thresh  │──► UPGRADE (if e-process permits)
                                   │ otherwise      │──► HOLD
                                   └───────────────┘

The PID controller provides smooth, reactive adaptation. The e-process gates decisions to ensure statistical validity — we only degrade when there is strong evidence of sustained overload, not just transient spikes.

Usage

use ftui_render::budget::{BudgetController, BudgetControllerConfig, DegradationLevel};
use std::time::Duration;

let mut controller = BudgetController::new(BudgetControllerConfig::default());

// After each frame, feed the observed frame time:
let decision = controller.update(Duration::from_millis(20)); // slow frame
// decision tells you what to do: Hold, Degrade, or Upgrade

Implementations

impl BudgetController

pub fn new(config: BudgetControllerConfig) -> Self

Create a new budget controller with the given configuration.

pub fn update(&mut self, frame_time: Duration) -> BudgetDecision

Feed a frame time observation and get a decision.

Call this once per frame with the measured frame duration.

pub fn level(&self) -> DegradationLevel

Get the current degradation level.

pub fn sync_level(&mut self, level: DegradationLevel)

Synchronize the controller’s level with an externally applied change.

RenderBudget calls this whenever its degradation level is mutated outside the controller’s own decision (guardrail emergencies, the conformal risk gate, manual set_degradation). Without it the controller keeps reasoning from a stale level: believing it is at Full it reports AtFullQuality and holds forever, so an externally degraded UI never recovers, and its floor clamp computes from the wrong base. Starts a cooldown window, since a transition just happened.

pub fn e_value(&self) -> f64

Get the current e-process value (for diagnostics/logging).

pub fn eprocess_sigma_ms(&self) -> f64

Get the current e-process sigma estimate (ms).

pub fn pid_integral(&self) -> f64

Get the current PID integral term (for diagnostics/logging).

pub fn frames_observed(&self) -> u32

Get the number of frames observed by the e-process.

pub fn telemetry(&self) -> BudgetTelemetry

Capture a telemetry snapshot of the controller state.

This is allocation-free and suitable for calling every frame. Forward the result to a debug overlay or structured logger.

pub fn reset(&mut self)

Reset the controller to initial state.

pub fn config(&self) -> &BudgetControllerConfig

Get a reference to the controller configuration.

Trait Implementations

impl Clone for BudgetController

fn clone(&self) -> BudgetController

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BudgetController

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.