Struct MetricLifecycle 

pub struct MetricLifecycle { /* private fields */ }

Stateful tracker for font metric changes and cache invalidation.

Maintains the current cell metrics, generation counter, and pending invalidations. The lifecycle ensures a deterministic sequence:

1. Invalidation event arrives (font load, DPR change, etc.)
2. Generation is bumped, pending flag is set
3. Caller calls MetricLifecycle::refit with new metrics
4. If grid dimensions changed, resize propagates through the pipeline

This prevents stale glyph metrics and geometry jumps by enforcing that all consumers see consistent metric state.

Implementations

impl MetricLifecycle

pub fn new(cell_metrics: CellMetrics, policy: FitPolicy) -> Self

Create a new lifecycle with default cell metrics and no viewport.

pub fn cell_metrics(&self) -> &CellMetrics

Current cell metrics.

pub fn generation(&self) -> MetricGeneration

Current metric generation.

pub fn is_pending(&self) -> bool

Whether a refit is pending.

pub fn last_fit(&self) -> Option<&FitResult>

Last computed fit result.

pub fn total_invalidations(&self) -> u64

Total invalidation count.

pub fn total_refits(&self) -> u64

Total refit count.

pub fn invalidate( &mut self, reason: MetricInvalidation, new_metrics: Option<CellMetrics>, )

Record an invalidation event.

Bumps the generation and marks a refit as pending. If cell metrics changed, the new metrics are stored immediately.

pub fn set_viewport(&mut self, viewport: ContainerViewport)

Update the container viewport.

If the viewport changed, marks a refit as pending.

pub fn set_policy(&mut self, policy: FitPolicy)

Update the fit policy.

pub fn refit(&mut self) -> Option<FitResult>

Perform the pending refit computation.

Returns Some(FitResult) if the grid dimensions changed, None if no refit was needed or dimensions are unchanged.

Clears the pending flag regardless of outcome.

pub fn snapshot(&self) -> MetricSnapshot

Diagnostic snapshot for JSONL evidence logging.

Trait Implementations

impl Clone for MetricLifecycle

fn clone(&self) -> MetricLifecycle

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MetricLifecycle

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

Formats the value using the given formatter.