Struct HistoryView

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pub struct HistoryView { /* private fields */ }

Expand description

The Time Lens cursor over a ring (§2.1).

Holds no reference to the ring, so it can live in application state next to one and be copied freely. Every method takes the ring it should be resolved against.

Implementations§

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impl HistoryView

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pub const fn live() -> Self

A view following the newest sample.

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pub const fn position(self) -> HistoryPosition

Where the cursor is.

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pub const fn is_live(self) -> bool

Whether the view is following live data.

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pub const fn allows_process_actions(self) -> bool

Whether process-control actions may be offered.

§2.1 and §15.1 both require process actions to be disabled while inspecting history: the process shown may not exist any more, and its PID may since have been reused. Encoding the rule here keeps every call site from having to remember it.

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pub const fn return_live(&mut self)

Returns to live, the single explicit action §2.1 specifies for L.

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pub fn selected_absolute(self, ring: &HistoryRing) -> Option<u64>

The absolute index the cursor resolves to, clamped into what is retained.

Constant time. A selection whose sample has since been evicted resolves to the oldest retained sample rather than to nothing, so the panel does not blank out while the user is reading it.

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pub fn selected(self, ring: &HistoryRing) -> Option<&HistoricalSample>

The selected sample, or the newest one when live.

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pub fn step_back(&mut self, ring: &HistoryRing, steps: usize) -> SeekOutcome

Moves steps samples towards the past ([, or Shift+[ with HISTORY_STEP_MULTIPLIER).

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pub fn step_forward(&mut self, ring: &HistoryRing, steps: usize) -> SeekOutcome

Moves steps samples towards the present (], or Shift+]).

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pub fn seek_to_offset( &mut self, ring: &HistoryRing, offset: Duration, ) -> SeekOutcome

Selects the newest sample at least offset behind the newest one.

Effectively constant time: sample offsets increase monotonically, so this is a binary search rather than a scan (§21 M4). An offset reaching past the oldest retained sample clamps there and says so.

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pub fn offset_from_live(self, ring: &HistoryRing) -> Duration

How far behind live the selected sample is.

Computed from monotonic offsets, so a wall-clock change cannot make the header count backwards (§8.1). Zero when live.

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pub fn format_offset(self, ring: &HistoryRing) -> String

The header offset text: LIVE, or -00:37 (§2.1, §5.6).

Reports the offset only. §2.1’s third header state, PAUSED, is a UI state — a paused view that has not been scrubbed sits at offset zero — and is distinguished with Self::is_live.

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pub fn compare( self, ring: &HistoryRing, metric: HistoryMetric, baseline: ComparisonBaseline, ) -> Option<MetricComparison>

Compares the selected sample’s metric against an earlier sample (§2.5).

Returns None, never a zero delta, when the baseline does not exist or when either sample’s input was unavailable. That is what stops a counter reset from being rendered as a spike (§21 M4) and what honours §26’s “unavailable is not zero”.

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