/**
 * The `p`th percentile (0..100) of `values`, by linear interpolation between
 * closest ranks - the same definition as NumPy's default and a spreadsheet's
 * PERCENTILE. Returns null for an empty input rather than inventing a zero.
 */
export declare function percentile(values: readonly number[], p: number): number | null;
/** Consecutive differences of a monotonic series of timestamps. */
export declare function intervals(timestamps: readonly number[]): number[];
/** Fixed-width histogram of `values`, with an explicit overflow bucket. */
export declare function histogram(values: readonly number[], bucketMs?: number, buckets?: number): Histogram;
/**
 * Snap a measured frame period to the nearest common refresh rate when it is
 * within `tolerance` of one, so 8.33 ms reads as 120 Hz rather than 120.05 Hz.
 * Returns the unsnapped rate when nothing is close.
 */
export declare function snapRefreshRate(periodMs: number, tolerance?: number): number;
/**
 * Frames that should have been presented and were not.
 *
 * An interval of 2.0 periods means one frame was skipped; 1.4 periods is late
 * but not a skipped frame. Rounding is the usual convention (it matches what a
 * frame-time graph shows as a missing bar).
 */
export declare function droppedFrames(frameIntervals: readonly number[], periodMs: number): number;
/**
 * Summarise a run of `requestAnimationFrame` timestamps against a target rate.
 *
 * `targetHz` should be the display's refresh rate when it is known, because
 * that is the rate a game wants. Pass the rate rAF itself runs at to count
 * drops against what the web view actually delivers - the two differ when the
 * web view caps rAF below the display (WebKit's 60 Hz cap on ProMotion panels).
 */
export declare function framePacing(timestamps: readonly number[], targetHz: number): FramePacingStats | null;
/** Percentile summary of latency samples, or null when there were none. */
export declare function latency(samples: readonly number[]): LatencyStats | null;
/**
 * The refresh rate in a `system_profiler SPDisplaysDataType` resolution string
 * such as `1512 x 982 @ 120.00Hz`, or null when it names none.
 */
export declare function parseRefreshHz(resolution: string | undefined): number | null;
/**
 * The arithmetic behind the interactive-content probe (stacksjs/stacks#877).
 *
 * Kept pure and DOM-free so the numbers the probe page reports can be checked
 * without a window: the page collects raw `requestAnimationFrame` timestamps and
 * event-to-frame deltas, and everything that turns those into a histogram, a
 * percentile or a dropped-frame count lives here, where a unit test can reach it.
 */
/** Refresh rates a display can plausibly run at, used to snap a measured period. */
export declare const COMMON_REFRESH_RATES: readonly number[];
export declare interface Histogram {
  bucketMs: number
  counts: number[]
  overflow: number
}
export declare interface FramePacingStats {
  frames: number
  durationMs: number
  fps: number
  p50Ms: number
  p95Ms: number
  p99Ms: number
  maxMs: number
  targetPeriodMs: number
  targetHz: number
  droppedFrames: number
  longFrames: number
  histogram: Histogram
}
export declare interface LatencyStats {
  samples: number
  p50Ms: number
  p95Ms: number
  maxMs: number
}