import type { ChartPadding } from "../draw/line";
/**
 * Composite sine squiggly — two overlapping frequencies with a breathing
 * amplitude envelope. Matches the original web LiveChart loading animation.
 *
 * amplitude = base * (0.4 + 0.6 * sin(0.8 * t·speed))   // 0.4×→1.0× base
 * y = centerY + amplitude * (sin(0.035*x + 1.2*t·speed) + 0.45*sin(0.08*x + 2.1*t·speed))
 *
 * `base` (default `14`) scales the wave height; `speed` (default `1`) scales the
 * time phase so the ripple/breathing runs faster or slower (`0` freezes it).
 */
export declare function squigglyYAt(x: number, centerY: number, t: number, base?: number, speed?: number): number;
/**
 * Build a flat [x0,y0,x1,y1,...] point array for a standalone squiggly line
 * spanning the full chart area (used in loading / empty state).
 * Points are spaced ~4px apart for smooth curves.
 * Pass `out` to reuse a caller-owned frame scratch.
 */
export declare function buildSquigglyPts(canvasWidth: number, canvasHeight: number, padding: ChartPadding, t: number, base?: number, speed?: number, out?: number[]): number[];
/**
 * Given a real flat-pts array (from buildLinePoints), replace each Y with the
 * squiggly Y at the same X. Used during the morph reveal.
 * Pass `out` to reuse a caller-owned frame scratch.
 */
export declare function squigglifyPts(flatPts: number[], t: number, centerY: number, base?: number, speed?: number, out?: number[]): number[];
/**
 * Smoothstep — maps t ∈ [0,1] to a smooth 0→1 curve (no clamping required
 * when t is already in range, but clamps gracefully outside).
 */
export declare function smoothstep(t: number): number;
/**
 * Blend two flat-pts arrays center-out, driven by morphT ∈ [0,1].
 * Points near the horizontal centre of the chart reveal first; edges last.
 *
 * For each point, a per-point weight is computed:
 *   distFromCentre = |x - chartCentreX| / (chartW / 2)   // 0=centre, 1=edge
 *   weight = smoothstep((morphT - distFromCentre * 0.5) / 0.5)
 *   blendedY = fromY + (toY - fromY) * weight
 * Pass `out` to reuse a caller-owned frame scratch.
 */
export declare function blendPtsY(from: number[], to: number[], morphT: number, padding: ChartPadding, canvasWidth: number, out?: number[]): number[];
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