/**
 * Forced line breaks inside a paragraph (#620): the parser writes a
 * backslash ending a source line, or `\\`, as `BREAK_PLACEHOLDER` (U+2028,
 * LINE SEPARATOR). The text between two breaks is broken on its own, by
 * whichever breaker sets the paragraph (Knuth–Plass or line by line, the
 * word-by-word breaker or the CJK composer): a forced break splits a
 * Knuth–Plass paragraph into independent problems (the break is an infinite
 * penalty after glue that fills the line), so breaking each piece alone
 * finds the same lines. The pieces are then stacked as one paragraph:
 *
 * - every option that counts lines counts them through the whole paragraph:
 *   a piece that starts on line `n` gets the indents, the measures
 *   (`restWidths`), the lines that should not end on a hyphen
 *   (`avoidHyphenAtLines`) and the kept breaks (`keepBreaks`) of lines
 *   `n`, `n + 1`…;
 * - the line before a break is set at its natural width, as a paragraph's
 *   last line is (`isLastLine`), and flagged `hardBreak`;
 * - the runt penalty and `lastLineRunt` are the last piece's, the
 *   paragraph's end; `looseness` is taken by the last piece that can take
 *   it, then the one before;
 * - the break trace (`MeasuredBlock.breaks`) numbers the item positions of
 *   piece `k` from `k × PIECE_STRIDE`, so a trace cut to its first lines
 *   still tells each piece its own.
 *
 * Two breaks in a row are one (the parser merges them); a piece with no
 * text sets no line.
 */
import type { InlineSpan } from '../parse/types.js';
import type { MeasureBlockOptions, MeasuredBlock } from './types.js';
/** The forced line break in a paragraph's text (`BREAK_PLACEHOLDER`). */
export declare const FORCED_BREAK = "\u2028";
/** Where the item positions of each piece start in a combined break trace. */
export declare const PIECE_STRIDE: number;
/** The spans cut at the forced breaks, the breaks dropped. A span set
 *  whole (a reference, a formula) holds none. */
export declare function splitAtForcedBreaks(spans: readonly InlineSpan[]): InlineSpan[][];
/** The options of the piece that starts on line `n` of the paragraph
 *  (see the module comment). */
export declare function pieceOptions(options: MeasureBlockOptions | undefined, maxWidthPx: number, piece: number, n: number, last: boolean, looseness: number): MeasureBlockOptions;
/**
 * Measure a paragraph whose spans hold forced line breaks (see the module
 * comment): `measurePiece` breaks the text of one piece with the options
 * given, as the paragraph's own breaker would.
 */
export declare function measureForcedBreaks(spans: readonly InlineSpan[], maxWidthPx: number, lineHeightPx: number, options: MeasureBlockOptions | undefined, measurePiece: (piece: InlineSpan[], options: MeasureBlockOptions) => MeasuredBlock): MeasuredBlock;
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