/**
 * Tracked words keep their ligatures (#663).
 *
 * A tracked word is measured as its natural width plus the tracking times
 * its letters (`measure/rich.ts`, `knuthPlass/tracking.ts`), and its natural
 * width counts the ligatures of the face (fi, fl, ffi…). Painted with the
 * context's `letterSpacing`, the browser shapes it without them (CSS Text:
 * no optional ligatures where the letter-spacing is not zero): "first" in
 * Newsreader comes out 4.5 px wider at 40 px than the place the layout
 * holds for it, and runs into the word space after it. The canvas has no
 * way to ask for the ligatures back, so such a word is painted in pieces:
 * each ligature alone with no letter-spacing, the letters between them
 * tracked, every piece where the natural shaping puts it. The PDF does the
 * same by construction (it shapes the word and spaces its glyphs).
 *
 * Which words: the ones whose width at a letter-spacing, less that
 * letter-spacing, is not their natural width. A word the browser shapes
 * the same either way (nearly all of them) is painted as before, with one
 * `fillText`.
 *
 * The same holds for any tracked text painted with one `fillText` (#703):
 * a line or a run of a design text (running heads, openers, callout
 * titles, balloon lettering) and the sideways Latin run of a vertical
 * line come through here as a word does.
 *
 * Three rules of direction (#685, #703):
 * - the pieces are one run. On a right-to-left page, painted through a
 *   mirror that turns every `fillText` back about its own box
 *   (`mirrorFrame.ts`), the word is turned once, about the box it was
 *   measured in, and its pieces are set inside it from its left end, as on
 *   a left-to-right page. Turned one by one they stood in the mirror's
 *   order: "five" read "vefi";
 * - a word that holds a letter of a joining script (Arabic…) is never cut,
 *   whoever asks: painted in pieces it loses its joins. Nor is a text in
 *   two directions (a Hebrew word with a number or a Latin letter in it):
 *   its pieces would not stand in one order;
 * - a right-to-left word of a script that does not join (Hebrew) is cut
 *   like any other, where the painter set the context right to left for
 *   it (`fillSegmentWord`, `paintRunInDirection`): its pieces are set from
 *   the right end of its box, each painted right to left.
 *
 * The tracking of a ligature (#770). The layout counts the tracking once
 * a letter: a word is its natural width and the tracking times its
 * letters, and that is what the browser paints wherever the
 * letter-spacing dissolves nothing (Geist's `fi` is one glyph as wide as
 * `f` and `i`: under a letter-spacing the two letters are set apart, each
 * with the tracking after it). A ligature painted alone advanced by one
 * tracking, as one glyph, so a word that held one ended a tracking short
 * of its box for each letter the ligature had joined: `shift` in Source
 * Serif 4 at 19.58 px on a line justified with 0.39 px a letter, box
 * 43.37 px, painted 42.98 px, and `efit` on a line tightened by 0.34 px
 * ran 0.34 px over the word after it. In a document shaped in its own
 * language ({@link setLetterTracking}) the piece after a ligature starts
 * the tracking of every letter before it further on, the ligature's
 * letters each counted: the word ends where its box does, and the HTML
 * and the PDF set it the same. A document that keeps its host's language
 * is painted as it was, and so is a right-to-left word of any document
 * (a Hebrew face with a ligature): one tracking a ligature in the three
 * outputs.
 *
 * What a letter-spacing takes away besides ligatures (#770). Chrome sets
 * no contextual alternate either under a letter-spacing (`calt`, with
 * `liga` and `clig`), and the canvas cannot ask for them back. Cormorant
 * SC draws the hyphen between two capitals 1.47 px wider at 17.71 px: the
 * running head `A MAD TEA-PARTY`, tracked 2.5 px, was measured 192.76 px
 * and painted 191.30 px, no pair of its letters being a ligature. Playpen
 * Sans gives nearly every letter another form by its neighbours, so most
 * pairs read as ligatures and their pieces stood where no shaping puts
 * them: `UNIT 12` at 18.75 px, measured 98.52 px, ended at 97.70 px, and
 * `FOR PARENTS AND CARERS` 1.31 px past its 322.85 px. In a document
 * shaped in its own language a word whose pieces do not end where the
 * word was measured to end, or that the letter-spacing reshapes with no
 * ligature to keep, is painted whole at the letter-spacing that ends it
 * there: the tracking, and what the reshaping took or gave shared among
 * its letters (2.66 px a letter for `TEA-PARTY`). A text of several words
 * is then painted word by word, each where the natural shaping puts it
 * with the tracking of every letter before it, as the HTML sets its boxes
 * ({@link fittedParts}). The forms are the ones the browser draws under a
 * letter-spacing; the widths are the ones measured.
 *
 * A ligature and a form by the neighbours told apart (#770). To the probe
 * they read the same: two neighbours whose width under a letter-spacing,
 * the spacing taken off, is not their natural width. A ligature is one
 * glyph, which no spacing opens; a form by the neighbours is still a
 * glyph a letter, and under a letter-spacing the browser sets the same
 * letters in their plain forms, each spaced. Playpen Sans reshapes `FO`
 * and `OR` so: `FOR`, read as a ligature of three, was painted with no
 * tracking inside and the tracking of its three letters after it. In
 * `FOR PARENTS AND CARERS` at 17.71 px, tracked 3.125 px, its letters
 * stood as close as in untracked text, those of the three other words
 * 2.9 to 3.2 px apart, and 18.2 px lay between `FOR` and `PARENTS`
 * against 12 px between the other words. A zero width non-joiner between
 * the two letters tells them apart: it dissolves a ligature and leaves a
 * form by the neighbours as it is. Chrome 154: `fi` in Source Serif 4 at
 * 40 px is 26.16 px, 28.92 px under a letter-spacing and 28.92 px across
 * a non-joiner; `FO` in Playpen Sans at 17.71 px 24.178, 24.107 and
 * 24.178 px. The kerning stands across it: `AV` in Source Serif 4 is
 * 52.08 px with and without, 56.84 px its two letters apart.
 * In a document shaped in its own language two neighbours as wide across
 * a non-joiner as without one are no ligature ({@link ligated}), and a
 * word with none is painted whole at the letter-spacing that ends it on
 * its box, as any other the letter-spacing reshapes: `FOR` at 2.68 px a
 * letter. A document that keeps its host's language is painted as it
 * was, and so is a right-to-left word of any document, which is never
 * painted at a letter-spacing of its own.
 */
/** One piece of a word painted apart from the rest. */
export interface TrackedPiece {
    text: string;
    /** Where the piece starts in the word's natural shaping, px from its
     *  start: its left end, or its right end for a right-to-left word. */
    offset: number;
    /** Glyphs of the word before the piece: each takes the tracking once (a
     *  ligature is one glyph, as in the PDF of a document that keeps its
     *  host's language). */
    glyphsBefore: number;
    /** Letters (graphemes) of the word before the piece, the letters of a
     *  ligature each counted: what the layout counted the tracking of. */
    lettersBefore: number;
    /** A ligature: painted with no letter-spacing. */
    ligature: boolean;
}
/** Give a ligature of a tracked word the tracking of every letter it
 *  joins from now on (`on`), as the layout counted it, or of one glyph as
 *  up to postext 1.29: the page painter says which for the document it
 *  paints (`bodyText.shapingLanguage`, through `setSegmentLanguages`). */
export declare function setLetterTracking(on: boolean): void;
/**
 * Whether the browser shapes `text`, in the context's font, otherwise once
 * a letter-spacing is set: its width at a letter-spacing, that spacing
 * taken off, is not its natural width (it holds a ligature the
 * letter-spacing turns off). False where the context measures no
 * letter-spacing. The context's `letterSpacing` is put back as it was
 * found.
 */
export declare function shapedOtherwise(ctx: CanvasRenderingContext2D, text: string): boolean;
/**
 * The pieces a tracked word is painted in, in the context's font and
 * direction, or null when it is painted whole (the browser shapes it the
 * same under letter-spacing, the context measures none, the word holds a
 * joining letter or text in two directions, or the context paints the
 * other way). The context's `letterSpacing` is put back as it was found.
 */
export declare function trackedPieces(ctx: CanvasRenderingContext2D, text: string): readonly TrackedPiece[] | null;
/**
 * Paint a word of a tracked line, or any tracked text set as one run (a
 * line or a run of a design text, a sideways run of a vertical line), with
 * `paint` (the caller's `fillText`) at `x`, `y`: its left end on a
 * left-to-right page, the start of its box in a mirrored frame. `tracking`
 * is the context's `letterSpacing` on entry, px, and on return. A text
 * that would lose its ligatures to it is painted in its
 * {@link trackedPieces}, as one run (`paintAsOneRun`): its box is the one
 * the frame turns a text painted whole about, its natural width and the
 * tracking after each letter. A right-to-left word (the context set right
 * to left and aligned on its left edge by the caller) has its pieces set
 * from the right end of that box. Any other text with one `paint`.
 * Returns the advance of a text painted in pieces, the width it was
 * measured at, and undefined for one painted whole.
 */
export declare function fillTrackedWord(ctx: CanvasRenderingContext2D, text: string, x: number, y: number, tracking: number, paint: (text: string, x: number, y: number) => void): number | undefined;
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