/**
 * MSDF font atlas definition — parses `msdf-atlas-gen` style JSON (the format emitted by
 * `tools/msdf-atlas.mjs`) or legacy BMFont JSON into a normalized, em-relative glyph table.
 *
 * All plane metrics (glyph bounds, advances, line metrics) are stored in em units so layout
 * is a plain multiply by `fontSize`; atlas bounds are stored as UV rects for the companion
 * KTX2 texture (raw RGBA8, flipY = false → v grows downward from the top row).
 *
 * @module MSDFFont
 */
/** Four normalized atlas or plane coordinates in left/bottom/right/top order. */
export type MSDFRect = [left: number, bottom: number, right: number, top: number];
/** Four texture coordinates in u0/v0/u1/v1 order. */
export type MSDFUVRect = [u0: number, v0: number, u1: number, v1: number];
/** One normalized glyph entry stored by {@link MSDFFont}. */
export interface MSDFGlyph {
    /** Horizontal pen advance in em units. */
    advance: number;
    /** Glyph plane bounds in em units relative to the baseline. */
    planeBounds: MSDFRect;
    /** Glyph rectangle within the companion atlas texture. */
    uvRect: MSDFUVRect;
}
/** Options applied while normalizing font metadata. */
export interface ParseMSDFFontOptions {
    /** Whether atlas V coordinates must account for a vertically flipped texture upload. */
    flipY?: boolean;
}
/**
 * A parsed MSDF font atlas: glyph metrics in em units plus UV rects into the atlas texture.
 *
 * @class MSDFFont
 * @short Normalized MSDF atlas metrics (glyphs, kernings, line metrics) for text layout.
 * @category Text
 * @tags WebGPU, WebGL
 */
export declare class MSDFFont {
    /** Normalized glyph metrics keyed by Unicode code point. */
    glyphs: Map<number, MSDFGlyph>;
    /** Kerning adjustments in em units keyed by `left:right` code-point pairs. */
    kernings: Map<string, number>;
    /** Default line-box height in em units. */
    lineHeight: number;
    /** Ascender height above the baseline in em units. */
    ascender: number;
    /** Descender position below the baseline in em units. */
    descender: number;
    /** Recommended underline position in em units. */
    underlineY: number;
    /** Recommended underline thickness in em units. */
    underlineThickness: number;
    /** Signed-distance range encoded by the atlas, measured in atlas pixels. */
    distanceRange: number;
    /** Source font size used to generate the atlas, measured in pixels per em. */
    size: number;
    /** Atlas texture width in pixels. */
    atlasWidth: number;
    /** Atlas texture height in pixels. */
    atlasHeight: number;
    /** Informational font-family name from the source metadata. */
    name: string;
    /** Creates an empty normalized font record with safe fallback metrics. */
    constructor();
    /**
     * Reports whether the atlas contains a glyph for a Unicode code point.
     *
     * @param {number} codePoint
     * @returns {boolean} Whether the atlas contains this glyph.
     */
    has(codePoint: number): boolean;
    /**
     * Looks up a glyph with fallback to U+FFFD then '?'. Returns null only when the atlas has
     * neither the glyph nor a fallback (e.g. an icon-only atlas).
     *
     * @param {number} codePoint
     * @returns {{advance: number, planeBounds: number[], uvRect: number[]}|null}
     */
    getGlyph(codePoint: number): MSDFGlyph | null;
    /**
     * Reads the kerning adjustment for two adjacent Unicode code points.
     *
     * @param {number} left - Codepoint of the left glyph.
     * @param {number} right - Codepoint of the right glyph.
     * @returns {number} Kerning adjustment in em (0 when the pair is unknown).
     */
    getKerning(left: number, right: number): number;
}
/**
 * Parses MSDF font metadata JSON into an {@link MSDFFont}.
 *
 * Accepts the `msdf-atlas-gen` layout (`{ atlas, metrics, glyphs: [{ unicode, advance,
 * planeBounds, atlasBounds }], kerning }`) — em-relative, `yOrigin` top or bottom — or the
 * BMFont layout (`{ info, common, chars: [{ id, x, y, width, height, xoffset, yoffset,
 * xadvance }], kernings }`) — pixel-relative, normalized here by `info.size`.
 *
 * @param {Object} json - Parsed font metadata.
 * @param {Object} [options]
 * @param {boolean} [options.flipY=false] - Set true when the atlas texture uploads with
 * `flipY` (e.g. PNG via TextureLoader); raw KTX2 `DataTexture`s do not flip.
 * @returns {MSDFFont}
 * @short Parse msdf-atlas-gen or BMFont JSON into a normalized MSDFFont.
 * @category Text
 * @tags WebGPU, WebGL
 */
export declare function parseMSDFFont(json: unknown, { flipY }?: ParseMSDFFontOptions): MSDFFont;