/** A face as the engine asks for it: a family, a numeric weight and a
 *  slant (`oblique` reads as italic). */
export interface FontFaceRequest {
    family: string;
    weight: number;
    style: 'normal' | 'italic';
}
/** A font's `<n>px` size: `font.slice(start, end)` is the whole match and
 *  `value` its number. */
export interface PxSize {
    start: number;
    end: number;
    value: string;
}
/**
 * The first `px` size of a CSS font string from `from` on, as
 * `/(\d*\.?\d+)px/` finds it (`/(\d+(?:\.\d+)?)px/` with
 * `leadingDigit`), or null. A scan in one pass: the expression's leading
 * repetition is slow on a long run of digits with no unit after it.
 */
export declare function findPxSize(font: string, from?: number, leadingDigit?: boolean): PxSize | null;
/** `font` with its first `px` size (see {@link findPxSize}) set to
 *  `sizePx`. */
export declare function withPxSize(font: string, sizePx: (value: string) => number): string;
/**
 * A font shorthand split at its size, as
 * `/^(.*?)(\d*\.?\d+)px\s+(.+)$/` splits it (with `lineHeight`,
 * `/^(.*?)(\d*\.?\d+)px(\s*\/\s*[^\s]+)?\s+(.+)$/`): `prefix` the style
 * and weight words before the size (its spaces kept), `family` the family
 * list after it (and after a `/ line-height`). Null when the string has no
 * such size. A scan in one pass, where the expressions backtrack.
 */
export declare function splitAtFontSize(font: string, lineHeight?: boolean): {
    prefix: string;
    family: string;
} | null;
/** The face a canvas font shorthand names (`'700 37.5px Open Sans'`,
 *  `'italic 400 13px "Source Serif 4"'`), or null when the string has no
 *  `px` size. A string with no weight is 400; `bold` is 700. */
export declare function parseFontString(font: string): FontFaceRequest | null;
/** Every family a canvas font shorthand lists, in order, unquoted
 *  (`'700 16px "Lora", "Noto Serif", serif'` → Lora, Noto Serif, serif);
 *  empty when the string has no `px` size. */
export declare function fontStringFamilies(font: string): string[];
/** The family of a canvas font shorthand, or null. */
export declare function fontStringFamily(font: string): string | null;
/** `font` with its family list replaced by `family`, its style, weight and
 *  size kept; null when the string names no size. For asking a measurer
 *  for the same face in a family it cannot have (see `measuresOwnFace`). */
export declare function fontStringWithFamily(font: string, family: string): string | null;
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