/**
 * Returns true when running in a browser-like environment.
 *
 * Checks for both `window` and `document` so service-worker and
 * partially-mocked contexts are correctly reported as non-browser.
 *
 * @example
 * ```ts
 * if (isBrowser()) window.addEventListener('resize', onResize);
 * ```
 */
export declare const isBrowser: () => boolean;
/**
 * Sets CSS custom properties on an element. Safely no-ops when element is null.
 *
 * @example
 * ```ts
 * setStyleProperties(el, { '--primary': '#3b82f6', '--gap': '1rem' });
 * ```
 */
export declare const setStyleProperties: (el: HTMLElement | null, cssVars: Record<string, string>) => void;
interface CheckVisibilityOptions {
    /** Require the element to intersect the viewport. Default: true. */
    checkViewport?: boolean;
    /** Require computed `display` to be non-"none". Default: true. */
    checkDisplay?: boolean;
    /** Require computed `visibility` to be "visible". Default: true. */
    checkVisibility?: boolean;
    /** Require computed `opacity` to be > 0. Default: true. */
    checkOpacity?: boolean;
}
/**
 * Checks whether an element is visible to the user.
 *
 * By default verifies: attached to DOM, `display` not `none`,
 * `visibility` is `visible`, `opacity > 0`, and intersects the viewport
 * on both axes. Each check can be toggled via options.
 *
 * @example
 * ```ts
 * if (checkVisibility(el)) el.classList.add('seen');
 * checkVisibility(el, { checkViewport: false }); // visible per CSS only
 * ```
 */
export declare const checkVisibility: (element: HTMLElement, options?: CheckVisibilityOptions) => boolean;
/**
 * @internal Resets the cached canvas - for tests only.
 */
export declare const __resetTextMeasurementCache: () => void;
interface IViewportOptions {
    /** Require vertical intersection. Default: true. */
    vertical?: boolean;
    /** Require horizontal intersection. Default: true. */
    horizontal?: boolean;
}
/**
 * Returns true when the element's bounding rect intersects the viewport.
 * Pure geometry - ignores CSS visibility. Use `checkVisibility` for a full
 * visibility check.
 *
 * Zero-sized rects (no layout yet) return true - we can't clip against
 * nothing, and failing them would produce false negatives in test environments.
 *
 * @example
 * ```ts
 * if (isInViewport(el)) track();
 * isInViewport(el, { horizontal: false }); // vertical only
 * ```
 */
export declare const isInViewport: (element: HTMLElement, options?: IViewportOptions) => boolean;
/**
 * Measures the rendered width of text in pixels using a cached off-screen
 * canvas. Returns `0` when 2D context is unavailable.
 *
 * @example
 * ```ts
 * calculateRenderedTextWidth('Hello World', 16);
 * calculateRenderedTextWidth('Hi', 14, true, 'Arial');
 * ```
 */
export declare const calculateRenderedTextWidth: (text: string, fontSize: number, isUppercase?: boolean, fontFamily?: string) => number;
export {};