/**
 * What each element keeps in its `ElementInternals`: custom states, the form
 * value and validity. Internals are private to the element that attached
 * them, so the only way to see them from outside is to be there when
 * `attachInternals()` hands them over. {@link installInternalsHook} wraps it
 * to keep each element's internals, and the calls that change them, in a
 * weak map; the element gets the same object back and behaves as before.
 *
 * Only elements that attach their internals after the hook is installed are
 * seen, so it runs ahead of the app: the dev server's head script, the
 * standalone script and the extension's `document_start` script install it.
 */
import type { InspectorFormValue, InspectorInternals } from '../../types/inspector.js';
/**
 * Wraps `HTMLElement.prototype.attachInternals` to track what each element
 * attaches. Idempotent across runtimes, and a no-op where there is no
 * `attachInternals`.
 */
export declare const installInternalsHook: () => void;
/**
 * Calls `onChange` after `el`'s custom states, form value or validity
 * change through its internals. Returns a function that stops it; a no-op
 * for an element with no tracked internals.
 */
export declare const onInternalsChange: (el: Element, onChange: () => void) => (() => void);
/**
 * A value `setFormValue()` takes, summarized for the panel. Anything else
 * reads as its string, as the browser would convert it.
 */
export declare const summarizeFormValue: (v: unknown) => InspectorFormValue;
/**
 * `el`'s custom states, form value and validity, read now; `undefined` for
 * an element whose internals the hook did not see. Never throws.
 */
export declare const readInternals: (el: Element) => InspectorInternals | undefined;
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