license import { OverlayReference } from '../overlay-reference' ; /**
 * Describes a strategy that will be used by an overlay to handle scroll events while it is open.
 */ export interface ScrollStrategy { /** Enable this scroll strategy (called when the attached overlay is attached to a portal). */ enable : ( ) => void ; /** Disable this scroll strategy (called when the attached overlay is detached from a portal). */ disable : ( ) => void ; /** Attaches this `ScrollStrategy` to an overlay. */ attach : ( overlayRef : OverlayReference ) => void ; /** Detaches the scroll strategy from the current overlay. */ detach ? : ( ) => void ; } /**
 * Returns an error to be thrown when attempting to attach an already-attached scroll strategy.
 */ export function getMatScrollStrategyAlreadyAttachedError ( ) { return Error ( `Scroll strategy has already been attached.` ) ; }