export interface ScaleChangingEvent {
    source: any;
    /** Numerical scale factor. If the page is displayed in original size, this scale equals 1.0. */
    scale: number;
    /** Prefefined value, or undefined, if the new scale is a percentage. */
    presetValue: 'auto' | 'page-actual' | 'page-fit' | 'page-width' | undefined;
    /** Previous numerical scale factor. If the page was displayed in original size, this scale equals 1.0. */
    previousScale: number;
    /** Previous prefefined value, or undefined, if a percentage was used. */
    previousPresetValue: 'auto' | 'page-actual' | 'page-fit' | 'page-width' | undefined;
}