/**
 * Opens an external flow (e.g. Meld, Swapped) in a centered popup.
 *
 * iOS and Safari block window.open() calls that don't happen synchronously
 * inside a user-gesture handler. Because the URL often isn't known until after
 * an async fetch, we open about:blank immediately (within the gesture), show a
 * spinner, and then set popup.location.href once the URL resolves. This keeps
 * us inside the trusted-event window while still supporting async URL fetching.
 *
 * Returns true if the popup was opened, false if it was blocked.
 */
export declare function openExternalFlowPopup(linkGetter: () => Promise<{
    widgetUrl: string;
}>, options: {
    dimensions: {
        width: number;
        height: number;
    };
    loaderTheme: 'light' | 'dark';
    loaderTitle: string;
}): Promise<boolean>;