/**
 * floating-container.ts
 *
 * Shared low-level utility for creating a `position:fixed` container element
 * that lives on `document.body` (or a custom target).
 *
 * All portal-style primitives in this library (`portal`, `popup`,
 * `cascading-popup-list`, etc.) ultimately need the same three operations:
 *   1. Create a fixed-position div with a z-index above everything else.
 *   2. Lazily attach it to the DOM exactly once — only when content needs to
 *      be shown, never eagerly on component mount.
 *   3. Remove it cleanly when the component unmounts or the panel closes.
 *
 * Centralising this here ensures every floating surface shares identical
 * defaults, avoids the "orphaned div" bug that comes from eagerly calling
 * `document.body.appendChild` at mount time, and gives one place to tweak
 * z-index, default styles, or target element logic across the whole library.
 *
 * ─── Usage ────────────────────────────────────────────────────────────────────
 *
 * ```ts
 * // Create (not yet in DOM)
 * const { el, attach, detach, isAttached } = createFloatingContainer();
 *
 * // Lazily attach when you actually need to show something
 * attach();
 * el.style.top = "100px";
 * el.style.left = "200px";
 * litRender(myTemplate, el);
 *
 * // Detach when done
 * detach();
 * ```
 *
 * Apply extra styles at creation time:
 * ```ts
 * const { el, attach, detach } = createFloatingContainer({
 *   style: {
 *     minWidth: "10rem",
 *     background: "var(--md-color-surface)",
 *     border: "0.06rem solid var(--md-color-border)",
 *     borderRadius: "var(--md-radius-sm)",
 *     boxShadow: "var(--md-shadow-dropdown)",
 *     overflow: "hidden",
 *   },
 * });
 * ```
 */
export interface FloatingContainerOptions {
    /**
     * Extra CSS properties merged onto the container element at creation time.
     * These are applied on top of the mandatory base styles
     * (`position:fixed`, `z-index`, `display:none`).
     */
    style?: Partial<CSSStyleDeclaration>;
    /**
     * Where to mount the container.
     * Accepts an `Element` directly, a CSS selector string, or omit/`null` to
     * default to `document.body`.
     *
     * @default document.body
     */
    target?: Element | string | null;
    /**
     * Override the default `z-index` value.
     *
     * @default "9999"
     */
    zIndex?: string | number;
}
export interface FloatingContainer {
    /**
     * The raw `<div>` element.  You can read/write styles, measure, and render
     * lit-html templates into this element directly.  It is NOT in the DOM until
     * `attach()` is called.
     */
    readonly el: HTMLDivElement;
    /**
     * Append `el` to the target (default: `document.body`) if it is not already
     * attached.  Safe to call multiple times — subsequent calls are no-ops.
     */
    attach(): void;
    /**
     * Remove `el` from the DOM.  Safe to call when already detached — it is a
     * no-op in that case.  After calling `detach()` you may call `attach()`
     * again to re-insert the same element.
     */
    detach(): void;
    /**
     * Returns `true` when `el` is currently in the DOM (i.e. `attach()` has
     * been called and `detach()` has not been called since).
     */
    isAttached(): boolean;
}
/**
 * Create a reusable floating container element.
 *
 * The element is created synchronously but is **not** appended to the DOM.
 * Call `attach()` exactly when you need to make it visible or measure it.
 * Call `detach()` (or `el.remove()`) to clean up.
 *
 * This function is intentionally pure — it does NOT call `onCleanup()` or
 * any other framework hook.  The caller is responsible for calling `detach()`
 * at the right time (e.g. inside `onCleanup` / `onCleanup` of an `eleHook`
 * or `htmlHook` lifecycle).
 *
 * @example
 * // Inside an eleHook mountFn:
 * const fc = createFloatingContainer({ style: { minWidth: "160px" } });
 *
 * const open = () => {
 *   fc.attach();
 *   litRender(content, fc.el);
 *   position(anchor, fc.el);
 *   fc.el.style.display = "block";
 * };
 *
 * const close = () => {
 *   fc.el.style.display = "none";
 * };
 *
 * return {
 *   onCleanup() {
 *     fc.detach();
 *   },
 * };
 */
export declare function createFloatingContainer(opts?: FloatingContainerOptions): FloatingContainer;
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