/**
 * Mobile fullscreen sizing — industry pattern (Zulip, NeoKai, classic `--vh`).
 *
 * Root cause on iOS Safari: the layout viewport does not shrink for the
 * keyboard; the visual viewport does (and may pan via offsetTop). A shell
 * sized with plain 100vh / bottom:0 therefore sits under the keyboard or
 * becomes a taller scrollable surface that iOS pans, dragging the composer.
 *
 * Fix (write CSS vars from visualViewport on every resize *and* scroll; let
 * CSS size the shell):
 * 1. `--vh` = vv.height / 100
 * 2. `--keyboard-height` = clientHeight − vv.height − vv.offsetTop
 * 3. `--vt-vv-top/left/width` for the visible rectangle origin
 * 4. Shell: `top: var(--vt-vv-top); bottom: var(--keyboard-height)`
 *    (fills exactly the visual viewport — Zulip/NeoKai bottom-pin pattern)
 *
 * Always re-apply on visualViewport `scroll`. Freezing `--vt-vv-top` after
 * keyboard-up left a white gap when iOS focus-pans `offsetTop` (composer
 * stranded above the keyboard). Unwanted finger pans are blocked separately
 * via overflow / touch-action / body scroll lock — not by desyncing the shell.
 */
export interface VisualViewportSnapshot {
    width: number;
    height: number;
    offsetTop: number;
    offsetLeft: number;
}
export interface VisualViewportCssVars {
    /** `top` — visualViewport.offsetTop */
    top: string;
    left: string;
    width: string;
    /** Classic `--vh`: 1% of visualViewport.height */
    vh: string;
    /** Zulip/NeoKai: space below the visual viewport (keyboard + chrome) */
    keyboardHeight: string;
}
/**
 * Pure math: visual-viewport snapshot + layout baseline → CSS custom props.
 */
export declare function visualViewportCssVars(vv: VisualViewportSnapshot, layoutHeight: number): VisualViewportCssVars;
/** @deprecated Use visualViewportCssVars — kept as alias for existing imports. */
export declare function visualViewportMobileFrame(vv: VisualViewportSnapshot, layoutHeight?: number): VisualViewportCssVars & {
    height: string;
};
/** Layout baseline — Zulip prefers clientHeight over innerHeight on iOS. */
export declare function layoutViewportHeight(): number;
export declare const KEYBOARD_HEIGHT_GAP_PX = 100;
export declare function isVisualViewportKeyboardUp(visualHeight: number, layoutHeight: number, gapPx?: number): boolean;