import { Extension } from '@codemirror/state';
/**
 * Basic theme for vertical writing mode (90deg rotation).
 *
 * Note: We explicitly avoid setting `writing-mode: vertical-rl` on CodeMirror itself.
 * Browser implementations of vertical-rl often introduce bugs in CodeMirror 6,
 * such as misaligned cursors, poor scroll performance, and broken viewport calculation.
 *
 * Instead, we force standard horizontal-tb and rotate the entire editor globally.
 */
export declare const verticalTheme: (options?: {
    fontFamily?: string;
    fontSize?: string;
    textColor?: string;
}) => Extension;
