client/src/utils/gridVisibleRange.ts - develop - kan64/spreadsheet-lab

client/src/utils/gridVisibleRange.ts
85 строк2 KB
Anton Kravchenkov
perf(ui): Migration table to canvas
20 мар 2026, 22:57
20 мар 2026, 22:5767c88be
import { TOTAL_ROWS } from '../types/types';

/**
 * Бинарный поиск по префиксам высот строк — O(log n) вместо O(n) при TOTAL_ROWS ~ 1000.
 */
export function findVisibleRowRange(
  rowPositions: number[],
  bodyScrollTop: number,
  bodyViewH: number
): { startRow: number; endRow: number } {
  const bodyBottom = bodyScrollTop + bodyViewH;

  let lo = 0;
  let hi = TOTAL_ROWS - 1;
  while (lo < hi) {
    const mid = (lo + hi) >> 1;
    if ((rowPositions[mid + 1] ?? 0) <= bodyScrollTop) {
      lo = mid + 1;
    } else {
      hi = mid;
    }
  }
  const startRow = lo;

  lo = 0;
  hi = TOTAL_ROWS - 1;
  let endRow = 0;
  while (lo <= hi) {
    const mid = (lo + hi) >> 1;
    if ((rowPositions[mid] ?? 0) < bodyBottom) {
      endRow = mid;
      lo = mid + 1;
    } else {
      hi = mid - 1;
    }
  }

  return { startRow, endRow };
}

/**
 * O(log n) по числу столбцов (при бесконечном скролле вправо колонок может быть тысячи).
 */
export function findVisibleColRange(
  colPositions: number[],
  bodyScrollLeft: number,
  bodyViewW: number,
  cols: number
): { startCol: number; endCol: number } {
  if (cols <= 0) return { startCol: 0, endCol: 0 };
  const bodyRight = bodyScrollLeft + bodyViewW;

  let lo = 0;
  let hi = cols - 1;
  while (lo < hi) {
    const mid = (lo + hi) >> 1;
    if ((colPositions[mid + 1] ?? 0) <= bodyScrollLeft) {
      lo = mid + 1;
    } else {
      hi = mid;
    }
  }
  const startCol = lo;

  lo = 0;
  hi = cols - 1;
  let endCol = 0;
  while (lo <= hi) {
    const mid = (lo + hi) >> 1;
    if ((colPositions[mid] ?? 0) < bodyRight) {
      endCol = mid;
      lo = mid + 1;
    } else {
      hi = mid - 1;
    }
  }

  return { startCol, endCol };
}

export type VisibleRange = { startRow: number; endRow: number; startCol: number; endCol: number };

export function visibleRangeToKey(r: VisibleRange): string {
  return `${r.startRow}:${r.endRow}:${r.startCol}:${r.endCol}`;
}