text.js — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

import type {Rect} from '../../view-base';

import {rectEqualToRect} from '../../view-base';
import {COLORS, FONT_SIZE, TEXT_PADDING} from '../constants';

const cachedTextWidths = new Map<string, number>();

export function getTextWidth(
  context: CanvasRenderingContext2D,
  text: string,
): number {
  let measuredWidth = cachedTextWidths.get(text);
  if (measuredWidth == null) {
    measuredWidth = context.measureText(text).width;
    cachedTextWidths.set(text, measuredWidth);
  }

  return ((measuredWidth: any): number);
}

export function trimText(
  context: CanvasRenderingContext2D,
  text: string,
  width: number,
): string | null {
  const maxIndex = text.length - 1;

  let startIndex = 0;
  let stopIndex = maxIndex;

  let longestValidIndex = 0;
  let longestValidText = null;

  // Trimming long text could be really slow if we decrease only 1 character at a time.
  // Trimming with more of a binary search approach is faster in the worst cases.
  while (startIndex <= stopIndex) {
    const currentIndex = Math.floor((startIndex + stopIndex) / 2);
    const trimmedText =
      currentIndex === maxIndex ? text : text.slice(0, currentIndex) + '…';

    if (getTextWidth(context, trimmedText) <= width) {
      if (longestValidIndex < currentIndex) {
        longestValidIndex = currentIndex;
        longestValidText = trimmedText;
      }

      startIndex = currentIndex + 1;
    } else {
      stopIndex = currentIndex - 1;
    }
  }
// ... (75 more lines)