Method displayWidthToStringIndex

src/utils/Cursor.ts:1240–1265

(text: string, targetWidth: number)

  // Convert display width to string index
  public displayWidthToStringIndex(text: string, targetWidth: number): number {
    if (targetWidth <= 0) return 0
    if (!text) return 0

    // If the text matches our text, use the precomputed graphemes
    if (text === this.text) {
      return this.offsetAtDisplayWidth(targetWidth)
    }

    // Otherwise compute on the fly
    let currentWidth = 0
    let currentOffset = 0

    for (const { segment, index } of getGraphemeSegmenter().segment(text)) {
      const segmentWidth = stringWidth(segment)

      if (currentWidth + segmentWidth > targetWidth) {
        break
      }

      currentWidth += segmentWidth
      currentOffset = index + segment.length
    }

    return currentOffset
  }

  /**
   * Find the string offset that corresponds to a target display width.