private @NotNull String assertMessage(char @NotNull [] lineChars, int start, int end, boolean isRtl, @NotNull FontInfo fontInfo) {
    return String.join(
      ", ",
      "lineChars: '" + new String(lineChars) + "'",
      "start: " + start,
      "end: " + end,
      "isRtl: " + isRtl,
      "fontInfo: " + fontInfo,
      "myCharPositions: " + Arrays.toString(myCharPositions),
      "myCodePoint2Offset: " + Arrays.toString(myCodePoint2Offset)
    );
  }
private @NotNull String assertMessage(char @NotNull [] lineChars, int start, int end, boolean isRtl, @NotNull FontInfo fontInfo)