Container Box Drawing

1"use client";
2 
3import { useEffect, useLayoutEffect, useMemo, useRef, useState } from "react";
4 
5type Role = "corner-tl" | "corner-tr" | "corner-bl" | "corner-br" | "h" | "v";
6type Cell = { char: string } | { refIndex: number; role: Role };
7 
8const SINGLE: Record<Role, string> = {
9  "corner-tl": "┌",
10  "corner-tr": "┐",
11  "corner-bl": "└",
12  "corner-br": "┘",
13  h: "─",
14  v: "│",
15};
16const DOUBLE: Record<Role, string> = {
17  "corner-tl": "╔",
18  "corner-tr": "╗",
19  "corner-bl": "╚",
20  "corner-br": "╝",
21  h: "═",
22  v: "║",
23};
24 
25const LINE_HEIGHT = 1.4;
26 
27export interface RuleFrameProps {
28  /** sits inline in the top rule, like a fieldset legend */
29  title?: string;
30  children?: React.ReactNode;
31  className?: string;
32}
33 
34// Builds every border position once, as plain data, in true clockwise order
35// starting at the top-left corner: each rule-character position gets a
36// stable `refIndex` (0..N-1) assigned by pure traversal order, never by a
37// ref-callback side effect. That matters because React tears down and sets
38// up a ref callback on every render whose identity changed (ours always
39// does, since it closes over per-render data) — if the index came from an
40// incrementing counter read inside the callback itself, an old callback's
41// teardown firing after a new callback's setup would scramble the count.
42// Indexing from precomputed data sidesteps that: every callback, old or
43// new, only ever writes to the one slot it was built for.
44function buildPerimeter(cols: number, rows: number, title?: string) {
45  const role: Role[] = [];
46  let n = 0;
47  const alloc = (r: Role) => {
48    role[n] = r;
49    return n++;
50  };
51 
52  // `cols`/`rows` are the FULL measured box in character units, corners
53  // included. Each straight edge holds two of those cells for its own
54  // corners, so the run of dash/bar glyphs between them is cols-2 / rows-2
55  // long, not cols / rows — using the full count here was the bug: it made
56  // every straight edge two characters longer than the box it was supposed
57  // to tile, so the perimeter never closed.
58  const innerCols = Math.max(0, cols - 2);
59  const innerRows = Math.max(0, rows - 2);
60 
61  const titleText = title ? ` ${title} ` : "";
62  const titleCols = Math.min(titleText.length, innerCols);
63  const leftDashes = Math.max(0, Math.floor((innerCols - titleCols) / 2));
64 
65  const tl: Cell = { refIndex: alloc("corner-tl"), role: "corner-tl" };
66  const top: Cell[] = [];
67  for (let i = 0; i < innerCols; i++) {
68// … truncated