[READ-ONLY] Mirror of https://github.com/bombshell-dev/tty. Platform independent 2D layout engine for terminal applications based on Clay
test: failing repro for string-width
Nate Moore
(Jun 4, 2026, 12:33 AM -0500)
4c49974b
d75fb4b6
+37
+37
test/string-width.test.ts
+37
test/string-width.test.ts
···
1
+
import { describe, expect, it } from "./suite.ts";
2
+
import * as mod from "../mod.ts";
3
+
4
+
// stringWidth/charWidth are not exported yet. Cast keeps this type-checking
5
+
// (the cast makes them `any`) while the runtime values are `undefined` today,
6
+
// so calling them throws -> the assertions below fail at runtime, not compile.
7
+
let charWidth = (mod as Record<string, unknown>).charWidth as (
8
+
cp: number,
9
+
) => number;
10
+
let stringWidth = (mod as Record<string, unknown>).stringWidth as (
11
+
s: string,
12
+
) => number;
13
+
14
+
describe("display-width helpers", () => {
15
+
it("charWidth returns terminal cell columns per codepoint", () => {
16
+
expect(charWidth(0x41)).toBe(1); // 'A' ASCII occupies 1 cell
17
+
expect(charWidth(0x4f60)).toBe(2); // CJK 你 is wide -> 2 cells
18
+
expect(charWidth(0x301)).toBe(0); // combining acute (Mn) -> 0 cells
19
+
expect(charWidth(0x07)).toBe(0); // BEL control clamped to 0, not -1
20
+
});
21
+
22
+
it("stringWidth sums per-codepoint display width", () => {
23
+
expect(stringWidth("hello")).toBe(5); // 5 ASCII cells
24
+
expect(stringWidth("你好")).toBe(4); // two wide CJK -> 4 cells
25
+
expect(stringWidth("🍔")).toBe(2); // astral emoji is wide -> 2 cells
26
+
});
27
+
28
+
it("stringWidth ignores zero-width combining marks", () => {
29
+
// decomposed: 'e' (U+0065) + combining acute (U+0301), not precomposed U+00E9
30
+
expect(stringWidth("é")).toBe(1); // 1 (e) + 0 (mark) = 1 cell
31
+
});
32
+
33
+
it("stringWidth treats a VS16 emoji cluster as 2 cells", () => {
34
+
// U+2764 (1) + U+FE0F (0): VS16 promotes the cluster to emoji width
35
+
expect(stringWidth("❤️")).toBe(2);
36
+
});
37
+
});