clanker-agent/packages/tui/test/tui-overlay-style-leak.test.ts

import assert from "node:assert";
import { describe, it } from "node:test";
import type { Terminal as XtermTerminalType } from "@xterm/headless";
import { type Component, TUI } from "../src/tui.js";
import { VirtualTerminal } from "./virtual-terminal.js";

class StaticLines implements Component {
  constructor(private readonly lines: string[]) {}

  render(): string[] {
    return this.lines;
  }

  invalidate(): void {}
}

class StaticOverlay implements Component {
  constructor(private readonly line: string) {}

  render(): string[] {
    return [this.line];
  }

  invalidate(): void {}
}

function getCellItalic(
  terminal: VirtualTerminal,
  row: number,
  col: number,
): number {
  const xterm = (terminal as unknown as { xterm: XtermTerminalType }).xterm;
  const buffer = xterm.buffer.active;
  const line = buffer.getLine(buffer.viewportY + row);
  assert.ok(line, `Missing buffer line at row ${row}`);
  const cell = line.getCell(col);
  assert.ok(cell, `Missing cell at row ${row} col ${col}`);
  return cell.isItalic();
}

async function renderAndFlush(
  tui: TUI,
  terminal: VirtualTerminal,
): Promise<void> {
  tui.requestRender(true);
  await new Promise<void>((resolve) => process.nextTick(resolve));
  await terminal.flush();
}

describe("TUI overlay compositing", () => {
  it("should not leak styles when a trailing reset sits beyond the last visible column (no overlay)", async () => {
    const width = 20;
    const baseLine = `\x1b[3m${"X".repeat(width)}\x1b[23m`;

    const terminal = new VirtualTerminal(width, 6);
    const tui = new TUI(terminal);
    tui.addChild(new StaticLines([baseLine, "INPUT"]));
    tui.start();
    await renderAndFlush(tui, terminal);
    assert.strictEqual(getCellItalic(terminal, 1, 0), 0);
    tui.stop();
  });

  it("should not leak styles when overlay slicing drops trailing SGR resets", async () => {
    const width = 20;
    const baseLine = `\x1b[3m${"X".repeat(width)}\x1b[23m`;

    const terminal = new VirtualTerminal(width, 6);
    const tui = new TUI(terminal);
    tui.addChild(new StaticLines([baseLine, "INPUT"]));

    tui.showOverlay(new StaticOverlay("OVR"), { row: 0, col: 5, width: 3 });
    tui.start();
    await renderAndFlush(tui, terminal);

    assert.strictEqual(getCellItalic(terminal, 1, 0), 0);
    tui.stop();
  });
});