qwenlm/terminal-capture

Terminal Capture — CLI Terminal Screenshot Automation

Drive terminal interactions and screenshots via TypeScript configuration, used for visual verification during PR reviews.

Prerequisites

Ensure the following dependencies are installed before running:

npm install       # Install project dependencies (including node-pty, xterm, playwright, etc.)
npx playwright install chromium   # Install Playwright browser

Architecture

node-pty (pseudo-terminal) → ANSI byte stream → xterm.js (Playwright headless) → Screenshot

Core files:

| File | Purpose | | -------------------------------------------------------- | ------------------------------------------------------------------------ | | integration-tests/terminal-capture/terminal-capture.ts | Low-level engine (PTY + xterm.js + Playwright) | | integration-tests/terminal-capture/scenario-runner.ts | Scenario executor (parses config, drives interactions, auto-screenshots) | | integration-tests/terminal-capture/run.ts | CLI entry point (batch run scenarios) | | integration-tests/terminal-capture/scenarios/*.ts | Scenario configuration files |

Quick Start

1. Write Scenario Configuration

Create a .ts file under integration-tests/terminal-capture/scenarios/:

import type { ScenarioConfig } from '../scenario-runner.js';

export default {
  name: '/about',
  spawn: ['node', 'dist/cli.js', '--yolo'],
  terminal: { title: 'qwen-code', cwd: '../../..' }, // Relative to this config file's location
  flow: [
    { type: 'Hi, can you help me understand this codebase?' },
    { type: '/about' },
  ],
} satisfies ScenarioConfig;

2. Run

# Single scenario
npx tsx integration-tests/terminal-capture/run.ts integration-tests/terminal-capture/scenarios/about.ts

# Batch (entire directory)
npx tsx integration-tests/terminal-capture/run.ts integration-tests/terminal-capture/scenarios/

3. Output

Screenshots are saved to integration-tests/terminal-capture/scenarios/screenshots/{name}/:

| File | Description | | --------------- | ---------------------------------- | | 01-01.png | Step 1 input state | | 01-02.png | Step 1 execution result | | 02-01.png | Step 2 input state | | 02-02.png | Step 2 execution result | | full-flow.png | Final state full-length screenshot |

FlowStep API

Each flow step can contain the following fields:

type: string — Input Text

Automatic behavior: Input text → Screenshot (01) → Press Enter → Wait for output to stabilize → Screenshot (02).

{
  type: 'Hello';
} // Plain text
{
  type: '/about';
} // Slash command (auto-completion handled automatically)

Special rule: If the next step is key, do not auto-press Enter (hand over control to the key sequence).

key: string | string[] — Send Key Press

Used for menu selection, Tab completion, and other interactions. Does not auto-press Enter or auto-screenshot.

Supported key names: ArrowUp, ArrowDown, ArrowLeft, ArrowRight, Enter, Tab, Escape, Backspace, Space, Home, End, PageUp, PageDown, Delete

{
  key: 'ArrowDown';
} // Single key
{
  key: ['ArrowDown', 'ArrowDown', 'Enter'];
} // Multiple keys

Auto-screenshot is triggered after the key sequence ends (when the next step is not a key).

streaming — Capture During Execution

Capture multiple screenshots at intervals during long-running output (e.g., progress bars). Optionally generates an animated GIF.

{
  type: 'Run this command: bash progress.sh',
  streaming: {
    delayMs: 7000,    // Wait before first capture (skip initial waiting phase)
    intervalMs: 500,  // Interval between captures
    count: 20,        // Maximum number of captures
    gif: true,        // Generate animated GIF (default: true, requires ffmpeg)
  },
}

• delayMs (optional): Milliseconds to wait after pressing Enter before starting captures. Useful for skipping model thinking/approval time.
• Captures stop early if terminal output is unchanged for 3 consecutive intervals.
• Duplicate frames (no output change) are automatically skipped.

GIF prerequisite: If the scenario uses streaming with GIF enabled (default), check if ffmpeg is installed before running. If not, ask the user whether they'd like to install it:

# Check
which ffmpeg

# Install (macOS)
brew install ffmpeg

If the user declines, the scenario still runs — GIF generation is skipped with a warning.

capture / captureFull — Explicit Screenshot

Use as a standalone step, or override automatic naming:

{
  capture: 'initial.png';
} // Screenshot current viewport only
{
  captureFull: 'all-output.png';
} // Screenshot full scrollback buffer

Scenario Examples

Basic: Input + Command

flow: [{ type: 'explain this project' }, { type: '/about' }];

Secondary Menu Selection (/auth)

flow: [
  { type: '/auth' },
  { key: 'ArrowDown' }, // Select API Key option
  { key: 'Enter' }, // Confirm
  { type: 'sk-xxx' }, // Input API key
];

Tab Completion Selection (/export)

flow: [
  { type: 'Tell me about yourself' },
  { type: '/export' }, // No auto-Enter (next step is key)
  { key: 'Tab' }, // Pop format selection
  { key: 'ArrowDown' }, // Select format
  { key: 'Enter' }, // Confirm → auto-screenshot
];

Array Batch (Multiple Scenarios in One File)

export default [
  { name: '/about', spawn: [...], flow: [...] },
  { name: '/context', spawn: [...], flow: [...] },
] satisfies ScenarioConfig[];

Integration with PR Review

This tool is commonly used for visual verification during PR reviews.

Troubleshooting

| Issue | Cause | Solution | | ------------------------------------ | ------------------------------------- | ---------------------------------------------------- | | Playwright error browser not found | Browser not installed | npx playwright install chromium | | Blank screenshot | Process starts slowly or build failed | Ensure npm run build succeeds, check spawn command | | PTY-related errors | node-pty native module not compiled | npm rebuild node-pty | | Unstable screenshot output | Terminal output not fully rendered | Check if the scenario needs additional wait time |

Full ScenarioConfig Type

interface FlowStep {
  type?: string; // Input text
  key?: string | string[]; // Key press(es)
  capture?: string; // Viewport screenshot filename
  captureFull?: string; // Full scrollback screenshot filename
  streaming?: {
    delayMs?: number; // Delay before first capture (default: 0)
    intervalMs: number; // Interval between captures in ms
    count: number; // Maximum number of captures
    gif?: boolean; // Generate animated GIF (default: true)
  };
}

interface ScenarioConfig {
  name: string; // Scenario name (also used as screenshot subdirectory name)
  spawn: string[]; // Launch command ["node", "dist/cli.js", "--yolo"]
  flow: FlowStep[]; // Interaction steps
  terminal?: {
    cols?: number; // Number of columns, default 100
    rows?: number; // Number of rows, default 28
    theme?: string; // Theme: dracula|one-dark|github-dark|monokai|night-owl
    chrome?: boolean; // macOS window decorations, default true
    title?: string; // Window title, default "Terminal"
    fontSize?: number; // Font size
    cwd?: string; // Working directory (relative to config file)
  };
  outputDir?: string; // Screenshot output directory (relative to config file)
}