xvfb-ts/dist/index.js

Easily start and stop an X Virtual Frame Buffer from your node app

import { spawn } from 'node:child_process';
import fs from 'node:fs';
async function sleep(ms) {
    return new Promise((resolve) => setTimeout(resolve, ms));
}
class Xvfb {
    _display;
    _reuse;
    _timeout;
    _silent;
    _xvfb_args;
    _process;
    _oldDisplay;
    constructor(options = {}) {
        this._display =
            options.displayNum || options.displayNum === 0 ? `:${options.displayNum}` : null;
        this._reuse = options.reuse ?? false;
        this._timeout = options.timeout ?? 500;
        this._silent = options.silent ?? false;
        this._xvfb_args = options.xvfb_args || [];
    }
    async start() {
        if (this._process) {
            return this._process;
        }
        const lockFile = this._lockFile();
        this._setDisplayEnvVariable();
        this._spawnProcess(fs.existsSync(lockFile));
        let totalTime = 0;
        while (!fs.existsSync(lockFile)) {
            if (totalTime > this._timeout) {
                throw new Error('Could not start Xvfb.');
            }
            await sleep(10);
            totalTime += 10;
        }
        return this._process;
    }
    async stop() {
        if (!this._process) {
            return;
        }
        this._killProcess();
        this._restoreDisplayEnvVariable();
        const lockFile = this._lockFile();
        let totalTime = 0;
        while (fs.existsSync(lockFile)) {
            if (totalTime > this._timeout) {
                throw new Error('Could not stop Xvfb.');
            }
            await sleep(10);
            totalTime += 10;
        }
    }
    display() {
        if (this._display) {
            return this._display;
        }
        let displayNum = 98;
        let lockFile;
        do {
            displayNum++;
            lockFile = this._lockFile(displayNum);
        } while (!this._reuse && fs.existsSync(lockFile));
        this._display = `:${displayNum}`;
        return this._display;
    }
    _setDisplayEnvVariable() {
        this._oldDisplay = process.env.DISPLAY;
        process.env.DISPLAY = this.display();
    }
    _restoreDisplayEnvVariable() {
        process.env.DISPLAY = this._oldDisplay;
    }
    _spawnProcess(lockFileExists) {
        const display = this.display();
        if (lockFileExists) {
            if (!this._reuse) {
                throw new Error(`Display ${display} is already in use and the "reuse" option is false.`);
            }
        }
        else {
            this._process = spawn('Xvfb', [display].concat(this._xvfb_args));
            if (!this._process || !this._process.stderr) {
                throw new Error('Could not start Xvfb.');
            }
            this._process.stderr.on('data', (data) => {
                if (!this._silent) {
                    process.stderr.write(data);
                }
            });
        }
    }
    _killProcess() {
        if (!this._process) {
            return;
        }
        this._process.kill();
        this._process = undefined;
    }
    _lockFile(displayNum) {
        return `/tmp/.X${displayNum || this.display().toString().replace(/^:/, '')}-lock`;
    }
}
export { Xvfb };
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