electron-pdf: A JavaScript repository from SnowRunescape

Electron-PDF

Electron-PDF is a powerful command-line tool that leverages Electron to generate PDF files from URLs, HTML, or Markdown files.

Electron-PDF
Version Compatibility
Installation
Node.js Usage
Events
Environment Variables
Command Line Usage
Rendering Options
- To specify browser options
- Observing your own event
All Available Options
Debugging
License

Version Compatibility

Starting from version 4.0.x, the master branch of Electron-PDF will always align with the latest Electron version.

Semantic Versioning is followed, and the version numbers correspond to Electron versions as follows:

electron-pdf 25.0.x (master) => electron=25.4.0, node=16.15.0, chrome=114.0.5735.248
electron-pdf 20.0.x => electron=20.0.2, node=16.15.0, chrome=104.0.5112.81
electron-pdf 15.0.x => electron=15.1.1, node=16.5.0, chrome=94.0.4606.61
electron-pdf 10.0.x => electron=10.1.3, node=12.16.3, chrome=85.0.4183.121
electron-pdf 7.0.x => electron 7.x (Chromium 78, Node 12.8.1)
electron-pdf 4.0.x => electron 4.x (Chromium 69, Node 10.11.0)
electron-pdf 1.3.x => electron 1.6.x (Chromium 56, Node 7.4)
electron-pdf 1.2.x => electron 1.4.x (Chromium 53, Node 6.5)

Please note that the choice of Chromium version affects the functionality you can utilize. Choose the version that aligns with your needs.

Installation

Install Electron-PDF via npm:

npm install electron-pdf

If you're installing as root using system-level npm (rather than a user-level install like with NVM), use the following command:

sudo npm install electron-pdf -g --unsafe-perm

Please see the npm docs for more information.

For GNU/Linux installations without a graphical environment, you need to install xvfb and set up a virtual display:

sudo apt-get install xvfb # or equivalent
export DISPLAY=':99.0'
Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
electron-pdf ...

A Docker machine example is available here.

Node.js Usage

Electron-PDF can be integrated into your application or used as a rendering engine for a PDF service. Below are examples of usage.

Application Setup

In your package.json:

"scripts": {
  "start": "DEBUG=electronpdf:* electron index.js",
  "watch": "DEBUG=electronpdf:* nodemon --exec electron index.js"
}

Using Electron-PDF

const ElectronPDF = require('electron-pdf')
const express = require('express')
const bodyParser = require('body-parser')
const app = express()
app.use(bodyParser.json())

const exporter = new ElectronPDF()
exporter.on('charged', () => {
  app.listen(port, hostname, () => {
    console.log(`Export Server running at http://${hostname}:${port}`)
  })
})
exporter.start()

Handling Multiple Export Jobs

app.post('/pdfexport', (req, res) => {
  const jobOptions = {
  /*
    r.results[] will contain the following based on inMemory
    false: the fully qualified path to a PDF file on disk
    true: The Buffer Object as returned by Electron
    Note: the default is false, this can not be set using the CLI
  */
    inMemory: false // Set inMemory to true for Buffer export
  }
  const options = {
    pageSize: "A4"
  }
  
  exporter.createJob(source, target, options, jobOptions).then(job => {
    job.on('job-complete', r => {
      console.log('pdf files:', r.results)
      // Process the PDF file(s) here
    })
    job.render()
  })
})

Using In-Memory Buffer

If you set the inMemory setting to true, you must also set closeWindow=false or you will get a segmentation fault anytime the window is closed before the buffer is sent on the response. You then need to invoke job.destroy to close the window.

const jobOptions = { inMemory: true, closeWindow: false }
exporter.createJob(source, target, options, jobOptions).then(job => {
  job.on('job-complete', r => {
    // Send the Buffer here
    process.nextTick(() => { job.destroy() })
  })
})

Events

Electron-PDF emits events to provide insights into its operations. A full documentation of events is a work in progress.

Environment Variables

ELECTRONPDF_RENDERER_MAX_MEMORY: Specify the --max-old-space-size option for each Electron renderer process (browser window) default: 75% of total system memory up to 8GB
ELECTRONPDF_WINDOW_CLEANUP_INTERVAL: Interval to check for hung windows, in milliseconds default: 30 seconds
ELECTRONPDF_WINDOW_LIFE_THRESHOLD: How long a window can remain open before it is terminated, in milliseconds default: 5 minutes
ELECTRONPDF_PNG_CAPTURE_DELAY: Delay before invoking WebContents.capturePage for PNG exports default: 100ms

Command Line Usage

Electron-PDF provides a versatile command-line interface (CLI) for various conversions and exports.

Generate a PDF from an HTML file

$ electron-pdf index.html ~/Desktop/index.pdf

Generate a PDF from a Markdown file

$ electron-pdf index.md ~/Desktop/index.pdf

Generate a PDF from a Markdown file with custom CSS

$ electron-pdf index.html ~/Desktop/index.pdf -c my-awesome-css.css

Generate a PDF from a URL

$ electron-pdf https://fraserxu.me ~/Desktop/fraserxu.pdf

Rendering Options

Electron PDF gives you complete control of how the BrowserWindow should be configured, and when the window contents should be captured.

To specify browser options

The BrowserWindow supports many options which you may define by passing a JSON Object to the --browserConfig option.

Some common use cases may include:

height and width - electron-pdf calculates the browser height and width based off of the dimensions of PDF page size multiplied by the HTML standard of 96 pixels/inch. So only set these values if you need to override this behavior
show - to display the browser window during generation

$ electron-pdf https://fraserxu.me ~/Desktop/fraserxu.pdf --browserConfig '{"show":true}'

To generate a PDF after the an async task in the HTML

electron-pdf ./index.html ~/Desktop/README.pdf -e

In your application, at the point which the view is ready for rendering

document.body.dispatchEvent(new Event('view-ready'))

Warning: It is possible that your application will be ready and emit the event before the main electron process has had a chance execute the javascript in the renderer process which listens for this event.

If you are finding that the event is not effective and your page waits until the full timeout has occurred, then you should use setInterval to emit the event until it is acknowledged like so:

  var eventEmitInterval = setInterval(function () {
    document.body.dispatchEvent(new Event('view-ready'))
  }, 25)

  document.body.addEventListener('view-ready-acknowledged', function(){
    clearInterval(eventEmitInterval)
  })

When the main process first receives your ready event it will emit a single acknowlegement on document.body with whatever event name you are using suffixed with -acknowledged. So the default would be view-ready-acknowledged

Observing your own event

If the page you are rending is under your control, and you wish to modify the behavior of the rendering process you can use a CustomEvent and an observer that will be triggered after the view is ready but before it is captured.

your-page.html

document.body.dispatchEvent(new CustomEvent('view-ready', { detail: {layout: landscape} }))

your-exporter.js

You are required to provide a function that accepts the detail object from the CustomEvent and returns a Promise. You may optionally fulfill the promise with and object that will amend/override any of the contextual attributes assigned to resource (url) currently being exported.

As an example, suppose you wanted to change the orientation of the PDF, and capture the output as PNG instead of a PDF.

job.observeReadyEvent( (detail) => {
    return new Promise( (resolve,reject) => {
      const context = {}
      if( detail && detail.landscape ){
        job.changeArgValue('landscape', true)
        context.type = 'png'
      }
      resolve(context)
    })
})

Note: Future versions of the library will only allow you to provide context overrides, and not allow you to change job level attributes.

All Available Options

Electron PDF exposes the printToPDF settings (i.e. pageSize, orientation, margins, etc.) available from the Electron API. See the following options for usage.


  A command line tool to generate PDF from URL, HTML or Markdown files

  Options
    --help                     Show this help
    --version                  Current version of package
    
    -i | --input               String - The path to the HTML file or url
    -o | --output              String - The path of the output PDF
    
    -b | --printBackground     Boolean - Whether to print CSS backgrounds.
    
    --acceptLanguage           String - A valid value for the 'Accept-Language' http request header
    
    --browserConfig            String - A valid JSON String that will be parsed into the options passed to electron.BrowserWindow
    
    -c | --css                 String - The path to custom CSS (can be specified more than once)
    
    -d | --disableCache        Boolean - Disable HTTP caching
                                 false - default
    
    -e | --waitForJSEvent      String - The name of the event to wait before PDF creation
                                 'view-ready' - default
    
    -l | --landscape           Boolean - true for landscape, false for portrait (don't pass a string on the CLI, just the `-l` flag)
                                 false - default
    
    -m | --marginsType         Integer - Specify the type of margins to use
                                 0 - default margins
                                 1 - no margins (electron-pdf default setting)
                                 2 - minimum margins
    
    --noprint                  Boolean - Do not run printToPDF, useful if the page downloads a file that needs captured instead of a PDF.  
                                         The Electron `win.webContents.session.on('will-download')` event will be implemented 
                                         and the file saved to the location provided in `--output`.
                                         Currently only supports a single import url.
                                         The page is responsible for initiating the download itself.
    
    -p | --pageSize            String - Can be A3, A4, A5, Legal, Letter, Tabloid or an Object containing height and width in microns
                                 "A4" - default
    
    -r | --requestHeaders      String - A valid JSON String that will be parsed into an Object where each key/value pair is: <headerName>: <headerValue>
                                 Example: '{"Authorization": "Bearer token", "X-Custom-Header": "Hello World"}'  
    
    -s | --printSelectionOnly  Boolean - Whether to print selection only
                                 false - default
                                 
    -t | --trustRemoteContent  Boolean - Whether to trust remote content loaded in the Electron webview.  False by default.
    --type                     String - The type of export, will dictate the output file type.  'png': PNG image, anything else: PDF File
    
    -w | --outputWait          Integer – Time to wait (in MS) between page load and PDF creation.  
                                         If used in conjunction with -e this will override the default timeout of 10 seconds    
    --ignoreCertificateErrors  Boolean - If true, all certificate errors thrown by Electron will be ignored.  This can be used to accept self-signed and untrusted certificates.  You should be aware of the security implications of setting this flag.
                             false - default

Find more information on Electron Security here.

Debugging

Sentry

If you have a Sentry account and setup a new app to get a new DSN, you can set a SENTRY_DSN environment variable which will activate sentry logs. See lib/sentry.js for implementation details.

This will allow you to easily see/monitor errors that are occuring inside of the Chromium renderer (browser window). It also automatically integrates with Electron's Crash Reporter

CLI Usage

You can see some additional logging (if you're getting errors or unexpected output) by setting DEBUG=electron* For example: DEBUG=electron* electron-pdf <input> <output> -l

  Usage
    $ electron-pdf <input> <output>
    $ electron-pdf <input> <output> -l

  Examples
    $ electron-pdf http://fraserxu.me ~/Desktop/fraserxu.pdf
    $ electron-pdf ./index.html ~/Desktop/index.pdf
    $ electron-pdf ./README.md ~/Desktop/README.pdf -l
    $ electron-pdf ./README.md ~/Desktop/README.pdf -l -c my-awesome-css.css

Inspired by electron-mocha

Other Formats

Want to use the same options, but export to PNG or snapshot the rendered HTML? Just set the output filename to end in .png or .html instead!

  Examples
    $ electron-pdf http://fraserxu.me ~/Desktop/fraserxu.pdf
    $ electron-pdf http://fraserxu.me ~/Desktop/fraserxu.html
    $ electron-pdf http://fraserxu.me ~/Desktop/fraserxu.png

Extensions

If you need powerpoint support, pdf-powerpoint picks up where Electron PDF leaves off by converting each page in the PDF to a PNG and placing them on individual slides.

License

MIT

SnowRunescape/electron-pdf