Ninja Printer

Ninja Printer is a browser based solution for printing from authorised website(s) using Google Chrome.

Technically the solution is based on the NativeMessaging feature of the browser and runs a simple Java application in the background to execute printing on the local machine. Currently it only supports Windows and OSX, but it should be easy to adjust to other unix-like systems.

One of the main design goals was to be able to pick the printer to be used from the web application, meaning obviously that the application needs to be aware of the available printers on the users machine. NinjaPrinter ships with support for 2 different type of documents: ZPL (label) and the PDF, but extending it should be fairly straight forward.

Security & Customisation

Since the base implementation only supports Westwing domains, localhost and 127.0.0.1, you will need to create your own extension if you intend to use it in production.

Development

For development purposes it's best to use a local development:

1. Fork this repo (or get the code elsehow)
2. chrome-extension/browser/manifest.json
   1. Open the file in an editor
   2. Amend the json array for the key content_scripts.matches to match your needs
   3. Amend the json array for the key permissions to match your needs
   4. Save file
3. Chrome Extensions page in Google Chrome*
   1. Open page
   2. Make sure Developer Mode is ticked
   3. Click Load unpacked extension...
   4. Navigate to the chrome-extension/browser directory of your source code.
   5. Note the ID of your newly installed extension
4. For OSX: chrome-extension/host/de.westwing.chrome.printer.ninja.json
   1. Open the file in an editor
   2. Amend allowed_origins to have an entry like "chrome-extension://{YOUR_EXTENSION_ID}/"
   3. Save file
   4. Execute install_host.sh
5. For Windows: chrome-extension/host/de.westwing.chrome.printer.ninja-win.json
   1. Open the file in an editor
   2. Amend allowed_origins to have an entry like "chrome-extension://{YOUR_EXTENSION_ID}/"
   3. Save file
   4. Execute install_host.bat

*: It might work similarly with Chromium and derivative browsers, but has only been tested using Google Chrome.

Production

For production you'll need to follow the above steps for the host (Step 4 or 5), but for the browser extension you'll need upload your chrome-extension/browser directory to chrome web store and install from there. This makes distribution easier for clients.

Installation

Basic installation instructions for Ninja Printer.

On Windows

1. Install the extension

You can always test the provided example application via the official extension. Or you can setup your development version:

• Fork or download the source code
• Open chrome and click on the ‘Tools’ icon on the right hand corner
• Select ‘Extensions’
• On the top right hand side tick ‘Developer mode’
• Click ‘Load unpacked extension’
• Select the ‘browser’ folder inside the original file ‘chrome-extension’
• You will see the extension already enabled in your list of chrome extension

Note: If you tick ‘allow on incognito mode’ than you will always need to enable the extension on the incognito window.

2. Install the host

• Go to chrome-extension\host
• Double click: install_host.bat

On OSX

1. Install the extension

You can always test the provided example application via the official extension. Or you can setup your development version:

• Fork or download the source code
• Open chrome and click on the hamburger menu on the right hand corner
• Go to 'More tools' > ‘Extensions’
• On the top right hand side tick ‘Developer mode’
• Click ‘Load unpacked extension’
• Select the ‘browser’ folder inside the original file ‘chrome-extension’
• You will see the extension already enabled in your list of chrome extension

Note: If you tick ‘allow on incognito mode’ than you will always need to enable the extension on the incognito window.

2. Install the host

• Go to chrome-extension/host
• Double click: install_host.sh

Usage / API

The extension will inject NinjaPrinter.js into your website which containes the NinjaPrinter JavaScript object.

The NinjaPrinter object defines:

• 3 public methods for printing:
• printZpl
• printPdf
• 3 events to listen to:
  • ninjaprinter.result
  • ninjaprinter.beforePrint
  • ninjaprinter.afterPrint
• 2 methods to manage event subscription:
  • on
  • off

For some minimalist usage examples, please check out the contents of the examples directory.

Note: You can always read the source code, but if you want to test the example application, than you'll need to use some webserver to make the example page available as localhost or 127.0.0.1. Otherwise the content script will not be injected. For example with php it's just php -S localhost:8080.

Development (OSX)

Extension

Regarding the browser extension all required documentation should be accessable in the official Chrome documentation. The only part which is somewhat less usual is the Native Messaging.

Both the injected script and the browser extension log extensively to the console log, both are visible in Chrome DevTools. The later can be found clicking the background page link at the inspect views part on the browser extension page.

Host

Requirements

The Java host requires Java 8 to be installed, both for running the app (JRE) and for development (JDK).

Compiling the host application

You can setup Eclipse or Netbeans to build the project, but the easiest way is instaling ant (brew install ant), and running ./chrome-extension/host/compile.sh.

Alternatively you can also choose to run ant test and ant from java directory.

Running the host application

It's also possible to run the host application manually, it expects messages on the standard input and logs to the standard output.

java -jar ./chrome-extension/host/NinjaPrinter.jar

The host also logs extensively to chrome-extension/host/print-debug.log.