Presto 3 Print Provider Guide

A guide to augmenting built-in Presto support for print providers.

Overview

The Presto system allows administrators to plug in custom print providers to augment Presto's built-in support for discovering and printing to your system's print queues. This facility also allows system administrators to advertise virtual print queues to Presto Users.

Presto print provider plugins run as scripts or programs that output their results to stdout as JSON formatted text.

Integrating a Print Provider

To integrate an additional print provider into the Presto system, follow these steps:

1. Edit the agent.conf file, found in the following location:

Windows

c:\ProgramData\collobos\presto\etc\agent.conf

Mac

/Library/Application Support/Collobos/Presto/etc/agent.conf

Linux

/etc/collobos/presto/agent.conf

This file is formatted as JSON text. It describes additional configuration that the Presto service will use to manage users and discover services on the network.

2. Add a new custom print provider section by pasting in the following text. After editing the agent.conf file and saving the changes to it, the Presto service will automatically re-read the file and add the new print provider to the Presto system.

{
	"plugins": {
		"print": [
			{
				"name": “Example Print Provider",
				"lookup_printers": {
					"path": "C:\Program Files\nodejs\node",
					"args": [
						“C:\provider.js”,
						"--lookup-printers"
					]
				},
				"start_job": {
					"path": “C:\Program Files\nodejs\node”,
					"args": [
						“C:\provider.js”,
						"--start-job"
					]
				},
 
				"cancel_job": {
					"path": "C:\Program Files\nodejs\node",
					"args": [
						“C:\provider.js”,
						"--cancel-job"
					]
				}
			}
		]
	}
	

3. Create a script, with a path and file name matching that of c:\provider.js in the agent.conf file, that can be passed the following commands:
   • lookup_printers - to discover available printers
   • start_job - to submit a print job
   • cancel_job - to cancel a print job

A sample script for a print provider plugin can be found  here.

Looking up Printers

Input

The lookup_printers command is passed no parameters

Output

The output of the lookup_printers command must be JSON formatted text.  In this example, the plugin will send the following output to stdout and return a 0 exit code.

{
	"bpp": 8,
	"note": "",
	"info": "Brother HL-5250DN (Windows Development)",
	"resource": "winspool://127.0.0.1/brother_hl_5250dn__windows_development_",
	"name": "Brother HL-5250DN (Windows Development)",
	"uuid": "Brother HL-5250DN (Windows Development)",
	"make-and-model": "Brother HL-5250DN",
	"media": [
		{
			"name": "na_letter_8.5x11in",
			"klass": 0,
			"width": 21590,
			"width_points": 612,
			"type": 5,
			"height": 27940,
			"height_points": 792,
			"tag": 1
		},
		{
			"name": "na_legal_8.5x14in",
			"width_points": 612,
			"width": 21590,
			"klass": 0,
			"type": 4,
			"height": 35560,
			"height_points": 1008,
			"tag": 5
		}
	],
	"media_ready": [
		"na_letter_8.5x11in"
	],
	"kind": 1,
	"device_id": "",
	"side_default": 0,
	"copy": 99,
	"quality_default": 4,
	"orientation_default": 3,
	"quality_supported": [
		3,
		4,
		5
	],
	"orientation_supported": [
		3,
		4
	],
	"side_supported": [
		0,
		1,
		2
	],
	"document_format_default": "application/pdf",
	"document_format_supported": [
		"application/pdf",
		"image/jpeg",
		"image/png",
		"image/urf"
	],
	"media_default": "na_letter_8.5x11in",
	"state": 3,
	"reasons": 0,
}

The various enumeration types are defined as follows:

enum QualitySupported
{ draft = 3, normal = 4, high = 5
}
enum Side
{
none = 0, long_edge = 1, short_edge = 2
}
enum Orientation
{ portrait = 3, landscape = 4, reverse_landscape = 5, reverse_portrait = 6
}
enum State
{ idle = 3, processing = 4, stopped = 5
}

enum Reasons
{
none	= 0x0000, other	= 0x0001, cover_open	= 0x0002, input_tray_missing	= 0x0004, marker_supply_empty	= 0x0008, marker_supply_low	= 0x0010, marker_waste_almost_full = 0x0020, marker_waste_full	= 0x0040,
media_empty	= 0x0080,
media_jam	= 0x0100,
media_low	= 0x0200,
media_needed	= 0x0400,
offline	= 0x0800, paused = 0x1000, spool_area_full	= 0x2000, toner_empty	= 0x4000, toner_low	= 0x8000
}

Submit a Print Job

Input

The start_job command is passed a JSON object through stdin.

The JSON object has four keys: 'user', 'dest', 'job' and 'file'.

• user (who started the print job)
• dest (destination printer)
• job (# of copies, duplex, etc.)
• file (fully qualified)

The user parameter is passed as JSON encoded text in the following format:

{
	address: '192.168.1.92',
	user:
	{
		guid: '9868E611-176E-4DFF-B008-77A818777E07',
	display_name: 'John Doe',
	name: 'jdoe',
		tags:
		[
		],
		domain: 'collobos.com',
	}
}

The dest parameter is passed as JSON encoded text and will be in the same format as what was returned from the lookup_printers command.

The job parameters are passed as JSON encoded text with the following format:

{
	margins:
	{
		bottom: 635, right: 635, top: 635, left: 635
	},
	orientation: 3,
	copies: 1,
	side: 0,
	bpp: 24,
	media:
	{
		height_points: 792,
		width_points: 612,
		height: 27940,
		width: 21590,
		type: 5,
		klass: 0,
		name: 'na_letter_8.5x11in'
	}
	format: 'application/pdf',
	first_page: 0,
	print_quality: 4,
	last_page: 0,
	fit_to_page: true,
	name: 'untitled'
}

Output

The output of the start_job command must be JSON encoded text in the following format, written to stdout:

{
	resource: "ipp://localhost/jobs/7",
	id: 7,
	name: "the_name",
	owner: "jdoe",
	pages: 7,
	start_time: 1497562592,
	end_time: 1497562598,
	state: 9,
}

The plugin can return this object multiple times from start_job to let Presto know the status of the job over time.

Cancel a Print Job

Input

The cancel_job command is passed a JSON object through stdin. The JSON object has the two keys: 'dest' and 'job'.

• dest (the destination printer) - passed as JSON encoded text in the same format as what was returned from lookup-printers.
• job (the job that is being printed) - passed as JSON encoded text in the same format as what was returned from start_job.

Output

There is no output from the cancel_job command. Success is inferred by returning a 0 exit code.  Failure is inferred by any exit code other than 0.