# Layout

Semantic Accessibility
The Model

The Zaikio layout engine is highly flexible, and provides a fully-comprehensive method for describing how a Part is constructed.

# Semantic Accessibility

We are striving for a world where every print Job can be fully described with a machine readable layout that exhaustively explains its construction. However, that is unlikely to be the case immediately for many systems. We would urge all partners to integrate the layout engine as best they can, hopefully over time being able to improve and enhance the completeness of the model they present.

A layout is not required for a Part, however not providing one reduces the ability of connected applications to perform their tasks to the best of their ability. Zaikio can form the foundation of a fully automated workflow, but it can only do that if there is fully comprehensive data being provided.

# The Model

We have derived our layout engine from the CSS Box Model (opens new window), used in every single web page on the planet to describe how items should be laid out. For those familiar with this, we obviously have not carried over all concepts, and where relevant we have renamed fields to make them more print-appropriate.

The major difference from the CSS model is that, like PDF, our co-ordinate system works from the registration point in the bottom left of the layout or parent box. I.e. co-ordinate [0, 0] or { x: 0, y: 0 } corresponds to the bottom left. Width and height measurements then are calculated from this point.

box model example

In a more complicated example with nested boxes, the origin point of subsequent measurements is always the bottom left of the parent box, as shown in the example below.

box model nested

# The Layout Container

All layouts start with a top-level container.

{
  "contents": [],
  "format": "box",
  "unit": "mm",
  "version": 1
}

The top-level container for the layout provides a small number of shared attributes:

name	kind	required	description
contents	list of layout components	yes, can be empty	the components within this layout
format	string	yes	the format of this layout, can be "box" or "path", currently only "box" supported
unit	string	yes	the unit of all measurements within this layout
version	integer	yes	the layout engine to use for a given format. Currently only 1 supported for box

A layout can contain many components, describing concepts such as pages, finishings, folds etc.

# "Part" level components

All of these constructs represent components of a Part. A Part layout could start with a page or a spread, or represent a three dimensional object. All of these share the same basic attributes.

name	kind	description
dimensions	Dimensions object	An object containing the width and height of this component
position	Coordinates object	An object containing the `x` and `y` offset of this component from the bottom-left position of the layout
bleeds	Box object	An object containing the `left`, `top`, `right` and `bottom` distances for the bleeds of this component. These are expressed outside the dimensions, resulting in a larger total surface than the dimensions advertise
print_free_margins	Box object	An object containing the `left`, `top`, `right` and `bottom` distances for the print free margins of this component. These are expressed inside the dimensions

An example of what this looks like is below.

{
  "dimensions": {
    "width": 210,
    "height": 297
  },
  "position": {
    "x": 0,
    "y": 0
  },
  "bleeds": {
    "left": 0,
    "right": 0,
    "top": 0,
    "bottom": 0
  },
  "print_free_margins": {
    "left": 0,
    "right": 0,
    "top": 0,
    "bottom": 0
  }
  // ... other relevant attributes
}

# Page

A page represents a single (potentially double-sided) page to print. This could be the main item within a Part layout, or it could be contained within a Spread.

{
  "kind": "page",
  "id": "0f383558-5b86-4f2f-8360-9e7d3fa5fb16",
  "sides": "headtohead",
  "front": {
    "page_number": 1
  },
  "back": {
    "page_number": 2
  }
  // ... shared attributes such as dimensions/position
}

The sides attribute represents the sidedness of the page.

value	description
one	One sided printing, the `back` attribute must be null
headtohead	'Traditional' two sided printing
headtofoot	Flipped two sided printing

The front and back attributes are page side models, which represent data for what will be printed on the relevant sides of the page.

attribute	kind	required	description
page_number	integer	yes	The number of the page being printed on this side. This should be considered as the reference within the file to print, not the absolute page number within the `Job`
orientation	integer	no	The orientation of the printing relative to the page
reference	string	no	Normally the `FileReference` of the `Part` should be used to pull in the print data for this page, but you can provide an additional reference here if required, to provide a different file to print on this page.

# Spread

A Spread is a simple layout of Pages.

{
  "kind": "spread",
  "id": "0f383558-5b86-4f2f-8360-9e7d3fa5fb16",
  "children": [
    {
      "kind": "page",
      "dimensions": { "width": 100, "height": 100 },
      "position": { "x": 0, "y": 0 }
    },
    {
      "kind": "page",
      "dimensions": { "width": 100, "height": 100 },
      "position": { "x": 100, "y": 0 }
    }
  ]
  // ... shared attributes such as dimensions/position
}

# Additional Component Types

# Spine

The spine of a book or other folded points

# Finishing

An additional applied process, such as lamination, foiling, drilling etc See the [finishings documentation] for more information about Finishings and how they are applied to Parts.

# Flap

A foldable additional area of a spread.

# Mark

A printers mark or other additional metadata

Data Platform

Reference