Layout model

IDML's layout model is the set of containers that decides where content lands: spreads, the pages in them, and the page items placed on them.

In short An IDML document is a sequence of spreads, one part per spread. A spread holds its pages and its page items side by side: frames, shapes and groups are children of the <Spread>, positioned in the spread's coordinate space, and each page is a rectangle placed in that same space. Which page an item is on follows from geometry. Master spreads hold items that repeat on every page that applies them, and a page can override single master items. This chapter walks that nesting from the outside in.

The containers

• Document. designmap.xml lists the spreads and master spreads in order, along with the document-wide layers, sections and preferences.
• Spread. One Spreads/Spread_*.xml part per spread. The spread's space has its origin on the spine.
• Page. A <Page> inside the spread: a rectangle (GeometricBounds) placed by its own ItemTransform, with a master, margins, columns and guides.
• Page item. Every visible thing: TextFrame, Rectangle, Oval, GraphicLine, Polygon, Group. Items are siblings of the pages; their order in the spread is their stacking order.
• Master spread. The same structure, in MasterSpreads/MasterSpread_*.xml, referenced from pages by AppliedMaster.

Pages in this chapter

• Spreads and pages: the Spread and Page elements, what InDesign requires on them, margins and guides.
• Page items and stacking: what a spread contains and how document order and layers set the paint order.
• Master spreads: the concept in one screen; the details are in Master spreads & overrides.

The shapes themselves are covered under Frames & paths, and the coordinate arithmetic under Geometry & coordinates.

Frequently asked questions

What is the layout model in IDML? The nesting of containers that positions content: a document of spreads, each spread holding pages and page items, with master spreads supplying repeated items to the pages that apply them.

Are page items children of pages? No. Page items are children of the <Spread>, next to the <Page> elements, and they are positioned in spread coordinates. The page an item belongs to is the one its geometry falls on.

How does a master spread relate to a body page? A body page names a master in AppliedMaster. The master page at the same position in the master spread supplies its items to the body page, behind the page's own items, unless the page has overridden them.