Layout model

IDML's layout model is the nest of containers that decides where content lands on the page.

In short: A story holds text, but the text has to land somewhere, and the layout model is the set of containers that decide where. An IDML document is a sequence of spreads; each spread holds one or more pages; each page is filled by page items — the frames, rectangles, ovals, lines, and polygons that carry the visible content. Layered on top, a master spread supplies items that repeat across many pages, and a body page can selectively override any master item it wants to replace. This chapter walks that nesting from the outside in, explaining what the renderer needs from each layer to predict what appears on a given page.

This chapter follows that nesting from the outside in: the spread, then its pages, then the items inside them, then the master layer that feeds them.

Why a reader ends up here

Open any real-world Spreads/Spread_*.xml and you are looking at this model. The geometry of every frame is expressed relative to a page, the page relative to its spread, and the spread relative to the document's pasteboard. Master pages add a second source of items that get stamped onto body pages at render time. To predict what appears on a given page — and in what order — you need all four pieces.

The order below is reader progression, not the source spec's arrangement: we start with the container you meet first and work toward the resolution rule you meet last.

• Spreads and pages — the Spread and Page elements and the attributes that position them.
• Page items and stacking — what lives inside a spread, and how document order becomes z-order.
• Master spreads — the repeating-layout layer and how a page points at it.
• Override resolution — how a body page replaces individual master items.

The frame types themselves — TextFrame, Rectangle, Oval, GraphicLine, Polygon — have their own geometry and paint attributes covered under Frames & paths. The point coordinates those frames use are explained under Geometry & coordinates. This chapter is about the containers and the stacking, not the shapes.

Frequently asked questions

What is the layout model in IDML? The layout model is the nesting of containers that positions content: a document is a sequence of spreads, each spread holds one or more pages, and each page is filled by page items. Master spreads sit on top of this, supplying repeating items that body pages can selectively override.

What is the difference between a spread, a page, and a page item? A spread is the outer container — the pasteboard that holds the pages of one opening. A page is a bounded rectangle within a spread that maps its own coordinates into spread space. A page item is a visible shape — a text frame, rectangle, oval, line, or polygon — that sits on a spread and carries the actual content.

How does a master spread relate to a body page? A master spread holds repeating layout — headers, footers, page-number placeholders — and a body page links to it through its AppliedMaster attribute. At render time the master's items are stamped onto each page that names it, and a page can use its OverrideList to replace individual master items with its own.