Document model

reticle-model is the hierarchical document that everything edits and renders.

Hierarchy is the source of scale

A document is a set of named cells. A cell owns flat geometry (shapes on layers) and placements of other cells: single instances and regular arrays (rows and columns with a pitch). Placements carry a transform (orientation, magnification, translation), and they nest, so a modest cell arrayed thousands of times expands to effectively billions of leaf shapes.

Crucially the hierarchy is never flattened for browsing. Each cell caches the bounding box of its own geometry, so the renderer can cull whole instances and arrays that fall outside the view and pay only for what is visible. Flattening is available when a tool genuinely needs the expanded geometry, and so is the inverse.

Transactional editing

Edits are expressed as a small vocabulary of reversible operations (add or remove a shape, add an instance or array, add or remove a cell). Applying an edit records its inverse on an undo stack, so undo and redo are exact and unbounded. This same operation log is what the collaboration layer replicates; see Collaboration.

The trait surface

The model also defines the stable traits the higher subsystems implement: DocumentStore for editable access, RuleSet for design-rule checking, Router for routing, Importer and Exporter for file formats, and Renderer for drawing. Keeping these here lets the core stay free of the GPU, IO, and async stacks while still describing how they plug in.