Crate fission_layout 

Constraint-based layout engine for the Fission UI framework.

This crate takes a flat list of LayoutInputNodes (produced from the fission-ir intermediate representation) and computes the absolute position and size of every node on screen. It implements:

• Box layout – constrained containers with padding, min/max, and aspect ratio.
• Flexbox – single-axis distribution with grow, shrink, wrap, alignment, and justification.
• CSS Grid – two-dimensional track-based layout with fr, %, and fixed sizing.
• Scroll containers – clipped viewports with infinite content axes.
• Absolute positioning – top/left/right/bottom offsets.
• ZStack – overlapping children.
• Flyout anchoring – popups positioned relative to an anchor node.

The engine is pure computation with no platform dependencies. Give it nodes and a viewport size, and it returns a LayoutSnapshot mapping every NodeId to a LayoutRect.

Example

use fission_layout::*;
use fission_ir::{NodeId, LayoutOp};

let mut engine = LayoutEngine::new();
let root_id = NodeId::explicit("root");
// ... build LayoutInputNode list ...
// let snapshot = engine.compute_layout(&nodes, root_id, viewport, &|_| 0.0).unwrap();

Structs

BoxConstraints

Minimum and maximum width/height bounds passed from parent to child during layout.

LayoutEngine

The constraint-based layout solver.

LayoutInputNode

A flattened representation of a layout node, ready for the layout engine.

LayoutNodeGeometry

The computed geometry of a single layout node.

LayoutPoint

A 2D point in layout coordinate space.

LayoutRect

An axis-aligned rectangle: an origin point plus a size.

LayoutSize

A 2D size in layout coordinate space.

LayoutSnapshot

The complete output of a layout pass.

LineMetric

Per-line metrics returned by text measurement.

Enums

FlexDirection

The primary axis direction for a flex or scroll container.

GridPlacement

Where a grid item is placed within its grid container.

GridTrack

A track sizing function for CSS Grid-style columns or rows.

LayoutOp

A layout operation that sizes and positions a node and its children.

Traits

ScrollDataSource

A source of scroll offsets for scroll containers.

TextMeasurer

A platform-provided text measurement backend.

Type Aliases

LayoutUnit

The scalar type used for all layout measurements.