fission-ir

The intermediate representation (IR) for the Fission UI framework.

What is this?

fission-ir defines the node graph that sits between the high-level widget tree and the low-level layout and paint pipelines. Every widget compiles down to one or more IR nodes, each carrying a single [Op] that describes what the node does: lay out children, draw something on screen, group subtrees, or declare accessibility semantics.

The IR is platform-agnostic and serializable. It can be diffed, hashed, sent across process boundaries, and inspected by tooling without pulling in any rendering backend.

Core concepts

Type	Purpose
[`CoreIR`]	Root container that owns every node and tracks the tree root.
[`CoreNode`]	A single node: an ID, an operation, child links, and a content hash.
[`NodeId`]	Content-addressed 128-bit identity (BLAKE3). Stable across rebuilds when the structure is unchanged.
[`Op`]	What a node does. One of four categories: `Layout`, `Paint`, `Structural`, or `Semantics`.

Operations at a glance

Layout -- how children are sized and positioned: Box, Flex, Grid, GridItem, Scroll, ZStack, Align, Positioned, AbsoluteFill, Embed, Flyout, Transform, Clip.

Paint -- what gets drawn: DrawRect, DrawText, DrawRichText, DrawImage, DrawPath, DrawSvg.

Structural -- grouping without visual effect: Group.

Semantics -- accessibility and interaction metadata: role, label, actions, focus, drag-and-drop, scroll axes, and more.

Quick example

use fission_ir::{CoreIR, NodeId, Op, LayoutOp};

let mut ir = CoreIR::new();

let root = NodeId::explicit("root");
let child = NodeId::explicit("child");

ir.add_node(child, Op::Layout(LayoutOp::Box {
    width: Some(100.0),
    height: Some(50.0),
    min_width: None,
    max_width: None,
    min_height: None,
    max_height: None,
    padding: [0.0; 4],
    flex_grow: 0.0,
    flex_shrink: 1.0,
    aspect_ratio: None,
}), vec![]);

ir.add_node(root, Op::Layout(LayoutOp::Flex {
    direction: fission_ir::FlexDirection::Column,
    wrap: fission_ir::FlexWrap::NoWrap,
    flex_grow: 1.0,
    flex_shrink: 1.0,
    padding: [8.0; 4],
    gap: Some(4.0),
    align_items: fission_ir::AlignItems::Start,
    justify_content: fission_ir::JustifyContent::Start,
}), vec![child]);

ir.set_root(root);

Serialization

All types derive serde::Serialize and serde::Deserialize, so the entire IR can be round-tripped through JSON, MessagePack, or any other serde-compatible format.

License

MIT