Jellyflow Layout

Optional headless layout adapters for Jellyflow graphs.

The crate keeps layout engines outside jellyflow-core and returns normal Jellyflow transactions so hosts can decide when to apply or animate layout results.

Engine Boundary

jellyflow-layout exposes a small engine protocol:

• LayoutEngine is implemented by built-in or host-provided engines.
• LayoutEngineRegistry maps stable LayoutEngineId values to engines.
• LayoutEngineRequest selects one engine and carries a LayoutRequest.
• LayoutContext carries runtime-only facts such as measured node sizes and fallback node origin.
• LayoutFamilyMetadata and LayoutEngineMetadata expose discovery-only family/capability data without changing the stable engine-id dispatch contract.

The built-in dugong engine is registered under DUGONG_LAYOUT_ENGINE_ID ("dugong"). The built-in radial mind-map engine is registered under MIND_MAP_RADIAL_LAYOUT_ENGINE_ID ("mind_map_radial"). The built-in freeform mind-map engine is registered under MIND_MAP_FREEFORM_LAYOUT_ENGINE_ID ("mind_map_freeform"). It currently keeps the input canvas feel and only resolves overlaps while preserving pinned nodes. Compatibility helpers such as layout_graph_with_dugong remain available, but new host code should prefer the registry path when it needs runtime selection or custom engines. The built-in dugong engine is grouped under the layered_dag family, while the radial and freeform mind-map engines are grouped under the mind_map family.

use jellyflow_core::Graph;
use jellyflow_layout::{
    LayoutContext, LayoutEngineRequest, LayoutRequest, builtin_layout_engine_registry,
    layout_graph_to_transaction_with_engine,
};

fn plan_builtin_layout(graph: &Graph) -> Result<(), jellyflow_layout::LayoutError> {
    let registry = builtin_layout_engine_registry();
    let request = LayoutEngineRequest::dugong(LayoutRequest::all());
    let context = LayoutContext::new();

    let tx = layout_graph_to_transaction_with_engine(graph, &request, &registry, &context)?;
    assert_eq!(tx.label(), Some("Layout graph"));
    Ok(())
}

For interactive editors, keep product-specific behavior in custom engines. A radial, freeform, or mind-map engine can implement LayoutEngine, use LayoutContext for measured sizes or pinned nodes, and still return the same LayoutResult / GraphTransaction shape as the built-in engine.