nordisk/facett

egui-xyflow evaluation — DO NOT WRAP (yet)

Date: 2026-06-12 Subject: https://github.com/avinkrisv/egui-xyflow (crate egui_xyflow) Verdict: Do not wrap now. Hard egui-version incompatibility. Revisit when egui-xyflow ships a release built against egui 0.34 (see "Unblock condition").

1. Upstream facts

API surface (from README)

Builder-pattern nodes/edges, trait-based custom widgets, an event-returning canvas, and a fat config struct for theming:

// Node
Node::builder("my-node")
    .position(egui::pos2(200.0, 150.0))
    .data("Hello".to_string())
    .handle(NodeHandle::source(Position::Right))
    .size(180.0, 60.0)
    .build()

// Edge
Edge::builder("e2", "a", "b")
    .edge_type(EdgeType::SmoothStep)
    .color(egui::Color32::from_rgb(59, 130, 246))
    .stroke_width(3.0)
    .animated(true)
    .label("1,284 rows/s")

// Render + interaction
let events: FlowEvents = FlowCanvas::show(ui); // connections, clicks, selection, viewport

• Custom rendering: implement NodeWidget / EdgeWidget; DefaultNodeWidget is provided.
• Interaction: FlowCanvas::show(ui) returns FlowEvents (connection-created, click, selection-change, viewport-change). This is a real editor (drag, connect handles, pan/zoom).
• Theming: FlowConfig with 60+ options (colors, snap-to-grid, zoom bounds, edge types, background patterns).

This is genuinely the "React Flow for egui" niche: an interactive, editable flow graph with draggable nodes and user-drawn connections — not just a render-only view.

2. Compatibility verdict vs facett (egui 0.34)

INCOMPATIBLE — will not type-unify.

• facett pins egui = "0.34" workspace-wide (Cargo.toml [workspace.dependencies]), e.g. facett-plot uses egui_plot = "0.35" which is the egui-0.34-aligned line.
• egui-xyflow 0.4.3 (the newest and only current release) depends on egui/emath/epaint = "0.31" — two minor majors behind.
• egui makes breaking changes every minor; 0.31 and 0.34 Color32/Ui/Painter/Pos2 types are distinct, non-interchangeable types in the dependency graph. Cargo would pull both egui 0.31 and 0.34 into the tree, and any value crossing the boundary (a Ui, a FlowEvents) would be a type-mismatch at the wrap seam. You cannot pass facett's &mut egui::Ui (0.34) into FlowCanvas::show (expects 0.34? no — 0.31).
• Therefore a facett-flow wrapper implementing Facet::ui(&mut self, ui: &mut egui::Ui) cannot forward ui into egui-xyflow. No wrap is possible without a fork/backport.

No broken dependency was added to the workspace. Cargo.toml members, the umbrella facett crate, and Cargo.lock are untouched.

3. egui-xyflow vs snarl vs facett-graph — when to use which

Three node/edge tools are now in play around facett/nornir:

Recommendation:

• For read-only graph viz (the bulk of korp/nornir needs today): stay on facett-graph / facett-graph3d. They're in-house, 0.34-native, headless-testable, and have the wgpu fast-path roadmap.
• For interactive node-wiring editors right now: use egui-snarl — it is already egui-current and battle-tested in nornir's Funnel. If facett ever wants a generic "node editor" facet, wrap snarl, not xyflow.
• egui-xyflow is the most visually polished flow-editor of the three and the natural pick for a future "pipeline/workflow builder" facet (animated dataflow edges, throughput labels — exactly the knut/skade pipeline-viewer aesthetic) — but only once it targets egui 0.34. Until then snarl covers the same need without a version conflict.

4. Unblock condition (when to revisit)

Revisit and scaffold facett-flow when egui-xyflow publishes a release whose egui/emath/epaint dependency is 0.34 (or whatever facett's egui is at the time).

Concretely, before re-attempting:

1. cargo search egui_xyflow (or check crates.io) for a version > 0.4.3.
2. Confirm its Cargo.toml has egui = "0.34" (raw URL: https://raw.githubusercontent.com/avinkrisv/egui-xyflow/master/Cargo.toml).
3. If yes: scaffold a thin facett-flow crate mirroring facett-plot's shape — a FlowView implementing facett-core::Facet (title / ui / state_json), a tiny node/edge demo, add to workspace members + umbrella facett re-export (pub use facett_flow as flow;), and a smoke test. Map xyflow's FlowEvents selection/click state into state_json for headless assertions.

Alternative (only if there's strong demand and xyflow stays stale): fork/backport xyflow 0.4.x to egui 0.34 — but that is a real maintenance burden and not worth it while egui-snarl already serves the interactive-editor need at 0.34.