TreeNode

Layer: cell · Path: src/cells/tree_node.rs · Exports: tree_node::TreeNode

An indented hierarchy row: a depth-based indent, an optional expand/collapse caret, an optional icon, and a label. Modelled on Unity/O3DE tree views. Expansion and selection are inputs, not state — show returns the [Response] and the consumer toggles expand/selection itself.

Design

Purpose / when to use — Scene graphs, file trees, outliners — any flattened hierarchy rendered row-by-row with per-row depth.
Anatomy — A Surface (interactive, padded) wrapping a horizontal layout: indent space (depth × core::SPACE_4), a caret Icon (CARET_DOWN/CARET_RIGHT, small, muted) or an core::ICON_SM spacer when not expandable, optional muted Icon, then the Text label.

Variants / states

State	Effect
default	`Surface::fill_none().border_none()`
selected (`selected(true)`)	`Surface::muted()` fill
expandable + collapsed	`light::CARET_RIGHT` caret
expandable + expanded	`light::CARET_DOWN` caret
not expandable	`core::ICON_SM` spacer (keeps labels aligned with carets)
indent	`depth as f32 * core::SPACE_4` leading space

Tokens / layout consumed — core::SPACE_4 (16px per depth level), core::SPACE_1 (4px outer pad + gaps), core::ICON_SM (14px caret slot), core::RADIUS_SM (4px). See tokens.
Accessibility — Selection/expansion are visual inputs; pair with a real tree model.

API

Method	Signature	Effect
`new`	`new(label: impl Into<String>) -> Self`	Construct at `depth=0`, not expandable, not selected.
`depth`	`depth(self, depth: usize) -> Self`	Indent level (× `core::SPACE_4`).
`icon`	`icon(self, glyph: &'static str) -> Self`	Leading muted icon (after the caret slot).
`expandable`	`expandable(self, expanded: bool) -> Self`	Mark expandable and set the expanded flag (caret direction) in one call.
`selected`	`selected(self, selected: bool) -> Self`	Toggle the `muted` selected fill.
`id_source`	`id_source(self, id: impl std::hash::Hash) -> Self`	Stable id for the underlying `Surface`.
`show`	`show(self, ui: &mut Ui) -> Response`	Render; returns the `Surface` response (`.clicked()`).

Usage

#![allow(unused)]
fn main() {
use ouroboros_ui::cells::TreeNode;
use ouroboros_ui::egui_phosphor::light;

TreeNode::new("Scene").icon(light::FOLDER).expandable(true).id_source("tn0").show(ui);
}

#![allow(unused)]
fn main() {
// realistic — a flattened tree with depths and selection
TreeNode::new("Scene").icon(light::FOLDER).expandable(true).id_source("tn0").show(ui);
TreeNode::new("Player").depth(1).icon(light::CUBE).expandable(false).selected(true).id_source("tn1").show(ui);
TreeNode::new("Camera").depth(1).icon(light::CUBE).id_source("tn2").show(ui);
TreeNode::new("Mesh").depth(2).icon(light::CUBE).id_source("tn3").show(ui);
}

Composition

Composes the Surface, Icon (caret + leading icon), and Text atoms only. It paints nothing — visuals come from Surface + atoms. Enforced by tests/no_painter_in_molecules.rs.

Notes

expandable(expanded) does double duty: it both marks the node expandable and sets the caret direction. There is no separate “is expandable” flag — calling it at all makes the node expandable.
Expansion/selection are not remembered by the cell. Drive them from a tree model and toggle on .clicked() (and detect a caret-vs-row click yourself if needed).
Non-expandable rows reserve an core::ICON_SM spacer so their labels align with sibling carets.
Caret glyphs come straight from egui_phosphor::light (CARET_DOWN / CARET_RIGHT).

Keyboard shortcuts

ouroboros-ui

TreeNode

Design

API

Usage

Composition

Notes