Struct TreeSource 

pub struct TreeSource {

    pub children_len: Rc<dyn Fn(Option<u64>) -> usize>,
    pub child_token: Rc<dyn Fn(Option<u64>, usize) -> u64>,
    pub expandable: Rc<dyn Fn(u64) -> bool>,
    pub section_header: Rc<dyn Fn(u64) -> bool>,
    pub expanded: Rc<dyn Fn(u64) -> bool>,
    pub bind_row: Rc<dyn Fn(u64, RawHandle)>,
    pub recycle: Rc<dyn Fn(RawHandle)>,
    pub layout_cell: Rc<dyn Fn(RawHandle, f64)>,
    pub layout_cell_size: Rc<dyn Fn(RawHandle, Size)>,
    pub cell_height: Rc<dyn Fn(RawHandle) -> f64>,
    pub type_select_text: Rc<dyn Fn(u64) -> String>,
    pub row_menu: Option<Rc<dyn Fn(u64) -> Vec<MenuItem>>>,
    pub moves: Option<TreeMoves>,
}

The synchronous row-pull closures for hierarchical trees (docs/tree.md): ListSource’s shape, addressed by token instead of row index, because expanding a row renumbers every index below it while tokens hold still. day-core injects one per TREE host via Toolkit::attach_tree; the backend answers its native data-source from it. The same synchronous discipline as ListSource: UI thread, outside any day-core borrow; bind_row flushes and lays the row out before returning.

Fields

children_len: Rc<dyn Fn(Option<u64>) -> usize>

How many children parent has (None = the root level).

child_token: Rc<dyn Fn(Option<u64>, usize) -> u64>

The i-th child of parent: the stable token every backend keys its rows by.

expandable: Rc<dyn Fn(u64) -> bool>

Whether this token can hold children at all: what draws (or omits) the disclosure.

section_header: Rc<dyn Fn(u64) -> bool>

Non-selectable section heading, separate from a navigation destination.

expanded: Rc<dyn Fn(u64) -> bool>

Current desired expansion, including restoration before the first native reload.

bind_row: Rc<dyn Fn(u64, RawHandle)>

Build (first use of this cell) or rebind (recycled cell) the row for token into the native cell.

recycle: Rc<dyn Fn(RawHandle)>

The native cell left the viewport; Day may drop per-cell bookkeeping (optional).

layout_cell: Rc<dyn Fn(RawHandle, f64)>

Re-lay the row bound to this cell at width, called from the cell’s own native layout pass. Trees need this where lists don’t: indentation makes every cell’s content width per-row, so the host-width layout bind_row did is only a first approximation. Skips quietly when called inside a day-core borrow (a snapshot pass).

layout_cell_size: Rc<dyn Fn(RawHandle, Size)>

Native bounds for controls whose group headers have a different height from leaves. Overrides the initial row-height estimate and preserves the native height on rebind.

cell_height: Rc<dyn Fn(RawHandle) -> f64>

The height day-core last laid this cell’s row at (see ListSource::cell_height).

type_select_text: Rc<dyn Fn(u64) -> String>

The row’s type-ahead string (docs/tree.md): what native type-select matches against.

row_menu: Option<Rc<dyn Fn(u64) -> Vec<MenuItem>>>

The row’s context menu, built when the menu is summoned (docs/menus.md “Dynamic context menus”), called on the UI thread from the platform’s own menu callback, outside any day-core borrow, like every closure here. None = rows carry no menu; an empty result suppresses the menu for that row.

moves: Option<TreeMoves>

Drag-to-move closures, present when TreeProps::movable (docs/tree.md). None on immovable trees; backends must not enable their drag machinery without it.

Trait Implementations

impl Clone for TreeSource

fn clone(&self) -> TreeSource

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.