Struct Tree 

pub struct Tree<Msg> { /* private fields */ }

Nested rows that open and close, like folders.

The application owns the nodes, which are open and which one is selected, identified by node keys; the tree reports changes through messages. Only the open part of the tree is flattened and only the rows on screen are drawn, so large trees stay fast. Children can be loaded when a node opens: mark it TreeNode::expandable, answer Tree::on_expand with a background command and mark the node TreeNode::loading meanwhile; its spinner only shows when the load is slow.

Rows are indented by space; openable rows carry a chevron. A hovered or selected row raises its surface and shows the pillar; only its icon and label slide one cell right. The indentation, the chevron (or the loading spinner in its place) and the detail never move, so the chevron is always where the pointer clicks it.

Keys while focused: ↑/↓ or k/j, PgUp/PgDn, Home/End move; → opens a node or moves to its first child; ← closes it or moves to its parent; Enter opens or closes a node with children and activates a leaf; Space activates. A click selects a row and opens, closes or activates it like Enter; a click on the chevron only opens or closes.

Two capabilities are off until asked for:

• reorderable: drag a node to move it among its siblings; the siblings make room, a ghost row follows the pointer and a tinted slot shows where it lands, while the dragged node’s own children fold away. Ctrl+Shift+↑/↓ moves the selected node one place. A node keeps its parent: moving under another parent is the application’s own action, offered in the context menu. Held on the top or bottom row, or past them, a drag scrolls the tree one row after 400 ms and then every 150 ms. With reordering on, a click opens, closes or activates on release, so pressing a row to drag it does not open it.
• context_menu: a right click on a row opens a menu of actions for that node at the pointer and keeps the row raised while it is open; the menu key or Shift+F10 opens the menu of the selected node below its row. Without it a right click does nothing.

Style keys: rows use list-item (hover, selected, focus, pressed), list-item.faint, list-detail and list-header (empty text) like List; tree-chevron (fg) with hover and selected; spinner for loading nodes; scrollbar. Icons: tree-collapsed, tree-expanded, spinner. A drag uses tab-drop for the landing slot and tab-ghost for the row following the pointer, like the tabs; the menu uses the keys of ContextItem.

Implementations

impl<Msg: 'static> Tree<Msg>

pub fn new(roots: impl IntoIterator<Item = TreeNode>) -> Self

A tree with top-level nodes roots.

pub fn selected(self, key: Option<&str>) -> Self

The key of the selected node.

pub fn empty_text(self, text: impl Into<String>) -> Self

Text shown when there are no nodes.

pub fn on_select(self, message: impl Fn(&str) -> Msg + 'static) -> Self

Message for moving the selection to a node.

pub fn on_activate(self, message: impl Fn(&str) -> Msg + 'static) -> Self

Message for activating a node: Enter on a leaf, Space, a click on a leaf.

pub fn on_expand(self, message: impl Fn(&str, bool) -> Msg + 'static) -> Self

Message asking to open (true) or close (false) a node.

pub fn reorderable(self, message: impl Fn(TreeMove) -> Msg + 'static) -> Self

Makes nodes reorderable among their siblings: message(TreeMove) asks the application to move one. TreeMove::apply applies it to the application’s list of siblings.

pub fn context_menu( self, items: impl Fn(&str) -> Vec<ContextItem<Msg>> + 'static, ) -> Self

Gives every node a context menu: items(key) builds the entries for the node with that key, such as Rename, Archive or Move to. Choosing an entry sends its message.

Trait Implementations

impl<Msg: 'static> Widget<Msg> for Tree<Msg>

fn measure(&self, _cx: &mut MeasureCx<'_>, available: Size) -> Size

The size the widget wants when it may use up to available.

fn paint(&self, cx: &mut PaintCx<'_>, area: Rect)

Draws the widget into area.

fn paint_overlay(&self, cx: &mut PaintCx<'_>, anchor: Rect)

Draws the widget’s overlay after the whole view was painted, when it asked for one with PaintCx::request_overlay. anchor is the area the widget was painted in.

fn event(&self, cx: &mut EventCx<'_, Msg>, event: &Event) -> bool

Handles input. Returns true when the event was used; unused key and scroll events bubble to the parent widget.

fn focusable(&self) -> bool

Whether the widget can take keyboard focus.

fn children(&self) -> &[Node<Msg>]

Child nodes, for widgets that contain other widgets.

fn children_mut(&mut self) -> &mut [Node<Msg>]

Mutable child nodes, used to assign ids.