add tree

crates/data/Cargo.toml

@@ -14,5 +14,6 @@ gpui = { workspace = true, features = ["test-support"] }
 
 [features]
 default = ["full"]
-full = ["list"]
+full = ["list", "tree"]
 list = []
+tree = []

crates/data/src/lib.rs

@@ -3,3 +3,6 @@
 
 #[cfg(feature = "list")]
 pub mod list;
+
+#[cfg(feature = "tree")]
+pub mod tree;

crates/data/src/tree.rs

@@ -0,0 +1,439 @@
+use std::rc::Rc;
+
+use gpui::prelude::FluentBuilder as _;
+use gpui::{
+    AnyElement, App, ElementId, FocusHandle, Hsla, InteractiveElement as _, IntoElement,
+    KeyDownEvent, ParentElement as _, Pixels, RenderOnce, Role, SharedString,
+    StatefulInteractiveElement as _, Styled as _, Window, div,
+};
+use gpui_native_icons::{IconRole, icon};
+use gpui_native_theme::ActiveTheme as _;
+
+/// The change reporter, fired with the next selection by pointer and keys.
+type ChangeHandler = Rc<dyn Fn(Option<usize>, &mut Window, &mut App)>;
+/// The disclosure reporter, fired with the toggled row's index.
+type DisclosureHandler = Rc<dyn Fn(usize, &mut Window, &mut App)>;
+type ItemsFn = Box<dyn Fn(&mut Window, &mut App) -> Vec<TreeItem>>;
+
+/// Tree item.
+#[derive(Clone)]
+pub struct TreeItem {
+    label: SharedString,
+    icon: Option<IconRole>,
+    depth: usize,
+    expandable: bool,
+    expanded: bool,
+    disabled: bool,
+}
+
+impl TreeItem {
+    /// Creates a leaf row with this label at the root depth.
+    pub fn new<L>(label: L) -> Self
+    where
+        L: Into<SharedString>,
+    {
+        Self {
+            label: label.into(),
+            icon: None,
+            depth: 0,
+            expandable: false,
+            expanded: false,
+            disabled: false,
+        }
+    }
+
+    /// Shows an icon leading the label.
+    pub fn icon(mut self, role: IconRole) -> Self {
+        self.icon = Some(role);
+        self
+    }
+
+    /// Nests the row one level per count.
+    pub fn depth(mut self, depth: usize) -> Self {
+        self.depth = depth;
+        self
+    }
+
+    /// Marks the row as having children.
+    pub fn expandable(mut self, expandable: bool) -> Self {
+        self.expandable = expandable;
+        self
+    }
+
+    /// Sets the row's disclosure state.
+    pub fn expanded(mut self, expanded: bool) -> Self {
+        self.expanded = expanded;
+        self
+    }
+
+    /// Renders the row dimmed; clicks and keyboard skip it.
+    pub fn disabled(mut self, disabled: bool) -> Self {
+        self.disabled = disabled;
+        self
+    }
+}
+
+/// A tree.
+#[derive(IntoElement)]
+pub struct Tree {
+    id: ElementId,
+    selected: Option<usize>,
+    a11y_label: Option<SharedString>,
+    on_change: Option<ChangeHandler>,
+    on_disclosure: Option<DisclosureHandler>,
+    items: Option<ItemsFn>,
+}
+
+impl Tree {
+    /// Creates a tree with nothing selected.
+    pub fn new<I>(id: I) -> Self
+    where
+        I: Into<ElementId>,
+    {
+        Self {
+            id: id.into(),
+            selected: None,
+            a11y_label: None,
+            on_change: None,
+            on_disclosure: None,
+            items: None,
+        }
+    }
+
+    /// Sets the current selection.
+    pub fn selected(mut self, selected: Option<usize>) -> Self {
+        self.selected = selected;
+        self
+    }
+
+    /// Reports the next selection, from clicks and keys alike.
+    pub fn on_change<F>(mut self, handler: F) -> Self
+    where
+        F: Fn(Option<usize>, &mut Window, &mut App) + 'static,
+    {
+        self.on_change = Some(Rc::new(handler));
+        self
+    }
+
+    /// Reports the row whose disclosure the user toggled.
+    pub fn on_disclosure<F>(mut self, handler: F) -> Self
+    where
+        F: Fn(usize, &mut Window, &mut App) + 'static,
+    {
+        self.on_disclosure = Some(Rc::new(handler));
+        self
+    }
+
+    /// Sets the visible rows, built fresh each render.
+    pub fn items<F>(mut self, items: F) -> Self
+    where
+        F: Fn(&mut Window, &mut App) -> Vec<TreeItem> + 'static,
+    {
+        self.items = Some(Box::new(items));
+        self
+    }
+
+    /// Overrides the accessibility label, which defaults to the id.
+    pub fn accessibility_label<L>(mut self, label: L) -> Self
+    where
+        L: Into<SharedString>,
+    {
+        self.a11y_label = Some(label.into());
+        self
+    }
+}
+
+struct TreeChrome {
+    foreground: Hsla,
+    muted: Hsla,
+    muted_foreground: Hsla,
+    primary: Hsla,
+    primary_foreground: Hsla,
+    radius_sm: Pixels,
+    icon_size: Pixels,
+    padding_x: Pixels,
+    text_size: Pixels,
+    /// The row count, for the rows' set-size a11y attributes.
+    count: usize,
+}
+
+impl RenderOnce for Tree {
+    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
+        let chrome = {
+            let theme = cx.theme();
+            TreeChrome {
+                foreground: theme.colors.foreground,
+                muted: theme.colors.muted,
+                muted_foreground: theme.colors.muted_foreground,
+                primary: theme.ramps.primary.base,
+                primary_foreground: theme.colors.primary_foreground,
+                radius_sm: theme.radius.sm,
+                icon_size: theme.sizes.medium.icon_size,
+                padding_x: theme.sizes.medium.padding_x,
+                text_size: theme.sizes.medium.text_size,
+                count: 0,
+            }
+        };
+
+        let items = match self.items {
+            Some(build) => build(window, cx),
+            None => Vec::new(),
+        };
+
+        let selectable: Vec<usize> = items
+            .iter()
+            .enumerate()
+            .filter(|(_, item)| !item.disabled)
+            .map(|(index, _)| index)
+            .collect();
+
+        // Keyboard focus rides the container across frames.
+        let focus_handle = window.with_element_namespace(self.id.clone(), |window| {
+            window.use_keyed_state("tree-focus", cx, |_, cx| cx.focus_handle())
+        });
+        let focus = focus_handle.read(cx).clone();
+
+        let label = self
+            .a11y_label
+            .clone()
+            .unwrap_or_else(|| SharedString::from(self.id.to_string()));
+
+        let chrome = TreeChrome {
+            count: items.len(),
+            ..chrome
+        };
+
+        let rows: Vec<AnyElement> = items
+            .iter()
+            .enumerate()
+            .map(|(index, item)| {
+                render_row(
+                    item,
+                    index,
+                    self.selected == Some(index),
+                    &chrome,
+                    &self.on_change,
+                    &self.on_disclosure,
+                    &focus,
+                )
+            })
+            .collect();
+
+        div()
+            .id(self.id)
+            .flex()
+            .flex_col()
+            .gap_0p5()
+            .text_size(chrome.text_size)
+            .track_focus(&focus)
+            .focusable()
+            .tab_stop(true)
+            .role(Role::Tree)
+            .aria_label(label)
+            .on_key_down({
+                let selected = self.selected;
+                let on_change = self.on_change.clone();
+                let on_disclosure = self.on_disclosure.clone();
+                move |event: &KeyDownEvent, window, cx| {
+                    match event.keystroke.key.as_str() {
+                        "down" => {
+                            if let Some(next) = adjacent(&selectable, selected, true)
+                                && Some(next) != selected
+                                && let Some(on_change) = &on_change
+                            {
+                                on_change(Some(next), window, cx);
+                            }
+                        }
+                        "up" => {
+                            if let Some(next) = adjacent(&selectable, selected, false)
+                                && Some(next) != selected
+                                && let Some(on_change) = &on_change
+                            {
+                                on_change(Some(next), window, cx);
+                            }
+                        }
+                        "home" => {
+                            if let Some(first) = selectable.first()
+                                && selected != Some(*first)
+                                && let Some(on_change) = &on_change
+                            {
+                                on_change(Some(*first), window, cx);
+                            }
+                        }
+                        "end" => {
+                            if let Some(last) = selectable.last()
+                                && selected != Some(*last)
+                                && let Some(on_change) = &on_change
+                            {
+                                on_change(Some(*last), window, cx);
+                            }
+                        }
+                        "left" | "right" => {
+                            let expanding = event.keystroke.key == "right";
+                            if let Some(index) = selected
+                                && let Some(item) = items.get(index)
+                                && item.expandable
+                                && !item.disabled
+                                && item.expanded != expanding
+                                && let Some(on_disclosure) = &on_disclosure
+                            {
+                                on_disclosure(index, window, cx);
+                            }
+                        }
+                        _ => return,
+                    }
+                    cx.stop_propagation();
+                }
+            })
+            .children(rows)
+    }
+}
+
+fn render_row(
+    item: &TreeItem,
+    index: usize,
+    selected: bool,
+    chrome: &TreeChrome,
+    on_change: &Option<ChangeHandler>,
+    on_disclosure: &Option<DisclosureHandler>,
+    focus: &FocusHandle,
+) -> AnyElement {
+    let label_color = row_color(item, selected, chrome);
+    let disabled = item.disabled;
+
+    // One indent step per depth level, on the theme's horizontal padding.
+    let indent = chrome.padding_x * (item.depth as f32 + 1.0);
+
+    div()
+        .id(("tree-item", index))
+        .flex()
+        .items_center()
+        .gap_2()
+        .pl(indent)
+        .pr_2()
+        .py_1()
+        .rounded(chrome.radius_sm)
+        .role(Role::TreeItem)
+        .aria_selected(selected)
+        .aria_level(item.depth + 1)
+        .aria_size_of_set(chrome.count)
+        .when(item.expandable, |row| row.aria_expanded(item.expanded))
+        .map(|row| {
+            if disabled {
+                row
+            } else if selected {
+                row.bg(chrome.primary)
+            } else {
+                row.hover(|row| row.bg(chrome.muted))
+            }
+        })
+        .when(!disabled, |row| {
+            row.cursor_pointer().on_click({
+                let on_change = on_change.clone();
+                let focus = focus.clone();
+                move |_, window, cx| {
+                    window.focus(&focus, cx);
+                    if let Some(on_change) = &on_change {
+                        on_change(Some(index), window, cx);
+                    }
+                }
+            })
+        })
+        .child(render_disclosure(
+            item,
+            index,
+            disabled,
+            selected,
+            chrome,
+            on_disclosure,
+        ))
+        .when_some(item.icon, |row, role| {
+            row.child(icon(role).size(chrome.icon_size).color(label_color))
+        })
+        .child(
+            div()
+                .flex_1()
+                .text_color(label_color)
+                .child(item.label.clone()),
+        )
+        .into_any_element()
+}
+
+/// The disclosure slot.
+fn render_disclosure(
+    item: &TreeItem,
+    index: usize,
+    disabled: bool,
+    selected: bool,
+    chrome: &TreeChrome,
+    on_disclosure: &Option<DisclosureHandler>,
+) -> AnyElement {
+    let glyph_color = if disabled {
+        chrome.muted_foreground
+    } else if selected {
+        chrome.primary_foreground
+    } else {
+        chrome.muted_foreground
+    };
+
+    let cell = div()
+        .flex_none()
+        .size(chrome.icon_size)
+        .flex()
+        .items_center()
+        .justify_center()
+        .child(
+            icon(if item.expanded {
+                IconRole::ChevronDown
+            } else {
+                IconRole::ChevronRight
+            })
+            .size(chrome.icon_size * 0.75)
+            .color(glyph_color),
+        );
+
+    if item.expandable && !disabled {
+        cell.id(("tree-disclosure", index))
+            .cursor_pointer()
+            .on_click({
+                let on_disclosure = on_disclosure.clone();
+                move |_, window, cx| {
+                    if let Some(on_disclosure) = &on_disclosure {
+                        on_disclosure(index, window, cx);
+                    }
+                    // The toggle is not a selection: keep it off the row.
+                    cx.stop_propagation();
+                }
+            })
+            .into_any_element()
+    } else {
+        cell.into_any_element()
+    }
+}
+
+/// The row's label/icon color.
+fn row_color(item: &TreeItem, selected: bool, chrome: &TreeChrome) -> Hsla {
+    if item.disabled {
+        chrome.muted_foreground
+    } else if selected {
+        chrome.primary_foreground
+    } else {
+        chrome.foreground
+    }
+}
+
+/// The next selectable row in the direction.
+fn adjacent(selectable: &[usize], selected: Option<usize>, forward: bool) -> Option<usize> {
+    if forward {
+        selectable
+            .iter()
+            .copied()
+            .find(|index| Some(*index) > selected)
+    } else {
+        selectable
+            .iter()
+            .copied()
+            .rev()
+            .find(|index| Some(*index) < selected)
+    }
+}

crates/data/tests/tree.rs

@@ -0,0 +1,191 @@
+use std::{cell::RefCell, rc::Rc};
+
+use gpui::{
+    Context, IntoElement, Modifiers, MouseButton, ParentElement as _, Render, Styled as _,
+    TestAppContext, VisualTestContext, Window, WindowHandle, div, point, px,
+};
+use gpui_native_data::tree::{Tree, TreeItem};
+use gpui_native_theme::Theme;
+
+type Changes = Rc<RefCell<Vec<Option<usize>>>>;
+type Disclosures = Rc<RefCell<Vec<usize>>>;
+
+struct Harness {
+    selected: Option<usize>,
+    changes: Changes,
+    disclosures: Disclosures,
+}
+
+impl Render for Harness {
+    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let changes = self.changes.clone();
+        let disclosures = self.disclosures.clone();
+        let view = cx.entity();
+        let change_view = view.clone();
+        div().size_full().child(
+            Tree::new("test-tree")
+                .selected(self.selected)
+                .on_change(move |next, _, cx| {
+                    changes.borrow_mut().push(next);
+                    change_view.update(cx, |harness, cx| {
+                        harness.selected = next;
+                        cx.notify();
+                    });
+                })
+                .on_disclosure(move |index, _, cx| {
+                    disclosures.borrow_mut().push(index);
+                    view.update(cx, |_, cx| cx.notify());
+                })
+                .items(|_, _| {
+                    vec![
+                        TreeItem::new("Root")
+                            .depth(0)
+                            .expandable(true)
+                            .expanded(true),
+                        TreeItem::new("Child").depth(1),
+                        TreeItem::new("Collapsed").depth(0).expandable(true),
+                        TreeItem::new("Untouchable").depth(1).disabled(true),
+                        TreeItem::new("Last").depth(0),
+                    ]
+                }),
+        )
+    }
+}
+
+/// Rows paint at the top-left, one per ~34 px band (same rhythm as the
+/// list), so clicks at `(50, 16/48/80/112/144)` land on Root / Child /
+/// Collapsed / the disabled Untouchable / Last. Each expandable row leads
+/// with a 16 px disclosure slot at its indent — a click at `(24, y)` hits
+/// row 0's chevron.
+fn tree_window() -> (
+    TestAppContext,
+    VisualTestContext,
+    WindowHandle<Harness>,
+    Changes,
+    Disclosures,
+) {
+    let mut cx = TestAppContext::single();
+    cx.update(Theme::init);
+    let changes = Rc::new(RefCell::new(Vec::new()));
+    let disclosures = Rc::new(RefCell::new(Vec::new()));
+    let harness_changes = changes.clone();
+    let harness_disclosures = disclosures.clone();
+    let window = cx.add_window(move |_, _| Harness {
+        selected: None,
+        changes: harness_changes,
+        disclosures: harness_disclosures,
+    });
+    let mut visual = VisualTestContext::from_window(window.into(), &cx);
+    visual.update(|window, cx| {
+        window.draw(cx).clear(cx);
+    });
+    (cx, visual, window, changes, disclosures)
+}
+
+fn draw(visual: &mut VisualTestContext) {
+    visual.update(|window, cx| {
+        window.draw(cx).clear(cx);
+    });
+}
+
+fn click(visual: &mut VisualTestContext, position: gpui::Point<gpui::Pixels>) {
+    visual.simulate_mouse_down(position, MouseButton::Left, Modifiers::default());
+    visual.simulate_mouse_up(position, MouseButton::Left, Modifiers::default());
+}
+
+#[test]
+fn clicking_a_row_selects_it_and_hands_the_tree_the_keyboard() {
+    let (_cx, mut visual, _window, changes, disclosures) = tree_window();
+
+    click(&mut visual, point(px(50.), px(16.)));
+    assert_eq!(*changes.borrow(), vec![Some(0)]);
+    assert!(disclosures.borrow().is_empty());
+
+    // The click focused the tree; arrows move within the visible rows.
+    visual.simulate_keystrokes("down");
+    draw(&mut visual);
+    assert_eq!(*changes.borrow(), vec![Some(0), Some(1)]);
+}
+
+#[test]
+fn clicking_the_disclosure_toggles_without_selecting() {
+    let (_cx, mut visual, _window, changes, disclosures) = tree_window();
+
+    // Row 0's chevron, not its label.
+    click(&mut visual, point(px(24.), px(16.)));
+    draw(&mut visual);
+    assert_eq!(*disclosures.borrow(), vec![0]);
+    assert!(
+        changes.borrow().is_empty(),
+        "a disclosure is not a selection"
+    );
+}
+
+#[test]
+fn arrow_right_expands_and_left_collapses_the_selected_row() {
+    let (_cx, mut visual, _window, changes, disclosures) = tree_window();
+
+    click(&mut visual, point(px(50.), px(16.))); // Root: expanded expandable
+    visual.simulate_keystrokes("left"); // collapse → reports
+    visual.simulate_keystrokes("right"); // still collapsed per the caller → nothing yet
+    visual.simulate_keystrokes("down"); // Child: a leaf → arrows are inert
+    visual.simulate_keystrokes("right");
+    visual.simulate_keystrokes("left");
+    draw(&mut visual);
+    assert_eq!(*disclosures.borrow(), vec![0]);
+    assert_eq!(
+        *changes.borrow(),
+        vec![Some(0), Some(1)],
+        "disclosure keys never change the selection"
+    );
+
+    // Select the collapsed expandable row and expand it.
+    click(&mut visual, point(px(50.), px(80.)));
+    visual.simulate_keystrokes("right");
+    draw(&mut visual);
+    assert_eq!(*disclosures.borrow(), vec![0, 2]);
+}
+
+#[test]
+fn keyboard_navigation_skips_disabled_rows_and_never_wraps() {
+    let (_cx, mut visual, _window, changes, _disclosures) = tree_window();
+
+    click(&mut visual, point(px(50.), px(16.)));
+    visual.simulate_keystrokes("down"); // Two
+    visual.simulate_keystrokes("down"); // Collapsed — selectable, not disabled
+    visual.simulate_keystrokes("down"); // over the disabled row → Last
+    visual.simulate_keystrokes("down"); // last selectable; no wrap
+    draw(&mut visual);
+    assert_eq!(*changes.borrow(), vec![Some(0), Some(1), Some(2), Some(4)]);
+
+    visual.simulate_keystrokes("home");
+    visual.simulate_keystrokes("end");
+    visual.simulate_keystrokes("up"); // over the disabled row
+    draw(&mut visual);
+    assert_eq!(
+        *changes.borrow(),
+        vec![
+            Some(0),
+            Some(1),
+            Some(2),
+            Some(4),
+            Some(0),
+            Some(4),
+            Some(2)
+        ]
+    );
+}
+
+#[test]
+fn disclosure_keys_skip_disabled_and_unselected_rows() {
+    let (_cx, mut visual, _window, changes, disclosures) = tree_window();
+
+    // Focus through the first row, then park the selection on the leaf.
+    click(&mut visual, point(px(50.), px(16.)));
+    visual.simulate_keystrokes("down"); // Child (leaf), focused tree
+    visual.simulate_keystrokes("left"); // leaf: no disclosure
+    visual.simulate_keystrokes("right"); // leaf: no disclosure
+    draw(&mut visual);
+    assert!(disclosures.borrow().is_empty());
+    assert_eq!(*changes.borrow(), vec![Some(0), Some(1)]);
+}

docs/PLAN.md

@@ -217,7 +217,7 @@ Each row is one review unit: build it, show it in the gallery, review, then move
 | 11 | core | Popover | ✅ Landed (2026-10-29). First overlay. Controlled `open` + `on_change` (Rc-shared handler); `trigger`/`content` element closures; panel = surface + `Radius.overlay` + `Elevations.popover` + border, role Dialog with label; `anchored()` + `deferred()` (window-overflow flip for free); enter fade via gpui `with_animation` at `Motion.overlay` (respects reduce-motion); claims keyboard focus while open; escape and click-outside dismiss (outside clicks swallowed). No scrim — native macOS popover model; the overlay token waits for Dialog. Known v1 gaps: no exit animation, trigger aria-expanded left to the app |
 | 11+ | core | Tooltip ✅ (2026-10-29), Dialog + AlertDialog ✅ (2026-10-29), Toast ✅ (2026-10-29) | One unit each, same gate. Tooltip rides gpui's own `.tooltip()` lifecycle (hover delay, anchoring, dismissal — all framework-owned); ours is the styled view (`surface` + border + `Radius.sm`, small text) plus a `Tooltip::text` closure and a Button passthrough. Dialog + AlertDialog (one component, `alert(true)` switches semantics): scrim (`colors.overlay`, occluding) + centered panel (surface, `Radius.overlay`, `Elevations.dialog`), role Dialog/AlertDialog, focus claimed while open; modal kind closes on escape + scrim click, alert kind is inert to both (the user answers through the actions); actions footer is caller-built elements closing through owner state. Toast: `Toasts` store entity (push/dismiss/clear + auto-dismiss timers on the GPUI executor, `Toast::DURATION` 5 s, zero = sticky) + `ToastsView` deferred stack (top-right, `Radius.overlay` + popover elevation, severity icon from the new success/warning ramps, close button, `on_dismiss` windowless handler). Toast landed the deferred `success`/`warning` tokens (§5.2). Sheet dropped from the roadmap |
 | 14 | core + theme | Motion (per component) | ✅ Landed in five passes (2026-10-30), replacing the reverted same-day framework attempt — no token tower, no `motion` module, no ghost panels; just gpui's own primitives used inline, one separately reviewed pass per component: (a) theme — `reapply` forwards `reduce_motion` via `cx.set_reduce_motion`, so gpui snaps every animation under the OS setting; (b) Switch — the thumb absolute-positions in the track and slides on `with_spring` (inline `SpringConfig::new(500, 35, 1)`, `Pixels` target, mounts at its target so the initial render never animates; velocity survives mid-flight retargets); (c) Toast — each toast slides up 8 px into its stack slot on `with_animation` at `Motion.overlay` with `ease_out_quint` (margin-driven, so only the entering toast moves; keyed per entry so the clock survives unrelated stack re-renders); (d) Dialog — the scrim enters with the panel (same timing and easing, its own `dialog-scrim-enter` animation id so the clocks start in the same frame); (e) Progress — the indeterminate sweep caps at 30 fps via `with_max_fps`. Overlay enter fades already existed from units 11/12. Exits and hover washes stay deferred — they were the complexity sink of the reverted attempt (§ deferred list) |
-| then | data (new) | List ✅ (2026-10-30), then Tree → Tabs → Sidebar | Created on demand, same gate. Table dropped from the roadmap. List: controlled single-selection rows (`selected: Option<usize>` + `on_change`); click selects and focuses the list, arrows/home/end move selection skipping disabled rows and never wrapping (native list behavior), hover is paint-only, click focus rides a keyed `FocusHandle` namespaced by the list id; roles List/ListItem with `aria_selected` and position/size-of-set; internal scrolling left to the caller's ScrollArea; `sheet` feature dropped from core as dead config |
+| then | data (new) | List ✅ (2026-10-30), Tree ✅ (2026-10-30), then Tabs → Sidebar | Created on demand, same gate. Table dropped from the roadmap. List: controlled single-selection rows (`selected: Option<usize>` + `on_change`); click selects and focuses the list, arrows/home/end move selection skipping disabled rows and never wrapping (native list behavior), hover is paint-only, click focus rides a keyed `FocusHandle` namespaced by the list id; roles List/ListItem with `aria_selected` and position/size-of-set; internal scrolling left to the caller's ScrollArea; `sheet` feature dropped from core as dead config. Tree: the caller flattens its tree into depth-annotated `TreeItem`s (bezel's model — the component never walks a tree); the caller owns expansion and receives toggles via `on_disclosure(index)` (chevron click, or left/right on the selected row); same controlled selection and row paint as List; roles Tree/TreeItem with `aria_selected`/`aria_level`/`aria_expanded`/set-size; indent guides deferred |
 | then | pickers or data | Calendar/DatePicker, TimeField, ColorPicker | Decide at unit time. |
 | editor | editor (new) | Text/code editor, syntax highlighting (D12) | Same gate. |
 
@@ -321,7 +321,7 @@ Dropped from rev 3: D2, D5, D9 (port-era decisions); the review gate returns in
 4. ~~Phase D input~~ ✅ — single-line Input (unit 10) + the §6.2 completion pass (modifiers, undo/redo, read-only, actions + key context, caret blink, paint polish). NumberInput and multiline remain open as deferred units.
 5. ~~Phase E overlays~~ ✅ — Popover (unit 11), ScrollArea (unit 11.5), Menu (unit 12), Tooltip + Dialog/AlertDialog + Toast (unit 11+ row; Sheet dropped). Phase gate held: escape/dismiss semantics and focus behavior per overlay.
 6. ~~Unit 14 — motion, per component (§6 row 14, D21)~~ ✅ Landed in five passes (2026-10-30): (a) theme `reduce_motion` → `cx.set_reduce_motion` in `reapply`; (b) Switch thumb `with_spring`; (c) Toast 8 px slide-in; (d) Dialog scrim enters with the panel; (e) Progress 30 fps cap. Exits and hover washes stay deferred (§6 deferred list).
-7. **Next: Phase F, data first** — ~~`crates/data` List~~ ✅ landed (2026-10-30; opened the crate, dropped the dead `sheet` feature from core). Then Tree → Tabs → Sidebar, same gate. Windows/GNOME/KDE/Omarchy theme sources and the Segoe Fluent/freedesktop icon resolvers slot in as verification environments allow — a source may state `Motion.overlay` when it needs platform timing (§5.5) — with side-by-side gallery screenshots per platform. NumberInput/multiline return as deferred units when needed.
+7. **Phase F, data first** — ~~`crates/data` List~~ ✅ landed (2026-10-30; opened the crate, dropped the dead `sheet` feature from core); ~~Tree~~ ✅ landed (2026-10-30). Next: **Tabs** → Sidebar, same gate. Windows/GNOME/KDE/Omarchy theme sources and the Segoe Fluent/freedesktop icon resolvers slot in as verification environments allow — a source may state `Motion.overlay` when it needs platform timing (§5.5) — with side-by-side gallery screenshots per platform. NumberInput/multiline return as deferred units when needed.
 8. Then — Phase G: pickers, polish, → 0.1; start `crates/editor` if wanted.
 
 Batched polish candidates between units: scrollbar auto-hide + horizontal thumb, `Undo`/`Redo` menu events.

examples/gallery/src/main.rs

@@ -24,6 +24,7 @@ use gpui_native_core::toast::{Toast, ToastSeverity, Toasts, ToastsView};
 use gpui_native_core::toggle::Toggle;
 use gpui_native_core::tooltip::Tooltip;
 use gpui_native_data::list::{List, ListItem};
+use gpui_native_data::tree::{Tree, TreeItem};
 use gpui_native_icons::{IconAssets, IconRole, icon};
 use gpui_native_theme::{ActiveTheme as _, Theme};
 use gpui_platform::application;
@@ -43,6 +44,66 @@ struct Gallery {
     toasts: Entity<Toasts>,
     scroll: gpui::ScrollHandle,
     list_selected: Option<usize>,
+    tree_nodes: Vec<GalleryNode>,
+    tree_selected: Option<usize>,
+}
+
+/// A demo model for the tree section: the app owns the real tree and its
+/// expansion set, and flattens the visible nodes for the component.
+#[derive(Clone)]
+struct GalleryNode {
+    label: SharedString,
+    icon: Option<IconRole>,
+    expanded: bool,
+    children: Vec<GalleryNode>,
+}
+
+fn flatten_tree(
+    nodes: &[GalleryNode],
+    depth: usize,
+    prefix: &[usize],
+    items: &mut Vec<TreeItem>,
+    paths: &mut Vec<Vec<usize>>,
+) {
+    for (index, node) in nodes.iter().enumerate() {
+        let mut path = prefix.to_vec();
+        path.push(index);
+
+        let mut item = TreeItem::new(node.label.clone())
+            .depth(depth)
+            .expandable(!node.children.is_empty())
+            .expanded(node.expanded);
+        if let Some(role) = node.icon {
+            item = item.icon(role);
+        }
+        items.push(item);
+        paths.push(path.clone());
+
+        if node.expanded {
+            flatten_tree(&node.children, depth + 1, &path, items, paths);
+        }
+    }
+}
+
+fn toggle_tree_path(nodes: &mut [GalleryNode], path: &[usize]) {
+    let Some(index) = path.first() else { return };
+    let Some(node) = nodes.get_mut(*index) else {
+        return;
+    };
+    if path.len() == 1 {
+        node.expanded = !node.expanded;
+    } else {
+        toggle_tree_path(&mut node.children, &path[1..]);
+    }
+}
+
+/// The visible-row paths of the current tree state, matching the flat index
+/// the tree component reports.
+fn tree_paths(nodes: &[GalleryNode]) -> Vec<Vec<usize>> {
+    let mut items = Vec::new();
+    let mut paths = Vec::new();
+    flatten_tree(nodes, 0, &[], &mut items, &mut paths);
+    paths
 }
 
 impl Render for Gallery {
@@ -377,6 +438,40 @@ impl Render for Gallery {
                             .child(format!("selected: {:?}", self.list_selected)),
                     ),
             )
+            .child(
+                v_flex()
+                    .gap_2()
+                    .child(section_label(
+                        "tree · native refs — NSOutlineView, WinUI TreeView, Adwaita expander rows, Breeze",
+                        colors,
+                    ))
+                    .child({
+                        let gallery = gallery.clone();
+                        let disclosure_gallery = gallery.clone();
+                        let mut items = Vec::new();
+                        let mut paths = Vec::new();
+                        flatten_tree(&self.tree_nodes, 0, &[], &mut items, &mut paths);
+
+                        Tree::new("gallery-tree")
+                            .selected(self.tree_selected)
+                            .on_change(move |selected, _, cx| {
+                                gallery.update(cx, |gallery, cx| {
+                                    gallery.tree_selected = selected;
+                                    cx.notify();
+                                });
+                            })
+                            .on_disclosure(move |index, _, cx| {
+                                disclosure_gallery.update(cx, |gallery, cx| {
+                                    let paths = tree_paths(&gallery.tree_nodes);
+                                    if let Some(path) = paths.get(index) {
+                                        toggle_tree_path(&mut gallery.tree_nodes, path);
+                                    }
+                                    cx.notify();
+                                });
+                            })
+                            .items(move |_, _| items.clone())
+                    }),
+            )
             .child(
                 v_flex()
                     .gap_2()
@@ -996,6 +1091,64 @@ fn main() {
                         toasts,
                         scroll: gpui::ScrollHandle::new(),
                         list_selected: None,
+                        tree_selected: None,
+                        tree_nodes: vec![
+                            GalleryNode {
+                                label: "Workspace".into(),
+                                icon: Some(IconRole::Folder),
+                                expanded: true,
+                                children: vec![GalleryNode {
+                                    label: "gpui-native-kit".into(),
+                                    icon: Some(IconRole::Folder),
+                                    expanded: true,
+                                    children: vec![
+                                        GalleryNode {
+                                            label: "crates".into(),
+                                            icon: Some(IconRole::Folder),
+                                            expanded: true,
+                                            children: vec![
+                                                GalleryNode {
+                                                    label: "theme".into(),
+                                                    icon: None,
+                                                    expanded: false,
+                                                    children: Vec::new(),
+                                                },
+                                                GalleryNode {
+                                                    label: "core".into(),
+                                                    icon: None,
+                                                    expanded: false,
+                                                    children: Vec::new(),
+                                                },
+                                                GalleryNode {
+                                                    label: "data".into(),
+                                                    icon: None,
+                                                    expanded: false,
+                                                    children: Vec::new(),
+                                                },
+                                            ],
+                                        },
+                                        GalleryNode {
+                                            label: "docs".into(),
+                                            icon: Some(IconRole::Folder),
+                                            expanded: false,
+                                            children: Vec::new(),
+                                        },
+                                        GalleryNode {
+                                            label: "Cargo.toml".into(),
+                                            icon: None,
+                                            expanded: false,
+                                            children: Vec::new(),
+                                        },
+                                    ],
+                                }],
+                            },
+                            GalleryNode {
+                                label: "Archive.zip".into(),
+                                icon: None,
+                                expanded: false,
+                                children: Vec::new(),
+                            },
+                        ],
                     }
                 })
             },