cranpose_ui/widgets/nodes/

layout_node.rs

#[cfg(test)]
use crate::layout::LayoutRuntimeDebugStats;
use crate::{
    layout::{LayoutRuntimeState, MeasuredNode},
    modifier::{
        Modifier, ModifierChainHandle, ModifierLocalSource, ModifierLocalToken,
        ModifierLocalsHandle, ModifierNodeSlices, Point, ResolvedModifierLocal, ResolvedModifiers,
        Size,
    },
};
use cranpose_core::{Node, NodeId};
use cranpose_foundation::{
    InvalidationKind, ModifierInvalidation, NodeCapabilities, SemanticsConfiguration,
};
use cranpose_ui_layout::{Constraints, MeasurePolicy};
use std::any::TypeId;
use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::hash::{Hash, Hasher};
use std::rc::Rc;

/// Retained layout state for a LayoutNode.
/// This mirrors Jetpack Compose's approach where each node stores its own
/// measured size and placed position, eliminating the need for per-frame
/// LayoutTree reconstruction.
#[derive(Clone, Debug)]
pub struct LayoutState {
    /// The measured size of this node (width, height).
    pub size: Size,
    /// Position relative to parent's content origin.
    pub position: Point,
    /// True if this node has been placed in the current layout pass.
    pub is_placed: bool,
    /// The constraints used for the last measurement.
    pub measurement_constraints: Constraints,
    /// Offset of the content box relative to the node origin (e.g. due to padding).
    pub content_offset: Point,
}

impl Default for LayoutState {
    fn default() -> Self {
        Self {
            size: Size::default(),
            position: Point::default(),
            is_placed: false,
            measurement_constraints: Constraints {
                min_width: 0.0,
                max_width: f32::INFINITY,
                min_height: 0.0,
                max_height: f32::INFINITY,
            },
            content_offset: Point::default(),
        }
    }
}

#[derive(Clone)]
struct MeasurementCacheEntry {
    constraints: Constraints,
    measured: Rc<MeasuredNode>,
}

#[derive(Clone, Copy, Debug)]
pub enum IntrinsicKind {
    MinWidth(f32),
    MaxWidth(f32),
    MinHeight(f32),
    MaxHeight(f32),
}

impl IntrinsicKind {
    fn discriminant(&self) -> u8 {
        match self {
            IntrinsicKind::MinWidth(_) => 0,
            IntrinsicKind::MaxWidth(_) => 1,
            IntrinsicKind::MinHeight(_) => 2,
            IntrinsicKind::MaxHeight(_) => 3,
        }
    }

    fn value_bits(&self) -> u32 {
        match self {
            IntrinsicKind::MinWidth(value)
            | IntrinsicKind::MaxWidth(value)
            | IntrinsicKind::MinHeight(value)
            | IntrinsicKind::MaxHeight(value) => value.to_bits(),
        }
    }
}

impl PartialEq for IntrinsicKind {
    fn eq(&self, other: &Self) -> bool {
        self.discriminant() == other.discriminant() && self.value_bits() == other.value_bits()
    }
}

impl Eq for IntrinsicKind {}

impl Hash for IntrinsicKind {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.discriminant().hash(state);
        self.value_bits().hash(state);
    }
}

#[derive(Default)]
struct NodeCacheState {
    epoch: u64,
    measurements: Vec<MeasurementCacheEntry>,
    intrinsics: Vec<(IntrinsicKind, f32)>,
}

#[derive(Clone, Default)]
pub(crate) struct LayoutNodeCacheHandles {
    state: Rc<RefCell<NodeCacheState>>,
}

impl LayoutNodeCacheHandles {
    pub(crate) fn clear(&self) {
        let mut state = self.state.borrow_mut();
        state.measurements.clear();
        state.intrinsics.clear();
        state.epoch = 0;
    }

    pub(crate) fn activate(&self, epoch: u64) {
        let mut state = self.state.borrow_mut();
        if state.epoch != epoch {
            state.measurements.clear();
            state.intrinsics.clear();
            state.epoch = epoch;
        }
    }

    pub(crate) fn epoch(&self) -> u64 {
        self.state.borrow().epoch
    }

    pub(crate) fn get_measurement(&self, constraints: Constraints) -> Option<Rc<MeasuredNode>> {
        let state = self.state.borrow();
        state
            .measurements
            .iter()
            .find(|entry| entry.constraints == constraints)
            .map(|entry| Rc::clone(&entry.measured))
    }

    pub(crate) fn store_measurement(&self, constraints: Constraints, measured: Rc<MeasuredNode>) {
        let mut state = self.state.borrow_mut();
        if let Some(entry) = state
            .measurements
            .iter_mut()
            .find(|entry| entry.constraints == constraints)
        {
            entry.measured = measured;
        } else {
            state.measurements.push(MeasurementCacheEntry {
                constraints,
                measured,
            });
        }
    }

    pub(crate) fn get_intrinsic(&self, kind: &IntrinsicKind) -> Option<f32> {
        let state = self.state.borrow();
        state
            .intrinsics
            .iter()
            .find(|(stored_kind, _)| stored_kind == kind)
            .map(|(_, value)| *value)
    }

    pub(crate) fn store_intrinsic(&self, kind: IntrinsicKind, value: f32) {
        let mut state = self.state.borrow_mut();
        if let Some((_, existing)) = state
            .intrinsics
            .iter_mut()
            .find(|(stored_kind, _)| stored_kind == &kind)
        {
            *existing = value;
        } else {
            state.intrinsics.push((kind, value));
        }
    }
}

pub struct LayoutNode {
    pub modifier: Modifier,
    modifier_chain: ModifierChainHandle,
    resolved_modifiers: ResolvedModifiers,
    modifier_capabilities: NodeCapabilities,
    modifier_child_capabilities: NodeCapabilities,
    pub measure_policy: Rc<dyn MeasurePolicy>,
    /// The actual children of this node (folded view - includes virtual nodes as-is)
    pub children: Vec<NodeId>,
    cache: LayoutNodeCacheHandles,
    // Dirty flags for selective measure/layout/render
    needs_measure: Cell<bool>,
    needs_layout: Cell<bool>,
    needs_semantics: Cell<bool>,
    needs_redraw: Cell<bool>,
    needs_pointer_pass: Cell<bool>,
    needs_focus_sync: Cell<bool>,
    /// Parent for dirty flag bubbling (skips virtual nodes)
    parent: Cell<Option<NodeId>>,
    /// Direct parent in the tree (may be virtual)
    folded_parent: Cell<Option<NodeId>>,
    // Node's own ID (set by applier after creation)
    id: Cell<Option<NodeId>>,
    owner_context_id: Cell<Option<crate::render_state::AppContextId>>,
    debug_modifiers: Cell<bool>,
    /// Virtual node flag - virtual nodes are transparent containers for subcomposition
    /// Their children are flattened into the parent's children list for measurement
    is_virtual: bool,
    /// Count of virtual children (for lazy unfolded children computation)
    virtual_children_count: Cell<usize>,

    modifier_slices_snapshot: RefCell<Rc<ModifierNodeSlices>>,
    modifier_slices_dirty: Cell<bool>,

    /// Retained layout state (size, position) for this node.
    /// Updated by measure/place and read by renderer.
    /// Wrapped in Rc to ensure state is shared across clones (e.g. SubcomposeLayout usage).
    layout_state: Rc<RefCell<LayoutState>>,
    layout_runtime_state: Rc<RefCell<LayoutRuntimeState>>,
}

pub(crate) const RECYCLED_LAYOUT_NODE_POOL_LIMIT: usize = 128;

thread_local! {
    static EMPTY_MEASURE_POLICY: Rc<dyn MeasurePolicy> =
        Rc::new(crate::layout::policies::EmptyMeasurePolicy);
}

fn empty_measure_policy() -> Rc<dyn MeasurePolicy> {
    EMPTY_MEASURE_POLICY.with(Rc::clone)
}

impl LayoutNode {
    pub fn new(modifier: Modifier, measure_policy: Rc<dyn MeasurePolicy>) -> Self {
        Self::new_with_virtual(modifier, measure_policy, false)
    }

    /// Create a virtual LayoutNode for subcomposition slot containers.
    /// Virtual nodes are transparent - their children are flattened into parent's children list.
    pub fn new_virtual() -> Self {
        Self::new_with_virtual(Modifier::empty(), empty_measure_policy(), true)
    }

    fn new_recycled_shell(is_virtual: bool) -> Self {
        let mut shell =
            Self::new_with_virtual(Modifier::empty(), empty_measure_policy(), is_virtual);
        shell.needs_measure.set(false);
        shell.needs_layout.set(false);
        shell.needs_semantics.set(false);
        shell.needs_redraw.set(false);
        shell.needs_pointer_pass.set(false);
        shell.needs_focus_sync.set(false);
        shell.parent.set(None);
        shell.folded_parent.set(None);
        shell.id.set(None);
        shell.owner_context_id.set(None);
        shell.debug_modifiers.set(false);
        shell.virtual_children_count.set(0);
        shell.cache = LayoutNodeCacheHandles::default();
        shell.modifier_slices_snapshot = RefCell::new(Rc::default());
        shell.modifier_slices_dirty = Cell::new(true);
        shell.layout_state = Rc::new(RefCell::new(LayoutState::default()));
        shell.layout_runtime_state = Rc::new(RefCell::new(LayoutRuntimeState::default()));
        shell
    }

    fn new_with_virtual(
        modifier: Modifier,
        measure_policy: Rc<dyn MeasurePolicy>,
        is_virtual: bool,
    ) -> Self {
        let mut node = Self {
            modifier,
            modifier_chain: ModifierChainHandle::new(),
            resolved_modifiers: ResolvedModifiers::default(),
            modifier_capabilities: NodeCapabilities::default(),
            modifier_child_capabilities: NodeCapabilities::default(),
            measure_policy,
            children: Vec::new(),
            cache: LayoutNodeCacheHandles::default(),
            needs_measure: Cell::new(true), // New nodes need initial measure
            needs_layout: Cell::new(true),  // New nodes need initial layout
            needs_semantics: Cell::new(true), // Semantics snapshot needs initial build
            needs_redraw: Cell::new(true),  // First render should draw the node
            needs_pointer_pass: Cell::new(false),
            needs_focus_sync: Cell::new(false),
            parent: Cell::new(None),        // Non-virtual parent for bubbling
            folded_parent: Cell::new(None), // Direct parent (may be virtual)
            id: Cell::new(None),            // ID set by applier after creation
            owner_context_id: Cell::new(None),
            debug_modifiers: Cell::new(false),
            is_virtual,
            virtual_children_count: Cell::new(0),
            modifier_slices_snapshot: RefCell::new(Rc::default()),
            modifier_slices_dirty: Cell::new(true),
            layout_state: Rc::new(RefCell::new(LayoutState::default())),
            layout_runtime_state: Rc::new(RefCell::new(LayoutRuntimeState::default())),
        };
        node.sync_modifier_chain();
        node
    }

    pub fn set_modifier(&mut self, modifier: Modifier) {
        // Always sync the modifier chain because element equality is used for node
        // matching/reuse, not for skipping updates. Closures may capture updated
        // state values that need to be passed to nodes even when the Modifier
        // compares as equal. This matches Jetpack Compose where update() is always
        // called on matched nodes.
        let modifier_changed = !self.modifier.structural_eq(&modifier);
        self.modifier = modifier;
        self.sync_modifier_chain();
        if modifier_changed {
            self.cache.clear();
            self.request_semantics_update();
        }
    }

    fn sync_modifier_chain(&mut self) {
        let prev_caps = self.modifier_capabilities;
        let start_parent = self.parent();
        let mut resolver = move |token: &ModifierLocalToken| {
            resolve_modifier_local_from_parent_chain(start_parent, token)
        };
        self.modifier_chain
            .set_debug_logging(self.debug_modifiers.get());
        self.modifier_chain.set_node_id(self.id.get());
        let modifier_local_invalidations = self
            .modifier_chain
            .update_with_resolver(&self.modifier, &mut resolver);
        self.resolved_modifiers = self.modifier_chain.resolved_modifiers();
        self.modifier_capabilities = self.modifier_chain.capabilities();
        self.modifier_child_capabilities = self.modifier_chain.aggregate_child_capabilities();

        self.update_modifier_slices_cache();

        let mut invalidations = self.modifier_chain.take_invalidations();
        invalidations.extend(modifier_local_invalidations);
        self.dispatch_modifier_invalidations_with_prev(&invalidations, prev_caps);
        self.refresh_registry_state();
    }

    fn update_modifier_slices_cache(&self) {
        use crate::modifier::collect_modifier_slices_into;

        let mut snapshot = self.modifier_slices_snapshot.borrow_mut();
        collect_modifier_slices_into(self.modifier_chain.chain(), Rc::make_mut(&mut snapshot));
        self.modifier_slices_dirty.set(false);
    }

    pub(crate) fn mark_modifier_slices_dirty(&self) {
        self.modifier_slices_dirty.set(true);
    }

    #[cfg(test)]
    fn dispatch_modifier_invalidations(&self, invalidations: &[ModifierInvalidation]) {
        self.dispatch_modifier_invalidations_with_prev(invalidations, NodeCapabilities::empty());
    }

    fn dispatch_modifier_invalidations_with_prev(
        &self,
        invalidations: &[ModifierInvalidation],
        prev_caps: NodeCapabilities,
    ) {
        let curr_caps = self.modifier_capabilities;
        for invalidation in invalidations {
            self.modifier_slices_dirty.set(true);
            match invalidation.kind() {
                InvalidationKind::Layout => {
                    if curr_caps.contains(NodeCapabilities::LAYOUT)
                        || prev_caps.contains(NodeCapabilities::LAYOUT)
                    {
                        self.mark_needs_measure();
                        if let Some(id) = self.id.get() {
                            let inside_composition =
                                cranpose_core::composer_context::try_with_composer(|_| ())
                                    .is_some();
                            if !inside_composition {
                                crate::schedule_layout_repass(id);
                            }
                        }
                    }
                }
                InvalidationKind::Draw => {
                    if curr_caps.contains(NodeCapabilities::DRAW)
                        || prev_caps.contains(NodeCapabilities::DRAW)
                    {
                        self.mark_needs_redraw();
                    }
                }
                InvalidationKind::PointerInput => {
                    if curr_caps.contains(NodeCapabilities::POINTER_INPUT)
                        || prev_caps.contains(NodeCapabilities::POINTER_INPUT)
                    {
                        self.mark_needs_pointer_pass();
                        crate::request_pointer_invalidation();
                        // Schedule pointer repass for this node
                        if let Some(id) = self.id.get() {
                            crate::schedule_pointer_repass(id);
                        }
                    }
                }
                InvalidationKind::Semantics => {
                    self.request_semantics_update();
                }
                InvalidationKind::Focus => {
                    if curr_caps.contains(NodeCapabilities::FOCUS)
                        || prev_caps.contains(NodeCapabilities::FOCUS)
                    {
                        self.mark_needs_focus_sync();
                        crate::request_focus_invalidation();
                        // Schedule focus invalidation for this node
                        if let Some(id) = self.id.get() {
                            crate::schedule_focus_invalidation(id);
                        }
                    }
                }
            }
        }
    }

    pub fn set_measure_policy(&mut self, policy: Rc<dyn MeasurePolicy>) {
        // Only mark dirty if policy actually changed (pointer comparison)
        if !Rc::ptr_eq(&self.measure_policy, &policy) {
            self.measure_policy = policy;
            self.cache.clear();
            self.mark_needs_measure();
            if let Some(id) = self.id.get() {
                cranpose_core::bubble_measure_dirty_in_composer(id);
            }
        }
    }

    /// Mark this node as needing measure. Also marks it as needing layout.
    pub fn mark_needs_measure(&self) {
        self.needs_measure.set(true);
        self.needs_layout.set(true);
    }

    /// Mark this node as needing layout (but not necessarily measure).
    pub fn mark_needs_layout(&self) {
        self.needs_layout.set(true);
    }

    /// Mark this node as needing redraw without forcing measure/layout.
    pub fn mark_needs_redraw(&self) {
        self.needs_redraw.set(true);
        if let Some(id) = self.id.get() {
            crate::schedule_draw_repass(id);
        }
        crate::request_render_invalidation();
    }

    /// Check if this node needs measure.
    pub fn needs_measure(&self) -> bool {
        self.needs_measure.get()
    }

    /// Check if this node needs layout.
    pub fn needs_layout(&self) -> bool {
        self.needs_layout.get()
    }

    /// Mark this node as needing semantics recomputation.
    pub fn mark_needs_semantics(&self) {
        self.needs_semantics.set(true);
    }

    /// Clear the semantics dirty flag after rebuilding semantics.
    pub(crate) fn clear_needs_semantics(&self) {
        self.needs_semantics.set(false);
    }

    /// Returns true when semantics need to be recomputed.
    pub fn needs_semantics(&self) -> bool {
        self.needs_semantics.get()
    }

    /// Returns true when this node requested a redraw since the last render pass.
    pub fn needs_redraw(&self) -> bool {
        self.needs_redraw.get()
    }

    pub fn clear_needs_redraw(&self) {
        self.needs_redraw.set(false);
    }

    fn request_semantics_update(&self) {
        let already_dirty = self.needs_semantics.replace(true);
        if already_dirty {
            return;
        }

        if let Some(id) = self.id.get() {
            cranpose_core::queue_semantics_invalidation(id);
        }
    }

    /// Clear the measure dirty flag after measuring.
    pub(crate) fn clear_needs_measure(&self) {
        self.needs_measure.set(false);
    }

    /// Clear the layout dirty flag after laying out.
    pub(crate) fn clear_needs_layout(&self) {
        self.needs_layout.set(false);
    }

    /// Marks this node as needing a fresh pointer-input pass.
    pub fn mark_needs_pointer_pass(&self) {
        self.needs_pointer_pass.set(true);
    }

    /// Returns true when pointer-input state needs to be recomputed.
    pub fn needs_pointer_pass(&self) -> bool {
        self.needs_pointer_pass.get()
    }

    /// Clears the pointer-input dirty flag after hosts service it.
    pub fn clear_needs_pointer_pass(&self) {
        self.needs_pointer_pass.set(false);
    }

    /// Marks this node as needing a focus synchronization.
    pub fn mark_needs_focus_sync(&self) {
        self.needs_focus_sync.set(true);
    }

    /// Returns true when focus state needs to be synchronized.
    pub fn needs_focus_sync(&self) -> bool {
        self.needs_focus_sync.get()
    }

    /// Clears the focus dirty flag after the focus manager processes it.
    pub fn clear_needs_focus_sync(&self) {
        self.needs_focus_sync.set(false);
    }

    /// Set this node's ID (called by applier after creation).
    pub fn set_node_id(&mut self, id: NodeId) {
        if let Some(existing) = self.id.replace(Some(id)) {
            if let Some(owner_context_id) = self.owner_context_id.take() {
                unregister_layout_node(owner_context_id, existing);
            }
        }
        let owner_context_id = register_layout_node(id, self);
        self.owner_context_id.set(Some(owner_context_id));
        self.refresh_registry_state();

        // Propagate the ID to the modifier chain. This triggers a lifecycle update
        // for nodes that depend on the node ID for invalidation (e.g., ScrollNode).
        self.modifier_chain.set_node_id(Some(id));
        self.update_modifier_slices_cache();
    }

    /// Get this node's ID.
    pub fn node_id(&self) -> Option<NodeId> {
        self.id.get()
    }

    /// Set this node's parent (called when node is added as child).
    /// Sets both folded_parent (direct) and parent (first non-virtual ancestor for bubbling).
    pub fn set_parent(&self, parent: NodeId) {
        self.folded_parent.set(Some(parent));
        // For now, parent = folded_parent. Virtual parent skipping requires applier access.
        // The actual virtual-skipping happens in bubble_measure_dirty via applier traversal.
        self.parent.set(Some(parent));
        self.refresh_registry_state();
    }

    /// Clear this node's parent (called when node is removed from parent).
    pub fn clear_parent(&self) {
        self.folded_parent.set(None);
        self.parent.set(None);
        self.refresh_registry_state();
    }

    /// Get this node's parent for dirty flag bubbling (may skip virtual nodes).
    pub fn parent(&self) -> Option<NodeId> {
        self.parent.get()
    }

    /// Get this node's direct parent (may be a virtual node).
    pub fn folded_parent(&self) -> Option<NodeId> {
        self.folded_parent.get()
    }

    /// Returns true if this is a virtual node (transparent container for subcomposition).
    pub fn is_virtual(&self) -> bool {
        self.is_virtual
    }

    pub(crate) fn cache_handles(&self) -> LayoutNodeCacheHandles {
        self.cache.clone()
    }

    pub fn resolved_modifiers(&self) -> ResolvedModifiers {
        self.resolved_modifiers
    }

    pub fn modifier_capabilities(&self) -> NodeCapabilities {
        self.modifier_capabilities
    }

    pub fn modifier_child_capabilities(&self) -> NodeCapabilities {
        self.modifier_child_capabilities
    }

    pub fn set_debug_modifiers(&mut self, enabled: bool) {
        self.debug_modifiers.set(enabled);
        self.modifier_chain.set_debug_logging(enabled);
    }

    pub fn debug_modifiers_enabled(&self) -> bool {
        self.debug_modifiers.get()
    }

    pub fn modifier_locals_handle(&self) -> ModifierLocalsHandle {
        self.modifier_chain.modifier_locals_handle()
    }

    pub fn has_layout_modifier_nodes(&self) -> bool {
        self.modifier_capabilities
            .contains(NodeCapabilities::LAYOUT)
    }

    pub fn has_draw_modifier_nodes(&self) -> bool {
        self.modifier_capabilities.contains(NodeCapabilities::DRAW)
    }

    pub fn has_pointer_input_modifier_nodes(&self) -> bool {
        self.modifier_capabilities
            .contains(NodeCapabilities::POINTER_INPUT)
    }

    pub fn has_semantics_modifier_nodes(&self) -> bool {
        self.modifier_capabilities
            .contains(NodeCapabilities::SEMANTICS)
    }

    pub fn has_focus_modifier_nodes(&self) -> bool {
        self.modifier_capabilities.contains(NodeCapabilities::FOCUS)
    }

    fn refresh_registry_state(&self) {
        if let (Some(id), Some(owner_context_id)) = (self.id.get(), self.owner_context_id.get()) {
            let parent = self.parent();
            let capabilities = self.modifier_child_capabilities();
            let modifier_locals = self.modifier_locals_handle();
            let _ = crate::render_state::with_layout_node_registry_by_app_context(
                owner_context_id,
                |registry| {
                    registry.update_entry(id, parent, capabilities, modifier_locals);
                },
            );
        }
    }

    pub fn modifier_slices_snapshot(&self) -> Rc<ModifierNodeSlices> {
        if self.modifier_slices_dirty.get() {
            self.update_modifier_slices_cache();
        }
        self.modifier_slices_snapshot.borrow().clone()
    }

    // ═══════════════════════════════════════════════════════════════════════
    // Retained Layout State API
    // ═══════════════════════════════════════════════════════════════════════

    /// Returns a clone of the current layout state.
    pub fn layout_state(&self) -> LayoutState {
        self.layout_state.borrow().clone()
    }

    /// Returns the measured size of this node.
    pub fn measured_size(&self) -> Size {
        self.layout_state.borrow().size
    }

    /// Returns the position of this node relative to its parent.
    pub fn position(&self) -> Point {
        self.layout_state.borrow().position
    }

    /// Returns true if this node has been placed in the current layout pass.
    pub fn is_placed(&self) -> bool {
        self.layout_state.borrow().is_placed
    }

    /// Updates the measured size of this node. Called during measurement.
    pub fn set_measured_size(&self, size: Size) {
        let mut state = self.layout_state.borrow_mut();
        state.size = size;
    }

    /// Updates the position of this node. Called during placement.
    pub fn set_position(&self, position: Point) {
        let mut state = self.layout_state.borrow_mut();
        state.position = position;
        state.is_placed = true;
    }

    /// Records the constraints used for measurement. Used for relayout optimization.
    pub fn set_measurement_constraints(&self, constraints: Constraints) {
        self.layout_state.borrow_mut().measurement_constraints = constraints;
    }

    /// Records the content offset (e.g. from padding).
    pub fn set_content_offset(&self, offset: Point) {
        self.layout_state.borrow_mut().content_offset = offset;
    }

    /// Clears the is_placed flag. Called at the start of a layout pass.
    pub fn clear_placed(&self) {
        self.layout_state.borrow_mut().is_placed = false;
    }

    pub fn semantics_configuration(&self) -> Option<SemanticsConfiguration> {
        crate::modifier::collect_semantics_from_chain(self.modifier_chain.chain())
    }

    /// Returns a reference to the modifier chain for layout/draw pipeline integration.
    pub(crate) fn modifier_chain(&self) -> &ModifierChainHandle {
        &self.modifier_chain
    }

    /// Access the text field modifier node (if present) with a mutable callback.
    ///
    /// This is used for keyboard event dispatch to text fields.
    /// Returns `None` if no text field modifier is found in the chain.
    pub fn with_text_field_modifier_mut<R>(
        &mut self,
        f: impl FnMut(&mut crate::TextFieldModifierNode) -> R,
    ) -> Option<R> {
        self.modifier_chain.with_text_field_modifier_mut(f)
    }

    /// Returns a handle to the shared layout state.
    /// Used by layout system to update state without borrowing the Applier.
    pub fn layout_state_handle(&self) -> Rc<RefCell<LayoutState>> {
        self.layout_state.clone()
    }

    pub(crate) fn layout_runtime_state_handle(&self) -> Rc<RefCell<LayoutRuntimeState>> {
        self.layout_runtime_state.clone()
    }

    #[cfg(test)]
    pub(crate) fn layout_runtime_debug_stats(&self) -> LayoutRuntimeDebugStats {
        self.layout_runtime_state.borrow().debug_stats()
    }
}
impl Clone for LayoutNode {
    fn clone(&self) -> Self {
        let mut node = Self {
            modifier: self.modifier.clone(),
            modifier_chain: ModifierChainHandle::new(),
            resolved_modifiers: ResolvedModifiers::default(),
            modifier_capabilities: self.modifier_capabilities,
            modifier_child_capabilities: self.modifier_child_capabilities,
            measure_policy: self.measure_policy.clone(),
            children: self.children.clone(),
            cache: self.cache.clone(),
            needs_measure: Cell::new(self.needs_measure.get()),
            needs_layout: Cell::new(self.needs_layout.get()),
            needs_semantics: Cell::new(self.needs_semantics.get()),
            needs_redraw: Cell::new(self.needs_redraw.get()),
            needs_pointer_pass: Cell::new(self.needs_pointer_pass.get()),
            needs_focus_sync: Cell::new(self.needs_focus_sync.get()),
            parent: Cell::new(self.parent.get()),
            folded_parent: Cell::new(self.folded_parent.get()),
            id: Cell::new(None),
            owner_context_id: Cell::new(None),
            debug_modifiers: Cell::new(self.debug_modifiers.get()),
            is_virtual: self.is_virtual,
            virtual_children_count: Cell::new(self.virtual_children_count.get()),
            modifier_slices_snapshot: RefCell::new(Rc::default()),
            modifier_slices_dirty: Cell::new(true),
            // Share the same layout state across clones
            layout_state: self.layout_state.clone(),
            layout_runtime_state: self.layout_runtime_state.clone(),
        };
        node.sync_modifier_chain();
        node
    }
}

impl Node for LayoutNode {
    fn mount(&mut self) {
        let (chain, mut context) = self.modifier_chain.chain_and_context_mut();
        chain.repair_chain();
        chain.attach_nodes(&mut *context);
    }

    fn unmount(&mut self) {
        self.modifier_chain.chain_mut().detach_nodes();
    }

    fn set_node_id(&mut self, id: NodeId) {
        // Delegate to inherent method to ensure proper registration and chain updates
        LayoutNode::set_node_id(self, id);
    }

    fn insert_child(&mut self, child: NodeId) {
        if self.children.contains(&child) {
            return;
        }
        if is_virtual_node(child) {
            let count = self.virtual_children_count.get();
            self.virtual_children_count.set(count + 1);
        }
        self.children.push(child);
        self.cache.clear();
        self.mark_needs_measure();
    }

    fn remove_child(&mut self, child: NodeId) {
        let before = self.children.len();
        self.children.retain(|&id| id != child);
        if self.children.len() < before {
            if is_virtual_node(child) {
                let count = self.virtual_children_count.get();
                if count > 0 {
                    self.virtual_children_count.set(count - 1);
                }
            }
            self.cache.clear();
            self.mark_needs_measure();
        }
    }

    fn move_child(&mut self, from: usize, to: usize) {
        if from == to || from >= self.children.len() {
            return;
        }
        let child = self.children.remove(from);
        let target = to.min(self.children.len());
        self.children.insert(target, child);
        self.cache.clear();
        self.mark_needs_measure();
    }

    fn update_children(&mut self, children: &[NodeId]) {
        self.children.clear();
        self.children.extend_from_slice(children);
        self.cache.clear();
        self.mark_needs_measure();
    }

    fn children(&self) -> Vec<NodeId> {
        self.children.clone()
    }

    fn collect_children_into(&self, out: &mut smallvec::SmallVec<[NodeId; 8]>) {
        out.clear();
        out.extend(self.children.iter().copied());
    }

    fn on_attached_to_parent(&mut self, parent: NodeId) {
        self.set_parent(parent);
    }

    fn on_removed_from_parent(&mut self) {
        self.clear_parent();
    }

    fn parent(&self) -> Option<NodeId> {
        self.parent.get()
    }

    fn mark_needs_layout(&self) {
        self.needs_layout.set(true);
    }

    fn needs_layout(&self) -> bool {
        self.needs_layout.get()
    }

    fn mark_needs_measure(&self) {
        self.needs_measure.set(true);
        self.needs_layout.set(true);
    }

    fn needs_measure(&self) -> bool {
        self.needs_measure.get()
    }

    fn mark_needs_semantics(&self) {
        self.needs_semantics.set(true);
    }

    fn needs_semantics(&self) -> bool {
        self.needs_semantics.get()
    }

    /// Minimal parent setter for dirty flag bubbling.
    /// Only sets the parent Cell without triggering registry updates.
    /// This is used during SubcomposeLayout measurement where we need parent
    /// pointers for bubble_measure_dirty but don't want full attachment side effects.
    fn set_parent_for_bubbling(&mut self, parent: NodeId) {
        self.parent.set(Some(parent));
    }

    fn recycle_key(&self) -> Option<TypeId> {
        Some(TypeId::of::<Self>())
    }

    fn recycle_pool_limit(&self) -> Option<usize> {
        Some(RECYCLED_LAYOUT_NODE_POOL_LIMIT)
    }

    fn prepare_for_recycle(&mut self) {
        *self = Self::new_recycled_shell(self.is_virtual);
    }

    fn rehouse_for_recycle(&self) -> Option<Box<dyn cranpose_core::Node>> {
        Some(Box::new(Self::new_recycled_shell(self.is_virtual)))
    }

    fn rehouse_for_live_compaction(&mut self) -> Option<Box<dyn cranpose_core::Node>> {
        let mut previous = std::mem::replace(self, Self::new_recycled_shell(self.is_virtual));
        let node_id = previous.id.replace(None);
        let parent = previous.parent.get();
        let folded_parent = previous.folded_parent.get();
        let debug_modifiers = previous.debug_modifiers.get();
        let needs_measure = previous.needs_measure.get();
        let needs_layout = previous.needs_layout.get();
        let needs_semantics = previous.needs_semantics.get();
        let needs_redraw = previous.needs_redraw.get();
        let needs_pointer_pass = previous.needs_pointer_pass.get();
        let needs_focus_sync = previous.needs_focus_sync.get();
        let virtual_children_count = previous.virtual_children_count.get();
        let children = previous.children.to_vec();
        let modifier = previous.modifier.rehouse_for_live_compaction();
        let measure_policy = previous.measure_policy.clone();
        let layout_state = previous.layout_state.clone();
        let layout_runtime_state = previous.layout_runtime_state.clone();

        previous.modifier_chain.chain_mut().detach_nodes();

        let mut compact = Self::new_with_virtual(modifier, measure_policy, previous.is_virtual);
        compact.children = children;
        compact.parent.set(parent);
        compact.folded_parent.set(folded_parent);
        compact.id.set(node_id);
        compact.debug_modifiers.set(debug_modifiers);
        compact.needs_measure.set(needs_measure);
        compact.needs_layout.set(needs_layout);
        compact.needs_semantics.set(needs_semantics);
        compact.needs_redraw.set(needs_redraw);
        compact.needs_pointer_pass.set(needs_pointer_pass);
        compact.needs_focus_sync.set(needs_focus_sync);
        compact.virtual_children_count.set(virtual_children_count);
        compact.layout_state = layout_state;
        compact.layout_runtime_state = layout_runtime_state;
        compact.sync_modifier_chain();
        if let Some(id) = node_id {
            let owner_context_id = register_layout_node(id, &compact);
            compact.owner_context_id.set(Some(owner_context_id));
        }

        Some(Box::new(compact))
    }
}

impl Drop for LayoutNode {
    fn drop(&mut self) {
        if let (Some(id), Some(owner_context_id)) = (self.id.get(), self.owner_context_id.get()) {
            unregister_layout_node(owner_context_id, id);
        }
    }
}

const MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY: usize = 128;
const VIRTUAL_NODE_ID_START: NodeId = 0xC0000000;

#[cfg(test)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
struct LayoutNodeRegistryDebugStats {
    len: usize,
    capacity: usize,
}

struct LayoutNodeRegistryEntry {
    parent: Option<NodeId>,
    modifier_child_capabilities: NodeCapabilities,
    modifier_locals: ModifierLocalsHandle,
    is_virtual: bool,
}

pub(crate) struct LayoutNodeRegistryState {
    entries: RefCell<HashMap<NodeId, LayoutNodeRegistryEntry>>,
    virtual_node_id_counter: Cell<NodeId>,
}

impl LayoutNodeRegistryState {
    pub(crate) fn new() -> Self {
        Self {
            entries: RefCell::new(HashMap::new()),
            virtual_node_id_counter: Cell::new(VIRTUAL_NODE_ID_START),
        }
    }

    fn register(&self, id: NodeId, node: &LayoutNode) {
        self.entries.borrow_mut().insert(
            id,
            LayoutNodeRegistryEntry {
                parent: node.parent(),
                modifier_child_capabilities: node.modifier_child_capabilities(),
                modifier_locals: node.modifier_locals_handle(),
                is_virtual: node.is_virtual(),
            },
        );
    }

    fn unregister(&self, id: NodeId) {
        let mut entries = self.entries.borrow_mut();
        entries.remove(&id);
        let should_shrink = (entries.len() <= MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY
            && entries.capacity() > MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY)
            || entries.capacity()
                > entries
                    .len()
                    .max(MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY)
                    .saturating_mul(4);
        if should_shrink {
            let retained = entries
                .len()
                .max(MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY);
            let mut rebuilt = HashMap::new();
            rebuilt.reserve(retained);
            rebuilt.extend(entries.drain());
            *entries = rebuilt;
        }
    }

    fn update_entry(
        &self,
        id: NodeId,
        parent: Option<NodeId>,
        modifier_child_capabilities: NodeCapabilities,
        modifier_locals: ModifierLocalsHandle,
    ) {
        if let Some(entry) = self.entries.borrow_mut().get_mut(&id) {
            entry.parent = parent;
            entry.modifier_child_capabilities = modifier_child_capabilities;
            entry.modifier_locals = modifier_locals;
        }
    }

    #[cfg(test)]
    fn stats(&self) -> LayoutNodeRegistryDebugStats {
        let entries = self.entries.borrow();
        LayoutNodeRegistryDebugStats {
            len: entries.len(),
            capacity: entries.capacity(),
        }
    }

    fn is_virtual_node(&self, id: NodeId) -> bool {
        self.entries
            .borrow()
            .get(&id)
            .map(|entry| entry.is_virtual)
            .unwrap_or(false)
    }

    fn allocate_virtual_node_id(&self) -> NodeId {
        let id = self.virtual_node_id_counter.get();
        self.virtual_node_id_counter.set(id.wrapping_add(1));
        id
    }

    fn resolve_modifier_local_from_parent_chain(
        &self,
        start: Option<NodeId>,
        token: &ModifierLocalToken,
    ) -> Option<ResolvedModifierLocal> {
        let mut current = start;
        while let Some(parent_id) = current {
            let (next_parent, resolved) = {
                let entries = self.entries.borrow();
                if let Some(entry) = entries.get(&parent_id) {
                    let resolved = if entry
                        .modifier_child_capabilities
                        .contains(NodeCapabilities::MODIFIER_LOCALS)
                    {
                        entry
                            .modifier_locals
                            .borrow()
                            .resolve(token)
                            .map(|value| value.with_source(ModifierLocalSource::Ancestor))
                    } else {
                        None
                    };
                    (entry.parent, resolved)
                } else {
                    (None, None)
                }
            };
            if let Some(value) = resolved {
                return Some(value);
            }
            current = next_parent;
        }
        None
    }
}

pub(crate) fn register_layout_node(
    id: NodeId,
    node: &LayoutNode,
) -> crate::render_state::AppContextId {
    let owner_context_id = crate::render_state::current_app_context_id();
    let _ = crate::render_state::with_layout_node_registry_by_app_context(
        owner_context_id,
        |registry| {
            registry.register(id, node);
        },
    );
    owner_context_id
}

pub(crate) fn unregister_layout_node(
    owner_context_id: crate::render_state::AppContextId,
    id: NodeId,
) {
    let _ = crate::render_state::with_layout_node_registry_by_app_context(
        owner_context_id,
        |registry| {
            registry.unregister(id);
        },
    );
}

#[cfg(test)]
fn layout_node_registry_stats() -> LayoutNodeRegistryDebugStats {
    crate::render_state::with_layout_node_registry(|registry| registry.stats())
}

pub(crate) fn is_virtual_node(id: NodeId) -> bool {
    crate::render_state::with_layout_node_registry(|registry| registry.is_virtual_node(id))
}

pub(crate) fn allocate_virtual_node_id() -> NodeId {
    crate::render_state::with_layout_node_registry(|registry| registry.allocate_virtual_node_id())
}

fn resolve_modifier_local_from_parent_chain(
    start: Option<NodeId>,
    token: &ModifierLocalToken,
) -> Option<ResolvedModifierLocal> {
    crate::render_state::with_layout_node_registry(|registry| {
        registry.resolve_modifier_local_from_parent_chain(start, token)
    })
}

#[cfg(test)]
mod tests {
    use super::*;
    use cranpose_ui_graphics::Size as GeometrySize;
    use cranpose_ui_layout::{Measurable, MeasureResult};
    use std::rc::Rc;

    #[derive(Default)]
    struct TestMeasurePolicy;

    impl MeasurePolicy for TestMeasurePolicy {
        fn measure(
            &self,
            _measurables: &[Box<dyn Measurable>],
            _constraints: Constraints,
        ) -> MeasureResult {
            MeasureResult::new(
                GeometrySize {
                    width: 0.0,
                    height: 0.0,
                },
                Vec::new(),
            )
        }

        fn min_intrinsic_width(&self, _measurables: &[Box<dyn Measurable>], _height: f32) -> f32 {
            0.0
        }

        fn max_intrinsic_width(&self, _measurables: &[Box<dyn Measurable>], _height: f32) -> f32 {
            0.0
        }

        fn min_intrinsic_height(&self, _measurables: &[Box<dyn Measurable>], _width: f32) -> f32 {
            0.0
        }

        fn max_intrinsic_height(&self, _measurables: &[Box<dyn Measurable>], _width: f32) -> f32 {
            0.0
        }
    }

    fn fresh_node() -> LayoutNode {
        LayoutNode::new(Modifier::empty(), Rc::new(TestMeasurePolicy))
    }

    #[test]
    fn modifier_slices_cache_reuses_unique_snapshot_allocation() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        let snapshot = node.modifier_slices_snapshot();
        let snapshot_ptr = Rc::as_ptr(&snapshot);
        drop(snapshot);

        node.set_modifier(Modifier::empty().padding(4.0));

        let updated = node.modifier_slices_snapshot();
        assert_eq!(Rc::as_ptr(&updated), snapshot_ptr);
    }

    #[test]
    fn modifier_slices_cache_preserves_live_snapshot_isolation() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        let old_snapshot = node.modifier_slices_snapshot();
        let old_snapshot_ptr = Rc::as_ptr(&old_snapshot);

        node.set_modifier(Modifier::empty().padding(4.0));

        let updated = node.modifier_slices_snapshot();
        assert_ne!(Rc::as_ptr(&updated), old_snapshot_ptr);
        assert_eq!(old_snapshot.draw_commands().len(), 0);
    }

    #[test]
    fn layout_node_registry_retains_warm_capacity_after_large_cleanup() {
        let _app_context = crate::render_state::app_context_test_scope();
        let app_context = crate::render_state::AppContext::new_with_density(1.0);
        app_context.enter(|| {
            let nodes: Vec<_> = (0..2048)
                .map(|_| {
                    let id = allocate_virtual_node_id();
                    let node = fresh_node();
                    let owner_context_id = register_layout_node(id, &node);
                    (id, owner_context_id, node)
                })
                .collect();

            for (id, owner_context_id, _) in &nodes {
                unregister_layout_node(*owner_context_id, *id);
            }

            let stats = layout_node_registry_stats();
            assert_eq!(stats.len, 0);
            assert!(
                (MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY
                    ..=MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY.saturating_mul(2))
                    .contains(&stats.capacity),
                "registry warm capacity {} fell outside expected retained range {}..={}",
                stats.capacity,
                MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY,
                MIN_RETAINED_LAYOUT_NODE_REGISTRY_CAPACITY.saturating_mul(2),
            );
        });
    }

    #[test]
    fn layout_node_registry_is_scoped_by_app_context() {
        let _app_context = crate::render_state::app_context_test_scope();
        let first = crate::render_state::AppContext::new_with_density(1.0);
        let second = crate::render_state::AppContext::new_with_density(1.0);

        let first_id = first.enter(allocate_virtual_node_id);
        let second_id = second.enter(allocate_virtual_node_id);

        assert_eq!(first_id, VIRTUAL_NODE_ID_START);
        assert_eq!(second_id, VIRTUAL_NODE_ID_START);

        let virtual_node = LayoutNode::new_virtual();
        let regular_node = fresh_node();

        first.enter(|| {
            register_layout_node(first_id, &virtual_node);
            register_layout_node(101, &regular_node);
            assert!(is_virtual_node(first_id));
            assert_eq!(layout_node_registry_stats().len, 2);
        });

        second.enter(|| {
            assert!(!is_virtual_node(first_id));
            assert_eq!(layout_node_registry_stats().len, 0);
            assert_eq!(allocate_virtual_node_id(), VIRTUAL_NODE_ID_START + 1);
        });

        first.enter(|| {
            let owner_context_id = crate::render_state::current_app_context_id();
            unregister_layout_node(owner_context_id, first_id);
            unregister_layout_node(owner_context_id, 101);
            assert_eq!(layout_node_registry_stats().len, 0);
        });
    }

    fn invalidation(kind: InvalidationKind) -> ModifierInvalidation {
        ModifierInvalidation::new(kind, NodeCapabilities::for_invalidation(kind))
    }

    #[test]
    fn layout_invalidation_requires_layout_capability() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_measure();
        node.clear_needs_layout();
        node.modifier_capabilities = NodeCapabilities::DRAW;
        node.modifier_child_capabilities = node.modifier_capabilities;

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Layout)]);

        assert!(!node.needs_measure());
        assert!(!node.needs_layout());
    }

    #[test]
    fn semantics_configuration_reflects_modifier_state() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.set_modifier(Modifier::empty().semantics(|config| {
            config.content_description = Some("greeting".into());
            config.is_clickable = true;
        }));

        let config = node
            .semantics_configuration()
            .expect("expected semantics configuration");
        assert_eq!(config.content_description.as_deref(), Some("greeting"));
        assert!(config.is_clickable);
    }

    #[test]
    fn layout_invalidation_marks_flags_when_capability_present() {
        let _app_context = crate::render_state::app_context_test_scope();
        let _guard = crate::render_state::render_state_test_guard();
        crate::reset_render_state_for_tests();
        let mut node = fresh_node();
        node.id.set(Some(11));
        node.clear_needs_measure();
        node.clear_needs_layout();
        node.modifier_capabilities = NodeCapabilities::LAYOUT;
        node.modifier_child_capabilities = node.modifier_capabilities;

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Layout)]);

        assert!(node.needs_measure());
        assert!(node.needs_layout());
        assert_eq!(crate::take_layout_repass_nodes(), vec![11]);
        assert!(crate::take_layout_invalidation());
    }

    #[test]
    fn layout_invalidation_skips_repass_while_composing() {
        let _app_context = crate::render_state::app_context_test_scope();
        let _guard = crate::render_state::render_state_test_guard();
        crate::reset_render_state_for_tests();

        let node = Rc::new(RefCell::new(fresh_node()));
        {
            let mut node = node.borrow_mut();
            node.id.set(Some(17));
            node.clear_needs_measure();
            node.clear_needs_layout();
            node.modifier_capabilities = NodeCapabilities::LAYOUT;
            node.modifier_child_capabilities = node.modifier_capabilities;
        }

        let node_for_composition = Rc::clone(&node);
        let _composition = crate::run_test_composition(move || {
            node_for_composition
                .borrow()
                .dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Layout)]);
        });

        let node = node.borrow();
        assert!(node.needs_measure());
        assert!(node.needs_layout());
        assert!(crate::take_layout_repass_nodes().is_empty());
        assert!(!crate::take_layout_invalidation());
    }

    #[test]
    fn draw_invalidation_marks_redraw_flag_when_capable() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_measure();
        node.clear_needs_layout();
        node.modifier_capabilities = NodeCapabilities::DRAW;
        node.modifier_child_capabilities = node.modifier_capabilities;

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Draw)]);

        assert!(node.needs_redraw());
        assert!(!node.needs_layout());
    }

    #[test]
    fn semantics_invalidation_sets_semantics_flag_only() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_measure();
        node.clear_needs_layout();
        node.clear_needs_semantics();
        node.modifier_capabilities = NodeCapabilities::SEMANTICS;
        node.modifier_child_capabilities = node.modifier_capabilities;

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Semantics)]);

        assert!(node.needs_semantics());
        assert!(!node.needs_measure());
        assert!(!node.needs_layout());
    }

    #[test]
    fn pointer_invalidation_requires_pointer_capability() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_pointer_pass();
        node.modifier_capabilities = NodeCapabilities::DRAW;
        node.modifier_child_capabilities = node.modifier_capabilities;
        // Note: We don't assert on global take_pointer_invalidation() because
        // it's shared across tests running in parallel and causes flakiness.
        // The node's local state is sufficient to verify correct dispatch behavior.

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::PointerInput)]);

        assert!(!node.needs_pointer_pass());
    }

    #[test]
    fn pointer_invalidation_marks_flag_and_requests_queue() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_pointer_pass();
        node.modifier_capabilities = NodeCapabilities::POINTER_INPUT;
        node.modifier_child_capabilities = node.modifier_capabilities;
        // Note: We don't assert on global take_pointer_invalidation() because
        // it's shared across tests running in parallel and causes flakiness.
        // The node's local state is sufficient to verify correct dispatch behavior.

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::PointerInput)]);

        assert!(node.needs_pointer_pass());
    }

    #[test]
    fn focus_invalidation_requires_focus_capability() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_focus_sync();
        node.modifier_capabilities = NodeCapabilities::DRAW;
        node.modifier_child_capabilities = node.modifier_capabilities;
        crate::take_focus_invalidation();

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Focus)]);

        assert!(!node.needs_focus_sync());
        assert!(!crate::take_focus_invalidation());
    }

    #[test]
    fn focus_invalidation_marks_flag_and_requests_queue() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_focus_sync();
        node.modifier_capabilities = NodeCapabilities::FOCUS;
        node.modifier_child_capabilities = node.modifier_capabilities;
        crate::take_focus_invalidation();

        node.dispatch_modifier_invalidations(&[invalidation(InvalidationKind::Focus)]);

        assert!(node.needs_focus_sync());
        assert!(crate::take_focus_invalidation());
    }

    #[test]
    fn set_modifier_marks_semantics_dirty() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.clear_needs_semantics();
        node.set_modifier(Modifier::empty().semantics(|config| {
            config.is_clickable = true;
        }));

        assert!(node.needs_semantics());
    }

    #[test]
    fn modifier_child_capabilities_reflect_chain_head() {
        let _app_context = crate::render_state::app_context_test_scope();
        let mut node = fresh_node();
        node.set_modifier(Modifier::empty().padding(4.0));
        assert!(
            node.modifier_child_capabilities()
                .contains(NodeCapabilities::LAYOUT),
            "padding should introduce layout capability"
        );
    }
}