Struct DeferredSubtree 

pub struct DeferredSubtree { /* private fields */ }

A child subtree built the first time reveal is true, then retained.

Construct through BuildContext::add_deferred and its siblings rather than directly — they are what give the host its stable id.

Implementations

impl DeferredSubtree

pub fn force(&mut self)

Materialize on the next build regardless of the reveal gate.

For content the framework shows on its own initiative — a tooltip body, whose dwell has no signal a widget could hand over. Pair it with a rebuild of this host (WidgetTree::materialize_deferred does both).

pub fn is_materialized(&self) -> bool

Whether the subtree has been built. Test hook, and the honest answer to “did deferring actually defer”.

pub fn materialized_child(&self) -> Option<WidgetId>

The materialized child, if the subtree has been built.

Lets a caller that must inspect the content — the accessibility walk reading a tooltip’s text off the node it is attached to — resolve past this host instead of probing the host itself and finding nothing.

Trait Implementations

impl Debug for DeferredSubtree

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Widget for DeferredSubtree

fn preserves_children_on_rebuild(&self) -> bool

Required, not an optimisation. The default rebuild path destroys a widget’s children before calling build(), so a host that caches its child id and returns it again would hand back a dead node — the content would vanish the first time anything rebuilt this host. Retaining the materialized subtree across rebuilds is the whole contract here.

fn accessibility(&self, builder: &mut AccessNodeBuilder)

Delegates to the un-built content, which is the whole reason this can be layered under a tooltip at all.

A plain tooltip is never auto-shown on focus, so the description copied onto the anchor is the entire screen-reader path for that tier — and it is read by probing the content widget’s own accessibility. Deferring the subtree must not cost that: the widget value is right here, un-built, and answering from it needs no arena node. Without this the tips still appear on hover and every screen-reader user silently loses them, which is the kind of regression that ships.

fn tooltip_has_content(&self) -> bool

Same delegation as accessibility, for the emptiness guard: a tooltip with nothing to say must not open a bubble, and the un-built body is the only thing that knows.

fn as_any_mut(&mut self) -> Option<&mut dyn Any>

Required by WidgetTree::materialize_deferred, which reaches this widget by id to force it.

fn build(&mut self, ctx: &mut BuildContext<'_>) -> Vec<WidgetId>

Compose child widgets. Called once after the widget is placed in the arena, and again on environment change (theme switch, locale switch). Takes &mut self — store child IDs, signal handles, any state needed later. Returns the list of root child IDs (empty for leaf widgets).

fn layout_response( &self, proposal: SizeProposal, ctx: &LayoutContext<'_>, ) -> LayoutResponse

Respond to the parent’s size proposal with this widget’s wanted size, grow/shrink weights, and compression floor (see LayoutResponse).

fn place_children( &self, bounds: Rect, _proposal: SizeProposal, children: &mut [WidgetPlacement], _ctx: &LayoutContext<'_>, )

Position children within the allocated bounds.

fn as_any(&self) -> Option<&dyn Any>

Downcast hook. Default implementation returns None; concrete widgets override with Some(self) when they want to expose their concrete type to test-level introspection or reflection. The trait already bounds on std::any::Any so concrete types satisfy the 'static requirement.

fn type_name(&self) -> &'static str

Concrete type name of this widget (e.g. "teksilo_widgets::button::Button"). The default implementation resolves at the impl site via std::any::type_name::<Self>(), so calls through &dyn Widget correctly dispatch to the monomorphized fn for the concrete type — getting the concrete name through the vtable without per-impl boilerplate.

fn cacheable_layout(&self) -> bool

Whether this widget’s layout_response may be memoized by the per-pass layout cache. Defaults to true.

fn paint(&self, _bounds: Rect, _canvas: &mut Canvas, _ctx: &PaintContext<'_>)

Draw the widget’s visual representation.

fn wants_after_paint(&self) -> bool

Whether this widget wants its after_paint hook to fire each frame. Returning false (the default) saves a virtual call per widget per frame for the vast majority of widgets that don’t aggregate descendant geometry.

fn after_paint(&self, _view: &WidgetTreeView<'_>, _ctx: &PaintContext<'_>)

Called once per frame after this widget’s subtree has finished painting. Receives a read-only view of the layout-resolved arena so a parent can read its descendants’ final bounds — e.g. TitleBar aggregates its drag region and control-button rects into a single HitRegions payload for the Windows backend’s WM_NCHITTEST.

fn wants_post_paint(&self) -> bool

Whether this widget wants its post_paint hook to fire each frame. Returning false (the default) saves a virtual call per widget per frame for the vast majority of widgets that don’t draw a foreground over their children.

fn post_paint( &self, _bounds: Rect, _canvas: &mut Canvas, _ctx: &PaintContext<'_>, )

Draw a foreground layer over this widget’s children.

fn wants_descendant_redirects(&self) -> bool

Whether this widget wants the AT walker to consult its a11y_redirect_descendant hook for every descendant during AT tree emission, not just its direct arena children.

fn a11y_redirect_descendant( &self, _self_id: WidgetId, _descendant: WidgetId, ) -> Option<NodeId>

Optional redirection hook for AT-tree placement of a child.

fn accessible_title_hint(&self) -> Option<String>

Suggest an accessible title to an enclosing container that wraps this widget as content — typically a modal / dialog shell that wants to propagate the inner content’s visible title as the shell’s own accessible name.

fn initial_focus_hint(&self) -> Option<WidgetId>

Optional hint that directs initial focus to a specific descendant when this widget is the root of a deferred-built modal surface.

fn context_menu_key_target(&self) -> Option<WidgetId>

Which descendant a keyboard request for a context menu should target.

fn children(&self) -> Vec<WidgetId>

Return the child widget IDs that this widget manages.

fn accessibility_children(&self) -> Option<Vec<WidgetId>>

Optional override for the child ORDER presented to assistive technology, when it must differ from the paint / z-order child order returned by children.

fn clips_children(&self) -> bool

Whether this widget clips its children to its bounds.

fn focus_reveal_rect(&self, _bounds: Rect) -> Option<Rect>

The rectangle (in absolute tree coordinates) that best represents this widget when the framework reveals it into an ancestor scroll area on focus gain. Returning None (the default) reveals the widget’s whole bounds — correct for most controls.

fn hit_shape(&self, _local_point: Point, _bounds: Rect) -> bool

Whether the point lies inside this widget’s actual shape, not just its rectangular bounds. Consulted by hit-testing right after the bounds check: returning false for a point that is inside the bounding box makes the widget transparent to the click there, so it falls through to whatever sibling is painted underneath (the same machinery as a fully pass-through node, but shape-aware).

fn declare_shortcuts(&self) -> Vec<Shortcut>

Declare the rebindable keyboard shortcuts this widget exposes, without installing handlers. The framework calls this at arena insertion time (before build()) and at certain lazy boundaries (e.g. Switcher walks declarations on its not-yet-mounted Pending slots), so settings UIs and the ShortcutRegistry see the keystrokes the moment the owning container mounts — even if build() hasn’t run.

fn take_handler_set(&mut self) -> Option<HandlerSet>

Extract attached handler set from a WidgetWithHandlers wrapper. Called during arena insertion to transfer handlers to the WidgetNode. Default: returns None (no attached handlers).