Struct BuildCtx 

pub struct BuildCtx<'a> { /* private fields */ }

Context threaded through View::build / View::rebuild: allocates unique WidgetIds from the render root’s counter and carries the effective focus chain (BuildCtx::has_focus) and element-replaced signal (BuildCtx::mark_element_replaced).

Implementations

impl<'a> BuildCtx<'a>

pub fn new(next_id: &'a mut u64) -> Self

Create a context borrowing the render root’s id counter.

The focus chain seeds true (“unknown, assume live”): over-releasing costs one tap, while under-releasing strands the shell’s IME surface over a dead widget. Seams that know the real value set it with BuildCtx::set_has_focus.

pub fn with_shortcut_hints(self, hints: Rc<[ShortcutHint]>) -> Self

Hand the context its root’s last paint snapshot (BuildCtx::shortcut_hints).

pub fn alloc_id(&mut self) -> WidgetId

Allocate a fresh, unique widget id.

pub fn has_focus(&self) -> bool

Whether the recorded focus path is live from the root to the node being built/rebuilt/torn down: the rebuild-pass mirror of PaintCtx::has_focus.

A blur clears the link at the nearest common ancestor only, so a focused ChildPod flag below it goes stale harmlessly. A reconciler raises mark_focus_orphaned only when ctx.has_focus() && pod.is_focused(): the session is actually live.

pub fn shortcut_hints(&self) -> Rc<[ShortcutHint]>

The previous paint’s shortcut declarations in paint order, unreachable ones included; label each chord with Chord::display. They lag this build by a frame, and are empty on a context its root did not seed.

pub fn set_has_focus(&mut self, has_focus: bool)

Seed the focus chain for a seam that starts one (RenderRoot’s view diff, or a component carrying its outer chain across an inner BuildCtx). A container descending into a pod uses BuildCtx::with_focus_link, which can only narrow.

pub fn with_focus_link<R>( &mut self, link_focused: bool, f: impl FnOnce(&mut Self) -> R, ) -> R

Run f with the focus chain extended by one link (link_focused is the pod’s is_focused flag), restoring it afterwards: the closure sees self.has_focus() && link_focused, so no descent can widen the chain.

pub fn mark_element_replaced(&mut self)

Report that this view’s rebuild replaced its element’s widget while keeping the element type (an enum view switching arms, e.g. Either).

A reconciler detects an AnyView type swap by type id and drops the child pod’s capture and focus links; an enum keeps one static type, so it raises this signal instead. The nearest enclosing track_element_replaced scope consumes it (a pod inside the swapped subtree consumes its own); with no scope it is inert or reaches the next one up: an over-release, never an under-release.

pub fn track_element_replaced<R>( &mut self, f: impl FnOnce(&mut Self) -> R, ) -> (R, bool)

Run f as a tracking scope for mark_element_replaced, returning f’s result and whether anything inside raised the signal. The caller’s pending value is saved and restored.