Struct BuildCx 

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

Per-frame, read-only context for App::build.

The runner snapshots the app’s crate::Theme before calling build and exposes it through cx.theme() / cx.palette() so app code can branch on the active palette (a custom widget that picks between two non-token colors based on dark vs. light, for instance). BuildCx is the explicit handle for this — token references inside widgets resolve through the palette automatically and don’t need it.

Future fields like viewport metrics or frame phase will live here so the API stays additive: adding a new accessor on BuildCx doesn’t break apps that ignore the context.

Implementations

impl<'a> BuildCx<'a>

pub fn new(theme: &'a Theme) -> Self

Construct a BuildCx borrowing the supplied theme. Hosts call this once per frame after App::theme and before App::build. Hosts that own a crate::state::UiState should chain Self::with_ui_state so the app can read interaction state (hover) during build via Self::hovered_key / Self::is_hovering_within.

pub fn with_ui_state(self, ui_state: &'a UiState) -> Self

Attach the runtime’s crate::state::UiState so build-time accessors (hovered_key, is_hovering_within) can answer. When omitted, those accessors return None / false — useful for headless rendering paths that don’t track interaction state.

pub fn with_diagnostics(self, diagnostics: &'a HostDiagnostics) -> Self

Attach a HostDiagnostics snapshot for this frame. Hosts call this when they want apps to surface debug overlays (e.g. the showcase status block); apps that don’t read diagnostics() pay nothing for it. Headless render paths leave it None.

pub fn diagnostics(&self) -> Option<&HostDiagnostics>

Per-frame diagnostic snapshot from the host (backend, frame cadence, trigger reason, etc.), or None when the host did not attach one. Apps display this in optional debug overlays.

pub fn theme(&self) -> &Theme

The active runtime theme for this frame.

pub fn palette(&self) -> &Palette

Shorthand for self.theme().palette().

pub fn hovered_key(&self) -> Option<&str>

Key of the leaf node currently under the pointer, or None when nothing is hovered or this BuildCx was built without a UiState (headless rendering paths).

Use for branching the build output on hover state without mirroring it via App::on_event handlers — e.g., a sidebar row that previews details in a side pane based on what’s currently hovered.

For region-aware queries (parent stays “hot” while a child is hovered), prefer Self::is_hovering_within.

pub fn is_hovering_within(&self, key: &str) -> bool

True iff key’s node — or any descendant of it — is the current hover target. Subtree-aware, matching the semantics of crate::tree::El::hover_alpha. Returns false when this BuildCx has no attached UiState or when key isn’t in the current tree.

Reads the underlying tracker, not the eased subtree envelope — the boolean flips immediately on hit-test identity change.

Trait Implementations

impl<'a> Clone for BuildCx<'a>

fn clone(&self) -> BuildCx<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for BuildCx<'a>

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

Formats the value using the given formatter.

impl<'a> Copy for BuildCx<'a>