Struct ButtonGroupView 

pub struct ButtonGroupView<State: 'static> { /* private fields */ }

A declarative M3 Expressive button group. See the module docs.

Implementations

impl<State: 'static> ButtonGroupView<State>

pub fn group_type(self, group_type: ButtonGroupType) -> Self

Set the connection treatment (the module docs’ types table).

pub fn density(self, density: ButtonGroupDensity) -> Self

Set the spacing compactness (the module docs’ gap table).

pub fn direction(self, direction: ButtonGroupDirection) -> Self

Set the primary layout axis.

pub fn spacing(self, spacing: f64) -> Self

Override the resolved member gap, in logical px.

pub fn variant(self, variant: ButtonVariant) -> Self

Set every member’s container treatment (M3EButtonGroup.style).

pub fn size(self, size: ToggleButtonSize) -> Self

Set every member’s size tier (M3EButtonGroup.size).

pub fn haptic(self, haptic: HapticSignal) -> Self

Set the haptic signal each member fires on a confirmed toggle.

pub fn selected_index(self, selected: Option<usize>) -> Self

The single-select selected index (M3EButtonGroup.selectedIndex).

pub fn selected_indices(self, indices: impl IntoIterator<Item = usize>) -> Self

The multi-select selection set (M3EButtonGroup.selectedIndices) — takes precedence over Self::selected_index.

pub fn on_select<F: Fn(&mut State, usize) + 'static>(self, on_select: F) -> Self

The legacy single-select callback: always the tapped index. Lowest precedence of the three (see the module docs’ selection order).

pub fn on_selected_index_changed<F: Fn(&mut State, Option<usize>) + 'static>( self, on_change: F, ) -> Self

onSelectedIndexChanged: the requested single selection, None when the tap deselects the currently-selected member.

pub fn on_selected_indices_changed<F: Fn(&mut State, Vec<usize>) + 'static>( self, on_change: F, ) -> Self

onSelectedIndicesChanged: the requested multi selection, ascending. Highest precedence of the three.

pub fn neighbor_squish(self, squish: bool) -> Self

Whether a press squishes its neighbours (default true) — see the module docs’ squish section for when it applies at all.

pub fn expanded_ratio(self, ratio: f64) -> Self

The fraction of its natural main extent a pressed member grows by (default [DEFAULT_EXPANDED_RATIO]).

pub fn overflow(self, overflow: ButtonGroupOverflow) -> Self

How members that do not fit are handled (the module docs’ Overflow table).

pub fn overflow_icon<F, V>(self, icon: F) -> Self

where F: Fn() -> V + 'static, V: View<State>,

Replace the overflow trigger’s icon (M3EButtonGroup.overflowIcon; the default is M3EIcons.more_horiz).

pub fn on_overflow<F: Fn(&mut State, usize) + 'static>( self, on_overflow: F, ) -> Self

Fired with the first hidden action’s index when the overflow trigger is tapped — where an app presents crate::show_bottom_sheet over actions[first_hidden..] (ButtonGroupOverflow::BottomSheet) or mounts Self::overflow_menu (ButtonGroupOverflow::Popup). See the module docs’ Overflow section.

pub fn overflow_anchor(self, anchor: &OverlayAnchor) -> Self

Capture the overflow trigger’s window rect into anchor on every paint — wire this alongside ButtonGroupOverflow::Popup so Self::overflow_menu has a rect to place against, the same OverlayAnchor handoff crate::dropdown::dropdown_field takes with crate::dropdown’s panel half. A no-op for every other ButtonGroupOverflow variant.

pub fn semantic_label(self, label: impl Into<String>) -> Self

The accessible name of the group as a whole (M3EButtonGroup.semanticLabel).

pub fn overflow_menu(&self, first_hidden: usize, open: bool) -> AnyView<State>

The popup-style overflow menu for ButtonGroupOverflow::Popup — mount this separately as the top of the app’s own frust::Stack (or a transparent navigator page), anchored to the same OverlayAnchor handed to Self::overflow_anchor. See the module docs’ Overflow section for why this is a second, app-mounted view rather than something ButtonGroupWidget paints itself.

first_hidden is the index Self::on_overflow reported when the trigger was tapped; open drives the anchored host’s ramp (the kept-mounted pattern crate::overlay::anchored documents — keep this view mounted and toggle open for the exit ramp rather than unmounting it, crate::dropdown’s own convention).

Each hidden member becomes a crate::menu::MenuToggleable row, checked exactly as Self::is_selected already resolves it for a visible member — upstream’s own overflow menu marks a hidden action checked the same way (_buildOverflowMenuVisibleItems/onItemSelected, m3e_toggle_button_group_layout.dart:181-:203). Activating one routes through this group’s own selection fan-out — Self::on_selected_indices_changed, Self::on_selected_index_changed, or Self::on_select, in that precedence — exactly as a visible member’s own tap does.

A member’s ButtonGroupAction::icon/ButtonGroupAction::checked_icon is an arbitrary view (a member button can paint anything), which a menu row’s crate::menu::MenuIcon slot cannot carry (it names a vector path, not a view) — a popup row therefore shows the member’s label only. An icon-only group (this crate’s usual toolbar shape) should give its actions a plain ButtonGroupAction::label alongside the icon so an overflowed member still reads in the popup.

Trait Implementations

impl<State: 'static> View<State> for ButtonGroupView<State>

type Element = ButtonGroupWidget

The retained widget this view produces.

fn build(&self, ctx: &mut BuildCtx<'_>) -> ButtonGroupWidget

Materialise a fresh widget for this view.

fn rebuild( &self, prev: &Self, element: &mut ButtonGroupWidget, ctx: &mut BuildCtx<'_>, ) -> ChangeFlags

Reconcile prev (the previous view of the same type) against the live element, mutating it in place and reporting what changed.

fn teardown(&self, element: &mut ButtonGroupWidget, ctx: &mut BuildCtx<'_>)

Tear down element when this view is being removed.

fn message(&self, _element: &mut Self::Element, _state: &mut State)

Deliver an event message to this view, mutating application state.