Struct ScrollBar 

pub struct ScrollBar { /* private fields */ }

A scroll bar that shares reactive scroll-position state with a ScrollArea.

Supports thumb drag, track-click page scroll, and keyboard Up/Down/Left/Right/Home/End navigation. Hidden from AT — see module docs.

Implementations

impl ScrollBar

pub fn new( orientation: ScrollBarOrientation, scroll_position: Signal<f32>, max_scroll: Signal<f32>, viewport_ratio: Signal<f32>, ) -> Self

Create a new ScrollBar with shared state.

• scroll_position: shared Signal<f32> for current scroll offset
• max_scroll: shared Signal<f32> for maximum scroll offset
• viewport_ratio: shared Signal<f32> for viewport/content ratio (0.0..1.0)

pub fn thickness(self, thickness: f32) -> Self

Set the bar thickness (width for vertical, height for horizontal).

pub fn min_thumb_length(self, len: f32) -> Self

Set the minimum thumb length in pixels, overriding the density.

Left unset the floor is SCROLLBAR_MIN_THUMB_LENGTH raised to the density’s target size — 24 dp at Compact, 44 dp at Touch — so a short thumb on a long document stays something a finger can land on.

pub fn reveal(self, revealed: Signal<bool>) -> Self

Show the bar for as long as revealed is true, whatever hover says.

An overlay bar is normally revealed by pointer proximity, which a contact never produces. ScrollArea raises this while a finger’s pan is in flight; a density whose RevealPolicy is Always seeds it true at build. It only ever adds a reveal — nothing here can hide a bar that hover has shown.

pub fn step_size(self, step: f32) -> Self

Set the scroll step for keyboard navigation.

pub fn visual(self, variant: ScrollBarVariant) -> Self

Set the visual variant. The active ScrollBarStyle picks how to paint each variant; the IntUI default ships Permanent / Overlay / Thin out of the box.

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

Alias for visual using the new variant naming.

pub fn style(self, style: impl ScrollBarStyle) -> Self

Override the active ScrollBarStyle for this widget instance only.

pub fn thumb_color(self, color: impl Into<ColorProp>) -> Self

Tint the thumb with an explicit colour instead of the theme’s scrollbar_thumb* tokens. Accepts anything impl Into<ColorProp> — a Color, a theme role (TextRole/SurfaceRole/…), or a Signal; resolved against the live theme at paint, so roles and signals stay reactive. The active ScrollBarStyle derives the idle/hover/pressed states from this tint. Use when the bar sits on a surface the surface-relative tokens don’t suit — a tooltip’s inverse chip, a branded panel. Mirrors Button::text_role.

Trait Implementations

impl Debug for ScrollBar

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

Formats the value using the given formatter.

impl Widget for ScrollBar

fn hit_outset(&self, kind: PointerKind, _tokens: &InputTokens) -> EdgeInsets

Widen the bar across its scroll axis for a coarse pointer, to the 48 dp Android reserves for a scrollbar touch target.

Hit-only: the 8–12 dp paint is untouched at every density, nothing relayouts, and a Compact build renders byte for byte as it did. Zero for a mouse and for a pen, both of which are precise enough to land on the bar as drawn — a pen’s tip is where its cursor is, and widening a precise pointer’s targets takes clicks away from the content.

Only the axis that is too thin grows. Growing the bar along the scroll axis would claim a strip of content above and below it for no benefit: the track already spans the viewport, and its ends are where the corner and the other bar live.

fn target_regions(&self, bounds: Rect) -> Vec<TargetRegion>

The thumb, and the track either side of it.

Both are paint geometry inside one leaf node: the bar’s body is a single private painter widget, so without this the thumb does not exist to anything outside paint — not to the target-conformance audit, and not to a router that would route a coarse press to the nearest target. The rectangles come from the same three numbers the painters read, so the geometry reported and the geometry drawn cannot drift.

A bar with nothing to scroll paints nothing and reports nothing.

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

Compose child widgets. Called once after the widget is placed in the arena, and again whenever the widget is marked for rebuild — a BindingLevel::Rebuild binding, rebuild_single_widget, or a density switch. A theme or locale switch does not rebuild: set_theme and set_locale mark layout + paint dirty and leave the built subtree standing, so anything derived from the theme or the locale must be read per pass or bound to a signal rather than captured here. 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 children(&self) -> Vec<WidgetId>

Return the child widget IDs that this widget manages.

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

Declare this widget’s accessibility identity.

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 culls_children(&self) -> bool

Whether this widget decides, on every layout pass, which of its children exist at all.

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 accessible_title_node(&self) -> Option<WidgetId>

The widget that paints this one’s title, when it has one.

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 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 as_any(&self) -> Option<&(dyn Any + 'static)>

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 as_any_mut(&mut self) -> Option<&mut (dyn Any + 'static)>

Mutable counterpart of as_any. Default returns None; widgets that want to expose mutable state to tests (e.g. so a test can mutate a Scene inside a SceneView post-layout) override with Some(self). Should follow the same opt-in pattern as as_any: only widgets that opt into & introspection should opt into &mut.

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 accepts_child_hit(&self, _child: WidgetId, _point: Point) -> bool

Veto a hit on one of this widget’s direct children, per point.

fn hit_slop(&self, _kind: PointerKind, _tokens: &InputTokens) -> Option<HitSlop>

This widget’s own say in the miss-only slop pass, overriding the density default for its node.

fn hit_distance(&self, local_point: Point, bounds: Rect) -> Option<f32>

How far a missed press is from this widget’s actual silhouette, in the widget’s own bounds space.

fn preserves_children_on_rebuild(&self) -> bool

How rebuild_single_widget treats this widget’s existing children when re-running its build().

fn tooltip_has_content(&self) -> bool

Whether this widget, used as tooltip content, currently has anything worth showing.

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).