Struct TouchTarget 

pub struct TouchTarget { /* private fields */ }

Give an undersized control a conforming touch target, growing the layout around it when nothing cheaper will do — and only at [TargetDensity::Touch].

When you need this, and when you do not

Teksilo has three ways to make a target reachable, and they are ordered by how much they disturb:

1. Widget::hit_outset — a thin grip claims the space around it. Hit-only; nothing moves. This is what a splitter gutter or a column resize strip uses.
2. The miss-only slop pass — an isolated small control catches a near miss. Hit-only; nothing moves. This is what a radio dot or a chart mark uses.
3. TouchTarget — this. The control genuinely needs room, because the thing beside it is also a target and there is no space to borrow. It changes layout, so siblings reflow.

Reach for (3) only when (1) and (2) cannot work: when a control sits in a tight row of other controls, so widening its hit area would take presses from its neighbours rather than from empty space. Everything else the density sweep already handles by projecting the recipes.

Why Touch only

At Compact and Comfortable this wrapper is the identity: it reports its child’s own response, unchanged, and adds no hit outset. Compact is the density every existing layout was designed at and every layout golden was recorded at, and Comfortable is served by the recipes’ own density projection, which raises a control’s own dimensions rather than padding around it. Touch is the ladder where a 24 dp control still falls 20 dp short of the target and no recipe can close the gap from inside.

// A 16 dp close affordance in a dense tab strip: at Touch it is given a
// 44 dp slot and centred in it; at Compact nothing changes at all.
TouchTarget::new().child(close_button)

reserve_space

• reserve_space(true) (the default) — the slot reports at least size on both axes and centres the child in it. Siblings reflow.
• reserve_space(false) — the slot reports the child’s own size and declares a [Widget::hit_outset] that brings the hit area up to size instead. Nothing moves; the target overlaps whatever is beside it. Use it when the row has slack in one direction but you cannot spend it.

Implementations

impl TouchTarget

pub fn new() -> Self

A new wrapper at the density’s own target_size. Attach content with child or child_id.

pub fn size(self, dp: f32) -> Self

Override the target size, in dp. Defaults to the density’s InputTokens::target_size (44 dp at Touch).

pub fn reserve_space(self, reserve: bool) -> Self

Whether the slot takes the room it needs (true, the default) or widens only the hit area (false). See the type docs.

pub fn child(self, widget: impl Widget + 'static) -> Self

Wrap an inline widget.

pub fn child_id(self, id: WidgetId) -> Self

Wrap a pre-registered widget by id.

Trait Implementations

impl Debug for TouchTarget

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

Formats the value using the given formatter.

impl Default for TouchTarget

fn default() -> Self

Returns the “default value” for a type.

impl Widget for TouchTarget

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 children(&self) -> Vec<WidgetId>

Return the child widget IDs that this widget manages.

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

How far outside its own bounds this widget still absorbs a press, per edge, for the pointer that is asking.

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 accessibility(&self, _builder: &mut AccessNodeBuilder)

Declare this widget’s accessibility identity.

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

The interactive sub-regions this widget paints inside its own single node — a scroll bar’s thumb, a slider’s knob, a header cell’s filter affordance.

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).