Struct ColumnFlow 

pub struct ColumnFlow { /* private fields */ }

A layout that flows its children into as many columns as the available width affords, re-partitioning every child when a column is gained or lost.

 wide                            narrower
┌────┐ ┌────┐ ┌────┐            ┌────┐ ┌────┐
│ 1  │ │ 3  │ │ 5  │            │ 1  │ │ 4  │
├────┤ ├────┤ ├────┤            ├────┤ ├────┤
│ 2  │ │ 4  │ │ 6  │    ───►    │ 2  │ │ 5  │
└────┘ └────┘ └────┘            ├────┤ ├────┤
                                │ 3  │ │ 6  │
                                └────┘ └────┘

Reading order is 1..6 at both widths. See the module docs.

Implementations

impl ColumnFlow

pub fn new() -> Self

Create a ColumnFlow with a 240 dp minimum column width, no maximum column width, and no column-count cap.

pub fn min_column_width(self, width: f32) -> Self

The narrowest a column may be. The column count is the largest N whose columns are all at least this wide — CSS column-width / SwiftUI GridItem(.adaptive(minimum:)) / Compose GridCells.Adaptive(minSize).

A value of zero or less pins the layout to a single column.

pub fn max_column_width(self, width: f32) -> Self

The widest a column may be. Unset by default, so columns stretch to share the full width evenly.

Set it to stop columns becoming unreadably wide when few of them fit a large display — the reason KDE’s Kirigami.CardsLayout pairs minimumColumnWidth with maximumColumnWidth. When it bites, the columns no longer fill the width and alignment decides where the block sits.

pub fn max_columns(self, max: usize) -> Self

Never use more than max columns however wide the layout gets.

Also decides the count when the width is unconstrained (inside a size-to-content parent such as a popover): unset, that case reports one column, matching CSS column-count: auto in a shrink-to-fit context. Clamped to at least 1.

pub fn column_spacing(self, spacing: impl Into<Prop<f32>>) -> Self

Horizontal gap between columns. Accepts an f32 or a Signal<f32>.

pub fn item_spacing(self, spacing: impl Into<Prop<f32>>) -> Self

Vertical gap between items within a column. Accepts an f32 or a Signal<f32>.

Named for items rather than rows because there are no rows here: a column’s items are independent of its neighbours’.

pub fn alignment(self, alignment: HAlignment) -> Self

Where the column block sits when it does not fill the available width.

Only observable once max_column_width clamps the columns narrower than their even share — otherwise the columns consume the whole width and there is nothing to align. Defaults to [HAlignment::Leading]; RTL-aware.

pub fn column_rule(self, width: f32, color: impl Into<ColorProp>) -> Self

Draw a rule of width dp, centred in every inter-column gap — CSS column-rule.

Purely decorative: it emits no accessibility node. Accepts a Color, a theme role, or a Signal. Pass BorderRole::Divider to track the theme’s divider colour.

pub fn semantic_list(self, enabled: bool) -> Self

Expose the children to assistive technology as a list.

The container becomes Role::List and every child is wrapped in a layout-transparent node reporting Role::ListItem with its position and the set size, so a screen reader announces “list, 30 items” and “item 5 of 30” rather than reading 30 unrelated widgets.

Off by default: a layout primitive should not invent semantics its content may not have. Turn it on when the children genuinely are a list of peers. Costs one extra node per child.

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

Add a pre-registered child by ID.

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

Add an inline child widget (deferred insertion).

pub fn children( self, iter: impl IntoIterator<Item = impl Widget + 'static>, ) -> Self

Add multiple inline children from an iterator.

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

Conditionally add a child. No-op if None.

pub fn column_count_signal(&self) -> Signal<usize>

The live column count, as a reactive signal.

Lets an app follow the reflow — swapping to a compact header at one column, say. Written from the layout pass behind an equality guard, so it only fires when the count actually changes.

Binding contract. Safe for RepaintOnly / AccessibilityOnly consumers, and for Relayout consumers that do not feed back into this widget’s own width. The count is a pure function of the width ColumnFlow is given — it never changes its own width, so it cannot oscillate on its own. But a Relayout consumer that resizes something which in turn resizes this ColumnFlow closes a feedback loop through the layout pass, which is exactly what Widget::place_children’s own documentation warns against.

Trait Implementations

impl Debug for ColumnFlow

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

Formats the value using the given formatter.

impl Default for ColumnFlow

fn default() -> Self

Returns the “default value” for a type.

impl Widget for ColumnFlow

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 paint(&self, bounds: Rect, canvas: &mut Canvas, ctx: &PaintContext<'_>)

Draw the widget’s visual representation.

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

Declare this widget’s accessibility identity.

fn children(&self) -> Vec<WidgetId>

Return the child widget IDs that this widget manages.

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 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 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 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 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 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).