Module tab_widget 

Tabbed-container widgets.

Two public entry points:

• TabBar<T> — a header strip driven by a ListModel<T> / ListDataSource and a TabDelegate<T>. Use it stand-alone when you want only the tab strip (e.g., a document tab strip whose content lives in a different panel or window).

• TabWidget — the all-in-one composition: bar above, content Switcher below, sharing one selection signal. Two construction flavors:

  • static_tab(info, content) — fixed tabs accumulated at construction.
  • dynamic_tab::<S>(kind, factory) + dynamic_model(model) — apps register a content factory per tab kind ("plain-text-doc", "image", …); the live tab list is a mutable ListModel<TabHandle> mutated at runtime (open / close / reorder).

Static tabs always render first, in declaration order; dynamic tabs follow. Selection is by stable TabId — drag-reorder and model mutations never silently send the active selection to a different tab.

Activating a tab scrolls it into view

When more tabs are open than the strip can show, activating one always reveals it — including when the activation is programmatic (writing the selection signal, the “show all tabs” overflow dropdown, an assistive-technology click). Pointer and keyboard activation move focus and would be revealed by the framework’s focus follow anyway; the other paths move no focus, so the bar scrolls the header in itself, by the minimum needed to bring it fully inside the viewport.

The reveal is edge-triggered on the selection changing, not an invariant re-asserted every layout pass: once the reader has scrolled away from the active tab by hand, a rebuild for an unrelated reason — a retitled tab, a locale change, a tab opened elsewhere in the strip — leaves the viewport where they left it.

Accessibility

Both TabWidget and TabBar emit Role::TabList on the bar and Role::Tab on each header. ARIA APG (tabs pattern) recommends providing an accessible name for the tab list whenever a page hosts more than one — call .access_label(tr!(editor_tabs())) on the widget so screen readers can distinguish “editor tabs” from “tool tabs”:

TabWidget::new(selected)
    .static_tab(TabInfo::new().title(tr!(welcome())), welcome_panel)
    // ...
    .access_label(tr!(editor_tabs()))

Panels with no focusable descendants (a static text-only “About” tab, a chart-only metrics tab) are unreachable by Tab key unless opted in via TabInfo::focusable_panel(true).

Structs

TabBar

A reactive header strip that pulls its tab list from a data source and writes the active tab into a shared Signal<Option<TabId>>.

TabBarDragData

Drag payload published by a tab header when the user starts dragging it.

TabDelegate

Resolves per-tab UI from a model item.

TabHandle

One tab’s identity, presentation, and state pointer.

TabId

Stable identity of a tab. Cheap to copy; persists across model reorders, rebuilds, and reorders triggered by drag-and-drop.

TabInfo

Per-tab presentation metadata. Build with TabInfo::new and fluent setters.

TabWidget

All-in-one tabbed container. Builds a TabBar above a Switcher of content panes, sharing one selection signal.

Enums

TabBarOrientation

Bar orientation. Selects between a horizontal row of tabs (default for browser-style document tabs) and a vertical column of pills (sidebar / IDE perspective convention).

TabBarVisibility

Controls whether a TabWidget’s tab strip is shown.

TabDisplayMode

Bar-level control over what each tab shows — its icon, its label, or both.

TabOverflowButton

When the trailing “show all tabs” overflow dropdown button appears.

TabSizing

How wide each tab is: shared across all unpinned tabs, chosen per-tab from content, or stretched to fill the bar.

Constants

DEFAULT_BAR_SLOT_SPACING

Default spacing between the bar’s leading slot, scroll area, and trailing slot.

DEFAULT_MAX_TAB_WIDTH

Default max width for an unpinned tab.

DEFAULT_MIN_TAB_WIDTH

Default min width for an unpinned tab.

DEFAULT_PINNED_TAB_WIDTH

Default width (in dp) of a pinned tab — icon-only squares.

DEFAULT_TAB_SPACING

Default spacing between tab headers in the row. 0.0 so tabs sit flush against each other (Firefox / Chrome convention) — adjacent tab boundaries are visually separated by the per-tab borders, not by an empty gap.

STATIC_KIND

Sentinel kind reserved for static tabs accumulated via TabWidget::static_tab. Application-level kind strings must not collide with this value — the framework panics with a clear message at registration if dynamic_tab is called with this name.

Type Aliases

ContextMenuFactory

A reusable widget factory the framework calls every time a context menu opens. Returns a fresh widget instance each call (the framework can’t reuse a single widget across multiple openings).

IconFactory

Reusable factory for an IconWidget. Boxed in Rc so TabInfo is Clone without forcing IconWidget: Clone.

StaticContentFactory

Closure that builds a static tab’s content widget. Called once per static tab — on the TabWidget’s first build that includes it. The resulting pane is then memoized: rebuilds caused by adjacent dynamic-model mutations reuse the same pane WidgetId, so internal state (focus, scroll, animation progress, …) survives.