NavigationMenu is a Tier B custom control set for a non-modal, hover/keyboard-disclosed site-navigation row: no native WPF control models this pattern, so it is built on ContentControl/ItemsControl with a NaviusAnchoredPopup-hosted content panel per open item. This port implements only per-item popup mode; the web contract’s shared/morphing viewport (one popup that resizes and re-anchors as the active item changes) is a stub that throws NotSupportedException when requested.

Usage

xmlns:navigationmenu="clr-namespace:Navius.Wpf.Primitives.Controls.NavigationMenu;assembly=Navius.Wpf.Primitives"

<navigationmenu:NaviusNavigationMenu Value="{Binding OpenItem, Mode=TwoWay}">
    <navigationmenu:NaviusNavigationMenuList>
        <navigationmenu:NaviusNavigationMenuItem Value="products">
            <navigationmenu:NaviusNavigationMenuTrigger Content="Products" />
            <navigationmenu:NaviusNavigationMenuContent>
                <StackPanel>
                    <navigationmenu:NaviusNavigationMenuLink Content="Overview" Href="/products" />
                    <navigationmenu:NaviusNavigationMenuLink Content="Pricing" Href="/pricing" />
                </StackPanel>
            </navigationmenu:NaviusNavigationMenuContent>
        </navigationmenu:NaviusNavigationMenuItem>
        <navigationmenu:NaviusNavigationMenuItem Value="docs">
            <navigationmenu:NaviusNavigationMenuLink Content="Docs" Href="/docs" />
        </navigationmenu:NaviusNavigationMenuItem>
    </navigationmenu:NaviusNavigationMenuList>
</navigationmenu:NaviusNavigationMenu>

NaviusNavigationMenuSub (nested submenu-in-a-panel) shares the same Value/Orientation/ Delay/CloseDelay host surface as the root (both derive from NavigationMenuHostBase), but defaults Orientation to "vertical" and renders as a plain ContentControl, not a <nav> landmark equivalent.

Properties

Property	Type	Default	From	Description
`Value`	`string?`	`null`	`NavigationMenuHostBase`	Value of the currently open item; two-way bindable. `null` = nothing open.
`Orientation`	`string`	`"horizontal"`	`NavigationMenuHostBase`	`"horizontal"` or `"vertical"`; drives the List’s roving-focus axis. `NaviusNavigationMenuSub` defaults this to `"vertical"` in its constructor.
`Delay`	`int`	`50`	`NavigationMenuHostBase`	Milliseconds before hover opens an item’s content.
`CloseDelay`	`int`	`50`	`NavigationMenuHostBase`	Milliseconds before leaving the menu closes open content.
`UseSharedViewport`	`bool`	`false`	`NaviusNavigationMenu`	Requests the shared/morphing-viewport layout; not implemented, throws `NotSupportedException` when set `true`.
`Value`	`string`	`""`	`NaviusNavigationMenuItem`	Matched against the ambient host’s open `Value`.
`NativeButton`	`bool`	`true`	`NaviusNavigationMenuTrigger`	Render-contract parity flag only; this is always a native `Button`, so it has no behavioral effect.
`IsOpen`	`bool`	`-`	`NaviusNavigationMenuIcon`	Read-only. Mirrors the owning item’s open state for a template trigger (rotate chevron).
`Href`	`string?`	`null`	`NaviusNavigationMenuLink`	Link target; informational only, no navigation side effect authored here.
`Active`	`bool`	`false`	`NaviusNavigationMenuLink`	Marks the current page: sets `AutomationProperties.ItemStatus="page"`.
`ForceMount`	`bool`	`false`	`NaviusNavigationMenuContent`	Keep the panel mounted while closed; accepted for API parity, no exit-animation phase exists to preserve.
`Side`	`PlacementSide`	`Bottom`	`NaviusNavigationMenuContent`	Positioning knob forwarded to the hosted `NaviusAnchoredPopup`.
`Align`	`PlacementAlign`	`Center`	`NaviusNavigationMenuContent`	-
`SideOffset`	`double`	`0`	`NaviusNavigationMenuContent`	-
`AlignOffset`	`double`	`0`	`NaviusNavigationMenuContent`	-
`IsOpen`	`bool`	`-`	`NaviusNavigationMenuContent`	Read-only. True while this panel is the open one.
`Width` / `Height`	`double`	`10` / `5`	`NaviusNavigationMenuArrow`	Reuses `FrameworkElement`’s own `Width`/`Height`, metadata-overridden.
`KeepMounted`	`bool`	`false`	`NaviusNavigationMenuBackdrop`	Keep the backdrop mounted while closed.
`ForceMount`	`bool`	`false`	`NaviusNavigationMenuViewport`	Accepted for API parity only; inert stub, only meaningful in shared-viewport mode (not implemented).

Methods

Method	Description
`RequestOpen(string value)`	Opens the given item if it is not already open.
`RequestClose(string value)`	Closes the given item if it is the currently open one.
`Toggle(string value)`	Opens the item if closed, closes it if already open.
`RequestOpenViaKeyboard(string value)`	Opens the item and marks it for the APG “enter content” pattern: its Content panel moves focus to its first focusable descendant once open.

All four live on NavigationMenuHostBase, shared by NaviusNavigationMenu and NaviusNavigationMenuSub.

Events

Event	Signature	Fires when
`ValueChanged`	`EventHandler<string?>`	`Value` changes, for any reason.
`OpenChangeComplete`	`EventHandler<bool>`	Fires synchronously right after `Value` changes; this port has no separate presence-transition phase to wait for.
`Select`	`EventHandler<NaviusNavigationMenuSelectEventArgs>`	`NaviusNavigationMenuLink` is activated, before the native click; cancelable via `PreventDefault()` (`Click` still raises).

Keyboard interactions

Key	Behavior
`Tab`	The trigger row is a single roving-tabindex seat: only the open item’s trigger (or the first) is in the Tab order.
`ArrowLeft`/`ArrowRight` (horizontal) or `ArrowUp`/`ArrowDown` (vertical)	`NaviusNavigationMenuList`’s own `PreviewKeyDown` roves focus across Trigger/Link descendants.
`Home` / `End`	Moves focus to the first/last rovable trigger or link.
`Space` / `Enter` (on Trigger)	Toggles this item’s content.
`ArrowDown` (Trigger, orientation=horizontal) / `ArrowRight` (Trigger, orientation=vertical)	“Enter content”: opens the item and moves focus to the first focusable descendant of its panel.
`Escape`	Closes the open item via a window-level `PreviewKeyDown` hook, or `NaviusNavigationMenuContent`’s own local handler when focus is inside that specific popup; focus returns to the trigger.

UIA mechanism

NaviusNavigationMenuTrigger ships a custom NaviusNavigationMenuTriggerAutomationPeer (a ButtonAutomationPeer implementing IExpandCollapseProvider), reflecting and driving the host’s Value; test-exercised. NaviusNavigationMenuBackdrop reuses OverlayBackdrop but registers its own DefaultStyleKey (a subclass that skips this does not reliably resolve the base type’s implicit style). The root (NaviusNavigationMenu/Sub) and the Content panel ship no custom automation peer; their AutomationControlType is left as the default FrameworkElementAutomationPeer inference, pending a cross-family consistency decision. NaviusNavigationMenuLink maps Active to AutomationProperties.ItemStatus="page" as an approximation of aria-current (no exact UIA equivalent).

Web deltas

Scope: only per-item popup mode is implemented. UseSharedViewport=true throws NotSupportedException immediately rather than faking the morph animation; NaviusNavigationMenuViewport is a present-but-inert stub, only meaningful in that unimplemented mode.
The contract’s NaviusNavigationMenuPopup/Positioner/Portal collapse onto NaviusNavigationMenuContent directly: its default template hosts a NaviusAnchoredPopup, with Side/Align/SideOffset/AlignOffset as the only positioning knobs the substrate exposes. Not implemented: Flip/AvoidCollisions as independent toggles (the substrate always flips and shifts), CollisionPadding, Sticky, HideWhenDetached, ArrowPadding, Container (moot; WPF’s Popup already renders outside the normal visual flow).
Captured unmatched attributes (Attributes) are not ported anywhere in this family.
data-activation-direction (a directional enter-animation cue) is not implemented.
Known residual (M6 audit): dismissal is window-hook-based (PreviewMouseDown/ PreviewKeyDown), which cannot see presses landing inside another host’s own open Content panel (a separate, transparent child HWND); a press inside one host’s popup while a different host’s (or a nested Sub’s) popup is open will not auto-close the other. Traces into NaviusAnchoredPopup’s separate-HWND rendering, outside this family’s edit boundary.
NaviusNavigationMenuLink.Active maps to AutomationProperties.ItemStatus="page" as a defensible but approximate stand-in for aria-current="page" (no exact UIA equivalent); noted for cross-family consistency review.

Captures

The Navigation Menu Gallery page rendered at the pinned commit, in each theme.