com.canonical.dbusmenu

The menu protocol paired with org.kde.StatusNotifierItem. UDA implements it in crates/uda-platform-linux/src/tray.rs; the exported object path is /MenuBar.

Layout node

Every node is a four-field tuple with the wire signature (ia{sv}ia{sv}v):

Field	Type	Contents
0	`i`	item id
1	`a{sv}`	property map
2	`ia{sv}`	child nodes (id + properties each, wrapped in a variant)
3	`v`	icon payload — always an empty structure for UDA

The root carries id 0 and no properties. Ids start at 1, because 0 is the protocol’s root sentinel.

Property map

Key	Value	Notes
`type`	`"standard"` / `"separator"`	a separator carries no label
`label`	string	omitted for separators
`enabled`	bool
`visible`	bool	always `true`; hiding is done by removing the row
`toggle-type`	`"checkmark"`	present only for checkbox rows — this is what makes a shell draw a real checkbox
`toggle-state`	`int`	`0` / `1`, checkbox value
`children-display`	`"submenu"`	present when the row has children

Id allocation

Ids come from a single monotonic sequence shared by the whole tree, including nested submenus. A submenu allocates its own id first, then its children, so each submenu owns a contiguous id range.

The sequence saturates rather than wrapping: a wrapped counter would alias a live row, and the shell would address the wrong one.

Methods

Method	Behaviour
`GetLayout(parentId, recursionDepth, propertyNames)`	Returns `(revision, rootNode)`. A depth of 0 means “unlimited”. With no menu attached, an empty root is returned rather than an error, so the shell renders nothing.
`GetGroupProperties(ids, propertyNames)`	Returns the `(id, props)` pairs for the requested ids, filtered to the requested names. An empty name list means “all”.
`GetProperty(id, name)`	A single property. An unknown id, an unknown name, or no menu at all is an `InvalidArgs` error.
`Event(id, eventId, data, timestamp)`	A shell-reported interaction. Only `clicked` is acted on; `hovered` is logged and dropped.
`EventGroup(events)`	A batched variant, applied sequentially — the protocol requires the events in order.
`AboutToShow(id)`	Always `true`: rows are snapshotted per call, so a re-read is cheap and the shell can never show a stale submenu.

Signals

ItemsPropertiesUpdated, LayoutUpdated(revision, parentId) and ItemActivationRequested are declared. UDA emits LayoutUpdated whenever the layout changes, because the shell cannot otherwise know to re-read.

Click dispatch

A row’s callback is captured into the layout snapshot at export time. When Event arrives, the row is looked up by id in that snapshot and the stored closure is invoked — never a re-walk of the host’s live TrayMenu, which may have been mutated since the layout was exported. This is what keeps a click addressed to the row the user actually saw.

The callback runs after the state lock is dropped: holding a guard across host code would stall every other D-Bus request.