DragContext

Interface: DragContext

Immutable context object describing the current drag operation.

A DragContext provides a stable, serializable view of MosaicJS’s internal drag state at a specific moment in time.

It is passed to lifecycle hooks and emitted with relevant events to allow external systems to observe drag behavior safely.

Remarks

A DragContext is read-only and frozen at creation time.
It represents a snapshot of state, not a live reference.
Consumers must not attempt to mutate or persist this object.

The shape of DragContext is considered part of MosaicJS’s stable public API.

Properties

activeNodeId

readonly activeNodeId: string | null;

Defined in: drag/context.ts:25

Currently dragged node ID, or null when idle

dropTargetId

readonly dropTargetId: string | null;

Defined in: drag/context.ts:28

Resolved drop target node ID, or null when none

groupId

readonly groupId: string | null;

Defined in: drag/context.ts:66

The active node’s group container id (#13’s convention), or null when ungrouped or selectors.group isn’t configured (#18).

Remarks

Sourced from the same value Mosaic.setState already forwards as its groupId argument — this field threads that same value into the DragContext seen by lifecycle hooks, which previously had no access to it.

hasSnapshot

readonly hasSnapshot: boolean;

Defined in: drag/context.ts:40

Whether a drag snapshot currently exists

mosaicInstanceId

readonly mosaicInstanceId: string;

Defined in: drag/context.ts:54

Uniquely identifies the originating Mosaic instance (#18).

Remarks

Unlike DragContext.mosaicRootId — which is derived from the root element’s DOM id and is not guaranteed unique (multiple pages, SPA route re-renders, or simple author oversight can collide) — mosaicInstanceId is generated once at Mosaic construction time and is guaranteed distinct across instances on the same page. Consumers observing multiple Mosaic instances should filter by this field, not mosaicRootId.