Presentation

Import these from @grafloria/renderer.

Functions

followPresenter

Slave this host's camera to the presenter's, for as long as the handle is alive.

The follower keeps its OWN canvas size and reconstructs the camera rectangle from the presenter's centre + zoom, so a follower on a different screen size sees the same content correctly framed — and, critically, its clientToWorld() stays the exact inverse of what it renders. Copying the presenter's rectangle wholesale would break that (see viewport-channel.ts).

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function followPresenter(
  host: PresentationHost,
  channel: ViewportChannel,
  options: FollowOptions = {}
): { stop: Unsubscribe }

isDocumentLocked

Is this engine's document locked against edits?

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function isDocumentLocked(engine: DiagramEngine): boolean

loadReadonlySnapshot

Build a READ-ONLY document from a snapshot — the "share a link to a frozen copy" case.

The load runs as a SYSTEM write, so it works even against an engine that is already in presentation mode. Otherwise the order of two host calls would decide whether the share link renders a diagram or an empty canvas: lock-then-load would have the lock (correctly!) refuse every node the loader tried to add.

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function loadReadonlySnapshot(
  engine: DiagramEngine,
  snapshot: SerializedDiagram
): DiagramModel

lockDocument

Lock (or unlock) the document through the engine's own mode.

Thin on purpose: it drives DiagramMode, which this wave finally wired to real enforcement in the model and the CommandManager. There is no second read-only flag here, because a second flag is how you end up with two read-only modes that disagree.

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function lockDocument(engine: DiagramEngine, locked = true): void

presentTo

Broadcast this host's camera to channel for as long as the returned handle is alive. Returns a stop() that unsubscribes and cancels any pending trailing send.

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function presentTo(
  host: PresentationHost,
  channel: ViewportChannel,
  options: PresentOptions = {}
): { stop: Unsubscribe }

Classes

InMemoryViewportChannel

A working, in-process implementation — the local/in-memory transport this card ships so the feature is demonstrably complete end-to-end rather than an interface with nothing behind it.

Genuinely useful beyond tests: it drives two createDiagram() instances on the same page (a presenter canvas and a follower/minimap canvas), which is a real product surface. Swap it for the network implementation and nothing else moves.

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class InMemoryViewportChannel implements ViewportChannel

Methods

• broadcastViewport(viewport: PresenterViewport): void — Publish the presenter's current view to every follower.
• onViewportBroadcast(callback: (viewport: PresenterViewport) => void): Unsubscribe — Subscribe to presenter broadcasts. Returns an unsubscribe function.
• getLast(): PresenterViewport | null — The most recent broadcast, or null.
• dispose(): void — Drop all subscribers (teardown).

Interfaces

FollowOptions

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interface FollowOptions

Properties

PresentationHost

The minimum a host must expose to be presented from / followed. DiagramInstance satisfies it.

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interface PresentationHost

Properties

Members

• render(): void — Queue a repaint.

PresenterViewport

What a presenter broadcasts. Centre + zoom, deliberately NOT a camera rect.

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interface PresenterViewport

Properties

PresentOptions

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interface PresentOptions

Properties

ViewportChannel

The transport seam. Two methods, no lifecycle, no assumptions about the wire. Implement over WebSocket / WebRTC / Yjs awareness / BroadcastChannel / postMessage.

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interface ViewportChannel

Members

• broadcastViewport(viewport: PresenterViewport): void — Publish the presenter's current view to every follower.
• onViewportBroadcast(callback: (viewport: PresenterViewport) => void): Unsubscribe — Subscribe to presenter broadcasts. Returns an unsubscribe function.