Comments & replies

Any annotation can carry a comment, its contents, and people can reply to it. Together they make a thread: the first comment and its replies, in order. useCommentThreads() gives you every thread in the document, ready for a sidebar:

sidebar.svelte

<script lang="ts">
  import { annotationKey, useCommentThreads } from '@embedpdf/svelte/annotation';

  const threads = useCommentThreads();
</script>

{#each threads.current as thread (annotationKey(thread.root.ref))}
  <article>
    <p>{thread.root.author}, page {thread.pageLabel}: {thread.root.contents}</p>
    {#each thread.replies as reply (annotationKey(reply.ref))}
      <p>{reply.author}: {reply.contents}</p>
    {/each}
  </article>
{/each}

Loading live preview…

<script lang="ts" module>
  import { DocumentGate, Viewer, type OpenInput } from '@embedpdf/svelte/runtime';
  import { Stage, stagePlugin } from '@embedpdf/svelte/stage';
  import { RenderLayer, renderPlugin } from '@embedpdf/svelte/render';
  import { interactionPlugin } from '@embedpdf/svelte/interaction';
  import { AnnotationLayer, annotationPlugin } from '@embedpdf/svelte/annotation';
  import { localEngine } from '@embedpdf/engine';
  import AddComments from './AddComments.svelte';
  import Comments from './Comments.svelte';

  import '../comments.css';

  const engine = localEngine();
  const plugins = [stagePlugin(), renderPlugin(), interactionPlugin(), annotationPlugin()];

  const ebook = async (): Promise<OpenInput> => {
    const response = await fetch('https://snippet.embedpdf.com/ebook.pdf');
    return { kind: 'bytes', id: 'ebook', bytes: new Uint8Array(await response.arrayBuffer()) };
  };
</script>

<Viewer
  {engine}
  {plugins}
  identity={{ userId: 'u_381', displayName: 'Dana Smith' }}
  initialDocuments={[{ source: ebook }]}
>
  <DocumentGate>
    {#snippet fallback()}
      <p class="loading">Loading…</p>
    {/snippet}
    <AddComments />
    <div class="viewer">
      <Stage class="stage">
        <RenderLayer />
        <AnnotationLayer />
      </Stage>
      <Comments />
    </div>
  </DocumentGate>
</Viewer>

Try it: reply to a thread, or press Show to go to its comment. Add a note on the page: it gets a thread of its own.

Threads come in reading order: by page, then from the top of the page. The list updates by itself when anyone adds, changes or deletes a comment, on this screen or, on a shared document, on someone else’s.

A thread has:

Field	What it is
`root`	The annotation that starts the thread: a note, a highlight, a shape.
`replies`	Every reply, oldest first. Replies to replies are included.
`review`	The review states people set, such as accepted or rejected (see Review states).
`page`	The page it’s on.
`pageLabel`	The page’s label to show, such as `'iv'` or `'7'`.

Reply, edit and delete#

const { annotation: reply } = await comments.reply(thread.root.ref, 'Checked, looks right.');
await comments.setText(reply.ref, 'Checked against the invoice, looks right.');
await comments.delete(reply.ref); // one comment
await comments.deleteThread(thread.root.ref); // the whole thread

A reply always goes to the thread’s first comment, whichever comment you pass. It’s saved the way Acrobat saves replies, so they show up as replies there too.

Deleting the first comment of a thread deletes the whole thread, as Acrobat does. deleteThread() does the same, all or nothing, and tells you what happened: when the thread has a comment you may not delete, such as someone else’s reply, nothing is deleted and failed lists what stopped it.

Review states#

A review state is a verdict on a thread: accepted, rejected, cancelled or completed. Each person sets their own, and a check mark is separate:

await comments.setStatus(thread.root.ref, 'accepted');
await comments.setMarked(thread.root.ref, true); // check it off
 
thread.review.lastChange?.state; // the latest verdict, from anyone
thread.review.byReviewer; // each person's latest verdict
thread.review.markedBy; // who has checked it off

States are saved as the PDF’s own review states, so Acrobat shows them in its comment list.

Loading live preview…

<script lang="ts" module>
  import { DocumentGate, Viewer, type OpenInput } from '@embedpdf/svelte/runtime';
  import { Stage, stagePlugin } from '@embedpdf/svelte/stage';
  import { RenderLayer, renderPlugin } from '@embedpdf/svelte/render';
  import { interactionPlugin } from '@embedpdf/svelte/interaction';
  import { AnnotationLayer, annotationPlugin } from '@embedpdf/svelte/annotation';
  import { localEngine } from '@embedpdf/engine';
  import AddNotes from './AddNotes.svelte';
  import Reviews from './Reviews.svelte';

  import '../review.css';

  const engine = localEngine();
  const plugins = [stagePlugin(), renderPlugin(), interactionPlugin(), annotationPlugin()];

  const ebook = async (): Promise<OpenInput> => {
    const response = await fetch('https://snippet.embedpdf.com/ebook.pdf');
    return { kind: 'bytes', id: 'ebook', bytes: new Uint8Array(await response.arrayBuffer()) };
  };
</script>

<Viewer
  {engine}
  {plugins}
  identity={{ userId: 'u_381', displayName: 'Dana Smith' }}
  initialDocuments={[{ source: ebook }]}
>
  <DocumentGate>
    {#snippet fallback()}
      <p class="loading">Loading…</p>
    {/snippet}
    <AddNotes />
    <div class="viewer">
      <Stage class="stage">
        <RenderLayer />
        <AnnotationLayer />
      </Stage>
      <Reviews />
    </div>
  </DocumentGate>
</Viewer>

Jump to a comment#

The thread’s root has a page and a rect, which is where the view should go:

jump.svelte

<script lang="ts">
  import { useAnnotation, type CommentThread } from '@embedpdf/svelte/annotation';
  import { useStage } from '@embedpdf/svelte/stage';

  let { thread }: { thread: CommentThread } = $props();

  const stage = useStage();
  const annotation = useAnnotation();

  function show() {
    stage.reveal(thread.page, { rect: thread.root.rect });
    annotation.selection.set([thread.root.ref]); // and select it
  }
</script>

<button onclick={show}>Show</button>

Methods#

Everything useComments() gives you. It’s the comments part of useAnnotation().

Method	What it does
`listThreads()`	Every thread, in reading order. In a component, use `useCommentThreads()`, which also gives each thread its `pageLabel`.
`getThread(ref)`	The thread a comment is in, whether you pass its first comment, a reply or a review state, or `null`. In a component, use `useCommentThread(ref)`.
`reply(ref, text)`	Replies to the thread’s first comment, whichever comment you pass. Resolves `{ annotation }`. Reply, edit and delete
`setText(ref, text)`	Changes a comment’s text
`delete(ref)`	Deletes a comment with its replies. The first comment of a thread deletes the whole thread.
`deleteThread(ref)`	Deletes a whole thread, all or nothing. Resolves `{ deleted, failed }`: when a comment in it may not be deleted, nothing goes and `failed` lists it.
`setStatus(ref, state)`	Sets the user’s review state on a thread, such as `'accepted'` or `'rejected'`. Review states
`setMarked(ref, marked)`	Checks a thread off for the user, or clears the check mark
`canReply(ref)`, `canSetText(ref)`, `canDelete(ref)`, `canDeleteThread(ref)`, `canSetStatus(ref)`, `canSetMarked(ref)`	Whether the user may do that to this comment. Permissions

Every method that returns a promise also takes a signal in its options, to cancel it.

Events#

events.svelte

<script lang="ts">
  import { useAnnotationEvent } from '@embedpdf/svelte/annotation';
  import { notifyThreadAuthor } from './notifications'; // your own

  useAnnotationEvent(
    (annotation) => annotation.comments.onThreadChanged,
    ({ rootRef, change }) => change === 'reply' && notifyThreadAuthor(rootRef),
  );
</script>

<aside><!-- … --></aside>

Event	Fires when	Carries
`comments.onThreadChanged`	A thread changed through this viewer	`rootRef`, `change`

change is 'reply', 'text', 'status', 'marked' or 'deleted'. For every change, including other people’s, use the annotation events; see Events, saving & sharing.

Permissions#

Every comment verb has a check that answers for one comment, so you show only the buttons that work:

permissions.svelte

<script lang="ts">
  import { useComments, type CommentThread } from '@embedpdf/svelte/annotation';

  let { thread }: { thread: CommentThread } = $props();
  const comments = useComments();
</script>

<button disabled={!comments.canReply(thread.root.ref)}>Reply</button>
<button disabled={!comments.canDeleteThread(thread.root.ref)}>Delete thread</button>

Permission	What it allows	Check
`annotations:create`	Replying, setting a review state, checking a comment off	`canReply(ref)`, `canSetStatus(ref)`, `canSetMarked(ref)`
`annotations:update`	Changing a comment’s text	`canSetText(ref)`
`annotations:delete`	Deleting a comment, or every comment in a thread	`canDelete(ref)`, `canDeleteThread(ref)`

A review state and a check mark are small replies of their own, the way Acrobat stores them, so they need the right to create, not to change. The checks also follow the comment’s own flags: lockedContents stops text edits, and locked stops deleting.

Good to know#

Comments without a note#

Any annotation can start a thread. A highlight with a comment is a thread whose root is the highlight. A plain note (the note tool) is a thread with an icon on the page.

Loading#

The status from useAnnotationState() is 'loading' until every annotation is in. Show a loading state in your sidebar until then, so an empty list doesn’t look like “no comments”.

Reviewing together#

On the local engine, a review stays with the file: the next person sees the comments once they have the downloaded PDF.

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