Framework Comparison

This guide helps you understand the differences between React and Svelte when using Annota.

Quick Reference

Imports

React

import {
  AnnotaProvider,
  Viewer as AnnotaViewer,
  Annotator,
  AnnotationPopup,
} from "annota/react";

import {
  useAnnotator,
  useAnnotations,
  useSelection,
  useTool,
} from "annota/react";

Svelte

<script>
  import {
    AnnotaProvider,
    Viewer as AnnotaViewer,
    Annotator,
    Popup,
  } from "annota/svelte";

  import {
    getAnnotator,
    annotations,
    selection,
    tool,
  } from "annota/svelte";
</script>

State Management

Accessing the Annotator

React

import { useAnnotator } from "annota/react";

function MyComponent() {
  const annotator = useAnnotator();

  if (!annotator) return null;

  return <div>Annotations: {annotator.state.store.all().length}</div>;
}

Svelte

<script>
  import { getAnnotator } from "annota/svelte";

  const getAnnotatorFn = getAnnotator();
  const annotator = $derived(getAnnotatorFn());
</script>

{#if annotator}
  <div>Annotations: {annotator.state.store.all().length}</div>
{/if}

Getting All Annotations

React

import { useAnnotations } from "annota/react";

function AnnotationList() {
  const annotations = useAnnotations();

  return (
    <ul>
      {annotations.map((ann) => (
        <li key={ann.id}>{ann.shape.type}</li>
      ))}
    </ul>
  );
}

Svelte

<script>
  import { annotations } from "annota/svelte";

  const allAnnotations = annotations();
</script>

<ul>
  {#each allAnnotations as ann (ann.id)}
    <li>{ann.shape.type}</li>
  {/each}
</ul>

Getting Selection

React

import { useSelection } from "annota/react";

function SelectionInfo() {
  const selection = useSelection();

  return <p>Selected: {selection.length}</p>;
}

Svelte

<script>
  import { selection } from "annota/svelte";

  const selectedAnnotations = selection();
</script>

<p>Selected: {selectedAnnotations.length}</p>

Tools

Activating a Tool

React

import { useTool } from "annota/react";
import { RectangleTool } from "annota/tools";

function ToolController({ viewer }) {
  const tool = new RectangleTool();

  useTool({
    viewer,
    handler: tool,
    enabled: true,
  });

  return null;
}

Svelte

<script>
  import { tool } from "annota/svelte";
  import { RectangleTool } from "annota/tools";

  let viewer = $state(null);

  const rectTool = $derived(new RectangleTool());

  $effect(() => {
    if (!viewer) return;

    tool({
      viewer: () => viewer,
      handler: () => rectTool,
      enabled: () => true,
    });
  });
</script>

Component Structure

Provider Setup

React

import { AnnotaProvider, Viewer as AnnotaViewer, Annotator } from "annota/react";

function App() {
  const [viewer, setViewer] = useState(null);

  return (
    <AnnotaProvider slideId="my-slide">
      <AnnotaViewer onViewerReady={setViewer} />
      <Annotator viewer={viewer} />
    </AnnotaProvider>
  );
}

Svelte

<script>
  import { AnnotaProvider, Viewer, Annotator } from "annota/svelte";

  let viewer = $state(null);
</script>

<AnnotaProvider slideId="my-slide">
  <Viewer onViewerReady={(v) => viewer = v} />
  {#if viewer}
    <Annotator {viewer} />
  {/if}
</AnnotaProvider>

Syntax Differences

Conditional Rendering

React	Svelte
{condition && <Component />}	{#if condition}<Component />{/if}
{condition ? <A /> : <B />}	{#if condition}<A />{:else}<B />{/if}
{!condition && <Component />}	{#if !condition}<Component />{/if}

Lists

React	Svelte
{items.map(item => <div key={item.id}>{item.name}</div>)}	{#each items as item (item.id)}<div>{item.name}</div>{/each}
Use key prop for keys	Use (item.id) for keys

State

React	Svelte
const [state, setState] = useState()	let state = $state()
const memo = useMemo(() => ..., [deps])	const memo = $derived(...)
useEffect(() => ..., [deps])	$effect(() => ...)
useCallback(fn, [deps])	Function declarations (no deps)

Common Patterns

Loading Annotations on Mount

React

import { useAnnotator } from "annota/react";
import { useEffect } from "react";

function LoadAnnotations({ slideId }) {
  const annotator = useAnnotator();

  useEffect(() => {
    if (!annotator) return;

    fetch(`/api/annotations/${slideId}`)
      .then(res => res.json())
      .then(anns => annotator.addAnnotations(anns));
  }, [annotator, slideId]);

  return null;
}

Svelte

<script>
  import { onMount } from "svelte";
  import { getAnnotator } from "annota/svelte";

  const { slideId } = $props();
  const getAnnotatorFn = getAnnotator();
  const annotator = $derived(getAnnotatorFn());

  onMount(() => {
    if (!$annotator) return;

    fetch(`/api/annotations/${slideId}`)
      .then(res => res.json())
      .then(anns => $annotator.addAnnotations(anns));
  });
</script>

Custom Styling Function

React

<Annotator
  viewer={viewer}
  style={(annotation) => ({
    fill: annotation.properties?.type === "tumor" ? "#FF0000" : "#00FF00",
    fillOpacity: 0.3,
  })}
/>

Svelte

<script>
  function getStyle(annotation) {
    return {
      fill: annotation.properties?.type === "tumor" ? "#FF0000" : "#00FF00",
      fillOpacity: 0.3,
    };
  }
</script>

<Annotator {viewer} style={getStyle} />

Migration Guide

From React to Svelte

1. Replace hooks with stores:

   • useAnnotator() → getAnnotator()() with $derived
   • useAnnotations() → annotations()
   • useSelection() → selection()

2. Update state syntax:

   • useState() → $state()
   • useMemo() → $derived()
   • useEffect() → $effect()

3. Change JSX to Svelte syntax:

   • className → class
   • style={{...}} → style="..."
   • onClick={...} → onclick={...}

4. Update imports:

   • from "annota/react" → from "annota/svelte"

From Svelte to React

1. Replace stores with hooks:

   • annotations() → useAnnotations()
   • selection() → useSelection()
   • getAnnotator()() → useAnnotator()

2. Update state syntax:

   • $state() → useState()
   • $derived() → useMemo()
   • $effect() → useEffect()

3. Change Svelte syntax to JSX:

   • class → className
   • onclick → onClick
   • {#if} → {&&} or ternary

4. Update imports:

   • from "annota/svelte" → from "annota/react"

See Also

• React Quick Start
• Svelte Quick Start
• React Hooks API
• Svelte Stores API