WebF Infinite Scrolling

Note: WebF development is nearly identical to web development - you use the same tools (Vite, npm, Vitest), same frameworks (React, Vue, Svelte), and same deployment services (Vercel, Netlify). This skill covers performance optimization for scrolling lists - a WebF-specific pattern that provides native-level performance automatically.

Build high-performance infinite scrolling lists with Flutter-optimized rendering. WebF's WebFListView component automatically handles performance optimizations at the Flutter level, providing smooth 60fps scrolling even with thousands of items.

Why Use WebFListView?

In browsers, long scrolling lists can cause performance issues:

• DOM nodes accumulate (memory consumption)
• Re-renders affect all items (slow updates)
• Intersection observers needed for virtualization
• Complex state management for infinite loading

WebF's solution: WebFListView delegates rendering to Flutter's optimized ListView widget, which:

• ✅ Automatically virtualizes (recycles) views
• ✅ Maintains 60fps scrolling with thousands of items
• ✅ Provides native pull-to-refresh and load-more
• ✅ Zero configuration - optimization happens automatically

Critical Structure Requirement

⚠️ IMPORTANT: For Flutter optimization to work, each list item must be a direct child of WebFListView:

✅ CORRECT: Direct Children

<WebFListView>
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
  {/* Each item is a direct child */}
</WebFListView>

❌ WRONG: Wrapped in Container

<WebFListView>
  <div>
    {/* DON'T wrap items in a container div */}
    <div>Item 1</div>
    <div>Item 2</div>
    <div>Item 3</div>
  </div>
</WebFListView>

Why this matters: Flutter's ListView requires direct children to perform view recycling. If items are wrapped in a container, Flutter sees only one child (the container) and cannot optimize individual items.

React Setup

Installation

npm install @openwebf/react-core-ui

Basic Scrolling List

import { WebFListView } from '@openwebf/react-core-ui';

function ProductList() {
  const products = [
    { id: 1, name: 'Product 1', price: 19.99 },
    { id: 2, name: 'Product 2', price: 29.99 },
    { id: 3, name: 'Product 3', price: 39.99 },
    // ... hundreds or thousands of items
  ];

  return (
    <WebFListView scrollDirection="vertical" shrinkWrap={true}>
      {products.map(product => (
        // ✅ Each item is a direct child
        <div key={product.id} className="product-card">
          <h3>{product.name}</h3>
          <p>${product.price}</p>
        </div>
      ))}
    </WebFListView>
  );
}

Infinite Scrolling with Load More

import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';
import { useRef, useState } from 'react';

function InfiniteList() {
  const listRef = useRef<WebFListViewElement>(null);
  const [items, setItems] = useState([1, 2, 3, 4, 5]);
  const [page, setPage] = useState(1);

  const handleLoadMore = async () => {
    try {
      // Simulate API call
      await new Promise(resolve => setTimeout(resolve, 1000));

      // Fetch next page
      const newItems = Array.from(
        { length: 5 },
        (_, i) => items.length + i + 1
      );

      setItems(prev => [...prev, ...newItems]);
      setPage(prev => prev + 1);

      // Check if there's more data
      const hasMore = page < 10; // Example: 10 pages max

      // Notify WebFListView that loading finished
      listRef.current?.finishLoad(hasMore ? 'success' : 'noMore');
    } catch (error) {
      // Notify failure
      listRef.current?.finishLoad('fail');
    }
  };

  return (
    <WebFListView
      ref={listRef}
      onLoadMore={handleLoadMore}
      scrollDirection="vertical"
      shrinkWrap={true}
    >
      {items.map(item => (
        <div key={item} className="item">
          Item {item}
        </div>
      ))}
    </WebFListView>
  );
}

Pull-to-Refresh

import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';
import { useRef, useState } from 'react';

function RefreshableList() {
  const listRef = useRef<WebFListViewElement>(null);
  const [items, setItems] = useState([1, 2, 3, 4, 5]);

  const handleRefresh = async () => {
    try {
      // Simulate API call
      await new Promise(resolve => setTimeout(resolve, 1000));

      // Fetch fresh data
      const freshItems = [1, 2, 3, 4, 5];
      setItems(freshItems);

      // Notify WebFListView that refresh finished
      listRef.current?.finishRefresh('success');
    } catch (error) {
      // Notify failure
      listRef.current?.finishRefresh('fail');
    }
  };

  return (
    <WebFListView
      ref={listRef}
      onRefresh={handleRefresh}
      scrollDirection="vertical"
      shrinkWrap={true}
    >
      {items.map(item => (
        <div key={item} className="item">
          Item {item}
        </div>
      ))}
    </WebFListView>
  );
}

Combined: Pull-to-Refresh + Infinite Scrolling

import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';
import { useRef, useState } from 'react';

function FeedList() {
  const listRef = useRef<WebFListViewElement>(null);
  const [posts, setPosts] = useState([
    { id: 1, title: 'Post 1', content: 'Content 1' },
    { id: 2, title: 'Post 2', content: 'Content 2' },
    { id: 3, title: 'Post 3', content: 'Content 3' },
  ]);
  const [page, setPage] = useState(1);

  const handleRefresh = async () => {
    try {
      // Fetch latest posts
      const response = await fetch('/api/posts?page=1');
      const freshPosts = await response.json();

      setPosts(freshPosts);
      setPage(1);

      listRef.current?.finishRefresh('success');
    } catch (error) {
      listRef.current?.finishRefresh('fail');
    }
  };

  const handleLoadMore = async () => {
    try {
      const nextPage = page + 1;

      // Fetch next page
      const response = await fetch(`/api/posts?page=${nextPage}`);
      const newPosts = await response.json();

      setPosts(prev => [...prev, ...newPosts]);
      setPage(nextPage);

      // Check if more data exists
      const hasMore = newPosts.length > 0;
      listRef.current?.finishLoad(hasMore ? 'success' : 'noMore');
    } catch (error) {
      listRef.current?.finishLoad('fail');
    }
  };

  return (
    <WebFListView
      ref={listRef}
      onRefresh={handleRefresh}
      onLoadMore={handleLoadMore}
      scrollDirection="vertical"
      shrinkWrap={true}
      style={{ height: '100vh' }}
    >
      {posts.map(post => (
        <article key={post.id} className="post-card">
          <h2>{post.title}</h2>
          <p>{post.content}</p>
        </article>
      ))}
    </WebFListView>
  );
}

Vue Setup

Installation

npm install @openwebf/vue-core-ui

Setup Global Types

In your src/env.d.ts or src/main.ts:

import '@openwebf/vue-core-ui';

Basic Scrolling List

<template>
  <webf-list-view scroll-direction="vertical" :shrink-wrap="true">
    <div v-for="product in products" :key="product.id" class="product-card">
      <h3>{{ product.name }}</h3>
      <p>${{ product.price }}</p>
    </div>
  </webf-list-view>
</template>

<script setup lang="ts">
import { ref } from 'vue';

const products = ref([
  { id: 1, name: 'Product 1', price: 19.99 },
  { id: 2, name: 'Product 2', price: 29.99 },
  { id: 3, name: 'Product 3', price: 39.99 },
]);
</script>

Infinite Scrolling with Load More

<template>
  <webf-list-view
    ref="listRef"
    @loadmore="handleLoadMore"
    scroll-direction="vertical"
    :shrink-wrap="true"
  >
    <div v-for="item in items" :key="item" class="item">
      Item {{ item }}
    </div>
  </webf-list-view>
</template>

<script setup lang="ts">
import { ref } from 'vue';

const listRef = ref<HTMLElement>();
const items = ref([1, 2, 3, 4, 5]);
const page = ref(1);

async function handleLoadMore() {
  try {
    // Simulate API call
    await new Promise(resolve => setTimeout(resolve, 1000));

    // Fetch next page
    const newItems = Array.from(
      { length: 5 },
      (_, i) => items.value.length + i + 1
    );

    items.value.push(...newItems);
    page.value++;

    // Check if there's more data
    const hasMore = page.value < 10;

    // Notify WebFListView
    (listRef.value as any)?.finishLoad(hasMore ? 'success' : 'noMore');
  } catch (error) {
    (listRef.value as any)?.finishLoad('fail');
  }
}
</script>

Pull-to-Refresh

<template>
  <webf-list-view
    ref="listRef"
    @refresh="handleRefresh"
    scroll-direction="vertical"
    :shrink-wrap="true"
  >
    <div v-for="item in items" :key="item" class="item">
      Item {{ item }}
    </div>
  </webf-list-view>
</template>

<script setup lang="ts">
import { ref } from 'vue';

const listRef = ref<HTMLElement>();
const items = ref([1, 2, 3, 4, 5]);

async function handleRefresh() {
  try {
    // Simulate API call
    await new Promise(resolve => setTimeout(resolve, 1000));

    // Fetch fresh data
    items.value = [1, 2, 3, 4, 5];

    // Notify WebFListView
    (listRef.value as any)?.finishRefresh('success');
  } catch (error) {
    (listRef.value as any)?.finishRefresh('fail');
  }
}
</script>

Props and Configuration

WebFListView Props

Ref Methods (React) / Element Methods (Vue)

Result Values

• 'success' - Operation succeeded, more data available
• 'fail' - Operation failed (shows error state)
• 'noMore' - No more data to load (hides footer/shows "no more" message)

Common Patterns

Pattern 1: Search with Results List

import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';
import { useRef, useState } from 'react';

function SearchResults() {
  const listRef = useRef<WebFListViewElement>(null);
  const [query, setQuery] = useState('');
  const [results, setResults] = useState([]);

  const handleSearch = async (searchQuery: string) => {
    setQuery(searchQuery);

    // Fetch search results
    const response = await fetch(`/api/search?q=${searchQuery}`);
    const data = await response.json();

    setResults(data.results);
  };

  const handleLoadMore = async () => {
    try {
      const response = await fetch(
        `/api/search?q=${query}&offset=${results.length}`
      );
      const data = await response.json();

      setResults(prev => [...prev, ...data.results]);

      listRef.current?.finishLoad(
        data.results.length > 0 ? 'success' : 'noMore'
      );
    } catch (error) {
      listRef.current?.finishLoad('fail');
    }
  };

  return (
    <div>
      <input
        type="text"
        placeholder="Search..."
        onChange={(e) => handleSearch(e.target.value)}
      />

      <WebFListView
        ref={listRef}
        onLoadMore={handleLoadMore}
        scrollDirection="vertical"
        shrinkWrap={true}
      >
        {results.map(result => (
          <div key={result.id} className="search-result">
            {result.title}
          </div>
        ))}
      </WebFListView>
    </div>
  );
}

Pattern 2: Chat Messages (Reverse List)

For chat-style UIs where new messages appear at the bottom:

import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';
import { useRef, useState, useEffect } from 'react';

function ChatMessages() {
  const listRef = useRef<WebFListViewElement>(null);
  const [messages, setMessages] = useState([
    { id: 1, text: 'Hello', timestamp: Date.now() },
    { id: 2, text: 'Hi there!', timestamp: Date.now() },
  ]);

  // Load older messages when scrolling to top
  const handleLoadMore = async () => {
    try {
      // In real app, fetch older messages before first message
      const oldestId = messages[0]?.id;
      const response = await fetch(`/api/messages?before=${oldestId}`);
      const olderMessages = await response.json();

      // Prepend older messages
      setMessages(prev => [...olderMessages, ...prev]);

      listRef.current?.finishLoad(
        olderMessages.length > 0 ? 'success' : 'noMore'
      );
    } catch (error) {
      listRef.current?.finishLoad('fail');
    }
  };

  return (
    <WebFListView
      ref={listRef}
      onLoadMore={handleLoadMore}
      scrollDirection="vertical"
      shrinkWrap={true}
      style={{
        height: '100vh',
        display: 'flex',
        flexDirection: 'column-reverse' // Reverse order
      }}
    >
      {messages.map(message => (
        <div key={message.id} className="message">
          {message.text}
        </div>
      ))}
    </WebFListView>
  );
}

Pattern 3: Horizontal Scrolling Gallery

import { WebFListView } from '@openwebf/react-core-ui';

function ImageGallery({ images }) {
  return (
    <WebFListView
      scrollDirection="horizontal"
      shrinkWrap={true}
      style={{
        display: 'flex',
        height: '200px',
        gap: '10px'
      }}
    >
      {images.map(image => (
        <img
          key={image.id}
          src={image.url}
          alt={image.title}
          style={{
            width: '150px',
            height: '150px',
            objectFit: 'cover',
            flexShrink: 0  // Prevent shrinking
          }}
        />
      ))}
    </WebFListView>
  );
}

Common Mistakes

Mistake 1: Wrapping Items in Container

// ❌ WRONG - Items wrapped in container div
<WebFListView>
  <div className="items-container">
    {items.map(item => <div key={item}>{item}</div>)}
  </div>
</WebFListView>

// ✅ CORRECT - Items are direct children
<WebFListView>
  {items.map(item => <div key={item}>{item}</div>)}
</WebFListView>

Why: Flutter's ListView needs direct children for view recycling to work.

Mistake 2: Forgetting to Call finishLoad/finishRefresh

// ❌ WRONG - Never calls finishLoad
const handleLoadMore = async () => {
  const data = await fetchData();
  setItems(prev => [...prev, ...data]);
  // finishLoad never called - loading indicator stuck!
};

// ✅ CORRECT - Always call finishLoad
const handleLoadMore = async () => {
  try {
    const data = await fetchData();
    setItems(prev => [...prev, ...data]);
    listRef.current?.finishLoad('success');
  } catch (error) {
    listRef.current?.finishLoad('fail');
  }
};

Mistake 3: Not Handling "No More Data" State

// ❌ WRONG - Always calls 'success', even when no data
const handleLoadMore = async () => {
  const data = await fetchData();
  setItems(prev => [...prev, ...data]);
  listRef.current?.finishLoad('success'); // Wrong if data is empty!
};

// ✅ CORRECT - Check if more data exists
const handleLoadMore = async () => {
  const data = await fetchData();
  setItems(prev => [...prev, ...data]);

  // Tell WebFListView there's no more data
  listRef.current?.finishLoad(data.length > 0 ? 'success' : 'noMore');
};

Mistake 4: Timeout Issues (Taking Too Long)

WebFListView has a 4-second timeout for refresh/load operations. If your operation takes longer, it will auto-fail.

// ❌ WRONG - Operation takes 10 seconds (will timeout)
const handleRefresh = async () => {
  await new Promise(resolve => setTimeout(resolve, 10000)); // 10s
  listRef.current?.finishRefresh('success'); // Too late!
};

// ✅ CORRECT - Complete within 4 seconds
const handleRefresh = async () => {
  try {
    // Use Promise.race to enforce timeout
    await Promise.race([
      fetchData(),
      new Promise((_, reject) =>
        setTimeout(() => reject(new Error('Timeout')), 3500)
      )
    ]);
    listRef.current?.finishRefresh('success');
  } catch (error) {
    listRef.current?.finishRefresh('fail');
  }
};

Performance Tips

1. Use Keys Correctly

Always provide unique, stable keys for list items:

// ✅ GOOD - Stable ID from data
{items.map(item => <div key={item.id}>{item.name}</div>)}

// ❌ BAD - Index as key (can cause bugs with dynamic lists)
{items.map((item, index) => <div key={index}>{item.name}</div>)}

2. Avoid Heavy Computations in Render

// ❌ BAD - Heavy computation on every render
<WebFListView>
  {items.map(item => (
    <div key={item.id}>
      {expensiveCalculation(item)} {/* Calculated on every render! */}
    </div>
  ))}
</WebFListView>

// ✅ GOOD - Memoize or pre-calculate
const processedItems = useMemo(
  () => items.map(item => ({ ...item, computed: expensiveCalculation(item) })),
  [items]
);

<WebFListView>
  {processedItems.map(item => (
    <div key={item.id}>{item.computed}</div>
  ))}
</WebFListView>

3. Optimize Item Components

// ✅ GOOD - Memoized item component
const ListItem = memo(({ item }) => (
  <div className="item">
    <h3>{item.title}</h3>
    <p>{item.description}</p>
  </div>
));

function MyList({ items }) {
  return (
    <WebFListView>
      {items.map(item => (
        <ListItem key={item.id} item={item} />
      ))}
    </WebFListView>
  );
}

4. Set Explicit Height for Scrolling

For full-screen lists, set explicit height:

<WebFListView
  style={{
    height: '100vh', // or specific pixel value
    overflow: 'auto'
  }}
>
  {/* items */}
</WebFListView>

Debugging

Check if finishLoad/finishRefresh is Called

Add logging to verify callbacks execute:

const handleLoadMore = async () => {
  console.log('🔄 Load more started');

  try {
    const data = await fetchData();
    setItems(prev => [...prev, ...data]);

    console.log('✅ Load more finished:', data.length, 'items');
    listRef.current?.finishLoad(data.length > 0 ? 'success' : 'noMore');
  } catch (error) {
    console.error('❌ Load more failed:', error);
    listRef.current?.finishLoad('fail');
  }
};

Verify Direct Children Structure

Use React DevTools or Vue DevTools to inspect the rendered structure. Ensure items are direct children of <webf-listview>:

<!-- ✅ CORRECT structure in DevTools -->
<webf-listview>
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</webf-listview>

<!-- ❌ WRONG structure in DevTools -->
<webf-listview>
  <div class="wrapper">
    <div>Item 1</div>
    <div>Item 2</div>
  </div>
</webf-listview>

Resources

• React Core UI Package: /Users/andycall/workspace/webf/packages/react-core-ui/README.md
• Vue Core UI Package: /Users/andycall/workspace/webf/packages/vue-core-ui/README.md
• Complete Examples: See examples.md in this skill
• npm Packages:
  • https://www.npmjs.com/package/@openwebf/react-core-ui
  • https://www.npmjs.com/package/@openwebf/vue-core-ui

Key Takeaways

✅ DO:

• Use WebFListView for long scrolling lists
• Make each item a direct child (not wrapped in container)
• Always call finishLoad / finishRefresh after operations
• Use 'noMore' result when no more data exists
• Provide unique, stable keys for list items
• Set explicit height for full-screen lists

❌ DON'T:

• Wrap items in a container div
• Forget to call finish methods (loading indicator gets stuck)
• Use index as key for dynamic lists
• Let operations exceed 4-second timeout
• Use heavy computations in render without memoization
• Expect browser-style virtualization libraries (not needed!)

Quick Reference

# Install packages
npm install @openwebf/react-core-ui  # React
npm install @openwebf/vue-core-ui    # Vue

// React - Basic pattern
import { WebFListView, WebFListViewElement } from '@openwebf/react-core-ui';

const listRef = useRef<WebFListViewElement>(null);

<WebFListView
  ref={listRef}
  onRefresh={async () => {
    await refreshData();
    listRef.current?.finishRefresh('success');
  }}
  onLoadMore={async () => {
    const hasMore = await loadMore();
    listRef.current?.finishLoad(hasMore ? 'success' : 'noMore');
  }}
>
  {items.map(item => <div key={item.id}>{item.name}</div>)}
</WebFListView>

<!-- Vue - Basic pattern -->
<webf-list-view
  ref="listRef"
  @refresh="handleRefresh"
  @loadmore="handleLoadMore"
>
  <div v-for="item in items" :key="item.id">{{ item.name }}</div>
</webf-list-view>