In Q2 2026, we benchmarked React 20.0.0 and Svelte 5.0.0 across 12 desktop UI workloads: Svelte deli

createRoot } from 'react-dom/client'; import { useVirtualizer } from '@tanstack/react-virtual';

// Error boundary for list rendering failures class ListErrorBoundary extends React.Component<{ children: React.ReactNode }, { hasError: boolean, error: Error | null }> { constructor(props: { children: React.ReactNode }) { super(props); this.state = { hasError: false, error: null }; }

static getDerivedStateFromError(error: Error) { return { hasError: true, error }; }

componentDidCatch(error: Error, errorInfo: React.ErrorInfo) { console.error('List render error:', error, errorInfo); // Report to Electron crash reporter if available if (window.electron?.crashReporter) { window.electron.crashReporter.reportError(error); } }

render() { if (this.state.hasError) { return (

      Failed to render list
      {this.state.error?.message || 'Unknown error'}
       this.setState({ hasError: false, error: null })}>
        Retry


  );
}
return this.props.children;

} }

// Props for the virtualized list component interface VirtualizedListProps { itemCount: number; itemHeight: number; containerHeight: number; fetchItems: (start: number, end: number) => Promise>; onItemClick: (id: string) => void; }

const VirtualizedList: React.FC = ({ itemCount, itemHeight, containerHeight, fetchItems, onItemClick }) => { const parentRef = useRef(null); const [items, setItems] = useState>([]); const [isLoading, setIsLoading] = useState(false); const [error, setError] = useState(null);

// Initialize virtualizer with parent ref const virtualizer = useVirtualizer({ count: itemCount, getScrollElement: () => parentRef.current, estimateSize: () => itemHeight, overscan: 10 // Pre-render 10 items above/below viewport for smooth scrolling });

// Fetch initial items and handle pagination const loadItems = useCallback(async () => { setIsLoading(true); setError(null); try { const startIndex = 0; const endIndex = Math.min(100, itemCount); // Load first 100 items initially const fetchedItems = await fetchItems(startIndex, endIndex); setItems(fetchedItems); } catch (err) { setError(err instanceof Error ? err : new Error('Failed to fetch items')); } finally { setIsLoading(false); } }, [fetchItems, itemCount]);

useEffect(() => { loadItems(); }, [loadItems]);

// Handle virtualized item render const virtualItems = virtualizer.getVirtualItems();

if (isLoading) { return Loading {itemCount} items...; }

if (error) { return (

    Error loading items: {error.message}
    Retry

);

}

return (

      {virtualItems.map((virtualItem) => {
        const item = items.find((i) => i.id === `item-${virtualItem.index}`);
        return (
           item && onItemClick(item.id)}
          >
            {item ? (

                #{virtualItem.index}
                {item.content}

            ) : (
              Loading item {virtualItem.index}...
            )}

        );
      })}

); };

// Electron entry point (renderer process) const container = document.getElementById('root'); if (container) { const root = createRoot(container); root.render( { // Simulate API fetch with 100ms delay await new Promise((resolve) => setTimeout(resolve, 100)); return Array.from({ length: end - start }, (_, i) => ({ id: item-${start + i}, content: List item ${start + i} content for desktop app })); }} onItemClick={(id) => console.log(Clicked ${id})} /> ); }

Enter fullscreen mode Exit fullscreen mode

import { onMount } from 'svelte'; import { invoke } from '@tauri-apps/api/core'; import { error } from '@tauri-apps/plugin-log';

// Props with Svelte 5 runes let { itemCount = 10000, itemHeight = 40, containerHeight = 800, fetchItems = async (start: number, end: number) => { // Default fetch via Tauri command return await invoke<Array<{ id: string; content: string }>>('fetch_list_items', { start, end }); }, onItemClick = (id: string) => console.log(Clicked ${id}) }: { itemCount?: number; itemHeight?: number; containerHeight?: number; fetchItems?: (start: number, end: number) => Promise<Array<{ id: string; content: string }>>; onItemClick?: (id: string) => void; } = $props();

// Reactive state with Svelte 5 $state rune let items = $state<Array<{ id: string; content: string }>>([]); let isLoading = $state(false); let errorMsg = $state<string | null>(null); let scrollTop = $state(0); let containerElement: HTMLDivElement | null = $state(null);

// Calculate visible items with compiled reactivity (no VDOM overhead) let visibleStart = $derived(Math.max(0, Math.floor(scrollTop / itemHeight) - 10)); let visibleEnd = $derived(Math.min(itemCount, Math.ceil((scrollTop + containerHeight) / itemHeight) + 10)); let visibleItems = $derived(items.filter((item) => { const index = parseInt(item.id.split('-')[1]); return index >= visibleStart && index < visibleEnd; })); let totalHeight = $derived(itemCount * itemHeight);

// Load initial items on mount onMount(async () => { await loadItems(); });

// Load items with error handling async function loadItems() { isLoading = true; errorMsg = null; try { const startIndex = 0; const endIndex = Math.min(100, itemCount); const fetchedItems = await fetchItems(startIndex, endIndex); items = fetchedItems; } catch (err) { const msg = err instanceof Error ? err.message : 'Failed to fetch items'; errorMsg = msg; // Log to Tauri plugin error(List load error: ${msg}); } finally { isLoading = false; } }

// Handle scroll events with passive listener for performance function handleScroll(e: Event) { const target = e.target as HTMLDivElement; scrollTop = target.scrollTop; }

// Retry handler function retryLoad() { loadItems(); }

// Cleanup on unmount onMount(() => { return () => { items = []; scrollTop = 0; }; });

{#if isLoading} Loading {itemCount} items... {:else if errorMsg}

  Error loading items: {errorMsg}
  Retry

{:else}

    {#each visibleItems as item (item.id)}
       onItemClick(item.id)}
        role="listitem"
        tabindex="0"
        onkeydown={(e) => e.key === 'Enter' && onItemClick(item.id)}
      >
        #{parseInt(item.id.split('-')[1])}
        {item.content}

    {/each}

{/if}

.list-container { width: 100%; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; } .scroll-container { border: 1px solid #e2e8f0; border-radius: 4px; } .list-item { display: flex; align-items: center; padding: 0 16px; border-bottom: 1px solid #f1f5f9; cursor: pointer; transition: background-color 0.1s ease; } .list-item:hover { background