feature(VirtualList): remove tanstack virtual list solution, add self written one

package.json

@@ -66,7 +66,6 @@
     "vitest-browser-svelte": "^2.0.1"
   },
   "dependencies": {
-    "@tanstack/svelte-query": "^6.0.14",
+    "@tanstack/svelte-query": "^6.0.14"
-    "@tanstack/svelte-virtual": "^3.13.17"
   }
 }

src/entities/Font/ui/FontList/FontList.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
 import { fontshareStore } from '$entities/Font/model/store/fontshareStore.svelte';
-import type { UnifiedFont } from '$entities/Font/model/types/normalize';
 import {
     Content as ItemContent,
     Root as ItemRoot,
@@ -13,34 +12,17 @@ import { VirtualList } from '$shared/ui';
  * Displays a virtualized list of fonts with loading, empty, and error states.
  * Uses unifiedFontStore from context for data, but can accept explicit fonts via props.
  */
-interface FontListProps {
-    /** Font items to display (defaults to filtered fonts from store) */
-    fonts?: UnifiedFont[];
-    /** Show loading state */
-    loading?: boolean;
-    /** Show empty state when no results */
-    showEmpty?: boolean;
-    /** Custom error message to display */
-    errorMessage?: string;
-}
-
-let {
-    fonts,
-    loading,
-    showEmpty = true,
-    errorMessage,
-}: FontListProps = $props();
-
-// const fontshareStore = getFontshareContext();
 </script>
 
-{#each fontshareStore.fonts as font (font.id)}
+<VirtualList items={fontshareStore.fonts} itemHeight={30}>
-    <ItemRoot>
+    {#snippet children({ item: font })}
-        <ItemContent>
+        <ItemRoot>
-            <ItemTitle>{font.name}</ItemTitle>
+            <ItemContent>
-            <span class="text-xs text-muted-foreground">
+                <ItemTitle>{font.name}</ItemTitle>
-                {font.category} • {font.provider}
+                <span class="text-xs text-muted-foreground">
-            </span>
+                    {font.category} • {font.provider}
-        </ItemContent>
+                </span>
-    </ItemRoot>
+            </ItemContent>
-{/each}
+        </ItemRoot>
+    {/snippet}
+</VirtualList>

src/shared/lib/helpers/createVirtualizer/createVirtualizer.svelte.ts

@@ -1,15 +1,159 @@
-import {
+import { untrack } from 'svelte';
-    createVirtualizer as coreCreateVirtualizer,
+
-    observeElementRect,
+export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
-} from '@tanstack/svelte-virtual';
+    // Reactive State
-import type { VirtualItem as CoreVirtualItem } from '@tanstack/virtual-core';
+    let scrollOffset = $state(0);
-import { get } from 'svelte/store';
+    let containerHeight = $state(0);
+    let measuredSizes = $state<Record<number, number>>({});
+
+    // Non-reactive ref for DOM manipulation (avoiding unnecessary state tracking)
+    let elementRef: HTMLElement | null = null;
+
+    // Reactive Options
+    const options = $derived(optionsGetter());
+
+    // Optimized Memoization (The Cache Layer)
+    // Only recalculates when item count or measured sizes change.
+    const offsets = $derived.by(() => {
+        const count = options.count;
+        const result = new Array(count);
+        let accumulated = 0;
+
+        for (let i = 0; i < count; i++) {
+            result[i] = accumulated;
+            accumulated += measuredSizes[i] ?? options.estimateSize(i);
+        }
+        return result;
+    });
+
+    const totalSize = $derived(
+        options.count > 0
+            ? offsets[options.count - 1]
+                + (measuredSizes[options.count - 1] ?? options.estimateSize(options.count - 1))
+            : 0,
+    );
+
+    // Visible Range Calculation
+    // Svelte tracks dependencies automatically here.
+    const items = $derived.by((): VirtualItem[] => {
+        const count = options.count;
+        if (count === 0 || containerHeight === 0) return [];
+
+        const overscan = options.overscan ?? 5;
+        const viewportStart = scrollOffset;
+        const viewportEnd = scrollOffset + containerHeight;
+
+        // Find Start (Linear Scan)
+        let startIdx = 0;
+        while (startIdx < count && offsets[startIdx + 1] < viewportStart) {
+            startIdx++;
+        }
+
+        // Find End
+        let endIdx = startIdx;
+        while (endIdx < count && offsets[endIdx] < viewportEnd) {
+            endIdx++;
+        }
+
+        const start = Math.max(0, startIdx - overscan);
+        const end = Math.min(count, endIdx + overscan);
+
+        const result: VirtualItem[] = [];
+        for (let i = start; i < end; i++) {
+            const size = measuredSizes[i] ?? options.estimateSize(i);
+            result.push({
+                index: i,
+                start: offsets[i],
+                size,
+                end: offsets[i] + size,
+                key: options.getItemKey?.(i) ?? i,
+            });
+        }
+        return result;
+    });
+
+    // Svelte Actions (The DOM Interface)
+    function container(node: HTMLElement) {
+        elementRef = node;
+        containerHeight = node.offsetHeight;
+
+        const handleScroll = () => {
+            scrollOffset = node.scrollTop;
+        };
+
+        const resizeObserver = new ResizeObserver(([entry]) => {
+            if (entry) containerHeight = entry.contentRect.height;
+        });
+
+        node.addEventListener('scroll', handleScroll, { passive: true });
+        resizeObserver.observe(node);
+
+        return {
+            destroy() {
+                node.removeEventListener('scroll', handleScroll);
+                resizeObserver.disconnect();
+                elementRef = null;
+            },
+        };
+    }
+
+    function measureElement(node: HTMLElement) {
+        // Use a ResizeObserver on individual items for dynamic height support
+        const resizeObserver = new ResizeObserver(([entry]) => {
+            if (entry) {
+                const index = parseInt(node.dataset.index || '', 10);
+                const height = entry.borderBoxSize[0]?.blockSize ?? node.offsetHeight;
+
+                // Only update if height actually changed to prevent loops
+                if (!isNaN(index) && measuredSizes[index] !== height) {
+                    measuredSizes[index] = height;
+                }
+            }
+        });
+
+        resizeObserver.observe(node);
+        return {
+            destroy: () => resizeObserver.disconnect(),
+        };
+    }
+
+    // Programmatic Scroll
+    function scrollToIndex(index: number, align: 'start' | 'center' | 'end' | 'auto' = 'auto') {
+        if (!elementRef || index < 0 || index >= options.count) return;
+
+        const itemStart = offsets[index];
+        const itemSize = measuredSizes[index] ?? options.estimateSize(index);
+        let target = itemStart;
+
+        if (align === 'center') target = itemStart - containerHeight / 2 + itemSize / 2;
+        if (align === 'end') target = itemStart - containerHeight + itemSize;
+
+        elementRef.scrollTo({ top: target, behavior: 'smooth' });
+    }
+
+    return {
+        get items() {
+            return items;
+        },
+        get totalSize() {
+            return totalSize;
+        },
+        container,
+        measureElement,
+        scrollToIndex,
+    };
+}
 
 export interface VirtualItem {
+    /** Index of the item in the data array */
     index: number;
+    /** Offset from the top of the list */
     start: number;
+    /** Height of the item */
     size: number;
+    /** End position (start + size) */
     end: number;
+    /** Unique key for the item (for Svelte's {#each} keying) */
     key: string | number;
 }
 
@@ -26,91 +170,4 @@ export interface VirtualizerOptions {
     scrollMargin?: number;
 }
 
-/**
- * Creates a reactive virtualizer using Svelte 5 runes and TanStack's core library.
- *
- * @example
- * ```ts
- * const virtualizer = createVirtualizer(() => ({
- *   count: items.length,
- *   estimateSize: () => 80,
- *   overscan: 5,
- * }));
- *
- * // In template:
- * // <div bind:this={virtualizer.scrollElement}>
- * //   {#each virtualizer.items as item}
- * //     <div style="transform: translateY({item.start}px)">
- * //       {items[item.index]}
- * //     </div>
- * //   {/each}
- * // </div>
- * ```
- */
-export function createVirtualizer(
-    optionsGetter: () => VirtualizerOptions,
-) {
-    let element = $state<HTMLElement | null>(null);
-
-    const internalStore = coreCreateVirtualizer({
-        get count() {
-            return optionsGetter().count;
-        },
-        get estimateSize() {
-            return optionsGetter().estimateSize;
-        },
-        get overscan() {
-            return optionsGetter().overscan ?? 5;
-        },
-        get scrollMargin() {
-            return optionsGetter().scrollMargin;
-        },
-        get getItemKey() {
-            return optionsGetter().getItemKey ?? (i => i);
-        },
-        getScrollElement: () => element,
-        observeElementRect: observeElementRect,
-    });
-
-    const state = $derived(get(internalStore));
-
-    const virtualItems = $derived(
-        state.getVirtualItems().map((item: CoreVirtualItem): VirtualItem => ({
-            index: item.index,
-            start: item.start,
-            size: item.size,
-            end: item.end,
-            key: typeof item.key === 'bigint' ? Number(item.key) : item.key,
-        })),
-    );
-
-    return {
-        get items() {
-            return virtualItems;
-        },
-
-        get totalSize() {
-            return state.getTotalSize();
-        },
-
-        get scrollOffset() {
-            return state.scrollOffset ?? 0;
-        },
-
-        get scrollElement() {
-            return element;
-        },
-        set scrollElement(el) {
-            element = el;
-        },
-
-        scrollToIndex: (idx: number, opt?: { align?: 'start' | 'center' | 'end' | 'auto' }) =>
-            state.scrollToIndex(idx, opt),
-
-        scrollToOffset: (off: number) => state.scrollToOffset(off),
-
-        measureElement: (el: HTMLElement) => state.measureElement(el),
-    };
-}
-
 export type Virtualizer = ReturnType<typeof createVirtualizer>;

src/shared/ui/VirtualList/VirtualList.svelte

@@ -55,53 +55,15 @@ interface Props {
 
 let { items, itemHeight = 80, overscan = 5, class: className, children }: Props = $props();
 
-let activeIndex = $state(0);
+const virtualizer = createVirtualizer(() => ({
-const itemRefs = new Map<number, HTMLElement>();
-
-const virtual = createVirtualizer(() => ({
     count: items.length,
     estimateSize: typeof itemHeight === 'function' ? itemHeight : () => itemHeight,
     overscan,
 }));
-
-function registerItem(node: HTMLElement, index: number) {
-    itemRefs.set(index, node);
-    return {
-        destroy() {
-            itemRefs.delete(index);
-        },
-    };
-}
-
-async function focusItem(index: number) {
-    activeIndex = index;
-    virtual.scrollToIndex(index, { align: 'auto' });
-    await tick();
-    itemRefs.get(index)?.focus();
-}
-
-async function handleKeydown(event: KeyboardEvent) {
-    let nextIndex = activeIndex;
-    if (event.key === 'ArrowDown') nextIndex++;
-    else if (event.key === 'ArrowUp') nextIndex--;
-    else if (event.key === 'Home') nextIndex = 0;
-    else if (event.key === 'End') nextIndex = items.length - 1;
-    else return;
-
-    if (nextIndex >= 0 && nextIndex < items.length) {
-        event.preventDefault();
-        await focusItem(nextIndex);
-    }
-}
 </script>
 
-<!--
-    Scroll container with single tab stop pattern:
-    - tabindex="0" on container, tabindex="-1" on items
-    - Arrow keys navigate within, Tab moves out
--->
 <div
-    bind:this={virtual.scrollElement}
+    use:virtualizer.container
     class={cn(
         'relative overflow-auto border rounded-md bg-background',
         'outline-none focus-visible:ring-2 ring-ring ring-offset-2',
@@ -110,29 +72,15 @@ async function handleKeydown(event: KeyboardEvent) {
     )}
     role="listbox"
     tabindex="0"
-    onkeydown={handleKeydown}
-    onfocusin={(e => e.target === virtual.scrollElement && focusItem(activeIndex))}
 >
-    <!-- Total scrollable height placeholder -->
+    {#each virtualizer.items as item (item.key)}
-    <div
+        <div
-        class="relative w-full"
+            use:virtualizer.measureElement
-        style:height="{virtual.totalSize}px"
+            data-index={item.index}
-    >
+            class="absolute top-0 left-0 w-full translate-y-[var(--offset)] will-change-transform"
-        {#each virtual.items as row (row.key)}
+            style:--offset="{item.start}px"
-            <!-- Individual item positioned absolutely via GPU-accelerated transform -->
+        >
-            <div
+            {@render children({ item: items[item.index], index: item.index })}
-                use:registerItem={row.index}
+        </div>
-                data-index={row.index}
+    {/each}
-                role="option"
-                aria-selected={activeIndex === row.index}
-                tabindex="-1"
-                onmousedown={() => (activeIndex = row.index)}
-                class="absolute top-0 left-0 w-full outline-none focus:bg-accent focus:text-accent-foreground"
-                style:height="{row.size}px"
-                style:transform="translateY({row.start}px)"
-            >
-                {@render children({ item: items[row.index], index: row.index })}
-            </div>
-        {/each}
-    </div>
 </div>

yarn.lock

@@ -1310,24 +1310,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@tanstack/svelte-virtual@npm:^3.13.17":
-  version: 3.13.17
-  resolution: "@tanstack/svelte-virtual@npm:3.13.17"
-  dependencies:
-    "@tanstack/virtual-core": "npm:3.13.17"
-  peerDependencies:
-    svelte: ^3.48.0 || ^4.0.0 || ^5.0.0
-  checksum: 10c0/8139a94d8b913c1a3aef0e7cda4cfd8451c3e46455a5bd5bae1df26ab7583bfde785ab93cacefba4f0f45f2e2cd13f43fa8cf672c45cb31d52b3232ffb37e69e
-  languageName: node
-  linkType: hard
-
-"@tanstack/virtual-core@npm:3.13.17":
-  version: 3.13.17
-  resolution: "@tanstack/virtual-core@npm:3.13.17"
-  checksum: 10c0/a021795b88856eff8518137ecb85b72f875399bc234ad10bea440ecb6ab48e5e72a74c9a712649a7765f0c37bc41b88263f5104d18df8256b3d50f6a97b32c48
-  languageName: node
-  linkType: hard
-
 "@testing-library/dom@npm:9.x.x || 10.x.x":
   version: 10.4.1
   resolution: "@testing-library/dom@npm:10.4.1"
@@ -2466,7 +2448,6 @@ __metadata:
     "@sveltejs/vite-plugin-svelte": "npm:^6.2.1"
     "@tailwindcss/vite": "npm:^4.1.18"
     "@tanstack/svelte-query": "npm:^6.0.14"
-    "@tanstack/svelte-virtual": "npm:^3.13.17"
     "@testing-library/jest-dom": "npm:^6.9.1"
     "@testing-library/svelte": "npm:^5.3.1"
     "@tsconfig/svelte": "npm:^5.0.6"