feat(MotionPreference): Create common logic to store information about prefers-reduced-motion

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

@@ -1,27 +1,31 @@
+<!--
+    Component: FontList
+
+    - 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.
+-->
 <script lang="ts">
-import { fontshareStore } from '$entities/Font/model/store/fontshareStore.svelte';
+import FontView from '$features/ShowFont/ui/FontView.svelte';
 import {
     Content as ItemContent,
     Root as ItemRoot,
     Title as ItemTitle,
 } from '$shared/shadcn/ui/item';
 import { VirtualList } from '$shared/ui';
-/**
- * FontList
- *
- * 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.
- */
+import { fontshareStore } from '../../model';
+
+$inspect(fontshareStore.fonts);
 </script>
 
-<VirtualList items={fontshareStore.fonts} itemHeight={30}>
+<VirtualList items={fontshareStore.fonts}>
     {#snippet children({ item: font })}
         <ItemRoot>
             <ItemContent>
-                <ItemTitle>{font.name}</ItemTitle>
+                <!-- <ItemTitle></ItemTitle> -->
                 <span class="text-xs text-muted-foreground">
-                    {font.category} • {font.provider}
+                    {font.provider} • {font.category}
                 </span>
+                <FontView id={font.id} slug={font.id} name={font.name}>{font.name}</FontView>
             </ItemContent>
         </ItemRoot>
     {/snippet}

src/features/GetFonts/ui/FontSearch/FontSearch.svelte

@@ -1,3 +1,8 @@
+<!--
+    Component: FontSearch
+
+    Combines search input with font list display
+-->
 <script lang="ts">
 import {
     FontList,
@@ -8,12 +13,6 @@ import { onMount } from 'svelte';
 import { mapManagerToParams } from '../../lib';
 import { filterManager } from '../../model';
 
-/**
- * FontSearch
- *
- * Font search component with search input and font list display.
- * Uses unifiedFontStore for all font operations and search state.
- */
 onMount(() => {
     /**
      * The Pairing:
@@ -24,8 +23,6 @@ onMount(() => {
 
     return unbind;
 });
-
-$inspect(filterManager.queryValue, filterManager.debouncedQueryValue);
 </script>
 
 <SearchBar

src/features/ShowFont/ui/FontView.svelte

@@ -0,0 +1,40 @@
+<!--
+    Component: FontView
+
+    Loads fonts from fontshare with link tag
+-->
+<script lang="ts">
+interface Props {
+    name: string;
+    slug: string;
+    id: string;
+    children?: import('svelte').Snippet;
+}
+
+let { name, slug, id, children }: Props = $props();
+let isLoaded = $state(false);
+
+// Construct the Fontshare API CSS URL
+// We specify the weight (400) or 'all'
+const cssUrl = $derived(`https://api.fontshare.com/v2/css?f[]=${id}&display=swap`);
+
+$effect(() => {
+    // Even though we use a link tag, we can still "watch"
+    // for the font to be ready for a smooth fade-in
+    document.fonts.load(`1em "${name}"`).then(() => {
+        isLoaded = true;
+    });
+});
+</script>
+
+<svelte:head>
+    <link rel="stylesheet" href={cssUrl} />
+</svelte:head>
+
+<div
+    style:--f={name}
+    style:font-family={name ? `'${name}', sans-serif` : 'inherit'}
+    class="transition-opacity duration-500 {isLoaded ? 'font-[var(--f)] opacity-100' : 'font-sans opacity-0'}"
+>
+    {@render children?.()}
+</div>

src/shared/lib/accessibility/motion.svelte.ts

@@ -0,0 +1,37 @@
+// Check if we are in a browser environment
+const isBrowser = typeof window !== 'undefined';
+
+class MotionPreference {
+    // Reactive state
+    #reduced = $state(false);
+    #mediaQuery: MediaQueryList = new MediaQueryList();
+
+    private handleChange = (e: MediaQueryListEvent) => {
+        this.#reduced = e.matches;
+    };
+
+    constructor() {
+        if (isBrowser) {
+            const mediaQuery = window.matchMedia('(prefers-reduced-motion: reduce)');
+
+            // Set initial value immediately
+            this.#reduced = mediaQuery.matches;
+
+            mediaQuery.addEventListener('change', this.handleChange);
+
+            this.#mediaQuery = mediaQuery;
+        }
+    }
+
+    // Getter allows us to use 'motion.reduced' reactively in components
+    get reduced() {
+        return this.#reduced;
+    }
+
+    destroy() {
+        this.#mediaQuery.removeEventListener('change', this.handleChange);
+    }
+}
+
+// Export a single instance to be used everywhere
+export const motion = new MotionPreference();

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

@@ -37,41 +37,43 @@ export function createFilter<TValue extends string>(initialState: FilterModel<TV
         })),
     );
 
+    // Helper to find a property by ID
+    const findProp = (id: string) => properties.find(p => p.id === id);
+
     return {
         get properties() {
             return properties;
         },
-
         get selectedProperties() {
             return properties.filter(p => p.selected);
         },
-
         get selectedCount() {
-            return this.selectedProperties.length;
+            return properties.filter(p => p.selected)?.length;
         },
 
-        // 3. Methods mutate the reactive state directly
         toggleProperty(id: string) {
-            const prop = properties.find(p => p.id === id);
-            if (prop) prop.selected = !prop.selected;
+            const property = findProp(id);
+            if (property) {
+                property.selected = !property.selected;
+            }
         },
-
         selectProperty(id: string) {
-            const prop = properties.find(p => p.id === id);
-            if (prop) prop.selected = true;
+            const property = findProp(id);
+            if (property) {
+                property.selected = true;
+            }
         },
-
         deselectProperty(id: string) {
-            const prop = properties.find(p => p.id === id);
-            if (prop) prop.selected = false;
+            const property = findProp(id);
+            if (property) {
+                property.selected = false;
+            }
         },
-
         selectAll() {
-            properties.forEach(p => p.selected = true);
+            properties.forEach(property => property.selected = true);
         },
-
         deselectAll() {
-            properties.forEach(p => p.selected = false);
+            properties.forEach(property => property.selected = false);
         },
     };
 }

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

@@ -79,27 +79,23 @@ export interface VirtualizerOptions {
  * </div>
  * ```
  */
-export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
-    // Reactive State
+export function createVirtualizer<T>(optionsGetter: () => VirtualizerOptions & { data: T[] }) {
     let scrollOffset = $state(0);
     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
+    // By wrapping the getter in $derived, we track everything inside it
     const options = $derived(optionsGetter());
 
-    // Optimized Memoization (The Cache Layer)
-    // Only recalculates when item count or measured sizes change.
+    // This derivation now tracks: count, measuredSizes, AND the data array itself
     const offsets = $derived.by(() => {
         const count = options.count;
-        const result = Array.from<number>({ length: count });
+        const result = new Float64Array(count);
         let accumulated = 0;
-
         for (let i = 0; i < count; i++) {
             result[i] = accumulated;
+            // Accessing measuredSizes here creates the subscription
             accumulated += measuredSizes[i] ?? options.estimateSize(i);
         }
         return result;
@@ -112,24 +108,30 @@ export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
             : 0,
     );
 
-    // Visible Range Calculation
-    // Svelte tracks dependencies automatically here.
     const items = $derived.by((): VirtualItem[] => {
-        const count = options.count;
-        if (count === 0 || containerHeight === 0) return [];
+        // We MUST read options.data here so Svelte knows to re-run
+        // this derivation when the items array is replaced!
+        const { count, data } = options;
+        if (count === 0 || containerHeight === 0 || !data) return [];
 
         const overscan = options.overscan ?? 5;
-        const viewportStart = scrollOffset;
-        const viewportEnd = scrollOffset + containerHeight;
 
-        // Find Start (Linear Scan)
+        // Binary search for efficiency
+        let low = 0;
+        let high = count - 1;
         let startIdx = 0;
-        while (startIdx < count && offsets[startIdx + 1] < viewportStart) {
-            startIdx++;
+        while (low <= high) {
+            const mid = Math.floor((low + high) / 2);
+            if (offsets[mid] <= scrollOffset) {
+                startIdx = mid;
+                low = mid + 1;
+            } else {
+                high = mid - 1;
+            }
         }
 
-        // Find End
         let endIdx = startIdx;
+        const viewportEnd = scrollOffset + containerHeight;
         while (endIdx < count && offsets[endIdx] < viewportEnd) {
             endIdx++;
         }
@@ -139,18 +141,16 @@ export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
 
         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,
+                size: measuredSizes[i] ?? options.estimateSize(i),
+                end: offsets[i] + (measuredSizes[i] ?? options.estimateSize(i)),
                 key: options.getItemKey?.(i) ?? i,
             });
         }
         return result;
     });
-
     // Svelte Actions (The DOM Interface)
 
     /**
@@ -185,6 +185,8 @@ export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
         };
     }
 
+    let measurementBuffer: Record<number, number> = {};
+    let frameId: number | null = null;
     /**
      * Svelte action to measure individual item elements for dynamic height support.
      *
@@ -195,23 +197,32 @@ export function createVirtualizer(optionsGetter: () => VirtualizerOptions) {
      * @returns Object with destroy method for cleanup
      */
     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;
+            if (!entry) return;
+            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;
+            if (!isNaN(index) && measuredSizes[index] !== height) {
+                // 1. Stuff the measurement into a temporary buffer
+                measurementBuffer[index] = height;
+
+                // 2. Schedule a single update for the next animation frame
+                if (frameId === null) {
+                    frameId = requestAnimationFrame(() => {
+                        // 3. Update the state once for all collected measurements
+                        // We use spread to trigger a single fine-grained update
+                        measuredSizes = { ...measuredSizes, ...measurementBuffer };
+
+                        // 4. Reset the buffer
+                        measurementBuffer = {};
+                        frameId = null;
+                    });
                 }
             }
         });
 
         resizeObserver.observe(node);
-        return {
-            destroy: () => resizeObserver.disconnect(),
-        };
+        return { destroy: () => resizeObserver.disconnect() };
     }
 
     // Programmatic Scroll

src/shared/lib/index.ts

@@ -13,3 +13,5 @@ export {
     type Virtualizer,
     type VirtualizerOptions,
 } from './helpers';
+
+export { motion } from './accessibility/motion.svelte';

src/shared/ui/CheckboxFilter/CheckboxFilter.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 import type { Filter } from '$shared/lib';
+import { motion } from '$shared/lib';
 import { Badge } from '$shared/shadcn/ui/badge';
 import { buttonVariants } from '$shared/shadcn/ui/button';
 import { Checkbox } from '$shared/shadcn/ui/checkbox';
@@ -37,29 +38,11 @@ const { displayedLabel, filter }: PropertyFilterProps = $props();
 
 // Toggle state - defaults to open for better discoverability
 let isOpen = $state(true);
-// Accessibility preference to disable animations
-let prefersReducedMotion = $state(false);
-
-// Check reduced motion preference on mount (window access required)
-// Event listener allows responding to system preference changes
-onMount(() => {
-    if (typeof window !== 'undefined') {
-        const mediaQuery = window.matchMedia('(prefers-reduced-motion: reduce)');
-        prefersReducedMotion = mediaQuery.matches;
-
-        const handleChange = (e: MediaQueryListEvent) => {
-            prefersReducedMotion = e.matches;
-        };
-
-        mediaQuery.addEventListener('change', handleChange);
-        return () => mediaQuery.removeEventListener('change', handleChange);
-    }
-});
 
 // Animation config respects user preferences - zero duration if reduced motion enabled
 // Local modifier prevents animation on initial render, only animates user interactions
 const slideConfig = $derived({
-    duration: prefersReducedMotion ? 0 : 250,
+    duration: motion.reduced ? 0 : 250,
     easing: cubicOut,
 });
 

src/shared/ui/SearchBar/SearchBar.svelte

@@ -1,3 +1,10 @@
+<!--
+    Component: SearchBar
+
+    Search input with popover dropdown for results/suggestions
+    - Features keyboard navigation (ArrowDown/Up/Enter) and auto-focus prevention on popover open.
+    - The input field serves as the popover trigger.
+-->
 <script lang="ts">
 import { Input } from '$shared/shadcn/ui/input';
 import { Label } from '$shared/shadcn/ui/label';
@@ -7,17 +14,20 @@ import {
     Trigger as PopoverTrigger,
 } from '$shared/shadcn/ui/popover';
 import { useId } from 'bits-ui';
-import {
-    type Snippet,
-    tick,
-} from 'svelte';
+import type { Snippet } from 'svelte';
 
 interface Props {
+    /** Unique identifier for the input element */
     id: string;
+    /** Current search value (bindable) */
     value: string;
+    /** Additional CSS classes for the container */
     class?: string;
+    /** Placeholder text for the input */
     placeholder?: string;
+    /** Optional label displayed above the input */
     label?: string;
+    /** Content to render inside the popover (receives unique content ID) */
     children: Snippet<[{ id: string }]> | undefined;
 }
 
@@ -35,13 +45,6 @@ let triggerRef = $state<HTMLInputElement>(null!);
 // svelte-ignore state_referenced_locally
 const contentId = useId(id);
 
-function closeAndFocusTrigger() {
-    open = false;
-    tick().then(() => {
-        triggerRef?.focus();
-    });
-}
-
 function handleKeyDown(event: KeyboardEvent) {
     if (event.key === 'ArrowDown' || event.key === 'ArrowUp' || event.key === 'Enter') {
         event.preventDefault();
@@ -50,16 +53,14 @@ function handleKeyDown(event: KeyboardEvent) {
 
 function handleInputClick() {
     open = true;
-    tick().then(() => {
-        triggerRef?.focus();
-    });
 }
 </script>
 
-<PopoverRoot>
+<PopoverRoot bind:open>
     <PopoverTrigger bind:ref={triggerRef}>
         {#snippet child({ props })}
-            <div {...props} class="flex flex-row flex-1 w-full">
+            {@const { onclick, ...rest } = props}
+            <div {...rest} class="flex flex-row flex-1 w-full">
                 {#if label}
                     <Label for={id}>{label}</Label>
                 {/if}
@@ -68,6 +69,7 @@ function handleInputClick() {
                     placeholder={placeholder}
                     bind:value={value}
                     onkeydown={handleKeyDown}
+                    onclick={handleInputClick}
                     class="flex flex-row flex-1"
                 />
             </div>
@@ -76,7 +78,12 @@ function handleInputClick() {
 
     <PopoverContent
         onOpenAutoFocus={e => e.preventDefault()}
-        class="w-max"
+        onInteractOutside={(e => {
+            if (e.target === triggerRef) {
+                e.preventDefault();
+            }
+        })}
+        class="w-(--bits-popover-anchor-width) min-w-(--bits-popover-anchor-width)"
     >
         {@render children?.({ id: contentId })}
     </PopoverContent>

src/shared/ui/VirtualList/VirtualList.svelte

@@ -10,10 +10,7 @@
 <script lang="ts" generics="T">
 import { createVirtualizer } from '$shared/lib';
 import { cn } from '$shared/shadcn/utils/shadcn-utils';
-import {
-    type Snippet,
-    tick,
-} from 'svelte';
+import type { Snippet } from 'svelte';
 
 interface Props {
     /**
@@ -57,6 +54,7 @@ let { items, itemHeight = 80, overscan = 5, class: className, children }: Props
 
 const virtualizer = createVirtualizer(() => ({
     count: items.length,
+    data: items,
     estimateSize: typeof itemHeight === 'function' ? itemHeight : () => itemHeight,
     overscan,
 }));
@@ -66,19 +64,22 @@ const virtualizer = createVirtualizer(() => ({
     use:virtualizer.container
     class={cn(
         'relative overflow-auto border rounded-md bg-background',
-        'outline-none focus-visible:ring-2 ring-ring ring-offset-2',
-        'h-full w-full',
+        'h-150 w-full',
         className,
     )}
-    role="listbox"
-    tabindex="0"
 >
+    <div
+        style:height="{virtualizer.totalSize}px"
+        class="w-full pointer-events-none"
+    >
+    </div>
+
     {#each virtualizer.items as item (item.key)}
         <div
             use:virtualizer.measureElement
             data-index={item.index}
-            class="absolute top-0 left-0 w-full translate-y-[var(--offset)] will-change-transform"
-            style:--offset="{item.start}px"
+            class="absolute top-0 left-0 w-full"
+            style:transform="translateY({item.start}px)"
         >
             {@render children({ item: items[item.index], index: item.index })}
         </div>

vitest.config.ts

@@ -53,6 +53,7 @@ export default defineConfig({
     },
 
     resolve: {
+        conditions: process.env.VITEST ? ['browser'] : undefined,
         alias: {
             $lib: path.resolve(__dirname, './src/lib'),
             $app: path.resolve(__dirname, './src/app'),