frontend-svelte/src/widgets/SampleList/ui/SampleList/SampleList.svelte

<!--
    Component: SampleList
    Renders a list of fonts in a virtualized list to improve performance.
    - Includes pagination with auto-loading when scrolling near the bottom.
    - Provides a typography menu for font setup.
-->
<script lang="ts">
import {
    FontListItem,
    FontVirtualList,
    unifiedFontStore,
} from '$entities/Font';
import { FontSampler } from '$features/DisplayFont';
import {
    TypographyMenu,
    controlManager,
} from '$features/SetupFont';
import { throttle } from '$shared/lib/utils';
import { Skeleton } from '$shared/ui';

let text = $state('The quick brown fox jumps over the lazy dog...');
let wrapper = $state<HTMLDivElement | null>(null);
// Binds to the actual window height
let innerHeight = $state(0);
// Is the component above the middle of the viewport?
let isAboveMiddle = $state(false);

/**
 * Calculate display range for pagination info
 */
const displayRange = $derived.by(() => {
    const { offset, limit, total } = unifiedFontStore.pagination;
    const loadedCount = Math.min(offset + limit, total);
    return `Showing ${loadedCount} of ${total} fonts`;
});

const checkPosition = throttle(() => {
    if (!wrapper) return;

    const rect = wrapper.getBoundingClientRect();
    const viewportMiddle = innerHeight / 2;

    isAboveMiddle = rect.top < viewportMiddle;
}, 100);
</script>

{#snippet skeleton()}
    <div class="flex flex-col gap-3 sm:gap-4 p-3 sm:p-4">
        {#each Array(5) as _, i}
            <div class="flex flex-col gap-1.5 sm:gap-2 p-3 sm:p-4 border rounded-lg sm:rounded-xl border-border-subtle bg-background-40">
                <div class="flex items-center justify-between mb-3 sm:mb-4">
                    <Skeleton class="h-6 sm:h-8 w-1/3" />
                    <Skeleton class="h-6 sm:h-8 w-6 sm:w-8 rounded-full" />
                </div>
                <Skeleton class="h-24 sm:h-32 w-full" />
            </div>
        {/each}
    </div>
{/snippet}

<svelte:window
    bind:innerHeight
    onscroll={checkPosition}
    onresize={checkPosition}
/>

<div bind:this={wrapper}>
    <FontVirtualList
        itemHeight={220}
        useWindowScroll={true}
        weight={controlManager.weight}
        {skeleton}
    >
        {#snippet children({
    item: font,
    isFullyVisible,
    isPartiallyVisible,
    proximity,
    index,
})}
            <FontListItem
                {font}
                {isFullyVisible}
                {isPartiallyVisible}
                {proximity}
            >
                <FontSampler {font} bind:text {index} />
            </FontListItem>
        {/snippet}
    </FontVirtualList>

    <TypographyMenu
        class="fixed bottom-4 sm:bottom-5 right-4 sm:left-1/2 sm:right-[unset] sm:-translate-x-1/2"
        hidden={!isAboveMiddle}
    />
</div>