refactor(web): convert memory observer to an attachment (#26646)

web/src/lib/actions/intersection-observer.ts

@@ -1,156 +0,0 @@
-type Config = IntersectionObserverActionProperties & {
-  observer?: IntersectionObserver;
-};
-type TrackedProperties = {
-  root?: Element | Document | null;
-  threshold?: number | number[];
-  top?: string;
-  right?: string;
-  bottom?: string;
-  left?: string;
-};
-type OnIntersectCallback = (entryOrElement: IntersectionObserverEntry | HTMLElement) => unknown;
-type OnSeparateCallback = (element: HTMLElement) => unknown;
-type IntersectionObserverActionProperties = {
-  key?: string;
-  disabled?: boolean;
-  /** Function to execute when the element leaves the viewport */
-  onSeparate?: OnSeparateCallback;
-  /** Function to execute when the element enters the viewport */
-  onIntersect?: OnIntersectCallback;
-
-  root?: Element | Document | null;
-  threshold?: number | number[];
-  top?: string;
-  right?: string;
-  bottom?: string;
-  left?: string;
-};
-type TaskKey = HTMLElement | string;
-
-function isEquivalent(a: TrackedProperties, b: TrackedProperties) {
-  return (
-    a?.bottom === b?.bottom &&
-    a?.top === b?.top &&
-    a?.left === b?.left &&
-    a?.right == b?.right &&
-    a?.threshold === b?.threshold &&
-    a?.root === b?.root
-  );
-}
-
-const elementToConfig = new Map<TaskKey, Config>();
-
-const observe = (key: HTMLElement | string, target: HTMLElement, properties: IntersectionObserverActionProperties) => {
-  if (!target.isConnected) {
-    elementToConfig.get(key)?.observer?.unobserve(target);
-    return;
-  }
-  const {
-    root,
-    threshold,
-    top = '0px',
-    right = '0px',
-    bottom = '0px',
-    left = '0px',
-    onSeparate,
-    onIntersect,
-  } = properties;
-  const rootMargin = `${top} ${right} ${bottom} ${left}`;
-  const observer = new IntersectionObserver(
-    (entries: IntersectionObserverEntry[]) => {
-      // This IntersectionObserver is limited to observing a single element, the one the
-      // action is attached to. If there are multiple entries, it means that this
-      // observer is being notified of multiple events that have occurred quickly together,
-      // and the latest element is the one we are interested in.
-
-      entries.sort((a, b) => a.time - b.time);
-
-      const latestEntry = entries.pop();
-      if (latestEntry?.isIntersecting) {
-        onIntersect?.(latestEntry);
-      } else {
-        onSeparate?.(target);
-      }
-    },
-    {
-      rootMargin,
-      threshold,
-      root,
-    },
-  );
-  observer.observe(target);
-  elementToConfig.set(key, { ...properties, observer });
-};
-
-function configure(key: HTMLElement | string, element: HTMLElement, properties: IntersectionObserverActionProperties) {
-  if (properties.disabled) {
-    const config = elementToConfig.get(key);
-    const { observer } = config || {};
-    observer?.unobserve(element);
-    elementToConfig.delete(key);
-  } else {
-    elementToConfig.set(key, properties);
-    observe(key, element, properties);
-  }
-}
-
-function _intersectionObserver(
-  key: HTMLElement | string,
-  element: HTMLElement,
-  properties: IntersectionObserverActionProperties,
-) {
-  configure(key, element, properties);
-  return {
-    update(properties: IntersectionObserverActionProperties) {
-      const config = elementToConfig.get(key);
-      if (!config) {
-        return;
-      }
-      if (isEquivalent(config, properties)) {
-        return;
-      }
-
-      configure(key, element, properties);
-    },
-    destroy: () => {
-      const config = elementToConfig.get(key);
-      const { observer } = config || {};
-      observer?.unobserve(element);
-      elementToConfig.delete(key);
-    },
-  };
-}
-
-/**
- * Monitors an element's visibility in the viewport and calls functions when it enters or leaves (based on a threshold).
- * @param element
- * @param properties One or multiple configurations for the IntersectionObserver(s)
- * @returns
- */
-export function intersectionObserver(
-  element: HTMLElement,
-  properties: IntersectionObserverActionProperties | IntersectionObserverActionProperties[],
-) {
-  // svelte doesn't allow multiple use:action directives of the same kind on the same element,
-  // so accept an array when multiple configurations are needed.
-  if (Array.isArray(properties)) {
-    if (!properties.every((p) => p.key)) {
-      throw new Error('Multiple configurations must specify key');
-    }
-    const observers = properties.map((p) => _intersectionObserver(p.key as string, element, p));
-    return {
-      update: (properties: IntersectionObserverActionProperties[]) => {
-        for (const [i, props] of properties.entries()) {
-          observers[i].update(props);
-        }
-      },
-      destroy: () => {
-        for (const observer of observers) {
-          observer.destroy();
-        }
-      },
-    };
-  }
-  return _intersectionObserver(properties.key || element, element, properties);
-}

web/src/lib/components/memory-page/memory-viewer.svelte

@@ -1,7 +1,6 @@
 <script lang="ts">
   import { afterNavigate, goto } from '$app/navigation';
   import { page } from '$app/state';
-  import { intersectionObserver } from '$lib/actions/intersection-observer';
   import { resizeObserver } from '$lib/actions/resize-observer';
   import { shortcuts } from '$lib/actions/shortcut';
   import MemoryPhotoViewer from '$lib/components/memory-page/memory-photo-viewer.svelte';
@@ -55,6 +54,7 @@
   import type { NavigationTarget, Page } from '@sveltejs/kit';
   import { DateTime } from 'luxon';
   import { t } from 'svelte-i18n';
+  import type { Attachment } from 'svelte/attachments';
   import { Tween } from 'svelte/motion';
 
   let memoryGallery: HTMLElement | undefined = $state();
@@ -236,6 +236,22 @@
     galleryFirstLoad = false;
   };
 
+  const galleryObserver: Attachment<HTMLElement> = (element) => {
+    const observer = new IntersectionObserver(
+      ([entry]) => {
+        if (entry?.isIntersecting) {
+          handleGalleryScrollsIntoView();
+        } else {
+          handleGalleryScrollsOutOfView();
+        }
+      },
+      { rootMargin: '0px 0px -200px 0px' },
+    );
+
+    observer.observe(element);
+    return () => observer.disconnect();
+  };
+
   const loadFromParams = (page: Page | NavigationTarget | null) => {
     const assetId = page?.params?.assetId ?? page?.url.searchParams.get(QueryParameter.ID) ?? undefined;
     return memoryStore.getMemoryAsset(assetId);
@@ -644,15 +660,7 @@
       />
     </div>
 
-    <div
-      id="gallery-memory"
-      use:intersectionObserver={{
-        onIntersect: handleGalleryScrollsIntoView,
-        onSeparate: handleGalleryScrollsOutOfView,
-        bottom: '-200px',
-      }}
-      bind:this={memoryGallery}
-    >
+    <div id="gallery-memory" {@attach galleryObserver} bind:this={memoryGallery}>
       <GalleryViewer
         assets={currentTimelineAssets}
         {viewerAssets}