From 7925e631065c6a7cd609b37c2785fb9e6d538b2f Mon Sep 17 00:00:00 2001
From: Simon Cambier <simon.cambier@protonmail.com>
Date: Sat, 15 Feb 2025 15:54:43 +0100
Subject: [PATCH] Yay lazy loading

At long last.
---
 src/components/ModalVault.svelte              |  49 +++--
 src/components/lazy-loader/LazyLoader.svelte  | 208 ++++++++++++++++++
 src/components/lazy-loader/Placeholder.svelte |  15 ++
 3 files changed, 253 insertions(+), 19 deletions(-)
 create mode 100644 src/components/lazy-loader/LazyLoader.svelte
 create mode 100644 src/components/lazy-loader/Placeholder.svelte

diff --git a/src/components/ModalVault.svelte b/src/components/ModalVault.svelte
index ad55ae0..e4e8f64 100644
--- a/src/components/ModalVault.svelte
+++ b/src/components/ModalVault.svelte
@@ -28,6 +28,7 @@
   import { cancelable, CancelablePromise } from 'cancelable-promise'
   import { debounce } from 'lodash-es'
   import type OmnisearchPlugin from '../main'
+  import LazyLoader from './lazy-loader/LazyLoader.svelte'
 
   export let modal: OmnisearchVaultModal
   export let previousQuery: string | undefined
@@ -111,9 +112,7 @@
 
   async function prevSearchHistory() {
     // Filter out the empty string, if it's there
-    const history = (await plugin.searchHistory.getHistory()).filter(
-      s => s
-    )
+    const history = (await plugin.searchHistory.getHistory()).filter(s => s)
     if (++historySearchIndex >= history.length) {
       historySearchIndex = 0
     }
@@ -122,9 +121,7 @@
   }
 
   async function nextSearchHistory() {
-    const history = (await plugin.searchHistory.getHistory()).filter(
-      s => s
-    )
+    const history = (await plugin.searchHistory.getHistory()).filter(s => s)
     if (--historySearchIndex < 0) {
       historySearchIndex = history.length ? history.length - 1 : 0
     }
@@ -240,10 +237,18 @@
     // Generate link
     let link: string
     if (file && active) {
-      link = plugin.app.fileManager.generateMarkdownLink(file, active.path, "", selectedNote.displayTitle)
+      link = plugin.app.fileManager.generateMarkdownLink(
+        file,
+        active.path,
+        '',
+        selectedNote.displayTitle
+      )
     } else {
-      const maybeDisplayTitle = selectedNote.displayTitle === "" ? "" : `|${selectedNote.displayTitle}`
-      link = `[[${selectedNote.basename}.${getExtension(selectedNote.path)}${maybeDisplayTitle}]]`
+      const maybeDisplayTitle =
+        selectedNote.displayTitle === '' ? '' : `|${selectedNote.displayTitle}`
+      link = `[[${selectedNote.basename}.${getExtension(
+        selectedNote.path
+      )}${maybeDisplayTitle}]]`
     }
 
     // Inject link
@@ -255,7 +260,7 @@
     modal.close()
   }
 
-  function      switchToInFileModal(): void {
+  function switchToInFileModal(): void {
     // Do nothing if the selectedNote is a PDF,
     // or if there is 0 match (e.g indexing in progress)
     if (
@@ -323,15 +328,21 @@
 
 <ModalContainer>
   {#each resultNotes as result, i}
-    <ResultItemVault
-      {plugin}
-      selected="{i === selectedIndex}"
-      note="{result}"
-      on:mousemove="{_ => (selectedIndex = i)}"
-      on:click="{onClick}"
-      on:auxclick="{evt => {
-        if (evt.button == 1) openNoteInNewPane()
-      }}" />
+    <LazyLoader
+      height="{100}"
+      offset="{500}"
+      keep="{true}"
+      fadeOption="{{ delay: 0, duration: 0 }}">
+      <ResultItemVault
+        plugin="{plugin}"
+        selected="{i === selectedIndex}"
+        note="{result}"
+        on:mousemove="{_ => (selectedIndex = i)}"
+        on:click="{onClick}"
+        on:auxclick="{evt => {
+          if (evt.button == 1) openNoteInNewPane()
+        }}" />
+    </LazyLoader>
   {/each}
   <div style="text-align: center;">
     {#if !resultNotes.length && searchQuery && !searching}
diff --git a/src/components/lazy-loader/LazyLoader.svelte b/src/components/lazy-loader/LazyLoader.svelte
new file mode 100644
index 0000000..fa942bf
--- /dev/null
+++ b/src/components/lazy-loader/LazyLoader.svelte
@@ -0,0 +1,208 @@
+<div use:load class={rootClass} style="height: {rootInitialHeight}">
+  {#if loaded}
+    <div
+      in:fade={fadeOption || {}}
+      class={contentClass}
+      style={contentStyle}
+    >
+      <slot>Lazy load content</slot>
+    </div>
+    {#if !contentShow && placeholder}
+      <Placeholder {placeholder} {placeholderProps} />
+    {/if}
+  {:else if placeholder}
+    <Placeholder {placeholder} {placeholderProps} />
+  {/if}
+</div>
+
+<script>
+  // https://github.com/leafOfTree/svelte-lazy
+  import { fade } from 'svelte/transition';
+  import Placeholder from './Placeholder.svelte';
+  export let keep = false;
+  export let height = 0;
+  export let offset = 150;
+  export let fadeOption = {
+    delay: 0,
+    duration: 400,
+  };
+  export let resetHeightDelay = 0;
+  export let onload = null;
+  export let placeholder = null;
+  export let placeholderProps = null;
+  let className = '';
+  export { className as class };
+
+  const rootClass = 'svelte-lazy'
+    + (className ? ' ' + className : '');
+  const contentClass = 'svelte-lazy-content';
+  const rootInitialHeight = getStyleHeight();
+  let loaded = false;
+
+  let contentShow = true;
+  $: contentStyle = !contentShow ? 'display: none' : '';
+
+  function load(node) {
+    setHeight(node);
+    const handler = createHandler(node);
+    addListeners(handler);
+    setTimeout(() => {
+      handler();
+    });
+    const observer = observeNode(node, handler);
+
+    return {
+      destroy: () => {
+        removeListeners(handler);
+        observer.unobserve(node);
+      },
+    };
+  }
+
+  function createHandler(node) {
+    const handler = throttle(e => {
+      const nodeTop = node.getBoundingClientRect().top;
+      const nodeBottom = node.getBoundingClientRect().bottom;
+      const expectedTop = getContainerHeight(e) + offset;
+
+      if (nodeTop <= expectedTop && nodeBottom > 0) {
+        loadNode(node);
+      } else if (!keep) {
+        unload(node)
+      }
+    }, 200);
+    return handler;
+  }
+
+  function observeNode(node, handler) {
+    const observer = new IntersectionObserver((entries) => {
+      if (entries[0].isIntersecting) {
+        loadNode(node);
+      }
+    })
+    observer.observe(node);
+    return observer;
+  }
+
+  function unload(node) {
+    setHeight(node);
+    loaded = false
+  }
+
+  function loadNode(node, handler) {
+    if (loaded) {
+      return;
+    }
+
+    loaded = true;
+    resetHeight(node);
+    if (onload) {
+      onload(node);
+    }
+  }
+
+  function addListeners(handler) {
+    document.addEventListener('scroll', handler, true);
+    window.addEventListener('resize', handler);
+  }
+
+  function removeListeners(handler) {
+    document.removeEventListener('scroll', handler, true);
+    window.removeEventListener('resize', handler);
+  }
+
+  function getStyleHeight() {
+    return (typeof height === 'number')
+      ? height + 'px'
+      : height;
+  }
+
+  function setHeight(node) {
+    if (height) {
+      node.style.height = getStyleHeight();
+    }
+  }
+
+  function resetHeight(node) {
+    setTimeout(() => {
+      const isLoading = checkImgLoadingStatus(node);
+      if (!isLoading) {
+        node.style.height = 'auto';
+      }
+    // Add a delay to wait for remote resources like images to load
+    }, resetHeightDelay);
+  }
+
+  function checkImgLoadingStatus(node) {
+    const img = node.querySelector('img');
+    if (!img) {
+      return false
+    }
+
+    if (!img.complete) {
+      contentShow = false;
+
+      node.addEventListener('load', () => {
+        // Use auto height if loading successfully
+        contentShow = true;
+        node.style.height = 'auto';
+      }, { capture: true, once: true });
+
+      node.addEventListener('error', () => {
+        // Show content with fixed height if there is error
+        contentShow = true;
+      }, { capture: true, once: true });
+
+      return true;
+    }
+
+    if (img.naturalHeight === 0) {
+      // Use fixed height if img has zero height
+      return true;
+    }
+
+    return false;
+  }
+
+  function getContainerHeight(e) {
+    if (e?.target?.getBoundingClientRect) {
+      return e.target.getBoundingClientRect().bottom;
+    } else {
+      return window.innerHeight;
+    }
+  }
+
+  // From underscore souce code
+  function throttle(func, wait, options) {
+    let context, args, result;
+    let timeout = null;
+    let previous = 0;
+    if (!options) options = {};
+    const later = function() {
+      previous = options.leading === false ? 0 : new Date();
+      timeout = null;
+      result = func.apply(context, args);
+      if (!timeout) context = args = null;
+    };
+
+    return function(event) {
+      const now = new Date();
+      if (!previous && options.leading === false) previous = now;
+      const remaining = wait - (now - previous);
+      context = this;
+      args = arguments;
+      if (remaining <= 0 || remaining > wait) {
+        if (timeout) {
+          clearTimeout(timeout);
+          timeout = null;
+        }
+        previous = now;
+        result = func.apply(context, args);
+        if (!timeout) context = args = null;
+      } else if (!timeout && options.trailing !== false) {
+        timeout = setTimeout(later, remaining);
+      }
+      return result;
+    };
+  }
+</script>
\ No newline at end of file
diff --git a/src/components/lazy-loader/Placeholder.svelte b/src/components/lazy-loader/Placeholder.svelte
new file mode 100644
index 0000000..cc5f9c4
--- /dev/null
+++ b/src/components/lazy-loader/Placeholder.svelte
@@ -0,0 +1,15 @@
+{#if placeholder}
+  <div class={placeholderClass}>
+    {#if typeof placeholder === 'string'}
+      <div>{placeholder}</div>
+    {:else if ['function', 'object'].includes(typeof placeholder)}
+      <svelte:component this={placeholder} {...placeholderProps} />
+    {/if}
+  </div>
+{/if}
+
+<script>
+  export let placeholder = null;
+  export let placeholderProps = null;
+  const placeholderClass = 'svelte-lazy-placeholder';
+</script>
\ No newline at end of file