add LazyRenderer component & update AppCatalog

app/src/components/LazyRenderer.vue

@@ -0,0 +1,59 @@
+<template>
+  <div class="lazy-renderer" :style="`min-height: ${fixedMinHeight}px`">
+    <slot v-if="render" />
+  </div>
+</template>
+
+<script>
+export default {
+  name: 'LazyRenderer',
+
+  props: {
+    unrender: { type: Boolean, default: true },
+    minHeight: { type: Number, default: 0 },
+    renderDelay: { type: Number, default: 100 },
+    unrenderDelay: { type: Number, default: 2000 },
+    rootMargin: { type: String, default: '300px' }
+  },
+
+  data () {
+    return {
+      observer: null,
+      render: false,
+      fixedMinHeight: this.minHeight
+    }
+  },
+
+  mounted () {
+    let unrenderTimer
+    let renderTimer
+    this.observer = new IntersectionObserver(entries => {
+      if (entries[0].isIntersecting) {
+        clearTimeout(unrenderTimer)
+        // Show the component after a delay (to avoid rendering while scrolling fast)
+        renderTimer = setTimeout(() => {
+          this.render = true
+        }, this.unrender ? this.renderDelay : 0)
+
+        if (!this.unrender) {
+          // Stop listening to intersections after first appearance if unrendering is not activated
+          this.observer.disconnect()
+        }
+      } else if (this.unrender) {
+        clearTimeout(renderTimer)
+        // Hide the component after a delay if it's no longer in the viewport
+        unrenderTimer = setTimeout(() => {
+          this.fixedMinHeight = this.$el.clientHeight
+          this.render = false
+        }, this.unrenderDelay)
+      }
+    }, { rootMargin: this.rootMargin })
+
+    this.observer.observe(this.$el)
+  },
+
+  beforeDestroy () {
+    this.observer.disconnect()
+  }
+}
+</script>

app/src/views/app/AppCatalog.vue

@@ -64,10 +64,12 @@
 
     <!-- APPS CARDS -->
     <b-card-group v-else deck>
-      <b-card no-body v-for="app in filteredApps" :key="app.id">
+      <lazy-renderer v-for="app in filteredApps" :key="app.id" :min-height="120">
+        <b-card no-body>
           <b-card-body class="d-flex flex-column">
             <b-card-title class="d-flex mb-2">
               {{ app.manifest.name }}
+
               <small v-if="app.state !== 'working'" class="d-flex align-items-center ml-2">
                 <b-badge
                   v-if="app.state !== 'highquality'"
@@ -76,6 +78,7 @@
                 >
                   {{ $t('app_state_' + app.state) }}
                 </b-badge>
+
                 <icon
                   v-else iname="star" class="star"
                   v-b-popover.hover.bottom="$t(`app_state_${app.state}_explanation`)"
@@ -110,6 +113,7 @@
             </b-button>
           </b-button-group>
         </b-card>
+      </lazy-renderer>
     </b-card-group>
 
     <template #bot>
@@ -155,12 +159,17 @@
 <script>
 import { validationMixin } from 'vuelidate'
 
+import LazyRenderer from '@/components/LazyRenderer'
 import { required, githubLink } from '@/helpers/validators'
 import { randint } from '@/helpers/commons'
 
 export default {
   name: 'AppCatalog',
 
+  components: {
+    LazyRenderer
+  },
+
   data () {
     return {
       queries: [
@@ -375,10 +384,11 @@ export default {
 }
 
 .card-deck {
-  .card {
+  > * {
-    border-color: $gray-400;
+    margin-left: 15px;
+    margin-right: 15px;
     margin-bottom: 2rem;
-    flex-basis: 90%;
+    flex-basis: 100%;
     @include media-breakpoint-up(md) {
       flex-basis: 50%;
       max-width: calc(50% - 30px);
@@ -388,6 +398,15 @@ export default {
       max-width: calc(33.3% - 30px);
     }
 
+    .card {
+      margin: 0;
+      height: 100%;
+    }
+  }
+
+  .card {
+    border-color: $gray-400;
+
     // not maintained info
     .alert-warning {
       font-size: .75em;
@@ -402,6 +421,8 @@ export default {
     @include media-breakpoint-up(sm) {
       min-height: 10rem;
     }
+
+    flex-basis: 90%;
     border: 0;
 
     .btn {