staggered, cancellable preloading of all section image assets, as soon as the section loads

2 files changed, 50 insertions, 4 deletions

diff --git a/animism-align/frontend/app/utils/annotation.utils.js b/animism-align/frontend/app/utils/annotation.utils.js
index a055d91..90ac498 100644
--- a/animism-align/frontend/app/utils/annotation.utils.js
+++ b/animism-align/frontend/app/utils/annotation.utils.js
@@ -72,6 +72,30 @@ export const displayThumbnailURL = media => {
   }
 }
 
+export const displayElementImageURL = (element, mediaItem) => {
+  // console.log(element, mediaItem)
+  if (!element || !mediaItem) return null
+  if (mediaItem.type === 'gallery') {
+    const index = parseInt(element.settings.frame_index)
+    const frame_id = mediaItem.settings.image_order[index]
+    const frame = mediaItem.settings.display_lookup[frame_id]
+    if (!frame) {
+      console.error("Slide not found:", element.settings.frame_index)
+      return null
+    }
+    return frame.url
+  }
+  return mediaItem.settings.display.url
+}
+
+// list all full-size images URLs for the vitrine
+export const galleryFullsizeImageURLS = media => {
+  const { image_order, image_lookup, display_lookup } = media.settings
+  return image_order.map(id => (
+    display_lookup[id] || image_lookup[id]
+  )).map(img => img.url)
+}
+
 export const posterURL = media => {
   if (!media.settings.video) return null
   if (media.settings.poster) return media.settings.poster.url
@@ -111,7 +135,7 @@ export const makeGalleryItems = (annotation, media) => {
   if (item.type !== 'gallery') return {}
   const gallery_items = item.settings.image_order.map((id, index) => {
     const caption = item.settings.caption_lookup && item.settings.caption_lookup[id]
-    console.log(caption)
+    // console.log(caption)
     return {
       name: index,
       label: (index + 1) + ") " + (caption ? (caption.title || "") : "")
diff --git a/animism-align/frontend/app/utils/image.utils.js b/animism-align/frontend/app/utils/image.utils.js
index d7b7508..358c91d 100644
--- a/animism-align/frontend/app/utils/image.utils.js
+++ b/animism-align/frontend/app/utils/image.utils.js
@@ -1,4 +1,24 @@
-const preloadedImages = {}
+import { displayElementImageURL, galleryFullsizeImageURLS } from 'app/utils/annotation.utils'
+
+export const preloadSectionImages = (section, mediaLookup) => {
+  // console.log(section)
+  let urls = []
+  section.fullscreenTimeline.forEach(element => {
+    // console.log(element)
+    const mediaItem = mediaLookup[element.settings.media_id]
+    if (!mediaItem) return
+    // console.log(mediaItem)
+    switch (mediaItem.type) {
+      case 'image':
+        urls.push(displayElementImageURL(element, mediaItem))
+        break
+      case 'gallery':
+        urls = urls.concat(galleryFullsizeImageURLS(mediaItem))
+        break
+    }
+  })
+  return preloadImages(urls)
+}
 
 export const preloadImages = urls => batchPromise(urls, 4, preloadImage)
 
@@ -41,12 +61,14 @@ export const batchPromise = (list, count, fn) => {
   }
 }
 
+const preloadedImageCache = {}
 export const preloadImage = (url, anonymous=false) => (
   new Promise((resolve, reject) => {
-    if (preloadedImages[url] || typeof url === 'object' && url instanceof Image) {
+    if (!url || preloadedImageCache[url] || typeof url === 'object' && url instanceof Image) {
       return resolve(url)
     }
-    preloadedImages[url] = true
+    // console.log('preload', url)
+    preloadedImageCache[url] = true
     const image = new Image()
     let loaded = false
     image.onload = () => {