Implementing next photo preloading

#134

Also fixing play button animation.

src/frontend/app/ui/gallery/lightbox/controls/controls.lightbox.gallery.component.css

@@ -154,6 +154,21 @@
   opacity: 1.0;
 }
 
+@keyframes blink {
+  0% {
+    opacity: 0.5;
+  }
+  25% {
+    opacity: 1.0;
+  }
+  75% {
+    opacity: 1.0;
+  }
+  100% {
+    opacity: 0.5;
+  }
+}
+
 @-webkit-keyframes blink {
   0% {
     opacity: 0.5;

src/frontend/app/ui/gallery/lightbox/controls/controls.lightbox.gallery.component.ts

@@ -257,12 +257,9 @@ export class ControlsLightboxComponent implements OnDestroy, OnInit, OnChanges {
     }
   }
 
-  public play(): void {
+  private showNextMedia = () => {
-    this.pause();
+    if (this.mediaElement.imageLoadFinished.this === false ||
-    this.timerSub = this.timer
+      this.mediaElement.imageLoadFinished.next === false) {
-      .pipe(filter((t) => t % 2 === 0))
-      .subscribe(() => {
-        if (this.mediaElement.imageLoadFinished === false) {
       return;
     }
     // do not skip video if its playing
@@ -274,25 +271,19 @@ export class ControlsLightboxComponent implements OnDestroy, OnInit, OnChanges {
       return;
     }
     this.nextPhoto.emit();
-      });
+  };
+
+  public play(): void {
+    this.pause();
+    this.timerSub = this.timer
+      .pipe(filter((t) => t % 2 === 0))
+      .subscribe(this.showNextMedia);
     this.playBackState = PlayBackStates.Play;
   }
 
   public fastForward(): void {
     this.pause();
-    this.timerSub = this.timer.subscribe(() => {
+    this.timerSub = this.timer.subscribe(this.showNextMedia);
-      if (this.mediaElement.imageLoadFinished === false) {
-        return;
-      }
-      if (
-        this.activePhoto &&
-        this.activePhoto.gridMedia.isVideo() &&
-        !this.mediaElement.Paused
-      ) {
-        return;
-      }
-      this.nextPhoto.emit();
-    });
     this.playBackState = PlayBackStates.FastForward;
   }
 

src/frontend/app/ui/gallery/lightbox/lightbox.gallery.component.html

@@ -6,6 +6,7 @@
 
   <div class="lightbox" #lightbox>
     <app-gallery-lightbox-media [gridMedia]="activePhoto ? activePhoto.gridMedia : null"
+                                [nextGridMedia]="NexGridMedia"
                                 [loadMedia]="!animating"
                                 [zoom]="controls ? controls.Zoom : 1"
                                 [drag]="controls ? controls.drag : {x:0,y:0}"

src/frontend/app/ui/gallery/lightbox/lightbox.gallery.component.ts

@@ -15,6 +15,7 @@ import {ContentService} from '../content.service';
 import {PhotoDTO} from '../../../../../common/entities/PhotoDTO';
 import {ControlsLightboxComponent} from './controls/controls.lightbox.gallery.component';
 import {SupportedFormats} from '../../../../../common/SupportedFormats';
+import {GridMedia} from '../grid/GridMedia';
 
 export enum LightboxStates {
   Open = 1,
@@ -389,7 +390,7 @@ export class GalleryLightboxComponent implements OnDestroy, OnInit {
     this.router
       .navigate([], {
         queryParams: this.queryService.getParams(
-          this.gridPhotoQL.toArray()[photoIndex].gridMedia.media
+          this.gridPhotoQL.get(photoIndex).gridMedia.media
         ),
       })
       .catch(console.error);
@@ -440,14 +441,12 @@ export class GalleryLightboxComponent implements OnDestroy, OnInit {
   }
 
   private updateActivePhoto(photoIndex: number, resize = true): void {
-    const pcList = this.gridPhotoQL.toArray();
-
     if (photoIndex < 0 || photoIndex > this.gridPhotoQL.length) {
       throw new Error('Can\'t find the media');
     }
     this.videoSourceError = false;
     this.activePhotoId = photoIndex;
-    this.activePhoto = pcList[photoIndex];
+    this.activePhoto = this.gridPhotoQL.get(photoIndex);
 
     if (resize) {
       this.animatePhoto(
@@ -455,7 +454,7 @@ export class GalleryLightboxComponent implements OnDestroy, OnInit {
       );
     }
     this.navigation.hasPrev = photoIndex > 0;
-    this.navigation.hasNext = photoIndex + 1 < pcList.length;
+    this.navigation.hasNext = photoIndex + 1 < this.gridPhotoQL.length;
 
     const to = this.activePhoto.getDimension();
 
@@ -501,5 +500,12 @@ export class GalleryLightboxComponent implements OnDestroy, OnInit {
 
     return {top, left, width, height} as Dimension;
   }
+
+  get NexGridMedia(): GridMedia {
+    if (this.activePhotoId + 1 < this.gridPhotoQL?.length) {
+      return this.gridPhotoQL.get(this.activePhotoId + 1)?.gridMedia;
+    }
+    return null;
+  }
 }
 

src/frontend/app/ui/gallery/lightbox/media/media.lightbox.gallery.component.html

@@ -22,7 +22,7 @@
          (error)="onImageError()"
          (timeupdate)="onVideoProgress()"
          #video>
-    <source [src]="gridMedia.getBestFitMediaPath()" (error)="onSourceError($event)">
+    <source [src]="gridMedia.getBestFitMediaPath()" (error)="onSourceError()">
     Something went wrong.
   </video>
 

src/frontend/app/ui/gallery/lightbox/media/media.lightbox.gallery.component.ts

@@ -20,7 +20,8 @@ import { Config } from '../../../../../../common/config/public/Config';
 })
 export class GalleryLightboxMediaComponent implements OnChanges {
   @Input() gridMedia: GridMedia;
-  @Input() loadMedia = false;
+  @Input() nextGridMedia: GridMedia;
+  @Input() loadMedia = false; // prevents loading media
   @Input() windowAspect = 1;
   @Input() zoom = 1;
   @Input() drag = {x: 0, y: 0};
@@ -31,17 +32,24 @@ export class GalleryLightboxMediaComponent implements OnChanges {
   prevGirdPhoto: GridMedia = null;
 
   public imageSize = {width: 'auto', height: '100'};
-  public imageLoadFinished = false;
+  private nextImage = new Image();
+  // do not skip to the next photo if not both are loaded (or resulted in an error)
+  public imageLoadFinished = {
+    this: false,
+    next: false
+  };
   thumbnailSrc: string = null;
   photo = {
     src: null as string,
     isBestFit: null as boolean,
   };
   public transcodeNeedVideos = SupportedFormats.TranscodeNeed.Videos;
+  // if media not loaded, show thumbnail
   private mediaLoaded = false;
   private videoProgress = 0;
 
-  constructor(public elementRef: ElementRef, private sanitizer: DomSanitizer) {}
+  constructor(public elementRef: ElementRef, private sanitizer: DomSanitizer) {
+  }
 
   get ImageTransform(): SafeStyle {
     return this.sanitizer.bypassSecurityTrustStyle(
@@ -120,8 +128,12 @@ export class GalleryLightboxMediaComponent implements OnChanges {
       this.prevGirdPhoto = this.gridMedia;
       this.thumbnailSrc = null;
       this.photo.src = null;
+      this.nextImage.src = "";
       this.mediaLoaded = false;
-      this.imageLoadFinished = false;
+      this.imageLoadFinished = {
+        this: false,
+        next: false
+      };
     }
     this.setImageSize();
     if (
@@ -156,16 +168,18 @@ export class GalleryLightboxMediaComponent implements OnChanges {
 
   onImageError(): void {
     // TODO:handle error
-    this.imageLoadFinished = true;
+    this.imageLoadFinished.this = true;
     console.error(
       'Error: cannot load media for lightbox url: ' +
       this.gridMedia.getBestFitMediaPath()
     );
+    this.loadNextPhoto();
   }
 
   onImageLoad(): void {
-    this.imageLoadFinished = true;
+    this.imageLoadFinished.this = true;
     this.mediaLoaded = true;
+    this.loadNextPhoto();
   }
 
   public showThumbnail(): boolean {
@@ -178,11 +192,34 @@ export class GalleryLightboxMediaComponent implements OnChanges {
     );
   }
 
-  onSourceError($event: any): void {
+  onSourceError(): void {
     this.mediaLoaded = false;
     this.videoSourceError.emit();
   }
 
+  /**
+   * Loads next photo to faster show it on navigation.
+   * Called after the current photo is loaded
+   * @private
+   */
+  private loadNextPhoto(): void {
+    if (!this.nextGridMedia || !this.loadMedia) {
+      return;
+    }
+    // Videos do not support preloading
+    if (!this.nextGridMedia.isPhoto()) {
+      this.imageLoadFinished.next = true;
+      return;
+    }
+    if (Config.Client.Media.Photo.Converting.enabled === true) {
+      this.nextImage.src = this.nextGridMedia.getBestFitMediaPath();
+    } else {
+      this.nextImage.src = this.nextGridMedia.getMediaPath();
+    }
+    this.nextImage.onload = () => this.imageLoadFinished.next = true;
+
+  }
+
   private loadPhoto(): void {
     if (!this.gridMedia || !this.loadMedia || !this.gridMedia.isPhoto()) {
       return;