add cache warming for album covers to album iterators

backend/albumiterator.go

@@ -14,6 +14,8 @@ type AlbumIterator interface {
 }
 
 type LibraryManager struct {
+	PreCacheCoverFn func(string)
+
 	s                *ServerManager
 	albumDetailCache gcache.Cache
 }
@@ -153,6 +155,11 @@ func (r *baseIter) Next() *subsonic.AlbumID3 {
 	}
 	r.prefetched = albums
 	r.prefetchedPos = 1
+	if r.l.PreCacheCoverFn != nil {
+		for _, album := range albums {
+			go r.l.PreCacheCoverFn(album.ID)
+		}
+	}
 
 	return r.prefetched[0]
 }
@@ -277,6 +284,9 @@ func (s *searchIter) addNewAlbums(al []*subsonic.AlbumID3) {
 			continue
 		}
 		s.prefetched = append(s.prefetched, album)
+		if s.l.PreCacheCoverFn != nil {
+			go s.l.PreCacheCoverFn(album.ID)
+		}
 		s.albumIDset[album.ID] = true
 	}
 }
@@ -328,6 +338,9 @@ func (r *randomIter) Next() *subsonic.AlbumID3 {
 				for _, album := range albums {
 					if _, ok := r.albumIDSet[album.ID]; !ok {
 						r.prefetched = append(r.prefetched, album)
+						if r.l.PreCacheCoverFn != nil {
+							go r.l.PreCacheCoverFn(album.ID)
+						}
 						r.albumIDSet[album.ID] = true
 					}
 				}
@@ -346,6 +359,9 @@ func (r *randomIter) Next() *subsonic.AlbumID3 {
 				if _, ok := r.albumIDSet[album.ID]; !ok {
 					hitCount++
 					r.prefetched = append(r.prefetched, album)
+					if r.l.PreCacheCoverFn != nil {
+						go r.l.PreCacheCoverFn(album.ID)
+					}
 					r.albumIDSet[album.ID] = true
 				}
 			}

backend/app.go

@@ -51,6 +51,9 @@ func StartupApp() (*App, error) {
 	a.PlaybackManager = NewPlaybackManager(a.bgrndCtx, a.ServerManager, a.Player)
 	a.LibraryManager = NewLibraryManager(a.ServerManager)
 	a.ImageManager = NewImageManager(a.ServerManager, configdir.LocalCache(AppName))
+	a.LibraryManager.PreCacheCoverFn = func(albumID string) {
+		_, _ = a.ImageManager.GetAlbumThumbnail(albumID)
+	}
 
 	return a, nil
 }

backend/imagemanager.go

@@ -32,6 +32,13 @@ func NewImageManager(s *ServerManager, baseCacheDir string) *ImageManager {
 	}
 }
 
+func (i *ImageManager) GetAlbumThumbnailFromCache(albumID string) (image.Image, bool) {
+	if img, err := i.thumbnailCache.Get(albumID); err == nil && img != nil {
+		return img.(image.Image), true
+	}
+	return nil, false
+}
+
 func (i *ImageManager) GetAlbumThumbnail(albumID string) (image.Image, error) {
 	// in-memory cache
 	if i.thumbnailCache.Has(albumID) {