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) {

ui/browsing/albumspage.go

@@ -67,7 +67,7 @@ func NewAlbumsPage(title string, sortOrder string, lm *backend.LibraryManager, i
 	a.sortOrder.OnChanged = a.onSortOrderChanged
 	sortVbox := container.NewVBox(layout.NewSpacer(), a.sortOrder, layout.NewSpacer())
 	iter := lm.AlbumsIter(backend.AlbumSortOrder(a.sortOrder.Selected))
-	a.grid = widgets.NewAlbumGrid(iter, im.GetAlbumThumbnail, false /*showYear*/)
+	a.grid = widgets.NewAlbumGrid(iter, im, false /*showYear*/)
 	a.grid.OnPlayAlbum = a.onPlayAlbum
 	a.grid.OnShowArtistPage = a.onShowArtistPage
 	a.grid.OnShowAlbumPage = a.onShowAlbumPage
@@ -116,7 +116,7 @@ func (a *AlbumsPage) Reload() {
 
 func (a *AlbumsPage) doSearch(query string) {
 	if a.searchGrid == nil {
-		a.searchGrid = widgets.NewAlbumGrid(a.lm.SearchIter(query), a.im.GetAlbumThumbnail, false /*showYear*/)
+		a.searchGrid = widgets.NewAlbumGrid(a.lm.SearchIter(query), a.im, false /*showYear*/)
 		a.searchGrid.OnPlayAlbum = a.onPlayAlbum
 		a.searchGrid.OnShowAlbumPage = a.onShowAlbumPage
 		a.searchGrid.OnShowArtistPage = a.onShowArtistPage

ui/browsing/artistpage.go

@@ -76,7 +76,7 @@ func (a *ArtistPage) loadAsync() {
 		}
 		a.titleDisp.Segments[0].(*widget.TextSegment).Text = artist.Name
 		a.titleDisp.Refresh()
-		ag := widgets.NewFixedAlbumGrid(artist.Album, a.im.GetAlbumThumbnail, true /*showYear*/)
+		ag := widgets.NewFixedAlbumGrid(artist.Album, a.im, true /*showYear*/)
 		ag.OnPlayAlbum = a.onPlayAlbum
 		ag.OnShowAlbumPage = a.onShowAlbumPage
 		a.container.Objects[0] = ag

ui/browsing/genrepage.go

@@ -45,7 +45,7 @@ func NewGenrePage(genre string, lm *backend.LibraryManager, im *backend.ImageMan
 		SizeName: theme.SizeNameHeadingText,
 	}
 	iter := g.lm.GenreIter(g.genre)
-	g.grid = widgets.NewAlbumGrid(iter, g.im.GetAlbumThumbnail, false)
+	g.grid = widgets.NewAlbumGrid(iter, g.im, false)
 	g.grid.OnPlayAlbum = g.onPlayAlbum
 	g.grid.OnShowArtistPage = g.onShowArtistPage
 	g.grid.OnShowAlbumPage = g.onShowAlbumPage
@@ -115,7 +115,7 @@ func (g *GenrePage) doSearch(query string) {
 		return al.Genre == g.genre
 	})
 	if g.searchGrid == nil {
-		g.searchGrid = widgets.NewAlbumGrid(iter, g.im.GetAlbumThumbnail, false /*showYear*/)
+		g.searchGrid = widgets.NewAlbumGrid(iter, g.im, false /*showYear*/)
 		g.searchGrid.OnPlayAlbum = g.onPlayAlbum
 		g.searchGrid.OnShowAlbumPage = g.onShowAlbumPage
 		g.searchGrid.OnShowArtistPage = g.onShowArtistPage

ui/widgets/albumgrid.go

@@ -10,7 +10,10 @@ import (
 	"github.com/dweymouth/go-subsonic"
 )
 
-type ImageFetcher func(string) (image.Image, error)
+type ImageFetcher interface {
+	GetAlbumThumbnailFromCache(string) (image.Image, bool)
+	GetAlbumThumbnail(string) (image.Image, error)
+}
 
 type AlbumIterator interface {
 	NextN(int, func(*subsonic.AlbumID3))
@@ -121,9 +124,13 @@ func (ag *AlbumGrid) doUpdateAlbumCard(albumIdx int, ac *AlbumCard) {
 		ac.ImgLoadCancel()
 		ac.ImgLoadCancel = nil
 	}
+	if img, ok := ag.imageFetcher.GetAlbumThumbnailFromCache(album.ID); ok {
+		ac.Cover.SetImage(img)
+		ac.Cover.Refresh()
+	} else {
 		ctx, cancel := context.WithCancel(context.Background())
 		go func(ctx context.Context) {
-		i, err := ag.imageFetcher(album.ID)
+			i, err := ag.imageFetcher.GetAlbumThumbnail(album.ID)
 			select {
 			case <-ctx.Done():
 				return
@@ -137,6 +144,7 @@ func (ag *AlbumGrid) doUpdateAlbumCard(albumIdx int, ac *AlbumCard) {
 			}
 		}(ctx)
 		ac.ImgLoadCancel = cancel
+	}
 
 	// TODO: remove magic number 10
 	if !ag.done && !ag.fetching && albumIdx > len(ag.albums)-10 {