big refactor to prepare for removing server hard-coding

ui/albumgrid.go

@@ -2,7 +2,7 @@ package ui
 
 import (
 	"context"
-	"gomuse/backend"
+	"supersonic/backend"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/widget"
@@ -12,18 +12,20 @@ import (
 type AlbumGrid struct {
 	widget.BaseWidget
 
-	grid     *widget.GridWrapList
-	albums   []*subsonic.AlbumID3
-	iter     backend.AlbumIterator
-	fetching bool
-	done     bool
+	grid         *widget.GridWrapList
+	albums       []*subsonic.AlbumID3
+	iter         backend.AlbumIterator
+	imageManager *backend.ImageManager
+	fetching     bool
+	done         bool
 }
 
 var _ fyne.Widget = (*AlbumGrid)(nil)
 
 func NewAlbumGrid(iter backend.AlbumIterator, pm *backend.PlaybackManager, im *backend.ImageManager) *AlbumGrid {
 	ag := &AlbumGrid{
-		iter: iter,
+		iter:         iter,
+		imageManager: im,
 	}
 	ag.ExtendBaseWidget(ag)
 
@@ -42,38 +44,7 @@ func NewAlbumGrid(iter backend.AlbumIterator, pm *backend.PlaybackManager, im *b
 		// update func
 		func(itemID int, obj fyne.CanvasObject) {
 			ac := obj.(*AlbumCard)
-			album := ag.albums[itemID]
-			if ac.PrevAlbumID == album.ID {
-				// nothing to do
-				return
-			}
-			ac.Update(album)
-			ac.PrevAlbumID = album.ID
-			// TODO: set image to a placeholder before spinning off async fetch
-			// cancel any previous image fetch
-			if ac.ImgLoadCancel != nil {
-				ac.ImgLoadCancel()
-				ac.ImgLoadCancel = nil
-			}
-			ctx, cancel := context.WithCancel(context.Background())
-			go func(ctx context.Context) {
-				i, err := im.GetAlbumThumbnail(album.ID)
-				select {
-				case <-ctx.Done():
-					return
-				default:
-					if err == nil {
-						ac.Cover.SetImage(i)
-						ac.Refresh()
-					}
-				}
-			}(ctx)
-			ac.ImgLoadCancel = cancel
-
-			// TODO: remove magic number 10
-			if !ag.done && !ag.fetching && itemID > len(ag.albums)-10 {
-				ag.fetchMoreAlbums(10)
-			}
+			ag.doUpdateAlbumCard(itemID, ac)
 		},
 	)
 	ag.grid = g
@@ -83,7 +54,45 @@ func NewAlbumGrid(iter backend.AlbumIterator, pm *backend.PlaybackManager, im *b
 	return ag
 }
 
+func (ag *AlbumGrid) doUpdateAlbumCard(albumIdx int, ac *AlbumCard) {
+	album := ag.albums[albumIdx]
+	if ac.PrevAlbumID == album.ID {
+		// nothing to do
+		return
+	}
+	ac.Update(album)
+	ac.PrevAlbumID = album.ID
+	// TODO: set image to a placeholder before spinning off async fetch
+	// cancel any previous image fetch
+	if ac.ImgLoadCancel != nil {
+		ac.ImgLoadCancel()
+		ac.ImgLoadCancel = nil
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	go func(ctx context.Context) {
+		i, err := ag.imageManager.GetAlbumThumbnail(album.ID)
+		select {
+		case <-ctx.Done():
+			return
+		default:
+			if err == nil {
+				ac.Cover.SetImage(i)
+				ac.Refresh()
+			}
+		}
+	}(ctx)
+	ac.ImgLoadCancel = cancel
+
+	// TODO: remove magic number 10
+	if !ag.done && !ag.fetching && albumIdx > len(ag.albums)-10 {
+		ag.fetchMoreAlbums(10)
+	}
+}
+
 func (a *AlbumGrid) fetchMoreAlbums(count int) {
+	if a.iter == nil {
+		a.done = true
+	}
 	i := 0
 	a.fetching = true
 	a.iter.NextN(count, func(al *subsonic.AlbumID3) {