refactor: move ImageLoader to ui/util

backend/imagemanager.go

@@ -188,55 +188,6 @@ func (i *ImageManager) RefreshCachedArtistImageIfExpired(artistID string, imgURL
 	return err
 }
 
-// ThumbnailLoader is a utility type that exposes a single API to load
-// a cover thumbnail by ID. If the image is immediately available in
-// the cache, OnLoaded will be called immediately. If it is not,
-// OnBeforeLoad will be called first, then OnLoaded will be called async
-// once the image is available.
-// Any subsequent calls to Load will cancel the previous load if not yet completed.
-type ThumbnailLoader struct {
-	prevLoadCancel context.CancelFunc
-	im             *ImageManager
-
-	OnBeforeLoad func()
-	OnLoaded     func(image.Image)
-}
-
-func (i *ImageManager) NewThumbnailLoader(onLoaded func(image.Image)) ThumbnailLoader {
-	return ThumbnailLoader{im: i, OnLoaded: onLoaded}
-}
-
-func (i *ThumbnailLoader) Load(coverID string) {
-	if i.prevLoadCancel != nil {
-		i.prevLoadCancel()
-	}
-	if coverID == "" {
-		i.callOnLoaded(nil)
-		return
-	}
-	if img, ok := i.im.GetCoverThumbnailFromCache(coverID); ok {
-		i.callOnLoaded(img)
-		return
-	}
-	if i.OnBeforeLoad != nil {
-		i.OnBeforeLoad()
-	}
-	i.prevLoadCancel = i.im.GetCoverThumbnailAsync(coverID, func(img image.Image, err error) {
-		if err != nil {
-			log.Printf("Error loading cover image: %s", err.Error())
-		} else {
-			i.callOnLoaded(img)
-		}
-		i.prevLoadCancel() // Done. Release resources associated with un-cancelled ctx
-	})
-}
-
-func (i *ThumbnailLoader) callOnLoaded(im image.Image) {
-	if i.OnLoaded != nil {
-		i.OnLoaded(im)
-	}
-}
-
 func (i *ImageManager) ensureCoverCacheDir() string {
 	// if user logged out with pending fetches in progress,
 	// make sure we don't write to nil (00000000-*0) cache directory

ui/dialogs/quicksearch.go

@@ -11,10 +11,10 @@ import (
 	"fyne.io/fyne/v2/layout"
 	"fyne.io/fyne/v2/theme"
 	"fyne.io/fyne/v2/widget"
-	"github.com/dweymouth/supersonic/backend"
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
 	"github.com/dweymouth/supersonic/ui/layouts"
 	myTheme "github.com/dweymouth/supersonic/ui/theme"
+	"github.com/dweymouth/supersonic/ui/util"
 	"github.com/dweymouth/supersonic/ui/widgets"
 )
 
@@ -26,8 +26,8 @@ type QuickSearch struct {
 
 	SearchEntry fyne.Focusable // exported so it can be focused by the Controller
 
-	mp mediaprovider.MediaProvider
+	mp        mediaprovider.MediaProvider
-	im *backend.ImageManager
+	imgSource util.ImageFetcher
 
 	resultsMutex  sync.RWMutex
 	searchResults []*mediaprovider.SearchResult
@@ -37,10 +37,10 @@ type QuickSearch struct {
 	content *fyne.Container
 }
 
-func NewQuickSearch(mp mediaprovider.MediaProvider, im *backend.ImageManager) *QuickSearch {
+func NewQuickSearch(mp mediaprovider.MediaProvider, im util.ImageFetcher) *QuickSearch {
 	q := &QuickSearch{
-		mp: mp,
+		mp:        mp,
-		im: im,
+		imgSource: im,
 	}
 	q.ExtendBaseWidget(q)
 
@@ -157,7 +157,7 @@ type quickSearchResult struct {
 	index       int
 	contentType mediaprovider.ContentType
 
-	imageLoader backend.ThumbnailLoader
+	imageLoader util.ThumbnailLoader
 
 	image     *widgets.ImagePlaceholder
 	title     *widget.Label
@@ -176,7 +176,7 @@ func newQuickSearchResult(parent *QuickSearch) *quickSearchResult {
 	qs.title.Wrapping = fyne.TextTruncate
 	qs.secondary.Wrapping = fyne.TextTruncate
 	qs.ExtendBaseWidget(qs)
-	qs.imageLoader = parent.im.NewThumbnailLoader(func(im image.Image) {
+	qs.imageLoader = util.NewThumbnailLoader(parent.imgSource, func(im image.Image) {
 		qs.image.SetImage(im, false)
 	})
 	qs.imageLoader.OnBeforeLoad = func() {

ui/util/thumbnailloader.go

@@ -0,0 +1,63 @@
+package util
+
+import (
+	"context"
+	"image"
+	"log"
+)
+
+// ThumbnailLoader is a utility type that exposes a single API to load
+// a cover thumbnail by ID. If the image is immediately available in
+// the cache, OnLoaded will be called immediately. If it is not,
+// OnBeforeLoad will be called first, then OnLoaded will be called async
+// once the image is available.
+// Any subsequent calls to Load will cancel the previous load if not yet completed.
+type ThumbnailLoader struct {
+	prevLoadCancel context.CancelFunc
+	im             ImageFetcher
+
+	OnBeforeLoad func()
+	OnLoaded     func(image.Image)
+}
+
+// Image backend interface for the ThumbnailLoader
+// impl: backend.ImageManager
+type ImageFetcher interface {
+	GetCoverThumbnailFromCache(string) (image.Image, bool)
+	GetCoverThumbnailAsync(string, func(image.Image, error)) context.CancelFunc
+}
+
+func NewThumbnailLoader(im ImageFetcher, onLoaded func(image.Image)) ThumbnailLoader {
+	return ThumbnailLoader{im: im, OnLoaded: onLoaded}
+}
+
+func (i *ThumbnailLoader) Load(coverID string) {
+	if i.prevLoadCancel != nil {
+		i.prevLoadCancel()
+	}
+	if coverID == "" {
+		i.callOnLoaded(nil)
+		return
+	}
+	if img, ok := i.im.GetCoverThumbnailFromCache(coverID); ok {
+		i.callOnLoaded(img)
+		return
+	}
+	if i.OnBeforeLoad != nil {
+		i.OnBeforeLoad()
+	}
+	i.prevLoadCancel = i.im.GetCoverThumbnailAsync(coverID, func(img image.Image, err error) {
+		if err != nil {
+			log.Printf("Error loading cover image: %s", err.Error())
+		} else {
+			i.callOnLoaded(img)
+		}
+		i.prevLoadCancel() // Done. Release resources associated with un-cancelled ctx
+	})
+}
+
+func (i *ThumbnailLoader) callOnLoaded(im image.Image) {
+	if i.OnLoaded != nil {
+		i.OnLoaded(im)
+	}
+}

ui/widgets/gridview.go

@@ -2,12 +2,11 @@ package widgets
 
 import (
 	"context"
-	"image"
 	"sync"
 
-	"github.com/dweymouth/supersonic/backend"
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
 	"github.com/dweymouth/supersonic/sharedutil"
+	"github.com/dweymouth/supersonic/ui/util"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/widget"
@@ -37,10 +36,6 @@ func (b *BatchingIterator) NextN(n int) []*mediaprovider.Album {
 	return results
 }
 
-type ThumbnailLoaderFactory interface {
-	NewThumbnailLoader(func(image.Image)) backend.ThumbnailLoader
-}
-
 type GridViewIterator interface {
 	NextN(int) []GridViewItemModel
 }
@@ -81,7 +76,7 @@ type GridView struct {
 type GridViewState struct {
 	items        []GridViewItemModel
 	iter         GridViewIterator
-	imageFetcher ThumbnailLoaderFactory
+	imageFetcher util.ImageFetcher
 	Placeholder  fyne.Resource
 	highestShown int
 	done         bool
@@ -98,7 +93,7 @@ type GridViewState struct {
 
 var _ fyne.Widget = (*GridView)(nil)
 
-func NewFixedGridView(items []GridViewItemModel, fetch ThumbnailLoaderFactory, placeholder fyne.Resource) *GridView {
+func NewFixedGridView(items []GridViewItemModel, fetch util.ImageFetcher, placeholder fyne.Resource) *GridView {
 	g := &GridView{
 		GridViewState: GridViewState{
 			items:        items,
@@ -112,7 +107,7 @@ func NewFixedGridView(items []GridViewItemModel, fetch ThumbnailLoaderFactory, p
 	return g
 }
 
-func NewGridView(iter GridViewIterator, fetch ThumbnailLoaderFactory, placeholder fyne.Resource) *GridView {
+func NewGridView(iter GridViewIterator, fetch util.ImageFetcher, placeholder fyne.Resource) *GridView {
 	g := &GridView{
 		GridViewState: GridViewState{
 			iter:         iter,
@@ -202,7 +197,7 @@ func (g *GridView) createGridWrap() {
 		// create func
 		func() fyne.CanvasObject {
 			card := NewGridViewItem(g.Placeholder)
-			card.ImgLoader = g.imageFetcher.NewThumbnailLoader(card.Cover.SetImage)
+			card.ImgLoader = util.NewThumbnailLoader(g.imageFetcher, card.Cover.SetImage)
 			card.ImgLoader.OnBeforeLoad = func() { card.Cover.SetImage(nil) }
 			card.OnPlay = func() { g.onPlay(card.ItemID(), false) }
 			card.OnShowSecondaryPage = func(id string) {

ui/widgets/gridviewitem.go

@@ -3,10 +3,10 @@ package widgets
 import (
 	"image"
 
-	"github.com/dweymouth/supersonic/backend"
 	"github.com/dweymouth/supersonic/res"
 	"github.com/dweymouth/supersonic/sharedutil"
 	"github.com/dweymouth/supersonic/ui/layouts"
+	"github.com/dweymouth/supersonic/ui/util"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/canvas"
@@ -141,7 +141,7 @@ type GridViewItem struct {
 
 	// updated by GridView
 	Cover     *coverImage
-	ImgLoader backend.ThumbnailLoader
+	ImgLoader util.ThumbnailLoader
 
 	OnPlay              func()
 	OnShowContextMenu   func(fyne.Position)