misc: Notify user of failed sharing using a dialog

ui/browsing/albumpage.go

@@ -253,7 +253,7 @@ func NewAlbumPageHeader(page *AlbumPage) *AlbumPageHeader {
 			_, canShare := page.mp.(mediaprovider.SupportsSharing)
 			if canShare {
 				share := fyne.NewMenuItem("Share...", func() {
-					a.page.contr.CreateShareURL(a.albumID)
+					a.page.contr.ShowShareDialog(a.albumID)
 				})
 				share.Icon = myTheme.ShareIcon
 				menuItems = append(menuItems, share)

ui/browsing/artistpage.go

@@ -329,7 +329,7 @@ func NewArtistPageHeader(page *ArtistPage) *ArtistPageHeader {
 		a.menuBtn.OnTapped = func() {
 			if pop == nil {
 				share := fyne.NewMenuItem("Share...", func() {
-					a.artistPage.contr.CreateShareURL(a.artistID)
+					a.artistPage.contr.ShowShareDialog(a.artistID)
 				})
 				share.Icon = myTheme.ShareIcon
 				menu := fyne.NewMenu("", share)

ui/controller/controller.go

@@ -7,6 +7,7 @@ import (
 	"image"
 	"io"
 	"log"
+	"net/url"
 	"os"
 	"path/filepath"
 	"time"
@@ -144,7 +145,7 @@ func (m *Controller) connectTracklistActionsWithReplayGainMode(tracklist *widget
 	_, canShare := m.App.ServerManager.Server.(mediaprovider.SupportsSharing)
 	if canShare {
 		tracklist.OnShare = func(trackID string) {
-			go m.CreateShareURL(trackID)
+			go m.ShowShareDialog(trackID)
 		}
 	}
 }
@@ -186,7 +187,7 @@ func (m *Controller) ConnectAlbumGridActions(grid *widgets.GridView) {
 	_, canShare := m.App.ServerManager.Server.(mediaprovider.SupportsSharing)
 	if canShare {
 		grid.OnShare = func(albumID string) {
-			go m.CreateShareURL(albumID)
+			go m.ShowShareDialog(albumID)
 		}
 	}
 }
@@ -678,16 +679,10 @@ func (c *Controller) SetTrackRatings(trackIDs []string, rating int) {
 	}
 }
 
-func (c *Controller) CreateShareURL(id string) {
+func (c *Controller) ShowShareDialog(id string) {
 	go func() {
-		r, ok := c.App.ServerManager.Server.(mediaprovider.SupportsSharing)
+		shareUrl, err := c.createShareURL(id)
-		if !ok {
-			return
-		}
-
-		shareUrl, err := r.CreateShareURL(id)
 		if err != nil {
-			log.Printf("error creating share URL: %v", err)
 			return
 		}
 
@@ -699,15 +694,11 @@ func (c *Controller) CreateShareURL(id string) {
 					c.MainWindow.Clipboard().SetContent(hyperlink.Text)
 				}),
 				widget.NewButtonWithIcon("", theme.ViewRefreshIcon(), func() {
-					shareUrl, err := r.CreateShareURL(id)
+					if shareUrl, err := c.createShareURL(id); err == nil {
-					if err != nil {
-						log.Printf("error creating share URL: %v", err)
-						return
-					}
-
 						hyperlink.Text = shareUrl.String()
 						hyperlink.URL = shareUrl
 						hyperlink.Refresh()
+					}
 				}),
 			),
 			c.MainWindow,
@@ -716,6 +707,24 @@ func (c *Controller) CreateShareURL(id string) {
 	}()
 }
 
+func (c *Controller) createShareURL(id string) (*url.URL, error) {
+	r, ok := c.App.ServerManager.Server.(mediaprovider.SupportsSharing)
+	if !ok {
+		return nil, fmt.Errorf("server does not support sharing")
+	}
+
+	shareUrl, err := r.CreateShareURL(id)
+	if err != nil {
+		log.Printf("error creating share URL: %v", err)
+		c.showError(
+			"Failed to share content. This commonly occurs when the server does not support sharing," +
+				"or has the feature disabled.\nPlease check the server's settings and try again.",
+		)
+		return nil, err
+	}
+	return shareUrl, nil
+}
+
 func (c *Controller) ShowDownloadDialog(tracks []*mediaprovider.Track, downloadName string) {
 	numTracks := len(tracks)
 	var fileName string
@@ -816,6 +825,11 @@ func (c *Controller) sendNotification(title, content string) {
 	})
 }
 
+func (c *Controller) showError(content string) {
+	// TODO: display an in-app toast message instead of a dialog.
+	dialog.ShowError(fmt.Errorf(content), c.MainWindow)
+}
+
 func (c *Controller) ShowAlbumInfoDialog(albumID, albumName string, albumCover image.Image) {
 	go func() {
 		albumInfo, err := c.App.ServerManager.Server.GetAlbumInfo(albumID)