New artist loading for followed artists

lib/include/lib/spotify/api.hpp

@@ -75,7 +75,7 @@ namespace lib
 
 			//region Follow
 
-			void followed_artists(lib::callback<std::vector<lib::spt::artist>> &callback);
+			void followed_artists(const paged_callback<spt::artist> &callback) const;
 
 			void follow(lib::follow_type type, const std::vector<std::string> &ids,
 				lib::callback<std::string> &callback);

lib/src/spotifyapi/follow.cpp

@@ -1,8 +1,9 @@
 #include "lib/spotify/api.hpp"
 
-void lib::spt::api::followed_artists(lib::callback<std::vector<lib::spt::artist>> &callback)
+void lib::spt::api::followed_artists(const paged_callback<spt::artist> &callback) const
 {
-	get_items("me/following?type=artist&limit=50", "artists", callback);
+	const std::string url("me/following?type=artist&limit=50");
+	request.get_page<spt::artist>(url, "artists", callback);
 }
 
 void lib::spt::api::follow(lib::follow_type type, const std::vector<std::string> &ids,

src/list/library.cpp

@@ -215,15 +215,27 @@ void List::Library::onExpanded(QTreeWidgetItem *item)
 	}
 	else if (item->text(0) == followedArtists)
 	{
-		spotify.followed_artists([item](const std::vector<lib::spt::artist> &artists)
+		spotify.followed_artists([item](const lib::result<lib::spt::page<lib::spt::artist>> &result)
 		{
+			if (!result.success())
+			{
+				StatusMessage::error(QString("Failed to get artists: %1")
+					.arg(QString::fromStdString(result.message())));
+
+				return false;
+			}
+
+			const auto &page = result.value();
 			std::vector<ListItem::Library> results;
-			results.reserve(artists.size());
-			for (const auto &artist: artists)
+			results.reserve(page.items.size());
+
+			for (const auto &artist: page.items)
 			{
 				results.emplace_back(artist);
 			}
-			List::Library::itemsLoaded(results, item);
+
+			itemsLoaded(results, item);
+			return page.has_next();
 		});
 	}
 	else if (item->text(0) == newReleases)