feat: add seamless lazy loading for genre and playlist views

Introduce paged loading with early prefetch for genre albums/playlists and playlist tracks, while preserving full-data behavior for deep shuffle and playlist play-all actions.

src/backend/qobuzbackend.cpp

@@ -95,6 +95,11 @@ void QobuzBackend::getPlaylist(qint64 playlistId, quint32 offset, quint32 limit)
     qobuz_backend_get_playlist(m_backend, playlistId, offset, limit);
 }
 
+void QobuzBackend::getPlaylistAll(qint64 playlistId)
+{
+    qobuz_backend_get_playlist_all(m_backend, playlistId);
+}
+
 void QobuzBackend::getGenres()
 {
     qobuz_backend_get_genres(m_backend);

src/backend/qobuzbackend.hpp

@@ -35,6 +35,7 @@ public:
     void getArtistReleases(qint64 artistId, const QString &releaseType, quint32 limit = 50, quint32 offset = 0);
     void getAlbumsTracks(const QStringList &albumIds);
     void getPlaylist(qint64 playlistId, quint32 offset = 0, quint32 limit = 500);
+    void getPlaylistAll(qint64 playlistId);
     void getGenres();
     void getFeaturedAlbums(const QString &genreIds, const QString &kind, quint32 limit = 50, quint32 offset = 0);
     void getFeaturedPlaylists(const QString &genreIds, const QString &kind, quint32 limit = 25, quint32 offset = 0);

src/list/tracks.cpp

@@ -5,6 +5,7 @@
 #include <QHeaderView>
 #include <QMenu>
 #include <QAction>
+#include <QScrollBar>
 
 namespace List
 {
@@ -41,12 +42,45 @@ Tracks::Tracks(QobuzBackend *backend, PlayQueue *queue, QWidget *parent)
             setFirstColumnSpanned(row, {}, true);
         setSortingEnabled(!m_model->hasMultipleDiscs());
     });
+    connect(verticalScrollBar(), &QScrollBar::valueChanged,
+            this, [this](int) { maybeLoadMorePlaylistTracks(); });
+
+    connect(m_backend, &QobuzBackend::playlistLoaded, this,
+            [this](const QJsonObject &playlist) {
+        if (!m_pendingPlayAll)
+            return;
+
+        const qint64 id = static_cast<qint64>(playlist["id"].toDouble());
+        if (id != m_playlistId)
+            return;
+
+        if (!playlist["full_load"].toBool())
+            return;
+
+        m_pendingPlayAll = false;
+        const bool shuffle = m_pendingPlayAllShuffle;
+        m_pendingPlayAllShuffle = false;
+
+        const QJsonArray items = playlist["tracks"].toObject()["items"].toArray();
+        if (items.isEmpty())
+            return;
+
+        m_queue->setContext(items, 0);
+        if (shuffle && !m_queue->shuffleEnabled())
+            m_queue->shuffleNow();
+
+        const qint64 firstId = static_cast<qint64>(m_queue->current()["id"].toDouble());
+        if (firstId > 0)
+            emit playTrackRequested(firstId);
+    });
 
 }
 
 void Tracks::loadTracks(const QJsonArray &tracks)
 {
     setPlaylistContext(0);
+    m_pendingPlayAll = false;
+    m_pendingPlayAllShuffle = false;
     setColumnHidden(TrackListModel::ColAlbum, false);
     m_model->setTracks(tracks, false, /*useSequential=*/true);
 }
@@ -54,6 +88,8 @@ void Tracks::loadTracks(const QJsonArray &tracks)
 void Tracks::loadAlbum(const QJsonObject &album)
 {
     setPlaylistContext(0);
+    m_pendingPlayAll = false;
+    m_pendingPlayAllShuffle = false;
     setColumnHidden(TrackListModel::ColAlbum, true);
     const QJsonArray items = album["tracks"].toObject()["items"].toArray();
     m_model->setTracks(items); // album: use track_number
@@ -67,21 +103,72 @@ void Tracks::loadPlaylist(const QJsonObject &playlist)
     const qint64 myId   = AppSettings::instance().userId();
     const bool isOwned  = (myId > 0 && ownId == myId);
     setPlaylistContext(id, isOwned);
-    const QJsonArray items = playlist["tracks"].toObject()["items"].toArray();
+    const QJsonObject tracksObj = playlist["tracks"].toObject();
+    const QJsonArray items = tracksObj["items"].toArray();
+    const int offset = tracksObj["offset"].toInt(0);
+    m_playlistTrackTotal = tracksObj["total"].toInt(items.size());
+    m_playlistLoadedCount = offset + items.size();
+    m_playlistLoadingMore = false;
     m_model->setTracks(items, /*usePosition=*/true);
+    maybeLoadMorePlaylistTracks();
+}
+
+void Tracks::appendPlaylistPage(const QJsonObject &playlist)
+{
+    if (m_playlistId <= 0)
+        return;
+
+    const qint64 id = static_cast<qint64>(playlist["id"].toDouble());
+    if (id != m_playlistId)
+        return;
+
+    const QJsonObject tracksObj = playlist["tracks"].toObject();
+    const QJsonArray items = tracksObj["items"].toArray();
+    const int offset = tracksObj["offset"].toInt(m_playlistLoadedCount);
+    const int total = tracksObj["total"].toInt(m_playlistTrackTotal);
+
+    if (total > 0)
+        m_playlistTrackTotal = total;
+
+    // Ignore stale/duplicate pages.
+    if (offset < m_playlistLoadedCount) {
+        m_playlistLoadingMore = false;
+        return;
+    }
+
+    if (!items.isEmpty()) {
+        m_model->appendTracks(items, /*usePosition=*/true);
+        m_playlistLoadedCount = offset + items.size();
+    } else {
+        m_playlistLoadedCount = qMax(m_playlistLoadedCount, offset);
+    }
+
+    m_playlistLoadingMore = false;
+    maybeLoadMorePlaylistTracks();
 }
 
 void Tracks::loadSearchTracks(const QJsonArray &tracks)
 {
     setPlaylistContext(0);
+    m_pendingPlayAll = false;
+    m_pendingPlayAllShuffle = false;
     setColumnHidden(TrackListModel::ColAlbum, false);
     m_model->setTracks(tracks, false, /*useSequential=*/true);
 }
 
 void Tracks::setPlaylistContext(qint64 playlistId, bool isOwned)
 {
+    if (m_playlistId != playlistId) {
+        m_pendingPlayAll = false;
+        m_pendingPlayAllShuffle = false;
+        m_playlistLoadingMore = false;
+    }
     m_playlistId = playlistId;
     m_playlistIsOwned = isOwned;
+    if (playlistId <= 0) {
+        m_playlistTrackTotal = 0;
+        m_playlistLoadedCount = 0;
+    }
 }
 
 void Tracks::setUserPlaylists(const QVector<QPair<qint64, QString>> &playlists)
@@ -113,6 +200,14 @@ void Tracks::playAll(bool shuffle)
 {
     const QJsonArray tracks = m_model->currentTracksJson();
     if (tracks.isEmpty()) return;
+
+    if (m_playlistId > 0 && m_playlistTrackTotal > tracks.size()) {
+        m_pendingPlayAll = true;
+        m_pendingPlayAllShuffle = shuffle;
+        m_backend->getPlaylistAll(m_playlistId);
+        return;
+    }
+
     m_queue->setContext(tracks, 0);
     // Shuffle once without touching the global shuffle flag — so a subsequent
     // double-click on a track plays in normal order (unless global shuffle is on).
@@ -123,6 +218,30 @@ void Tracks::playAll(bool shuffle)
         emit playTrackRequested(firstId);
 }
 
+void Tracks::maybeLoadMorePlaylistTracks()
+{
+    if (m_playlistId <= 0)
+        return;
+    if (m_pendingPlayAll)
+        return;
+    if (m_playlistLoadingMore)
+        return;
+    if (m_playlistTrackTotal > 0 && m_playlistLoadedCount >= m_playlistTrackTotal)
+        return;
+
+    QScrollBar *bar = verticalScrollBar();
+    if (!bar)
+        return;
+
+    // Start prefetching before the absolute bottom so paging feels seamless.
+    constexpr int kPrefetchPx = 180;
+    if (bar->maximum() > 0 && bar->value() < (bar->maximum() - kPrefetchPx))
+        return;
+
+    m_playlistLoadingMore = true;
+    m_backend->getPlaylist(m_playlistId, static_cast<quint32>(m_playlistLoadedCount), 500);
+}
+
 
 void Tracks::onDoubleClicked(const QModelIndex &index)
 {

src/list/tracks.hpp

@@ -24,6 +24,7 @@ namespace List
         void loadTracks(const QJsonArray &tracks);
         void loadAlbum(const QJsonObject &album);
         void loadPlaylist(const QJsonObject &playlist);
+        void appendPlaylistPage(const QJsonObject &playlist);
         void loadSearchTracks(const QJsonArray &tracks);
 
         /// Called when the backend fires EV_TRACK_CHANGED so the playing row is highlighted.
@@ -55,9 +56,16 @@ namespace List
         QobuzBackend   *m_backend = nullptr;
         PlayQueue      *m_queue   = nullptr;
         qint64          m_playlistId = 0;
+        int             m_playlistTrackTotal = 0;
+        int             m_playlistLoadedCount = 0;
         bool            m_playlistIsOwned = false;
+        bool            m_playlistLoadingMore = false;
+        bool            m_pendingPlayAll = false;
+        bool            m_pendingPlayAllShuffle = false;
         QVector<QPair<qint64, QString>> m_userPlaylists;
 
+        void maybeLoadMorePlaylistTracks();
+
         void onDoubleClicked(const QModelIndex &index);
         void onContextMenu(const QPoint &pos);
     };

src/mainwindow.cpp

@@ -150,6 +150,9 @@ MainWindow::MainWindow(QobuzBackend *backend, QWidget *parent)
     connect(m_library, &List::Library::userPlaylistIdsChanged,
             this, [this](const QSet<qint64> &playlistIds) {
         m_userPlaylistIds = playlistIds;
+        const qint64 currentPlaylistId = m_content->tracksList()->playlistId();
+        if (currentPlaylistId > 0)
+            m_content->setCurrentPlaylistFollowed(m_userPlaylistIds.contains(currentPlaylistId));
     });
     connect(m_library, &List::Library::userPlaylistsChanged,
             this, &MainWindow::onUserPlaylistsChanged);
@@ -537,6 +540,13 @@ void MainWindow::onArtistLoaded(const QJsonObject &artist)
 
 void MainWindow::onPlaylistLoaded(const QJsonObject &playlist)
 {
+    const bool fullLoad = playlist["full_load"].toBool(false);
+    const int trackOffset = playlist["tracks"].toObject()["offset"].toInt(0);
+    if (!fullLoad && trackOffset > 0) {
+        m_content->tracksList()->appendPlaylistPage(playlist);
+        return;
+    }
+
     const qint64 id = static_cast<qint64>(playlist["id"].toDouble());
     const qint64 ownerId = static_cast<qint64>(playlist["owner"].toObject()["id"].toDouble());
     const qint64 myId = AppSettings::instance().userId();

src/model/tracklistmodel.cpp

@@ -109,6 +109,92 @@ void TrackListModel::setTracks(const QJsonArray &tracks,
         emit sortApplied();
 }
 
+void TrackListModel::appendTracks(const QJsonArray &tracks,
+                                  bool usePosition,
+                                  bool useSequential)
+{
+    if (tracks.isEmpty())
+        return;
+
+    // Keep append path simple and stable: disc-header mode is handled by reset path.
+    if (m_hasMultipleDiscs && !usePosition && !useSequential) {
+        QJsonArray all = currentTracksJson();
+        for (const QJsonValue &v : tracks)
+            all.append(v);
+        setTracks(all, usePosition, useSequential);
+        return;
+    }
+
+    int seq = 1;
+    if (useSequential || usePosition) {
+        for (const TrackItem &t : m_tracks)
+            if (!t.isDiscHeader)
+                ++seq;
+    }
+
+    QVector<TrackItem> parsed;
+    parsed.reserve(tracks.size());
+    for (const QJsonValue &v : tracks) {
+        const QJsonObject t = v.toObject();
+        TrackItem item;
+        item.id               = static_cast<qint64>(t["id"].toDouble());
+        item.playlistTrackId  = static_cast<qint64>(t["playlist_track_id"].toDouble());
+        item.discNumber       = t["media_number"].toInt(1);
+        item.duration         = static_cast<qint64>(t["duration"].toDouble());
+        item.streamable       = t["streamable"].toBool(true);
+        item.hiRes            = t["hires_streamable"].toBool();
+        item.raw              = t;
+
+        const QString base    = t["title"].toString();
+        const QString version = t["version"].toString().trimmed();
+        item.title = version.isEmpty() ? base
+                   : base + QStringLiteral(" (") + version + QLatin1Char(')');
+
+        if (useSequential) {
+            item.number = seq++;
+        } else if (usePosition) {
+            const int pos = t["position"].toInt();
+            item.number = pos > 0 ? pos : seq;
+            ++seq;
+        } else {
+            item.number = t["track_number"].toInt();
+        }
+
+        const QJsonObject performer = t["performer"].toObject();
+        item.artist = performer["name"].toString();
+        if (item.artist.isEmpty()) {
+            const QJsonValue n = t["album"].toObject()["artist"].toObject()["name"];
+            item.artist = n.isObject() ? n.toObject()["display"].toString() : n.toString();
+        }
+        if (item.artist.isEmpty()) {
+            const QJsonValue n = t["artist"].toObject()["name"];
+            item.artist = n.isObject() ? n.toObject()["display"].toString() : n.toString();
+        }
+
+        const QJsonObject album = t["album"].toObject();
+        item.album   = album["title"].toString();
+        item.albumId = album["id"].toString();
+
+        parsed.append(item);
+    }
+
+    if (parsed.isEmpty())
+        return;
+
+    const int first = m_tracks.size();
+    const int last  = first + parsed.size() - 1;
+    beginInsertRows({}, first, last);
+    m_tracks += parsed;
+    endInsertRows();
+
+    if (!m_hasMultipleDiscs && m_sortColumn >= 0) {
+        emit layoutAboutToBeChanged();
+        sortData(m_sortColumn, m_sortOrder);
+        emit layoutChanged();
+        emit sortApplied();
+    }
+}
+
 void TrackListModel::clear()
 {
     beginResetModel();

src/model/tracklistmodel.hpp

@@ -51,6 +51,9 @@ public:
     void setTracks(const QJsonArray &tracks,
                    bool usePosition   = false,
                    bool useSequential = false);
+    void appendTracks(const QJsonArray &tracks,
+                      bool usePosition   = false,
+                      bool useSequential = false);
     void clear();
     void setPlayingId(qint64 id);
     qint64 playingId() const { return m_playingId; }

src/view/genrebrowser.cpp

@@ -176,6 +176,10 @@ GenreBrowserView::GenreBrowserView(QobuzBackend *backend, PlayQueue *queue, QWid
             this, &GenreBrowserView::onPlaylistActivated);
     connect(m_playlistList, &QTreeWidget::customContextMenuRequested,
             this, &GenreBrowserView::onPlaylistContextMenu);
+    connect(m_albumList->verticalScrollBar(), &QScrollBar::valueChanged,
+            this, &GenreBrowserView::onAlbumScroll);
+    connect(m_playlistList->verticalScrollBar(), &QScrollBar::valueChanged,
+            this, &GenreBrowserView::onPlaylistScroll);
 
     m_kindCombo->setCurrentIndex(0);
     refreshModeUi();
@@ -358,40 +362,125 @@ void GenreBrowserView::onGenresLoaded(const QJsonObject &result)
 void GenreBrowserView::onFeaturedAlbumsLoaded(const QJsonObject &result)
 {
     m_resultsStack->setCurrentIndex(0);
-    m_albumList->setAlbums(result["items"].toArray());
+    const QString genreIds = result["genre_ids"].toString();
+    const QString type = result["type"].toString();
+    const int offset = result["offset"].toInt();
+    if (genreIds != m_lastAlbumGenreIds || type != m_lastAlbumType)
+        return;
+
+    const QJsonArray items = result["items"].toArray();
+    if (offset <= 0)
+        m_albumList->setAlbums(items);
+    else
+        m_albumList->addAlbums(items);
+
+    m_albumTotal = result["total"].toInt();
+    m_albumOffset = offset + items.size();
+    if (items.isEmpty())
+        m_albumTotal = m_albumOffset;
+    m_loadingAlbums = false;
+
+    if (m_collectAlbumsForDeepShuffle) {
+        if (m_albumOffset < m_albumTotal) {
+            requestAlbumsPage(m_lastAlbumGenreIds, m_lastAlbumType, m_albumOffset, true);
+            return;
+        }
+        m_collectAlbumsForDeepShuffle = false;
+        startDeepShuffleFromLoadedAlbums();
+        return;
+    }
+
+    // If the viewport is not scrollable yet, eagerly fetch more pages.
+    QScrollBar *bar = m_albumList->verticalScrollBar();
+    if (bar && bar->maximum() == 0 && m_albumOffset < m_albumTotal)
+        requestAlbumsPage(m_lastAlbumGenreIds, m_lastAlbumType, m_albumOffset, true);
 }
 
 void GenreBrowserView::onFeaturedPlaylistsLoaded(const QJsonObject &result)
 {
     m_resultsStack->setCurrentIndex(1);
-    setPlaylistItems(result["items"].toArray());
+    const QString genreIds = result["genre_ids"].toString();
+    const QString type = result["type"].toString();
+    const int offset = result["offset"].toInt();
+    if (genreIds != m_lastPlaylistGenreIds || type != m_lastPlaylistType)
+        return;
+
+    const QJsonArray items = result["items"].toArray();
+    setPlaylistItems(items, offset > 0);
+    m_playlistTotal = result["total"].toInt();
+    m_playlistOffset = offset + items.size();
+    if (items.isEmpty())
+        m_playlistTotal = m_playlistOffset;
+    m_loadingPlaylists = false;
+
+    QScrollBar *bar = m_playlistList->verticalScrollBar();
+    if (bar && bar->maximum() == 0 && m_playlistOffset < m_playlistTotal)
+        requestPlaylistsPage(m_lastPlaylistGenreIds, m_lastPlaylistType, m_lastPlaylistTags, m_lastPlaylistQuery, m_playlistOffset, true);
 }
 
 void GenreBrowserView::onDiscoverPlaylistsLoaded(const QJsonObject &result)
 {
     m_resultsStack->setCurrentIndex(1);
-    setPlaylistItems(result["items"].toArray());
+    const QString genreIds = result["genre_ids"].toString();
+    const QString tags = result["tags"].toString();
+    const int offset = result["offset"].toInt();
+    if (genreIds != m_lastPlaylistGenreIds || tags != m_lastPlaylistTags)
+        return;
+
+    const QJsonArray items = result["items"].toArray();
+    setPlaylistItems(items, offset > 0);
+    m_playlistTotal = result["total"].toInt();
+    m_playlistOffset = offset + items.size();
+    if (items.isEmpty())
+        m_playlistTotal = m_playlistOffset;
+    m_loadingPlaylists = false;
+
+    QScrollBar *bar = m_playlistList->verticalScrollBar();
+    if (bar && bar->maximum() == 0 && m_playlistOffset < m_playlistTotal)
+        requestPlaylistsPage(m_lastPlaylistGenreIds, m_lastPlaylistType, m_lastPlaylistTags, m_lastPlaylistQuery, m_playlistOffset, true);
 }
 
 void GenreBrowserView::onPlaylistSearchLoaded(const QJsonObject &result)
 {
     m_resultsStack->setCurrentIndex(1);
-    setPlaylistItems(result["items"].toArray());
+    const QString query = result["query"].toString();
+    const int offset = result["offset"].toInt();
+    if (query != m_lastPlaylistQuery)
+        return;
+
+    const QJsonArray items = result["items"].toArray();
+    setPlaylistItems(items, offset > 0);
+    m_playlistTotal = result["total"].toInt();
+    m_playlistOffset = offset + items.size();
+    if (items.isEmpty())
+        m_playlistTotal = m_playlistOffset;
+    m_loadingPlaylists = false;
+
+    QScrollBar *bar = m_playlistList->verticalScrollBar();
+    if (bar && bar->maximum() == 0 && m_playlistOffset < m_playlistTotal)
+        requestPlaylistsPage(m_lastPlaylistGenreIds, m_lastPlaylistType, m_lastPlaylistTags, m_lastPlaylistQuery, m_playlistOffset, true);
 }
 
 void GenreBrowserView::onSelectionChanged()
 {
+    m_collectAlbumsForDeepShuffle = false;
+
     if (m_mode == BrowseMode::PlaylistSearch) {
         m_resultsStack->setCurrentIndex(1);
         m_playlistSearchLabel->setVisible(true);
         m_playlistSearchBox->setVisible(true);
         m_playlistSearchBtn->setVisible(true);
         m_deepShuffleBtn->setVisible(false);
+        m_deepShuffleBtn->setEnabled(true);
+        m_deepShuffleBtn->setText(tr("⇄  Deep Shuffle"));
         const QString query = m_playlistSearchBox->text().trimmed();
         if (query.size() < 2) {
             m_playlistList->clear();
+            m_playlistOffset = 0;
+            m_playlistTotal = 0;
+            m_loadingPlaylists = false;
         } else {
-            m_backend->searchPlaylists(query, 8, 0);
+            requestPlaylistsPage(QString(), QStringLiteral("search"), QString(), query, 0, false);
         }
         return;
     }
@@ -408,20 +497,25 @@ void GenreBrowserView::onSelectionChanged()
 
     if (kind == QStringLiteral("playlists")) {
         m_resultsStack->setCurrentIndex(1);
+        m_deepShuffleBtn->setVisible(false);
+        m_deepShuffleBtn->setEnabled(true);
+        m_deepShuffleBtn->setText(tr("⇄  Deep Shuffle"));
         if (type == QStringLiteral("discover-new"))
-            m_backend->discoverPlaylists(genreIds, QStringLiteral("new"), 25, 0);
+            requestPlaylistsPage(genreIds, type, QStringLiteral("new"), QString(), 0, false);
         else if (type == QStringLiteral("discover-hires"))
-            m_backend->discoverPlaylists(genreIds, QStringLiteral("hi-res"), 25, 0);
+            requestPlaylistsPage(genreIds, type, QStringLiteral("hi-res"), QString(), 0, false);
         else if (type == QStringLiteral("discover-focus"))
-            m_backend->discoverPlaylists(genreIds, QStringLiteral("focus"), 25, 0);
+            requestPlaylistsPage(genreIds, type, QStringLiteral("focus"), QString(), 0, false);
         else if (type == QStringLiteral("discover-qobuzdigs"))
-            m_backend->discoverPlaylists(genreIds, QStringLiteral("qobuzdigs"), 25, 0);
+            requestPlaylistsPage(genreIds, type, QStringLiteral("qobuzdigs"), QString(), 0, false);
         else
-            m_backend->getFeaturedPlaylists(genreIds, type, 25, 0);
+            requestPlaylistsPage(genreIds, type, QString(), QString(), 0, false);
     } else {
         m_resultsStack->setCurrentIndex(0);
         m_deepShuffleBtn->setVisible(m_mode == BrowseMode::Genres);
-        m_backend->getFeaturedAlbums(genreIds, type, 50, 0);
+        m_deepShuffleBtn->setEnabled(true);
+        m_deepShuffleBtn->setText(tr("⇄  Deep Shuffle"));
+        requestAlbumsPage(genreIds, type, 0, false);
     }
 }
 
@@ -436,11 +530,14 @@ QStringList GenreBrowserView::currentAlbumIds() const
     return ids;
 }
 
-void GenreBrowserView::onDeepShuffleClicked()
+void GenreBrowserView::startDeepShuffleFromLoadedAlbums()
 {
     const QStringList albumIds = currentAlbumIds();
-    if (albumIds.isEmpty())
+    if (albumIds.isEmpty()) {
+        m_deepShuffleBtn->setEnabled(true);
+        m_deepShuffleBtn->setText(tr("⇄  Deep Shuffle"));
         return;
+    }
 
     m_waitingDeepShuffle = true;
     m_deepShuffleBtn->setEnabled(false);
@@ -448,12 +545,113 @@ void GenreBrowserView::onDeepShuffleClicked()
     m_backend->getAlbumsTracks(albumIds);
 }
 
+void GenreBrowserView::requestAlbumsPage(const QString &genreIds, const QString &type, int offset, bool append)
+{
+    if (append && m_loadingAlbums)
+        return;
+
+    if (!append) {
+        m_loadingAlbums = false;
+        m_albumOffset = 0;
+        m_albumTotal = 0;
+    }
+
+    m_lastAlbumGenreIds = genreIds;
+    m_lastAlbumType = type;
+    m_loadingAlbums = true;
+    m_backend->getFeaturedAlbums(genreIds, type, 50, static_cast<quint32>(offset));
+}
+
+void GenreBrowserView::requestPlaylistsPage(const QString &genreIds, const QString &type, const QString &tags, const QString &query, int offset, bool append)
+{
+    if (append && m_loadingPlaylists)
+        return;
+
+    if (!append) {
+        m_loadingPlaylists = false;
+        m_playlistOffset = 0;
+        m_playlistTotal = 0;
+    }
+
+    m_lastPlaylistGenreIds = genreIds;
+    m_lastPlaylistType = type;
+    m_lastPlaylistTags = tags;
+    m_lastPlaylistQuery = query;
+    m_loadingPlaylists = true;
+
+    if (type == QStringLiteral("search")) {
+        m_backend->searchPlaylists(query, 8, static_cast<quint32>(offset));
+    } else if (type.startsWith(QStringLiteral("discover-"))) {
+        m_backend->discoverPlaylists(genreIds, tags, 25, static_cast<quint32>(offset));
+    } else {
+        m_backend->getFeaturedPlaylists(genreIds, type, 25, static_cast<quint32>(offset));
+    }
+}
+
+void GenreBrowserView::onAlbumScroll(int value)
+{
+    if (m_mode != BrowseMode::Genres)
+        return;
+    if (m_kindCombo->currentData().toString() != QStringLiteral("albums"))
+        return;
+    if (m_loadingAlbums)
+        return;
+    if (m_albumOffset >= m_albumTotal)
+        return;
+
+    QScrollBar *bar = m_albumList->verticalScrollBar();
+    if (!bar || value < (bar->maximum() - 12))
+        return;
+
+    requestAlbumsPage(m_lastAlbumGenreIds, m_lastAlbumType, m_albumOffset, true);
+}
+
+void GenreBrowserView::onPlaylistScroll(int value)
+{
+    if (m_loadingPlaylists)
+        return;
+    if (m_playlistOffset >= m_playlistTotal)
+        return;
+
+    QScrollBar *bar = m_playlistList->verticalScrollBar();
+    if (!bar || value < (bar->maximum() - 12))
+        return;
+
+    requestPlaylistsPage(
+        m_lastPlaylistGenreIds,
+        m_lastPlaylistType,
+        m_lastPlaylistTags,
+        m_lastPlaylistQuery,
+        m_playlistOffset,
+        true);
+}
+
+void GenreBrowserView::onDeepShuffleClicked()
+{
+    m_deepShuffleBtn->setEnabled(false);
+    m_deepShuffleBtn->setText(tr("Loading…"));
+
+    if (m_loadingAlbums) {
+        m_collectAlbumsForDeepShuffle = true;
+        return;
+    }
+
+    if (m_albumOffset < m_albumTotal) {
+        m_collectAlbumsForDeepShuffle = true;
+        requestAlbumsPage(m_lastAlbumGenreIds, m_lastAlbumType, m_albumOffset, true);
+        return;
+    }
+
+    startDeepShuffleFromLoadedAlbums();
+}
+
 bool GenreBrowserView::tryHandleDeepShuffleTracks(const QJsonArray &tracks)
 {
     if (!m_waitingDeepShuffle)
         return false;
 
     m_waitingDeepShuffle = false;
+    m_collectAlbumsForDeepShuffle = false;
     m_deepShuffleBtn->setEnabled(true);
     m_deepShuffleBtn->setText(tr("⇄  Deep Shuffle"));
 
@@ -523,9 +721,10 @@ void GenreBrowserView::onPlaylistContextMenu(const QPoint &pos)
     menu.exec(m_playlistList->viewport()->mapToGlobal(pos));
 }
 
-void GenreBrowserView::setPlaylistItems(const QJsonArray &items)
+void GenreBrowserView::setPlaylistItems(const QJsonArray &items, bool append)
 {
-    m_playlistList->clear();
+    if (!append)
+        m_playlistList->clear();
 
     QFont tagFont;
     tagFont.setBold(true);

src/view/genrebrowser.hpp

@@ -14,6 +14,7 @@
 #include <QStackedWidget>
 #include <QTreeWidget>
 #include <QWidget>
+#include <QScrollBar>
 
 class GenreBrowserView : public QWidget
 {
@@ -48,6 +49,8 @@ private slots:
     void onPlaylistActivated(QTreeWidgetItem *item, int column);
     void onPlaylistContextMenu(const QPoint &pos);
     void onDeepShuffleClicked();
+    void onAlbumScroll(int value);
+    void onPlaylistScroll(int value);
 
 private:
     QobuzBackend *m_backend = nullptr;
@@ -72,12 +75,28 @@ private:
     int m_lastGenreComboIndex = 0;
     QSet<qint64> m_multiGenreIds;
     bool m_waitingDeepShuffle = false;
+    bool m_collectAlbumsForDeepShuffle = false;
+    bool m_loadingAlbums = false;
+    bool m_loadingPlaylists = false;
+    int m_albumOffset = 0;
+    int m_albumTotal = 0;
+    int m_playlistOffset = 0;
+    int m_playlistTotal = 0;
+    QString m_lastAlbumGenreIds;
+    QString m_lastAlbumType;
+    QString m_lastPlaylistGenreIds;
+    QString m_lastPlaylistType;
+    QString m_lastPlaylistTags;
+    QString m_lastPlaylistQuery;
 
     void refreshModeUi();
     void refreshGenreTypeChoices();
     QString currentGenreIds() const;
     QStringList currentAlbumIds() const;
+    void startDeepShuffleFromLoadedAlbums();
+    void requestAlbumsPage(const QString &genreIds, const QString &type, int offset, bool append);
+    void requestPlaylistsPage(const QString &genreIds, const QString &type, const QString &tags, const QString &query, int offset, bool append);
     bool chooseMultiGenres();
     void updateMultiGenreLabel();
-    void setPlaylistItems(const QJsonArray &items);
+    void setPlaylistItems(const QJsonArray &items, bool append = false);
 };