Create and render moodbars in background threads to avoid blocking the UI

src/moodbar/moodbaritemdelegate.cpp

@@ -25,6 +25,12 @@
 
 #include <QApplication>
 #include <QPainter>
+#include <QtConcurrentRun>
+
+MoodbarItemDelegate::Data::Data()
+  : state_(State_None)
+{
+}
 
 MoodbarItemDelegate::MoodbarItemDelegate(Application* app, QObject* parent)
   : QItemDelegate(parent),
@@ -36,73 +42,154 @@ void MoodbarItemDelegate::paint(
     QPainter* painter, const QStyleOptionViewItem& option,
     const QModelIndex& index) const {
   QPixmap pixmap = const_cast<MoodbarItemDelegate*>(this)->PixmapForIndex(
-        index, option.rect.size(), option.palette);
+        index, option.rect.size());
   if (!pixmap.isNull()) {
     painter->drawPixmap(option.rect, pixmap);
   }
 }
 
 QPixmap MoodbarItemDelegate::PixmapForIndex(
-    const QModelIndex& index, const QSize& size, const QPalette& palette) {
-  // Do we have a pixmap already that's the right size?
-  QPixmap pixmap = index.data(Playlist::Role_MoodbarPixmap).value<QPixmap>();
-  if (!pixmap.isNull() && pixmap.size() == size) {
-    return pixmap;
+    const QModelIndex& index, const QSize& size) {
+  // Pixmaps are keyed off URL.
+  const QUrl url(index.sibling(index.row(), Playlist::Column_Filename).data().toUrl());
+
+  Data* data = data_[url];
+  if (!data) {
+    data = new Data;
+    data_.insert(url, data);
   }
 
-  // Do we have colors?
-  ColorVector colors = index.data(Playlist::Role_MoodbarColors).value<ColorVector>();
-  if (colors.isEmpty()) {
-    // Nope - we need to load a mood file for this song and generate some colors
-    // from it.
-    const QUrl url(index.sibling(index.row(), Playlist::Column_Filename).data().toUrl());
+  data->indexes_.insert(index);
+  data->desired_size_ = size;
 
-    QByteArray data;
-    MoodbarPipeline* pipeline = NULL;
-    switch (app_->moodbar_loader()->Load(url, &data, &pipeline)) {
-    case MoodbarLoader::CannotLoad:
-      return QPixmap();
+  switch (data->state_) {
+  case Data::State_CannotLoad:
+  case Data::State_LoadingData:
+  case Data::State_LoadingColors:
+  case Data::State_LoadingImage:
+    return data->pixmap_;
 
-    case MoodbarLoader::Loaded:
-      // Aww yeah
-      colors = MoodbarRenderer::Colors(data, MoodbarRenderer::Style_Normal, palette);
-      break;
-
-    case MoodbarLoader::WillLoadAsync:
-      // Maybe in a little while.
-      qLog(Debug) << "Loading" << pipeline;
-      NewClosure(pipeline, SIGNAL(Finished(bool)),
-                 this, SLOT(RequestFinished(MoodbarPipeline*,QModelIndex,QUrl)),
-                 pipeline, index, url);
-      return QPixmap();
+  case Data::State_Loaded:
+    // Is the pixmap the right size?
+    if (data->pixmap_.size() != size) {
+      StartLoadingImage(url, data);
     }
+
+    return data->pixmap_;
+
+  case Data::State_None:
+    break;
   }
 
-  // We've got colors, let's make a pixmap.
-  pixmap = QPixmap(size);
-  QPainter p(&pixmap);
-  MoodbarRenderer::Render(colors, &p, QRect(QPoint(0, 0), size));
-  p.end();
+  // We have to start loading the data from scratch.
+  data->state_ = Data::State_LoadingData;
 
-  // Set these on the item so we don't have to look them up again.
-  QAbstractItemModel* model = const_cast<QAbstractItemModel*>(index.model());
-  model->setData(index, QVariant::fromValue(colors), Playlist::Role_MoodbarColors);
-  model->setData(index, pixmap, Playlist::Role_MoodbarPixmap);
+  // Load a mood file for this song and generate some colors from it
+  QByteArray bytes;
+  MoodbarPipeline* pipeline = NULL;
+  switch (app_->moodbar_loader()->Load(url, &bytes, &pipeline)) {
+  case MoodbarLoader::CannotLoad:
+    data->state_ = Data::State_CannotLoad;
+    break;
 
-  return pixmap;
+  case MoodbarLoader::Loaded:
+    // We got the data immediately.
+    StartLoadingColors(url, bytes, data);
+    break;
+
+  case MoodbarLoader::WillLoadAsync:
+    // Maybe in a little while.
+    NewClosure(pipeline, SIGNAL(Finished(bool)),
+               this, SLOT(DataLoaded(QUrl,MoodbarPipeline*)),
+               url, pipeline);
+    break;
+  }
+
+  return QPixmap();
 }
 
-void MoodbarItemDelegate::RequestFinished(
-    MoodbarPipeline* pipeline, const QModelIndex& index, const QUrl& url) {
-  qLog(Debug) << "Finished" << pipeline;
-  // Is this index still valid, and does it still point to the same URL?
-  if (!index.isValid() || index.sibling(index.row(), Playlist::Column_Filename).data().toUrl() != url) {
+void MoodbarItemDelegate::DataLoaded( const QUrl& url, MoodbarPipeline* pipeline) {
+  Data* data = data_[url];
+  if (!data) {
     return;
   }
 
-  // It's good.  Create the color list and set them on the item.
-  ColorVector colors = MoodbarRenderer::Colors(
-        pipeline->data(), MoodbarRenderer::Style_Normal, qApp->palette());
-  QAbstractItemModel* model = const_cast<QAbstractItemModel*>(index.model());
-  model->setData(index, QVariant::fromValue(colors), Playlist::Role_MoodbarColors);
+  if (!pipeline->success()) {
+    data->state_ = Data::State_CannotLoad;
+    return;
+  }
+
+  // Load the colors next.
+  StartLoadingColors(url, pipeline->data(), data);
+}
+
+void MoodbarItemDelegate::StartLoadingColors(
+    const QUrl& url, const QByteArray& bytes, Data* data) {
+  data->state_ = Data::State_LoadingColors;
+
+  QFutureWatcher<ColorVector>* watcher = new QFutureWatcher<ColorVector>();
+  NewClosure(watcher, SIGNAL(finished()),
+             this, SLOT(ColorsLoaded(QUrl,QFutureWatcher<ColorVector>*)),
+             url, watcher);
+
+  QFuture<ColorVector> future = QtConcurrent::run(MoodbarRenderer::Colors,
+      bytes, MoodbarRenderer::Style_Normal, qApp->palette());
+  watcher->setFuture(future);
+}
+
+void MoodbarItemDelegate::ColorsLoaded(
+    const QUrl& url, QFutureWatcher<ColorVector>* watcher) {
+  watcher->deleteLater();
+
+  Data* data = data_[url];
+  if (!data) {
+    return;
+  }
+
+  data->colors_ = watcher->result();
+
+  // Load the image next.
+  StartLoadingImage(url, data);
+}
+
+void MoodbarItemDelegate::StartLoadingImage(const QUrl& url, Data* data) {
+  data->state_ = Data::State_LoadingImage;
+
+  QFutureWatcher<QImage>* watcher = new QFutureWatcher<QImage>();
+  NewClosure(watcher, SIGNAL(finished()),
+             this, SLOT(ImageLoaded(QUrl,QFutureWatcher<QImage>*)),
+             url, watcher);
+
+  QFuture<QImage> future = QtConcurrent::run(MoodbarRenderer::RenderToImage,
+      data->colors_, data->desired_size_);
+  watcher->setFuture(future);
+}
+
+void MoodbarItemDelegate::ImageLoaded(const QUrl& url, QFutureWatcher<QImage>* watcher) {
+  watcher->deleteLater();
+
+  Data* data = data_[url];
+  if (!data) {
+    return;
+  }
+
+  QImage image(watcher->result());
+
+  // If the desired size changed then don't even bother converting the image
+  // to a pixmap, just reload it at the new size.
+  if (!image.isNull() && data->desired_size_ != image.size()) {
+    StartLoadingImage(url, data);
+    return;
+  }
+
+  data->pixmap_ = QPixmap::fromImage(image);
+  data->state_ = Data::State_Loaded;
+
+  // Update all the indices with the new pixmap.
+  foreach (const QPersistentModelIndex& index, data->indexes_) {
+    if (index.isValid() && index.sibling(index.row(), Playlist::Column_Filename).data().toUrl() == url) {
+      const_cast<Playlist*>(reinterpret_cast<const Playlist*>(index.model()))
+          ->MoodbarUpdated(index);
+    }
+  }
 }

src/moodbar/moodbaritemdelegate.h

@@ -18,7 +18,12 @@
 #ifndef MOODBARITEMDELEGATE_H
 #define MOODBARITEMDELEGATE_H
 
+#include "moodbarrenderer.h"
+
+#include <QCache>
 #include <QItemDelegate>
+#include <QFutureWatcher>
+#include <QUrl>
 
 class Application;
 class MoodbarPipeline;
@@ -35,15 +40,39 @@ public:
              const QModelIndex& index) const;
 
 private slots:
-  void RequestFinished(MoodbarPipeline* pipeline, const QModelIndex& index,
-                       const QUrl& url);
+  void DataLoaded(const QUrl& url, MoodbarPipeline* pipeline);
+  void ColorsLoaded(const QUrl& url, QFutureWatcher<ColorVector>* watcher);
+  void ImageLoaded(const QUrl& url, QFutureWatcher<QImage>* watcher);
 
 private:
-  QPixmap PixmapForIndex(const QModelIndex& index, const QSize& size,
-                         const QPalette& palette);
+  struct Data {
+    Data();
+
+    enum State {
+      State_None,
+      State_CannotLoad,
+      State_LoadingData,
+      State_LoadingColors,
+      State_LoadingImage,
+      State_Loaded
+    };
+
+    QSet<QPersistentModelIndex> indexes_;
+
+    State state_;
+    ColorVector colors_;
+    QSize desired_size_;
+    QPixmap pixmap_;
+  };
+
+private:
+  QPixmap PixmapForIndex(const QModelIndex& index, const QSize& size);
+  void StartLoadingColors(const QUrl& url, const QByteArray& bytes, Data* data);
+  void StartLoadingImage(const QUrl& url, Data* data);
 
 private:
   Application* app_;
+  QCache<QUrl, Data> data_;
 };
 
 #endif // MOODBARITEMDELEGATE_H

src/moodbar/moodbarloader.cpp

@@ -32,7 +32,7 @@
 MoodbarLoader::MoodbarLoader(QObject* parent)
   : QObject(parent),
     cache_(new QNetworkDiskCache(this)),
-    kMaxActiveRequests(QThread::idealThreadCount()),
+    kMaxActiveRequests(QThread::idealThreadCount() / 2 + 1),
     save_alongside_originals_(false)
 {
   cache_->setCacheDirectory(Utilities::GetConfigPath(Utilities::Path_MoodbarCache));
@@ -62,9 +62,12 @@ MoodbarLoader::Result MoodbarLoader::Load(
   }
   
   // Are we in the middle of loading this moodbar already?
-  if (active_requests_.contains(url)) {
-    *async_pipeline = active_requests_[url];
-    return WillLoadAsync;
+  {
+    QMutexLocker l(&mutex_);
+    if (requests_.contains(url)) {
+      *async_pipeline = requests_[url];
+      return WillLoadAsync;
+    }
   }
   
   // Check if a mood file exists for this file already
@@ -93,29 +96,30 @@ MoodbarLoader::Result MoodbarLoader::Load(
              this, SLOT(RequestFinished(MoodbarPipeline*,QUrl)),
              pipeline, url);
 
-  active_requests_[url] = pipeline;
-
-  if (active_requests_.count() > kMaxActiveRequests) {
-    // Just queue this request now, start it later when another request
-    // finishes.
+  {
+    QMutexLocker l(&mutex_);
+    requests_[url] = pipeline;
     queued_requests_ << url;
-  } else if (!StartQueuedRequest(url)) {
-    return CannotLoad;
   }
 
+  QMetaObject::invokeMethod(this, "MaybeTakeNextRequest", Qt::QueuedConnection);
+
   *async_pipeline = pipeline;
   return WillLoadAsync;
 }
 
-bool MoodbarLoader::StartQueuedRequest(const QUrl& url) {
-  if (!active_requests_[url]->Start()) {
-    delete active_requests_.take(url);
-    return false;
+void MoodbarLoader::MaybeTakeNextRequest() {
+  QMutexLocker l(&mutex_);
+  if (active_requests_.count() > kMaxActiveRequests ||
+      queued_requests_.isEmpty()) {
+    return;
   }
 
-  qLog(Info) << "Creating moodbar data for" << url.toLocalFile();
+  const QUrl url = queued_requests_.takeFirst();
+  active_requests_ << url;
 
-  return true;
+  qLog(Info) << "Creating moodbar data for" << url.toLocalFile();
+  requests_[url]->Start();
 }
 
 void MoodbarLoader::RequestFinished(MoodbarPipeline* request, const QUrl& url) {
@@ -145,10 +149,12 @@ void MoodbarLoader::RequestFinished(MoodbarPipeline* request, const QUrl& url) {
   qLog(Debug) << "Deleting" << request;
 
   // Remove the request from the active list and delete it
-  active_requests_.take(url);
+  {
+    QMutexLocker l(&mutex_);
+    requests_.remove(url);
+    active_requests_.remove(url);
+  }
   QTimer::singleShot(10, request, SLOT(deleteLater()));
 
-  if (!queued_requests_.isEmpty()) {
-    StartQueuedRequest(queued_requests_.takeFirst());
-  }
+  QMetaObject::invokeMethod(this, "MaybeTakeNextRequest", Qt::QueuedConnection);
 }

src/moodbar/moodbarloader.h

@@ -19,8 +19,9 @@
 #define MOODBARLOADER_H
 
 #include <QMap>
+#include <QMutex>
 #include <QObject>
-#include <QPair>
+#include <QSet>
 
 class QNetworkDiskCache;
 class QUrl;
@@ -51,18 +52,20 @@ public:
 
 private slots:
   void RequestFinished(MoodbarPipeline* request, const QUrl& filename);
+  void MaybeTakeNextRequest();
 
 private:
   static QStringList MoodFilenames(const QString& song_filename);
-  bool StartQueuedRequest(const QUrl& url);
   
 private:
   QNetworkDiskCache* cache_;
 
   const int kMaxActiveRequests;
   
-  QMap<QUrl, MoodbarPipeline*> active_requests_;
+  QMutex mutex_;
+  QMap<QUrl, MoodbarPipeline*> requests_;
   QList<QUrl> queued_requests_;
+  QSet<QUrl> active_requests_;
 
   bool save_alongside_originals_;
 };

src/moodbar/moodbarpipeline.cpp

@@ -32,7 +32,6 @@ MoodbarPipeline::MoodbarPipeline(const QString& local_filename)
 }
 
 MoodbarPipeline::~MoodbarPipeline() {
-  qLog(Debug) << "Actually deleting" << this;
   Cleanup();
 }
 
@@ -84,6 +83,7 @@ bool MoodbarPipeline::Start() {
   
   if (!filesrc || !convert_element_ || !fftwspectrum || !moodbar || !appsink) {
     pipeline_ = NULL;
+    emit Finished(false);
     return false;
   }
 

src/moodbar/moodbarrenderer.cpp

@@ -139,3 +139,11 @@ void MoodbarRenderer::Render(const ColorVector& colors, QPainter* p, const QRect
     }
   }
 }
+
+QImage MoodbarRenderer::RenderToImage(const ColorVector& colors, const QSize& size) {
+  QImage image(size, QImage::Format_ARGB32_Premultiplied);
+  QPainter p(&image);
+  Render(colors, &p, image.rect());
+  p.end();
+  return image;
+}

src/moodbar/moodbarrenderer.h

@@ -41,6 +41,7 @@ public:
   static ColorVector Colors(const QByteArray& data, MoodbarStyle style,
                             const QPalette& palette);
   static void Render(const ColorVector& colors, QPainter* p, const QRect& rect);
+  static QImage RenderToImage(const ColorVector& colors, const QSize& size);
 
 private:
   MoodbarRenderer();

src/playlist/playlist.cpp

@@ -43,7 +43,6 @@
 #include "library/librarybackend.h"
 #include "library/librarymodel.h"
 #include "library/libraryplaylistitem.h"
-#include "moodbar/moodbarrenderer.h"
 #include "smartplaylists/generator.h"
 #include "smartplaylists/generatorinserter.h"
 #include "smartplaylists/generatormimedata.h"
@@ -244,12 +243,6 @@ QVariant Playlist::data(const QModelIndex& index, int role) const {
              items_[index.row()]->IsLocalLibraryItem() &&
              items_[index.row()]->Metadata().id() != -1;
 
-    case Role_MoodbarColors:
-      return QVariant::fromValue(items_[index.row()]->MoodbarColors());
-
-    case Role_MoodbarPixmap:
-      return items_[index.row()]->MoodbarPixmap();
-
     case Qt::EditRole:
     case Qt::ToolTipRole:
     case Qt::DisplayRole: {
@@ -316,21 +309,16 @@ QVariant Playlist::data(const QModelIndex& index, int role) const {
   }
 }
 
+void Playlist::MoodbarUpdated(const QModelIndex& index) {
+  emit dataChanged(index.sibling(index.row(), Column_Mood),
+                   index.sibling(index.row(), Column_Mood));
+}
+
 bool Playlist::setData(const QModelIndex& index, const QVariant& value, int role) {
   int row = index.row();
   PlaylistItemPtr item = item_at(row);
   Song song = item->Metadata();
 
-  if (role == Role_MoodbarColors) {
-    item->SetMoodbarColors(value.value<QVector<QColor> >());
-    emit dataChanged(index.sibling(index.row(), Column_Mood),
-                     index.sibling(index.row(), Column_Mood));
-    return true;
-  } else if (role == Role_MoodbarPixmap) {
-    item->SetMoodbarPixmap(value.value<QPixmap>());
-    return true;
-  }
-
   if (index.data() == value)
     return false;
 

src/playlist/playlist.h

@@ -122,8 +122,6 @@ class Playlist : public QAbstractListModel {
     Role_StopAfter,
     Role_QueuePosition,
     Role_CanSetRating,
-    Role_MoodbarColors,
-    Role_MoodbarPixmap,
   };
 
   enum LastFMStatus {
@@ -246,6 +244,9 @@ class Playlist : public QAbstractListModel {
   // Unregisters a SongInsertVetoListener object.
   void RemoveSongInsertVetoListener(SongInsertVetoListener* listener);
 
+  // Just emits the dataChanged() signal so the mood column is repainted.
+  void MoodbarUpdated(const QModelIndex& index);
+
   // QAbstractListModel
   int rowCount(const QModelIndex& = QModelIndex()) const { return items_.count(); }
   int columnCount(const QModelIndex& = QModelIndex()) const { return ColumnCount; }

src/playlist/playlistitem.cpp

@@ -33,7 +33,6 @@
 
 
 PlaylistItem::~PlaylistItem() {
-  delete moodbar_pixmap_;
 }
 
 PlaylistItem* PlaylistItem::NewFromType(const QString& type) {
@@ -124,17 +123,3 @@ QColor PlaylistItem::GetCurrentForegroundColor() const {
 bool PlaylistItem::HasCurrentForegroundColor() const {
   return !foreground_colors_.isEmpty();
 }
-
-QPixmap PlaylistItem::MoodbarPixmap() const {
-  if (!moodbar_pixmap_) {
-    return QPixmap();
-  }
-  return *moodbar_pixmap_;
-}
-
-void PlaylistItem::SetMoodbarPixmap(const QPixmap& pixmap) {
-  if (!moodbar_pixmap_) {
-    moodbar_pixmap_ = new QPixmap;
-  }
-  *moodbar_pixmap_ = pixmap;
-}

src/playlist/playlistitem.h

@@ -33,8 +33,7 @@ class SqlRow;
 class PlaylistItem : public boost::enable_shared_from_this<PlaylistItem> {
  public:
   PlaylistItem(const QString& type)
-    : type_(type),
-      moodbar_pixmap_(NULL) {}
+    : type_(type) {}
   virtual ~PlaylistItem();
 
   static PlaylistItem* NewFromType(const QString& type);
@@ -93,12 +92,6 @@ class PlaylistItem : public boost::enable_shared_from_this<PlaylistItem> {
   // before actually using it.
   virtual bool IsLocalLibraryItem() const { return false; }
 
-  // Moodbar accessors.  These are lazy-loaded by MoodbarItemDelegate.
-  const QVector<QColor>& MoodbarColors() const { return moodbar_colors_; }
-  void SetMoodbarColors(const QVector<QColor>& colors) { moodbar_colors_ = colors; }
-  QPixmap MoodbarPixmap() const;
-  void SetMoodbarPixmap(const QPixmap& pixmap);
-
  protected:
   enum DatabaseColumn {
     Column_LibraryId,
@@ -115,10 +108,6 @@ class PlaylistItem : public boost::enable_shared_from_this<PlaylistItem> {
 
   QMap<short, QColor> background_colors_;
   QMap<short, QColor> foreground_colors_;
-
-private:
-  QVector<QColor> moodbar_colors_;
-  QPixmap* moodbar_pixmap_;
 };
 typedef boost::shared_ptr<PlaylistItem> PlaylistItemPtr;
 typedef QList<PlaylistItemPtr> PlaylistItemList;