Move LibraryDirectoryModel out of LibraryModel.

There are several instances of the LibraryModel class used in the system. Each
of these creates a LibraryDirectoryModel instance, but only the instance held
by the main library is every used. Move this out of the LibraryModel class and
into the Library class.

src/core/application.cpp

@@ -287,7 +287,7 @@ LibraryBackend* Application::library_backend() const {
 }
 
 LibraryDirectoryModel* Application::directory_model() const {
-  return library()->model()->directory_model();
+  return library()->directory_model();
 }
 
 LibraryModel* Application::library_model() const { return library()->model(); }

src/library/library.cpp

@@ -17,14 +17,15 @@
 
 #include "library.h"
 
-#include "librarymodel.h"
-#include "librarybackend.h"
 #include "core/application.h"
 #include "core/database.h"
 #include "core/player.h"
 #include "core/tagreaderclient.h"
 #include "core/taskmanager.h"
 #include "core/thread.h"
+#include "librarybackend.h"
+#include "librarydirectorymodel.h"
+#include "librarymodel.h"
 #include "smartplaylists/generator.h"
 #include "smartplaylists/querygenerator.h"
 #include "smartplaylists/search.h"
@@ -56,6 +57,7 @@ Library::Library(Application* app, QObject* parent)
   using smart_playlists::SearchTerm;
 
   model_ = new LibraryModel(backend_, app_, this);
+  dir_model_ = new LibraryDirectoryModel(backend_.get(), this);
   model_->set_show_smart_playlists(true);
   model_->set_default_smart_playlists(
       LibraryModel::DefaultGenerators()

src/library/library.h

@@ -30,6 +30,7 @@ class Application;
 class Database;
 class LibraryBackend;
 class LibraryModel;
+class LibraryDirectoryModel;
 class LibraryWatcher;
 class TaskManager;
 class Thread;
@@ -50,6 +51,7 @@ class Library : public QObject {
 
   LibraryBackend* backend() const { return backend_.get(); }
   LibraryModel* model() const { return model_; }
+  LibraryDirectoryModel* directory_model() const { return dir_model_; }
 
   QString full_rescan_reason(int schema_version) const {
     return full_rescan_revisions_.value(schema_version, QString());
@@ -80,6 +82,7 @@ class Library : public QObject {
   Application* app_;
   std::shared_ptr<LibraryBackend> backend_;
   LibraryModel* model_;
+  LibraryDirectoryModel* dir_model_;
 
   LibraryWatcher* watcher_;
   Thread* watcher_thread_;

src/library/librarymodel.cpp

@@ -33,7 +33,6 @@
 
 #include "librarybackend.h"
 #include "libraryitem.h"
-#include "librarydirectorymodel.h"
 #include "libraryview.h"
 #include "sqlrow.h"
 #include "core/application.h"
@@ -79,7 +78,6 @@ LibraryModel::LibraryModel(std::shared_ptr<LibraryBackend> backend,
     : SimpleTreeModel<LibraryItem>(new LibraryItem(this), parent),
       backend_(backend),
       app_(app),
-      dir_model_(new LibraryDirectoryModel(backend.get(), this)),
       show_smart_playlists_(false),
       show_various_artists_(true),
       total_song_count_(0),

src/library/librarymodel.h

@@ -38,7 +38,6 @@
 
 class Application;
 class AlbumCoverLoader;
-class LibraryDirectoryModel;
 class LibraryBackend;
 namespace smart_playlists {
 class Search;
@@ -120,7 +119,6 @@ class LibraryModel : public SimpleTreeModel<LibraryItem> {
   };
 
   LibraryBackend* backend() const { return backend_.get(); }
-  LibraryDirectoryModel* directory_model() const { return dir_model_; }
 
   typedef QList<smart_playlists::GeneratorPtr> GeneratorList;
   typedef QList<GeneratorList> DefaultGenerators;
@@ -263,7 +261,6 @@ signals:
  private:
   std::shared_ptr<LibraryBackend> backend_;
   Application* app_;
-  LibraryDirectoryModel* dir_model_;
   bool show_smart_playlists_;
   DefaultGenerators default_smart_playlists_;
   bool show_various_artists_;