Move loading of devices from the database onto a different thread.

ext/libclementine-common/CMakeLists.txt

@@ -5,6 +5,7 @@ include_directories(${CMAKE_SOURCE_DIR}/src)
 
 set(SOURCES
   core/closure.cpp
+  core/concurrentrun.cpp
   core/encoding.cpp
   core/logging.cpp
   core/messagehandler.cpp

ext/libclementine-common/core/concurrentrun.cpp

@@ -0,0 +1,11 @@
+#include "concurrentrun.h"
+
+namespace ConcurrentRun {
+
+void Run(
+    QThreadPool* threadpool,
+    std::tr1::function<void ()> function) {
+  (new ThreadFunctorVoid(function))->Start(threadpool);
+}
+
+}  // namespace ConcurrentRun

ext/libclementine-common/core/concurrentrun.h

@@ -72,6 +72,22 @@ class ThreadFunctorBase : public QFutureInterface<ReturnType>, public QRunnable
   ReturnType result_;
 };
 
+// Use bool as a placeholder result.
+class ThreadFunctorVoid : public ThreadFunctorBase<bool> {
+ public:
+  ThreadFunctorVoid(std::tr1::function<void ()> function)
+    : function_(function)
+  { }
+
+  void run() {
+    function_();
+    ThreadFunctorBase<bool>::End();
+  }
+
+ private:
+  std::tr1::function<void ()> function_;
+};
+
 template<typename ReturnType, typename Arg>
 class ThreadFunctor1 : public ThreadFunctorBase<ReturnType> {
 public:
@@ -113,6 +129,9 @@ private:
 };
 
 namespace ConcurrentRun {
+  void Run(
+      QThreadPool* threadpool,
+      std::tr1::function<void ()> function);
 
   template<typename ReturnType, typename Arg>
   QFuture<ReturnType> Run(

src/devices/devicemanager.cpp

@@ -22,6 +22,7 @@
 #include "devicestatefiltermodel.h"
 #include "filesystemdevice.h"
 #include "core/application.h"
+#include "core/concurrentrun.h"
 #include "core/database.h"
 #include "core/logging.h"
 #include "core/musicstorage.h"
@@ -65,6 +66,9 @@
 #include <QSortFilterProxyModel>
 #include <QUrl>
 
+#include <tr1/functional>
+using std::tr1::bind;
+
 const int DeviceManager::kDeviceIconSize = 32;
 const int DeviceManager::kDeviceIconOverlaySize = 16;
 
@@ -179,12 +183,9 @@ DeviceManager::DeviceManager(Application* app, QObject *parent)
   backend_->moveToThread(app_->database()->thread());
   backend_->Init(app_->database());
 
-  DeviceDatabaseBackend::DeviceList devices = backend_->GetAllDevices();
-  foreach (const DeviceDatabaseBackend::Device& device, devices) {
-    DeviceInfo info;
-    info.InitFromDb(device);
-    devices_ << info;
-  }
+  // This reads from the database and contends on the database mutex, which can
+  // be very slow on startup.
+  ConcurrentRun::Run(&thread_pool_, bind(&DeviceManager::LoadAllDevices, this));
 
   // This proxy model only shows connected devices
   connected_devices_model_ = new DeviceStateFilterModel(this);
@@ -236,6 +237,16 @@ DeviceManager::~DeviceManager() {
   backend_->deleteLater();
 }
 
+void DeviceManager::LoadAllDevices() {
+  Q_ASSERT(QThread::currentThread() != qApp->thread());
+  DeviceDatabaseBackend::DeviceList devices = backend_->GetAllDevices();
+  foreach (const DeviceDatabaseBackend::Device& device, devices) {
+    DeviceInfo info;
+    info.InitFromDb(device);
+    devices_ << info;
+  }
+}
+
 int DeviceManager::rowCount(const QModelIndex&) const {
   return devices_.count();
 }

src/devices/devicemanager.h

@@ -23,6 +23,7 @@
 
 #include <QAbstractListModel>
 #include <QIcon>
+#include <QThreadPool>
 
 #include <boost/shared_ptr.hpp>
 
@@ -104,6 +105,7 @@ private slots:
   void DeviceTaskStarted(int id);
   void TasksChanged();
   void DeviceSongCountUpdated(int count);
+  void LoadAllDevices();
 
 private:
   // Devices can be in three different states:
@@ -176,6 +178,8 @@ private:
 
   // Map of task ID to device index
   QMap<int, QPersistentModelIndex> active_tasks_;
+
+  QThreadPool thread_pool_;
 };