DolphinQt2: Show cached games before checking whether they exist on disk

DolphinWX already has this improvement in startup time, and it matters
a lot when you have a large game list.

Source/Core/DolphinQt2/GameList/GameListModel.cpp

@@ -28,6 +28,8 @@ GameListModel::GameListModel(QObject* parent) : QAbstractTableModel(parent)
   for (const QString& dir : Settings::Instance().GetPaths())
     m_tracker.AddDirectory(dir);
 
+  m_tracker.Start();
+
   connect(&Settings::Instance(), &Settings::ThemeChanged, [this] {
     // Tell the view to repaint. The signal 'dataChanged' also seems like it would work here, but
     // unfortunately it won't cause a repaint until the view is focused.

Source/Core/DolphinQt2/GameList/GameTracker.cpp

@@ -30,8 +30,10 @@ GameTracker::GameTracker(QObject* parent) : QFileSystemWatcher(parent)
     switch (command.type)
     {
     case CommandType::LoadCache:
-      m_cache.Load();
+      LoadCache();
       break;
+    case CommandType::Start:
+      StartInternal();
     case CommandType::AddDirectory:
       AddDirectoryInternal(command.path);
       break;
@@ -52,6 +54,54 @@ GameTracker::GameTracker(QObject* parent) : QFileSystemWatcher(parent)
   // TODO: When language changes, reload m_title_database and call m_cache.UpdateAdditionalMetadata
 }
 
+void GameTracker::LoadCache()
+{
+  std::lock_guard<std::mutex> lk(m_mutex);
+  m_cache.Load();
+}
+
+void GameTracker::Start()
+{
+  if (m_initial_games_emitted)
+    return;
+
+  m_initial_games_emitted = true;
+
+  std::lock_guard<std::mutex> lk(m_mutex);
+
+  m_load_thread.EmplaceItem(Command{CommandType::Start, {}});
+
+  m_cache.ForEach(
+      [this](const std::shared_ptr<const UICommon::GameFile>& game) { emit GameLoaded(game); });
+}
+
+void GameTracker::StartInternal()
+{
+  if (m_started)
+    return;
+
+  m_started = true;
+
+  std::vector<std::string> paths;
+  paths.reserve(m_tracked_files.size());
+  for (const QString& path : m_tracked_files.keys())
+    paths.push_back(path.toStdString());
+
+  auto emit_game_loaded = [this](const std::shared_ptr<const UICommon::GameFile>& game) {
+    emit GameLoaded(std::move(game));
+  };
+  auto emit_game_removed = [this](const std::string& path) {
+    emit GameRemoved(QString::fromStdString(path));
+  };
+
+  std::lock_guard<std::mutex> lk(m_mutex);
+
+  bool cache_updated = m_cache.Update(paths, emit_game_loaded, emit_game_removed);
+  cache_updated |= m_cache.UpdateAdditionalMetadata(m_title_database, emit_game_loaded);
+  if (cache_updated)
+    m_cache.Save();
+}
+
 void GameTracker::AddDirectory(const QString& dir)
 {
   m_load_thread.EmplaceItem(Command{CommandType::AddDirectory, dir});
@@ -108,6 +158,7 @@ void GameTracker::RemoveDirectoryInternal(const QString& dir)
       {
         removePath(path);
         m_tracked_files.remove(path);
+        if (m_started)
           emit GameRemoved(path);
       }
     }
@@ -143,6 +194,7 @@ void GameTracker::UpdateDirectoryInternal(const QString& dir)
     if (tracked_file.empty())
     {
       m_tracked_files.remove(missing);
+      if (m_started)
         GameRemoved(missing);
     }
   }
@@ -152,6 +204,7 @@ void GameTracker::UpdateFileInternal(const QString& file)
 {
   if (QFileInfo(file).exists())
   {
+    if (m_started)
       GameRemoved(file);
     addPath(file);
     LoadGame(file);
@@ -159,6 +212,7 @@ void GameTracker::UpdateFileInternal(const QString& file)
   else if (removePath(file))
   {
     m_tracked_files.remove(file);
+    if (m_started)
       emit GameRemoved(file);
   }
 }
@@ -187,6 +241,9 @@ QSet<QString> GameTracker::FindMissingFiles(const QString& dir)
 
 void GameTracker::LoadGame(const QString& path)
 {
+  if (!m_started)
+    return;
+
   const std::string converted_path = path.toStdString();
   if (!DiscIO::ShouldHideFromGameList(converted_path))
   {

Source/Core/DolphinQt2/GameList/GameTracker.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <memory>
+#include <mutex>
 
 #include <QFileSystemWatcher>
 #include <QMap>
@@ -26,6 +27,12 @@ class GameTracker final : public QFileSystemWatcher
 public:
   explicit GameTracker(QObject* parent = nullptr);
 
+  // A GameTracker won't emit any signals until this function has been called.
+  // Before you call this function, make sure to call AddDirectory for all
+  // directories you want to track, otherwise games will briefly disappear
+  // until you call AddDirectory and the GameTracker finishes scanning the file system.
+  void Start();
+
   void AddDirectory(const QString& dir);
   void RemoveDirectory(const QString& dir);
   void ReloadDirectory(const QString& dir);
@@ -35,6 +42,8 @@ signals:
   void GameRemoved(const QString& path);
 
 private:
+  void LoadCache();
+  void StartInternal();
   void UpdateDirectory(const QString& dir);
   void UpdateFile(const QString& path);
   void AddDirectoryInternal(const QString& dir);
@@ -47,6 +56,7 @@ private:
   enum class CommandType
   {
     LoadCache,
+    Start,
     AddDirectory,
     RemoveDirectory,
     UpdateDirectory,
@@ -64,6 +74,9 @@ private:
   Common::WorkQueueThread<Command> m_load_thread;
   UICommon::GameFileCache m_cache;
   Core::TitleDatabase m_title_database;
+  std::mutex m_mutex;
+  bool m_started = false;
+  bool m_initial_games_emitted = false;
 };
 
 Q_DECLARE_METATYPE(std::shared_ptr<const UICommon::GameFile>)

Source/Core/UICommon/GameFileCache.cpp

@@ -73,7 +73,10 @@ std::shared_ptr<const GameFile> GameFileCache::AddOrGet(const std::string& path,
   return result;
 }
 
-bool GameFileCache::Update(const std::vector<std::string>& all_game_paths)
+bool GameFileCache::Update(
+    const std::vector<std::string>& all_game_paths,
+    std::function<void(const std::shared_ptr<const GameFile>&)> game_added_to_cache,
+    std::function<void(const std::string&)> game_removed_from_cache)
 {
   // Copy game paths into a set, except ones that match DiscIO::ShouldHideFromGameList.
   // TODO: Prevent DoFileSearch from looking inside /files/ directories of DirectoryBlobs at all?
@@ -102,21 +105,27 @@ bool GameFileCache::Update(const std::vector<std::string>& all_game_paths)
       }
       else
       {
+        if (game_removed_from_cache)
+          game_removed_from_cache((*it)->GetFilePath());
+
         cache_changed = true;
         --end;
         *it = std::move(*end);
+        m_cached_files.pop_back();
       }
     }
-    m_cached_files.erase(it, m_cached_files.end());
   }
 
   // Now that the previous loop has run, game_paths only contains paths that
   // aren't in m_cached_files, so we simply add all of them to m_cached_files.
-  for (const auto& path : game_paths)
+  for (const std::string& path : game_paths)
   {
     auto file = std::make_shared<GameFile>(path);
     if (file->IsValid())
     {
+      if (game_added_to_cache)
+        game_added_to_cache(file);
+
       cache_changed = true;
       m_cached_files.push_back(std::move(file));
     }
@@ -125,12 +134,19 @@ bool GameFileCache::Update(const std::vector<std::string>& all_game_paths)
   return cache_changed;
 }
 
-bool GameFileCache::UpdateAdditionalMetadata(const Core::TitleDatabase& title_database)
+bool GameFileCache::UpdateAdditionalMetadata(
+    const Core::TitleDatabase& title_database,
+    std::function<void(const std::shared_ptr<const GameFile>&)> game_updated)
 {
   bool cache_changed = false;
 
-  for (auto& file : m_cached_files)
-    cache_changed |= UpdateAdditionalMetadata(&file, title_database);
+  for (std::shared_ptr<GameFile>& file : m_cached_files)
+  {
+    const bool updated = UpdateAdditionalMetadata(&file, title_database);
+    cache_changed |= updated;
+    if (game_updated && updated)
+      game_updated(file);
+  }
 
   return cache_changed;
 }

Source/Core/UICommon/GameFileCache.h

@@ -40,8 +40,12 @@ public:
                                            const Core::TitleDatabase& title_database);
 
   // These functions return true if the call modified the cache.
-  bool Update(const std::vector<std::string>& all_game_paths);
-  bool UpdateAdditionalMetadata(const Core::TitleDatabase& title_database);
+  bool Update(const std::vector<std::string>& all_game_paths,
+              std::function<void(const std::shared_ptr<const GameFile>&)> game_added_to_cache = {},
+              std::function<void(const std::string&)> game_removed_from_cache = {});
+  bool UpdateAdditionalMetadata(
+      const Core::TitleDatabase& title_database,
+      std::function<void(const std::shared_ptr<const GameFile>&)> game_updated = {});
 
   bool Load();
   bool Save();