Fix things mentioned during code review

Ref: https://github.com/dolphin-emu/dolphin/pull/4917

Source/Core/Common/Config/Config.cpp

@@ -0,0 +1,140 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <list>
+#include <map>
+
+#include "Common/Assert.h"
+#include "Common/Config/Config.h"
+
+namespace Config
+{
+static Layers s_layers;
+static std::list<ConfigChangedCallback> s_callbacks;
+
+void InvokeConfigChangedCallbacks();
+
+Section* GetOrCreateSection(System system, const std::string& section_name)
+{
+  return s_layers[LayerType::Meta]->GetOrCreateSection(system, section_name);
+}
+
+Layers* GetLayers()
+{
+  return &s_layers;
+}
+
+void AddLayer(std::unique_ptr<Layer> layer)
+{
+  s_layers[layer->GetLayer()] = std::move(layer);
+  InvokeConfigChangedCallbacks();
+}
+
+void AddLayer(std::unique_ptr<ConfigLayerLoader> loader)
+{
+  AddLayer(std::make_unique<Layer>(std::move(loader)));
+}
+
+void AddLoadLayer(std::unique_ptr<Layer> layer)
+{
+  layer->Load();
+  AddLayer(std::move(layer));
+}
+
+void AddLoadLayer(std::unique_ptr<ConfigLayerLoader> loader)
+{
+  AddLoadLayer(std::make_unique<Layer>(std::move(loader)));
+}
+
+Layer* GetLayer(LayerType layer)
+{
+  if (!LayerExists(layer))
+    return nullptr;
+  return s_layers[layer].get();
+}
+
+void RemoveLayer(LayerType layer)
+{
+  s_layers.erase(layer);
+  InvokeConfigChangedCallbacks();
+}
+bool LayerExists(LayerType layer)
+{
+  return s_layers.find(layer) != s_layers.end();
+}
+
+void AddConfigChangedCallback(ConfigChangedCallback func)
+{
+  s_callbacks.emplace_back(func);
+}
+
+void InvokeConfigChangedCallbacks()
+{
+  for (const auto& callback : s_callbacks)
+    callback();
+}
+
+// Explicit load and save of layers
+void Load()
+{
+  for (auto& layer : s_layers)
+    layer.second->Load();
+}
+
+void Save()
+{
+  for (auto& layer : s_layers)
+    layer.second->Save();
+}
+
+void Init()
+{
+  // This layer always has to exist
+  s_layers[LayerType::Meta] = std::make_unique<RecursiveLayer>();
+}
+
+void Shutdown()
+{
+  s_layers.clear();
+  s_callbacks.clear();
+}
+
+static const std::map<System, std::string> system_to_name = {
+    {System::Main, "Dolphin"},          {System::GCPad, "GCPad"},  {System::WiiPad, "Wiimote"},
+    {System::GCKeyboard, "GCKeyboard"}, {System::GFX, "Graphics"}, {System::Logger, "Logger"},
+    {System::Debugger, "Debugger"},     {System::UI, "UI"},
+};
+
+const std::string& GetSystemName(System system)
+{
+  return system_to_name.at(system);
+}
+
+System GetSystemFromName(const std::string& name)
+{
+  const auto system = std::find_if(system_to_name.begin(), system_to_name.end(),
+                                   [&name](const auto& entry) { return entry.second == name; });
+  if (system != system_to_name.end())
+    return system->first;
+
+  _assert_msg_(COMMON, false, "Programming error! Couldn't convert '%s' to system!", name.c_str());
+  return System::Main;
+}
+
+const std::string& GetLayerName(LayerType layer)
+{
+  static const std::map<LayerType, std::string> layer_to_name = {
+      {LayerType::Base, "Base"},
+      {LayerType::GlobalGame, "Global GameINI"},
+      {LayerType::LocalGame, "Local GameINI"},
+      {LayerType::Netplay, "Netplay"},
+      {LayerType::Movie, "Movie"},
+      {LayerType::CommandLine, "Command Line"},
+      {LayerType::CurrentRun, "Current Run"},
+      {LayerType::Meta, "Top"},
+  };
+  return layer_to_name.at(layer);
+}
+}