Add "Fullscreen UI"

src/frontend-common/fullscreen_ui.h

@@ -0,0 +1,63 @@
+#pragma once
+#include "common/types.h"
+
+class CommonHostInterface;
+class SettingsInterface;
+struct Settings;
+
+namespace FrontendCommon {
+enum class ControllerNavigationButton : u32;
+}
+
+namespace FullscreenUI {
+enum class MainWindowType
+{
+  None,
+  Landing,
+  GameList,
+  Settings,
+  QuickMenu,
+  MoreQuickMenu
+};
+
+enum class SettingsPage
+{
+  InterfaceSettings,
+  GameListSettings,
+  ConsoleSettings,
+  EmulationSettings,
+  BIOSSettings,
+  ControllerSettings,
+  HotkeySettings,
+  MemoryCardSettings,
+  DisplaySettings,
+  EnhancementSettings,
+  AudioSettings,
+  AdvancedSettings,
+  Count
+};
+
+bool Initialize(CommonHostInterface* host_interface, SettingsInterface* settings_interface);
+bool HasActiveWindow();
+void SystemCreated();
+void SystemDestroyed();
+void SystemPaused(bool paused);
+void OpenQuickMenu();
+void CloseQuickMenu();
+void Shutdown();
+void Render();
+
+void EnsureGameListLoaded();
+
+Settings& GetSettingsCopy();
+void SaveAndApplySettings();
+void SetDebugMenuEnabled(bool enabled, bool save_to_ini = false);
+
+/// Only ImGuiNavInput_Activate, ImGuiNavInput_Cancel, and DPad should be forwarded.
+/// Returns true if the UI consumed the event, and it should not execute the normal handler.
+bool SetControllerNavInput(FrontendCommon::ControllerNavigationButton button, bool value);
+
+/// Forwards the controller navigation to ImGui for fullscreen navigation. Call before NewFrame().
+void SetImGuiNavInputs();
+
+} // namespace FullscreenUI