OSD: Add controller input display overlay

src/frontend-common/input_overlay_ui.h

@@ -0,0 +1,24 @@
+#pragma once
+#include "core/controller.h"
+#include <array>
+
+namespace FrontendCommon {
+
+class InputOverlayUI
+{
+public:
+  InputOverlayUI();
+  ~InputOverlayUI();
+
+  void Draw();
+
+private:
+  void UpdateNames();
+
+  std::array<Controller::AxisList, NUM_CONTROLLER_AND_CARD_PORTS> m_axis_names;
+  std::array<Controller::ButtonList, NUM_CONTROLLER_AND_CARD_PORTS> m_button_names;
+  std::array<ControllerType, NUM_CONTROLLER_AND_CARD_PORTS> m_types{};
+  u32 m_active_ports = 0;
+};
+
+} // namespace FrontendCommon