Let us start here, from square one. No, from Zero!

overlay/overlay.h

@@ -0,0 +1,100 @@
+#pragma once
+
+#include <memory>
+#include <mutex>
+#include <vector>
+#include <windows.h>
+#include <d3d9.h>
+
+#include "external/imgui/imgui.h"
+
+namespace overlay {
+    class Window;
+
+    enum class OverlayRenderer {
+        D3D9,
+        SOFTWARE,
+    };
+
+    // settings
+    extern bool ENABLED;
+
+    class SpiceOverlay {
+    public:
+
+        D3DDEVICE_CREATION_PARAMETERS creation_parameters {};
+        D3DADAPTER_IDENTIFIER9 adapter_identifier {};
+        bool hotkeys_enable = true;
+
+        explicit SpiceOverlay(HWND hWnd, IDirect3D9 *d3d, IDirect3DDevice9 *device);
+        explicit SpiceOverlay(HWND hWnd);
+        ~SpiceOverlay();
+
+        void window_add(Window *wnd);
+        void new_frame();
+        void render();
+        void update();
+        void toggle_active(bool overlay_key = false);
+        void set_active(bool active);
+        bool get_active();
+        bool has_focus();
+        bool hotkeys_triggered();
+
+        static bool update_cursor();
+        static void reset_invalidate();
+        static void reset_recreate();
+        void input_char(unsigned int c, bool rawinput = false);
+
+        uint32_t *sw_get_pixel_data(int *width, int *height);
+
+        inline bool uses_window(HWND hWnd) {
+            return this->hWnd == hWnd;
+        }
+        inline bool uses_context(IDirect3D9 *other) {
+            return this->d3d == other;
+        }
+        inline bool uses_device(IDirect3DDevice9 *other) {
+            return this->device == other;
+        }
+        inline IDirect3DDevice9 *get_device() {
+            return this->device;
+        }
+
+        // renderer
+        OverlayRenderer renderer;
+        float total_elapsed = 0.f;
+
+    private:
+
+        HWND hWnd = nullptr;
+
+        // D3D9
+        IDirect3D9 *d3d = nullptr;
+        IDirect3DDevice9 *device = nullptr;
+
+        // software
+        std::vector<uint32_t> pixel_data;
+        size_t pixel_data_width = 0;
+        size_t pixel_data_height = 0;
+
+        std::vector<std::unique_ptr<Window>> windows;
+        Window *window_fps = nullptr;
+
+        bool active = false;
+        bool toggle_down = false;
+        bool rawinput_char = true;
+        bool hotkey_toggle = false;
+        bool hotkey_toggle_last = false;
+
+        void init();
+    };
+
+    // global
+    extern std::mutex OVERLAY_MUTEX;
+    extern std::unique_ptr<overlay::SpiceOverlay> OVERLAY;
+
+    // synchronized helpers
+    void create_d3d9(HWND hWnd, IDirect3D9 *d3d, IDirect3DDevice9 *device);
+    void create_software(HWND hWnd);
+    void destroy(HWND hWnd = nullptr);
+}