ObsidianDragon - DragonX ImGui Wallet

Full-node GUI wallet for DragonX cryptocurrency.
Built with Dear ImGui, SDL3, and OpenGL3/DX11.

Features:
- Send/receive shielded and transparent transactions
- Autoshield with merged transaction display
- Built-in CPU mining (xmrig)
- Peer management and network monitoring
- Wallet encryption with PIN lock
- QR code generation for receive addresses
- Transaction history with pagination
- Console for direct RPC commands
- Cross-platform (Linux, Windows)

src/util/single_instance.h

@@ -0,0 +1,55 @@
+// DragonX Wallet - ImGui Edition
+// Copyright 2024-2026 The Hush Developers
+// Released under the GPLv3
+
+#pragma once
+
+#include <string>
+
+namespace dragonx {
+namespace util {
+
+/**
+ * @brief Ensures only one instance of the wallet runs at a time
+ * 
+ * Uses file locking on Linux/macOS and named mutex on Windows.
+ */
+class SingleInstance {
+public:
+    SingleInstance(const std::string& app_name = "dragonx-wallet");
+    ~SingleInstance();
+    
+    // Non-copyable
+    SingleInstance(const SingleInstance&) = delete;
+    SingleInstance& operator=(const SingleInstance&) = delete;
+    
+    /**
+     * @brief Try to acquire the single instance lock
+     * @return true if lock acquired (this is the only instance)
+     */
+    bool tryLock();
+    
+    /**
+     * @brief Release the lock
+     */
+    void unlock();
+    
+    /**
+     * @brief Check if lock is currently held
+     */
+    bool isLocked() const { return locked_; }
+    
+private:
+    std::string app_name_;
+    bool locked_ = false;
+    
+#ifdef _WIN32
+    void* mutex_handle_ = nullptr;
+#else
+    int lock_fd_ = -1;
+    std::string lock_path_;
+#endif
+};
+
+} // namespace util
+} // namespace dragonx