[feat] add lock screen on disconnect option, refs #125

apps/desktop/src/gui/runtime/disconnect_lock_policy.h

@@ -0,0 +1,41 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-10-25
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _DISCONNECT_LOCK_POLICY_H_
+#define _DISCONNECT_LOCK_POLICY_H_
+
+#include <string>
+#include <unordered_set>
+#include <utility>
+
+namespace crossdesk {
+
+// Guarded by GuiRuntime's connection_status_mutex_. Only incoming sessions
+// that reached Connected can request a lock; terminal callbacks may repeat.
+class DisconnectLockPolicy {
+ public:
+  void Connected(const std::string& remote_id) {
+    controllers_.insert(remote_id);
+    pending_ = false;
+  }
+
+  void Disconnected(const std::string& remote_id, bool enabled) {
+    if (controllers_.erase(remote_id) && controllers_.empty() && enabled)
+      pending_ = true;
+  }
+
+  bool TakeRequest(bool enabled) {
+    return std::exchange(pending_, false) && enabled && controllers_.empty();
+  }
+
+ private:
+  std::unordered_set<std::string> controllers_;
+  bool pending_ = false;
+};
+
+}  // namespace crossdesk
+
+#endif