[fix] move connection cleanup off the UI thread

apps/desktop/src/common/task_queue_lock_free.cpp

@@ -0,0 +1,79 @@
+#include "task_queue_lock_free.h"
+
+#include <exception>
+#include <new>
+#include <stdexcept>
+#include <utility>
+
+namespace crossdesk {
+
+TaskQueueLockFree::TaskQueueLockFree()
+    : producer_(task_queue_), worker_([this] { WorkerThread(); }) {}
+
+TaskQueueLockFree::~TaskQueueLockFree() { Stop(); }
+
+std::future<void> TaskQueueLockFree::PostTask(std::function<void()> task) {
+  TaskItem item;
+  item.run = std::move(task);
+  auto result = item.completion.get_future();
+  {
+    std::lock_guard lock(mutex_);
+    if (stopping_) {
+      throw std::runtime_error("Cannot post to a stopped task queue");
+    }
+
+    // Count before publishing: the worker may dequeue as soon as enqueue returns.
+    ++pending_tasks_;
+    if (!task_queue_.enqueue(producer_, std::move(item))) {
+      --pending_tasks_;
+      throw std::bad_alloc();
+    }
+  }
+  wake_.notify_one();
+  return result;
+}
+
+void TaskQueueLockFree::Stop() {
+  // Concurrent Stop callers all wait for the same worker shutdown to finish.
+  std::call_once(stop_once_, [this] {
+    {
+      std::lock_guard lock(mutex_);
+      stopping_ = true;
+    }
+    wake_.notify_all();
+    worker_.join();
+  });
+}
+
+void TaskQueueLockFree::WorkerThread() {
+  while (true) {
+    TaskItem item;
+    while (task_queue_.try_dequeue(item)) {
+      --pending_tasks_;
+
+      std::exception_ptr error;
+      try {
+        item.run();
+      } catch (...) {
+        error = std::current_exception();
+      }
+
+      // Release captured resources before marking the task complete.
+      item.run = nullptr;
+      if (error) {
+        item.completion.set_exception(error);
+      } else {
+        item.completion.set_value();
+      }
+    }
+
+    std::unique_lock lock(mutex_);
+    wake_.wait(lock, [this] { return stopping_ || pending_tasks_ > 0; });
+    // A stop request must not discard tasks submitted while the worker was idle.
+    if (stopping_ && pending_tasks_ == 0) {
+      return;
+    }
+  }
+}
+
+}  // namespace crossdesk