[feat] expose system controls and verify remote unlock completion

apps/desktop/src/platform/linux/screen_lock.cpp

@@ -7,11 +7,54 @@
 #include "screen_lock.h"
 
 #include <dbus/dbus.h>
+#include <unistd.h>
 
 #include "rd_log.h"
 
 namespace crossdesk {
 
+ScreenLockState QueryScreenLock() {
+  dbus_threads_init_default();
+  DBusConnection* connection = dbus_bus_get_private(DBUS_BUS_SYSTEM, nullptr);
+  if (!connection) return ScreenLockState::unknown;
+  dbus_connection_set_exit_on_disconnect(connection, false);
+  ScreenLockState state = ScreenLockState::unknown;
+  DBusMessage* query = dbus_message_new_method_call("org.freedesktop.login1",
+      "/org/freedesktop/login1", "org.freedesktop.login1.Manager", "GetSessionByPID");
+  if (query) {
+    dbus_uint32_t pid = getpid();
+    dbus_message_append_args(query, DBUS_TYPE_UINT32, &pid, DBUS_TYPE_INVALID);
+    DBusMessage* session = dbus_connection_send_with_reply_and_block(connection, query, 500, nullptr);
+    dbus_message_unref(query);
+    const char* path = nullptr;
+    if (session && dbus_message_get_args(session, nullptr, DBUS_TYPE_OBJECT_PATH, &path, DBUS_TYPE_INVALID)) {
+      query = dbus_message_new_method_call("org.freedesktop.login1", path,
+          "org.freedesktop.DBus.Properties", "Get");
+      const char* interface = "org.freedesktop.login1.Session";
+      const char* property = "LockedHint";
+      if (query) {
+        dbus_message_append_args(query, DBUS_TYPE_STRING, &interface, DBUS_TYPE_STRING, &property, DBUS_TYPE_INVALID);
+        DBusMessage* reply = dbus_connection_send_with_reply_and_block(connection, query, 500, nullptr);
+        dbus_message_unref(query);
+        DBusMessageIter outer, value;
+        if (reply && dbus_message_iter_init(reply, &outer) && dbus_message_iter_get_arg_type(&outer) == DBUS_TYPE_VARIANT) {
+          dbus_message_iter_recurse(&outer, &value);
+          if (dbus_message_iter_get_arg_type(&value) == DBUS_TYPE_BOOLEAN) {
+            dbus_bool_t locked = false;
+            dbus_message_iter_get_basic(&value, &locked);
+            state = locked ? ScreenLockState::locked : ScreenLockState::unlocked;
+          }
+        }
+        if (reply) dbus_message_unref(reply);
+      }
+    }
+    if (session) dbus_message_unref(session);
+  }
+  dbus_connection_close(connection);
+  dbus_connection_unref(connection);
+  return state;
+}
+
 bool LockScreen() {
   dbus_threads_init_default();
   DBusError error;