+/**
+ * Get AppID with surface and role.
+ *
+ * Returns AppID if found.
+ *
+ * @param unsigned[in] surfaceID
+ * @param string[in] role
+ * @param bool[in,out] AppID is found or not
+ * @return AppID
+ * @attention If AppID is not found, param found will be false.
+ */
+string AppList::getAppID(unsigned surface, const string& role, bool* found) const
+{
+ *found = false;
+ for (const auto &x : this->app2client)
+ {
+ if(x.second->surfaceID(role) == surface){
+ *found = true;
+ return x.second->appID();
+ }
+ }
+ return string("");
+}
+
+// =================== Request Date container API ===================
+
+/**
+ * Get current request number
+ *
+ * Request number is the numeric ID to designate the request.
+ * But returned request number from this function doesn't mean the request exists.
+ * This number is used as key to withdraw the WMRequest object.
+ *
+ * @param None
+ * @return current request number.
+ * @note request number is more than 0.
+ */