improve dialog and cloud browse icon text, deselect guide on mode leave

src/app.h

@@ -345,7 +345,6 @@ public:
     template<typename T, typename R = std::result_of<T()>::type>
     std::future<R> ui_task_async(T task)
     {
-#ifdef _WIN32
         std::packaged_task<R()> pt(task);
         std::future<R> f = pt.get_future();
         if (is_ui_thread())
@@ -361,13 +360,11 @@ public:
             ui_cv.notify_all();
         }
         return f;
-#endif // _WIN32
     }
 
     template<typename T, typename R = std::result_of<T()>::type>
     R ui_task(T task)
     {
-#ifdef _WIN32
         std::packaged_task<R()> pt(task);
         std::future<R> f = pt.get_future();
         if (is_ui_thread())
@@ -383,7 +380,6 @@ public:
             ui_cv.notify_all();
         }
         return ui_running ? f.get() : R();
-#endif // _WIN32
     }
 
     void ui_sync()