Do not poll printers when window is not active.

src/slic3r/GUI/MainFrame.cpp

@@ -272,8 +272,8 @@ DPIFrame(NULL, wxID_ANY, "", wxDefaultPosition, wxDefaultSize, wxDEFAULT_FRAME_S
     //FIXME it seems this method is not called on application start-up, at least not on Windows. Why?
     // The same applies to wxEVT_CREATE, it is not being called on startup on Windows.
     Bind(wxEVT_ACTIVATE, [this](wxActivateEvent& event) {
-        if (m_plater != nullptr && event.GetActive())
+        if (m_plater != nullptr)
-            m_plater->on_activate();
+            m_plater->on_activate(event.GetActive());
         event.Skip();
     });
 

src/slic3r/GUI/Plater.cpp

@@ -6300,9 +6300,12 @@ void Plater::force_print_bed_update()
 	p->config->opt_string("printer_model", true) = "\x01\x00\x01";
 }
 
-void Plater::on_activate()
+void Plater::on_activate(bool active)
 {
-	this->p->show_delayed_error_message();
+    this->p->user_account->on_activate_window(active);
+    if (active) {
+	    this->p->show_delayed_error_message();
+    }
 }
 
 // Get vector of extruder colors considering filament color, if extruder color is undefined.

src/slic3r/GUI/Plater.hpp

@@ -253,7 +253,7 @@ public:
     void force_filament_cb_update();
     void force_print_bed_update();
     // On activating the parent window.
-    void on_activate();
+    void on_activate(bool active);
     std::vector<std::string> get_extruder_colors_from_plater_config(const GCodeProcessorResult* const result = nullptr) const;
     std::vector<std::string> get_colors_for_color_print(const GCodeProcessorResult* const result = nullptr) const;
 

src/slic3r/GUI/UserAccount.hpp

@@ -58,6 +58,8 @@ public:
     bool on_connect_printers_success(const std::string& data, AppConfig* app_config, bool& out_printers_changed);
     bool on_connect_uiid_map_success(const std::string& data, AppConfig* app_config, bool& out_printers_changed);
 
+    void on_activate_window(bool active) { m_communication->on_activate_window(active); }
+
     std::string get_username() const { return m_username; }
     std::string get_access_token();
     std::string get_shared_session_key();

src/slic3r/GUI/UserAccountCommunication.cpp

@@ -360,6 +360,10 @@ void UserAccountCommunication::init_session_thread()
             if (m_thread_stop)
                 // Stop the worker thread.
                 break;
+            // Do not process_action_queue if window is not active and thread was not forced to wakeup
+            if (!m_window_is_active && !m_thread_wakeup) {
+                continue;
+            }
             m_thread_wakeup = false;
             {
                 std::lock_guard<std::mutex> lock(m_session_mutex);
@@ -369,6 +373,12 @@ void UserAccountCommunication::init_session_thread()
     });
 }
 
+void UserAccountCommunication::on_activate_window(bool active)
+{
+    std::lock_guard<std::mutex> lck(m_thread_stop_mutex);
+    m_window_is_active = active;
+}
+
 void UserAccountCommunication::wakeup_session_thread()
 {
     {

src/slic3r/GUI/UserAccountCommunication.hpp

@@ -51,6 +51,7 @@ public:
     // Exchanges code for tokens and shared_session_key
     void on_login_code_recieved(const std::string& url_message);
 
+    void on_activate_window(bool active);
 
     void set_username(const std::string& username);
     void set_remember_session(bool b);
@@ -71,6 +72,7 @@ private:
     std::condition_variable                 m_thread_stop_condition;
     bool                                    m_thread_stop { false };
     bool                                    m_thread_wakeup{ false };
+    bool                                    m_window_is_active{ true };
     std::string                             m_code_verifier;
     wxEvtHandler*                           m_evt_handler;
     AppConfig*                              m_app_config;