fix: Backwards compatible way of releasing SS2 in a less-safe manner

source/ArmarXGui/applications/ArmarXGui/Widgets/EmergencyStopWidget.cpp

@@ -185,8 +185,7 @@ namespace armarx
     {
         if (emergencyStopMasterPrx)
         {
-            lastKnownEmergencyStopState = emergencyStopMasterPrx->trySetEmergencyStopState(
-                EmergencyStopState::eEmergencyStopInactive);
+            lastKnownEmergencyStopState = releaseSS2OnMaster();
 
             if (lastKnownEmergencyStopState == EmergencyStopState::eEmergencyStopActive)
             {
@@ -213,8 +212,7 @@ namespace armarx
             case EmergencyStopState::eEmergencyStopActive:
             {
                 // Only release SS2 if the state we received still is "Active".  Fail otherwise.
-                lastKnownEmergencyStopState = emergencyStopMasterPrx->trySetEmergencyStopState(
-                    EmergencyStopState::eEmergencyStopInactive);
+                lastKnownEmergencyStopState = releaseSS2OnMaster();
                 if (lastKnownEmergencyStopState == EmergencyStopState::eEmergencyStopActive)
                 {
                     ARMARX_INFO << "SS2 cannot be released since it was just activated.";
@@ -235,6 +233,37 @@ namespace armarx
         return "EmergencyStopGuiWidget" + iceNameUUID;
     }
 
+
+    EmergencyStopState
+    EmergencyStopWidget::releaseSS2OnMaster() const
+    {
+        // If emergency stop master is not available, assume that SS2 is still active and cannot
+        // be released.
+        if (not emergencyStopMasterPrx)
+        {
+            return EmergencyStopState::eEmergencyStopActive;
+        }
+
+        try
+        {
+            return emergencyStopMasterPrx->trySetEmergencyStopState(
+                EmergencyStopState::eEmergencyStopInactive);
+        }
+        // This catch is only required as long as the stable robot workspaces are using the old
+        // interface.  The changes for the new interface were done in July 2024.  It can safely be
+        // removed after a few months.
+        catch (Ice::OperationNotExistException const&)
+        {
+            ARMARX_WARNING << "Cannot safely release SS2.  This only happens if your ArmarX GUI "
+                              "is using a newer version of the emergency stop interface than the "
+                              "emergency stop master or the robot unit provides.  Will use a less "
+                              "safe fallback interface method now.";
+            emergencyStopMasterPrx->setEmergencyStopState(
+                EmergencyStopState::eEmergencyStopInactive);
+            return emergencyStopMasterPrx->getEmergencyStopState();
+        }
+    }
+
     void
     EmergencyStopWidget::setChecked(const EmergencyStopState state)
     {

source/ArmarXGui/applications/ArmarXGui/Widgets/EmergencyStopWidget.h

@@ -69,6 +69,9 @@ namespace armarx
         void onDisconnectComponent() override;
         std::string getDefaultName() const override;
 
+        EmergencyStopState
+        releaseSS2OnMaster() const;
+
     private slots:
         void setChecked(const EmergencyStopState);
         void updateEmergencyStopState();