if no uuid for the terminal is available, use write the id of the terminal to the xml file, otherwise no connection can be done after saving

sources/qetgraphicsitem/conductor.cpp

@@ -982,11 +982,29 @@ QDomElement Conductor::toXml(QDomDocument & doc) const {
     dom_element.appendChild(createXmlProperty(doc, "y", pos().y()));
 
     // Terminal is uniquely identified by the uuid of the terminal and the element
-    dom_element.appendChild(createXmlProperty(doc, "element1", terminal1->parentElement()->uuid()));
+    QUuid terminal = terminal1->uuid();
-    dom_element.appendChild(createXmlProperty(doc, "terminal1", terminal1->uuid()));
+    QUuid terminalParent = terminal1->parentElement()->uuid();
+    if (terminalParent.isNull() || terminal.isNull()) {
+        // legacy when the terminal does not have a valid uuid
+        // do not store element1 information, because this is used to determine in the fromXml
+        // process that legacy file format
+        dom_element.appendChild(createXmlProperty(doc, "terminal1", terminal1->ID()));
+    } else {
+        dom_element.appendChild(createXmlProperty(doc, "element1", terminalParent));
+        dom_element.appendChild(createXmlProperty(doc, "terminal1", terminal));
+    }
 
+    terminal = terminal2->uuid();
+    terminalParent = terminal2->parentElement()->uuid();
+    if (terminalParent.isNull() || terminal.isNull()) {
+        // legacy when the terminal does not have a valid uuid
+        // do not store element1 information, because this is used to determine in the fromXml
+        // process that legacy file format
+        dom_element.appendChild(createXmlProperty(doc, "terminal2", terminal2->ID()));
+    } else {
         dom_element.appendChild(createXmlProperty(doc, "element2", terminal2->parentElement()->uuid()));
         dom_element.appendChild(createXmlProperty(doc, "terminal2", terminal2->uuid()));
+    }
 
     dom_element.appendChild(createXmlProperty(doc, "freezeLabel", m_freeze_label));
 

sources/qetgraphicsitem/element.cpp

@@ -662,6 +662,11 @@ bool Element::fromXml(QDomElement &e, QHash<int, Terminal *> &table_id_adr, bool
                     qFuzzyCompare(dockPos1.y(), dockPos2.y()) &&
                     p->orientation() == diagramTerminal.orientation()) { // check if the part in the collection is the same as in the diagram stored
                     qDebug() << "Matching Terminal found.";
+                    // store id for legacy purpose, because when opening a old project in the collection the terminal does not have an uuid. Therefore the id must be used
+                    if (p->uuid().isNull()) {
+                        p->setID(qde.attribute("id").toInt());
+                    }
+
 					priv_id_adr.insert(qde.attribute("id").toInt(), p);
 					terminal_trouvee = true;
 					// We used to break here, because we did not expect

sources/qetgraphicsitem/terminal.cpp

@@ -706,6 +706,10 @@ bool Terminal::canBeLinkedTo(Terminal *other_terminal)
 	return true;
 }
 
+void Terminal::setID(int id) {
+    m_id = id;
+}
+
 /**
 	@brief Terminal::conductors
 	@return La liste des conducteurs lies a cette borne
@@ -811,6 +815,10 @@ QUuid Terminal::uuid() const {
 	return d->m_uuid;
 }
 
+int Terminal::ID() const {
+    return m_id;
+}
+
 QPointF Terminal::dockPos() {
     return dock_elmt_;
 }

sources/qetgraphicsitem/terminal.h

@@ -77,6 +77,7 @@ class Terminal : public QGraphicsObject, public PropertiesInterface
 		Diagram  *diagram             () const;
 		Element  *parentElement       () const;
 		QUuid uuid                    () const;
+        int ID() const;
         QPointF dockPos();
         QPointF originPos();
 	
@@ -90,6 +91,7 @@ class Terminal : public QGraphicsObject, public PropertiesInterface
 		void updateConductor();
 		bool isLinkedTo(Terminal *);
 		bool canBeLinkedTo(Terminal *);
+        void setID(int id);
 	
 		// methods related to XML import/export
         static bool valideXml(const QDomElement  &);
@@ -152,6 +154,9 @@ class Terminal : public QGraphicsObject, public PropertiesInterface
 		QString number_terminal_;
         bool name_terminal_hidden{true};
 
+        /// legacy id used by the conductor to find the terminal. From 0.8x on the uuid is used instead.
+        int m_id{-1};
+	
 	private:
 		void init(QString number, QString name, bool hiddenName);
 		void init(QPointF pf, Qet::Orientation o, QString number,