Core: add method to XMLReader to access next element of an XML file

If the next element could be read-in successfully true is returned, and false otherwise.

src/Base/Reader.cpp

@@ -222,10 +222,38 @@ void Base::XMLReader::readElement(const char* ElementName)
              (ElementName && LocalName != ElementName));
 }
 
+bool Base::XMLReader::readNextElement()
+{
+    bool ok{};
+    while (true) {
+        ok = read();
+        if (!ok)
+            break;
+        if (ReadType == StartEndElement)
+            break;
+        if (ReadType == EndElement)
+            break;
+        if (ReadType == EndDocument)
+            break;
+    };
+
+    return (ReadType == StartEndElement);
+}
+
 int Base::XMLReader::level() const {
     return Level;
 }
 
+bool Base::XMLReader::isEndOfElement() const
+{
+    return (ReadType == EndElement);
+}
+
+bool Base::XMLReader::isEndOfDocument() const
+{
+    return (ReadType == EndDocument);
+}
+
 void Base::XMLReader::readEndElement(const char* ElementName, int level)
 {
     // if we are already at the end of the current element

src/Base/Reader.h

@@ -146,9 +146,19 @@ public:
     const char* localName() const;
     /// get the current element level
     int level() const;
+
+    /// return true if the end of an element is reached, false otherwise
+    bool isEndOfElement() const;
+
+    /// return true if the end of the document is reached, false otherwise
+    bool isEndOfDocument() const;
+
     /// read until a start element is found (\<name\>) or start-end element (\<name/\>) (with special name if given)
     void readElement   (const char* ElementName=nullptr);
 
+    /// Read in the next element. Return true if it succeeded and false otherwise
+    bool readNextElement();
+
     /** read until an end element is found
      *
      * @param ElementName: optional end element name to look for. If given, then

src/Gui/Document.cpp

@@ -1486,15 +1486,12 @@ void Document::RestoreDocFile(Base::Reader &reader)
             }
         }
 
-        //TODO: Implement a method to start the next element and returns its name
-        try {
-            localreader->readElement("ProjectUnitSystem");
-            d->projectUnitSystem = localreader->getAttributeAsInteger("US");
-            d->projectUnitSystemIgnore = localreader->getAttributeAsInteger("ignore");
-            localreader->readEndElement("Document");
-        }
-        catch (const Base::XMLParseException) {
-            // fails for older project files
+        if (localreader->readNextElement()) {
+            if (strcmp(localreader->localName(), "ProjectUnitSystem") == 0) {
+                d->projectUnitSystem = localreader->getAttributeAsInteger("US");
+                d->projectUnitSystemIgnore = localreader->getAttributeAsInteger("ignore");
+                localreader->readEndElement("Document");
+            }
         }
     }