PD: [skip ci] fixes #0004540: When manual size of DatumPlane is selected its Length property is not saved to the file and consequently not restored on opening

src/Mod/PartDesign/App/DatumPlane.cpp

@@ -78,6 +78,15 @@ Base::Vector3d Plane::getNormal()
     return normal;
 }
 
+void Plane::Restore(Base::XMLReader& reader)
+{
+    // set it to Manual to avoid to automatically adjust
+    // Length because it will be read before ResizeMode
+    // See bug #0004540
+    ResizeMode.setValue("Manual");
+    Datum::Restore(reader);
+}
+
 void Plane::onChanged(const App::Property *prop)
 {
     if (prop == &ResizeMode) {

src/Mod/PartDesign/App/DatumPlane.h

@@ -50,6 +50,9 @@ public:
 
     Base::Vector3d getNormal();
 
+protected:
+    virtual void Restore(Base::XMLReader& reader);
+
 private:
     static const char* ResizeModeEnums[];
 };