add access to value descriptor in DoubleLineEdit

GUI/Views/CommonWidgets/DoubleLineEdit.cpp

@@ -38,6 +38,11 @@ void DoubleLineEdit::setBaseValue(double baseValue)
     setText(QString::number(baseValue, 'g'));
 }
 
+const DoubleDescriptor& DoubleLineEdit::valueDescriptor() const
+{
+    return m_valueDescriptor;
+}
+
 void DoubleLineEdit::onEditingFinished()
 {
     const double new_value = text().toDouble();

GUI/Views/CommonWidgets/DoubleLineEdit.h

@@ -33,6 +33,9 @@ public:
     //! Set the base value (unit is the one of the contained descriptor).
     void setBaseValue(double baseValue);
 
+    //! The descriptor on which this line edit operates.
+    const DoubleDescriptor& valueDescriptor() const;
+
 signals:
     //! Emitted whenever the value changes.
     //!