Gui: don't make QuantitySpinBox dependent on implementation details of its base class

src/Gui/QuantitySpinBox.cpp

@@ -743,15 +743,7 @@ QString QuantitySpinBox::getUserString(const Base::Quantity& val) const
 
 void QuantitySpinBox::setExpression(std::shared_ptr<Expression> expr)
 {
-    Q_ASSERT(isBound());
-
-    try {
-        ExpressionBinding::setExpression(expr);
-        validateInput();
-    }
-    catch (const Base::Exception & e) {
-        showInvalidExpression(QString::fromLatin1(e.what()));
-    }
+    ExpressionSpinBox::setExpression(expr);
 }
 
 QAbstractSpinBox::StepEnabled QuantitySpinBox::stepEnabled() const

src/Gui/QuantitySpinBox.h

@@ -157,7 +157,7 @@ protected:
     void paintEvent(QPaintEvent *event) override;
 
 private:
-    void validateInput();
+    void validateInput() override;
     void updateText(const Base::Quantity&);
     void updateFromCache(bool notify, bool updateUnit = true);
     QString getUserString(const Base::Quantity& val, double& factor, QString& unitString) const;

src/Gui/SpinBox.cpp

@@ -76,6 +76,10 @@ void ExpressionSpinBox::showIcon()
     iconLabel->show();
 }
 
+void ExpressionSpinBox::validateInput()
+{
+}
+
 void ExpressionSpinBox::showInvalidExpression(const QString& tip)
 {
     spinbox->setReadOnly(true);
@@ -142,6 +146,7 @@ void ExpressionSpinBox::setExpression(std::shared_ptr<Expression> expr)
 
     try {
         ExpressionBinding::setExpression(expr);
+        validateInput();
     }
     catch (const Base::Exception & e) {
         showInvalidExpression(QString::fromLatin1(e.what()));

src/Gui/SpinBox.h

@@ -61,6 +61,7 @@ protected:
     void onChange() override;
     virtual void setNumberExpression(App::NumberExpression*) = 0;
     virtual void showIcon();
+    virtual void validateInput();
     void resizeWidget();
 
     bool handleKeyEvent(const QString&);