set value to null when pressed lineedit-clearbutton

Author: signedav

src/gui/qgsfeaturelistcombobox.cpp

@@ -54,6 +54,7 @@ QgsFeatureListComboBox::QgsFeatureListComboBox( QWidget *parent )
 
   mLineEdit = new QgsFilterLineEdit();
   mLineEdit->setSelectOnFocus( true );
+  connect( mLineEdit, &QgsFilterLineEdit::cleared, this, &QgsFeatureListComboBox::setValueToNull );
   setEditable( true );
   setLineEdit( mLineEdit );
   setModel( mModel );
@@ -249,3 +250,9 @@ void QgsFeatureListComboBox::LineEditState::restore( QLineEdit *lineEdit ) const
   if ( selectionStart > -1 )
     lineEdit->setSelection( selectionStart, selectionLength );
 }
+
+void QgsFeatureListComboBox::setValueToNull()
+{
+  if ( allowNull() )
+    setCurrentIndex( nullIndex() );
+}

src/gui/qgsfeaturelistcombobox.h

@@ -200,6 +200,7 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
     void storeLineEditState();
     void restoreLineEditState();
     void onDataChanged( const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles = QVector<int>() );
+    void setValueToNull();
 
   private:
     struct LineEditState