Add ability to set default values for QgsFilterLineEdit

and have clearing the widget reset to default rather than
null

python/gui/qgsfilterlineedit.sip

@@ -14,12 +14,31 @@ class QgsFilterLineEdit : QLineEdit
 %End
   public:
 
+    //! Behaviour when clearing value of widget
+    enum ClearMode
+    {
+      ClearToNull, //!< Reset value to null
+      ClearToDefault, //!< Reset value to default value (see defaultValue() )
+    };
+
     /** Constructor for QgsFilterLineEdit.
      * @param parent parent widget
      * @param nullValue string for representing null values
      */
     QgsFilterLineEdit( QWidget* parent /TransferThis/ = 0, const QString& nullValue = QString::null );
 
+    /** Returns the clear mode for the widget. The clear mode defines the behaviour of the
+     * widget when its value is cleared. This defaults to ClearToNull.
+     * @see setClearMode()
+     */
+    ClearMode clearMode() const;
+
+    /** Sets the clear mode for the widget. The clear mode defines the behaviour of the
+     * widget when its value is cleared. This defaults to ClearToNull.
+     * @see clearMode()
+     */
+    void setClearMode( ClearMode mode );
+
     /** Sets the string representation for null values in the widget. This does not
      * affect the values returned for null values by value(), rather it only affects
      * the text that is shown to users when the widget's value is null.
@@ -34,6 +53,23 @@ class QgsFilterLineEdit : QLineEdit
      */
     QString nullValue() const;
 
+    /** Sets the default value for the widget. The default value is a value
+     * which the widget will be reset to if it is cleared and the clearMode()
+     * is equal to ClearToDefault.
+     * @param defaultValue default value
+     * @see defaultValue()
+     * @see clearMode()
+     */
+    void setDefaultValue( const QString& defaultValue );
+
+    /** Returns the default value for the widget. The default value is a value
+     * which the widget will be reset to if it is cleared and the clearMode()
+     * is equal to ClearToDefault.
+     * @see setDefaultValue()
+     * @see clearMode()
+     */
+    QString defaultValue() const;
+
     /**
      * Sets the current text for the widget with support for handling null values.
      *

src/gui/qgsfilterlineedit.cpp

@@ -25,6 +25,7 @@
 
 QgsFilterLineEdit::QgsFilterLineEdit( QWidget* parent, const QString& nullValue )
     : QLineEdit( parent )
+    , mClearMode( ClearToNull )
     , mNullValue( nullValue )
     , mFocusInEvent( false )
     , mClearHover( false )
@@ -87,7 +88,18 @@ void QgsFilterLineEdit::focusInEvent( QFocusEvent* e )
 
 void QgsFilterLineEdit::clearValue()
 {
-  setText( mNullValue );
+  switch ( mClearMode )
+  {
+    case ClearToNull:
+      setText( mNullValue );
+      break;
+
+    case ClearToDefault:
+      setText( mDefaultValue );
+      break;
+
+  }
+
   setModified( true );
   emit cleared();
 }
@@ -133,7 +145,18 @@ void QgsFilterLineEdit::onTextChanged( const QString &text )
 
 bool QgsFilterLineEdit::shouldShowClear() const
 {
-  return isEnabled() && !isReadOnly() && !isNull();
+  if ( !isEnabled() || isReadOnly() )
+    return false;
+
+  switch ( mClearMode )
+  {
+    case ClearToNull:
+      return !isNull();
+
+    case ClearToDefault:
+      return value() != mDefaultValue;
+  }
+  return false; //avoid warnings
 }
 
 QRect QgsFilterLineEdit::clearRect() const

src/gui/qgsfilterlineedit.h

@@ -34,17 +34,39 @@ class QToolButton;
 class GUI_EXPORT QgsFilterLineEdit : public QLineEdit
 {
     Q_OBJECT
+    Q_ENUMS( ClearMode )
+    Q_PROPERTY( ClearMode clearMode READ clearMode WRITE setClearMode )
     Q_PROPERTY( QString nullValue READ nullValue WRITE setNullValue )
+    Q_PROPERTY( QString defaultValue READ defaultValue WRITE setDefaultValue )
     Q_PROPERTY( QString value READ value WRITE setValue NOTIFY valueChanged )
 
   public:
 
+    //! Behaviour when clearing value of widget
+    enum ClearMode
+    {
+      ClearToNull = 0, //!< Reset value to null
+      ClearToDefault, //!< Reset value to default value (see defaultValue() )
+    };
+
     /** Constructor for QgsFilterLineEdit.
      * @param parent parent widget
      * @param nullValue string for representing null values
      */
     QgsFilterLineEdit( QWidget* parent = nullptr, const QString& nullValue = QString::null );
 
+    /** Returns the clear mode for the widget. The clear mode defines the behaviour of the
+     * widget when its value is cleared. This defaults to ClearToNull.
+     * @see setClearMode()
+     */
+    ClearMode clearMode() const { return mClearMode; }
+
+    /** Sets the clear mode for the widget. The clear mode defines the behaviour of the
+     * widget when its value is cleared. This defaults to ClearToNull.
+     * @see clearMode()
+     */
+    void setClearMode( ClearMode mode ) { mClearMode = mode; }
+
     /** Sets the string representation for null values in the widget. This does not
      * affect the values returned for null values by value(), rather it only affects
      * the text that is shown to users when the widget's value is null.
@@ -59,6 +81,23 @@ class GUI_EXPORT QgsFilterLineEdit : public QLineEdit
      */
     QString nullValue() const { return mNullValue; }
 
+    /** Sets the default value for the widget. The default value is a value
+     * which the widget will be reset to if it is cleared and the clearMode()
+     * is equal to ClearToDefault.
+     * @param defaultValue default value
+     * @see defaultValue()
+     * @see clearMode()
+     */
+    void setDefaultValue( const QString& defaultValue ) { mDefaultValue = defaultValue; }
+
+    /** Returns the default value for the widget. The default value is a value
+     * which the widget will be reset to if it is cleared and the clearMode()
+     * is equal to ClearToDefault.
+     * @see setDefaultValue()
+     * @see clearMode()
+     */
+    QString defaultValue() const { return mDefaultValue; }
+
     /**
      * Sets the current text for the widget with support for handling null values.
      *
@@ -118,7 +157,11 @@ class GUI_EXPORT QgsFilterLineEdit : public QLineEdit
     void onTextChanged( const QString &text );
 
   private:
+
+    ClearMode mClearMode;
+
     QString mNullValue;
+    QString mDefaultValue;
     QString mStyleSheet;
     bool mFocusInEvent;
     bool mClearHover;

tests/src/python/test_qgsfilterlineedit.py

@@ -38,6 +38,10 @@ def testGettersSetters(self):
         w.setValue('value')
         self.assertEqual(w.value(), 'value')
         self.assertEqual(w.text(), 'value')
+        w.setDefaultValue('default')
+        self.assertEqual(w.defaultValue(), 'default')
+        w.setClearMode(QgsFilterLineEdit.ClearToDefault)
+        self.assertEqual(w.clearMode(), QgsFilterLineEdit.ClearToDefault)
 
     def testNullValueHandling(self):
         """ test widget handling of null values """
@@ -70,7 +74,7 @@ def testNullValueHandling(self):
         self.assertTrue(w.isNull())
         self.assertFalse(w.value())
 
-    def testClear(self):
+    def testClearToNull(self):
         """ test clearing widget """
         w = qgis.gui.QgsFilterLineEdit()
 
@@ -90,6 +94,27 @@ def testClear(self):
         self.assertTrue(w.isNull())
         self.assertFalse(w.value())
 
+    def testClearToDefault(self):
+        # test clearing to default value
+        w = qgis.gui.QgsFilterLineEdit()
+        w.setClearMode(QgsFilterLineEdit.ClearToDefault)
+
+        w.setValue('abc')
+        w.clearValue()
+        self.assertTrue(w.isNull())
+        self.assertFalse(w.value())
+        w.clearValue()
+        self.assertTrue(w.isNull())
+        self.assertFalse(w.value())
+
+        w.setDefaultValue('def')
+        w.setValue('abc')
+        self.assertFalse(w.isNull())
+        w.clearValue()
+        self.assertEqual(w.value(), 'def')
+        self.assertEqual(w.text(), 'def')
+        self.assertFalse(w.isNull())
+
     @unittest.skipIf(not use_signal_spy, "No QSignalSpy available")
     def test_ChangedSignals(self):
         """ test that signals are correctly emitted when clearing"""