Allow QgsExtentWidget to be optionally nulled

python/gui/auto_generated/qgsextentwidget.sip.in

@@ -158,6 +158,17 @@ Returns the name of the extent layer.
 Returns ``True`` if the widget is in a valid state, i.e. has an extent set.
 %End
 
+    void setNullValueAllowed( bool allowed, const QString &notSetText = QString() );
+%Docstring
+Sets whether the widget can be set to a "not set" (null) state.
+
+The specified ``notSetText`` will be used for showing null values.
+
+.. note::
+
+   This mode only applies to widgets in the condensed state!
+%End
+
   public slots:
 
     void setOutputExtentFromOriginal();
@@ -191,6 +202,11 @@ Sets a fixed aspect ratio to be used when dragging extent onto the canvas.
 To unset a fixed aspect ratio, set the width and height to zero.
 
 :param ratio: aspect ratio's width and height
+%End
+
+    void clear();
+%Docstring
+Clears the widget, setting it to a null value.
 %End
 
   signals:

src/gui/qgsextentwidget.cpp

@@ -39,6 +39,7 @@ QgsExtentWidget::QgsExtentWidget( QWidget *parent, WidgetStyle style )
   mCondensedRe = QRegularExpression( QStringLiteral( "\\s*([\\d\\.]+)\\s*,\\s*([\\d\\.]+)\\s*,\\s*([\\d\\.]+)\\s*,\\s*([\\d\\.]+)\\s*(\\[.*?\\])" ) );
   mCondensedLineEdit->setValidator( new QRegularExpressionValidator( mCondensedRe, this ) );
   mCondensedLineEdit->setShowClearButton( false );
+  connect( mCondensedLineEdit, &QgsFilterLineEdit::cleared, this, &QgsExtentWidget::clear );
 
   connect( mCondensedLineEdit, &QLineEdit::textEdited, this, &QgsExtentWidget::setOutputExtentFromCondensedLineEdit );
 
@@ -232,15 +233,36 @@ void QgsExtentWidget::setOutputExtentFromLineEdit()
 void QgsExtentWidget::setOutputExtentFromCondensedLineEdit()
 {
   const QString text = mCondensedLineEdit->text();
-  const QRegularExpressionMatch match = mCondensedRe.match( text );
-  if ( match.hasMatch() )
+  if ( text.isEmpty() )
   {
-    whileBlocking( mXMinLineEdit )->setText( match.captured( 1 ) );
-    whileBlocking( mXMaxLineEdit )->setText( match.captured( 2 ) );
-    whileBlocking( mYMinLineEdit )->setText( match.captured( 3 ) );
-    whileBlocking( mYMaxLineEdit )->setText( match.captured( 4 ) );
-    emit extentChanged( outputExtent() );
+    clear();
   }
+  else
+  {
+    const QRegularExpressionMatch match = mCondensedRe.match( text );
+    if ( match.hasMatch() )
+    {
+      whileBlocking( mXMinLineEdit )->setText( match.captured( 1 ) );
+      whileBlocking( mXMaxLineEdit )->setText( match.captured( 2 ) );
+      whileBlocking( mYMinLineEdit )->setText( match.captured( 3 ) );
+      whileBlocking( mYMaxLineEdit )->setText( match.captured( 4 ) );
+      emit extentChanged( outputExtent() );
+    }
+  }
+}
+
+void QgsExtentWidget::clear()
+{
+  bool prevWasNull = mIsValid;
+
+  whileBlocking( mXMinLineEdit )->clear();
+  whileBlocking( mXMaxLineEdit )->clear();
+  whileBlocking( mYMinLineEdit )->clear();
+  whileBlocking( mYMaxLineEdit )->clear();
+  setValid( false );
+
+  if ( prevWasNull )
+    emit extentChanged( outputExtent() );
 }
 
 QString QgsExtentWidget::extentLayerName() const
@@ -253,6 +275,12 @@ bool QgsExtentWidget::isValid() const
   return mIsValid;
 }
 
+void QgsExtentWidget::setNullValueAllowed( bool allowed, const QString &notSetText )
+{
+  mCondensedLineEdit->setShowClearButton( allowed );
+  mCondensedLineEdit->setNullValue( notSetText );
+}
+
 void QgsExtentWidget::setValid( bool valid )
 {
   if ( valid == mIsValid )

src/gui/qgsextentwidget.h

@@ -166,6 +166,15 @@ class GUI_EXPORT QgsExtentWidget : public QWidget, private Ui::QgsExtentGroupBox
      */
     bool isValid() const;
 
+    /**
+     * Sets whether the widget can be set to a "not set" (null) state.
+     *
+     * The specified \a notSetText will be used for showing null values.
+     *
+     * \note This mode only applies to widgets in the condensed state!
+     */
+    void setNullValueAllowed( bool allowed, const QString &notSetText = QString() );
+
   public slots:
 
     /**
@@ -200,6 +209,11 @@ class GUI_EXPORT QgsExtentWidget : public QWidget, private Ui::QgsExtentGroupBox
      */
     void setRatio( QSize ratio ) { mRatio = ratio; }
 
+    /**
+     * Clears the widget, setting it to a null value.
+     */
+    void clear();
+
   signals:
 
     /**

tests/src/python/test_qgsextentwidget.py

@@ -158,6 +158,34 @@ class TestQgsExtentWidget(unittest.TestCase):
         # just test this by restricting the test to 4 decimals
         self.assertEqual(w.outputExtent().toString(4), QgsRectangle(1, 2, 3, 4).toString(4))
 
+    def testClear(self):
+        w = QgsExtentWidget()
+        w.setNullValueAllowed(True, 'test')
+        valid_spy = QSignalSpy(w.validationChanged)
+        changed_spy = QSignalSpy(w.extentChanged)
+        self.assertFalse(w.isValid())
+        w.setOriginalExtent(QgsRectangle(1, 2, 3, 4), QgsCoordinateReferenceSystem('epsg:3111'))
+        w.setCurrentExtent(QgsRectangle(11, 12, 13, 14), QgsCoordinateReferenceSystem('epsg:3113'))
+        w.setOutputExtentFromOriginal()
+        self.assertEqual(len(valid_spy), 1)
+        self.assertEqual(len(changed_spy), 1)
+        self.assertTrue(w.isValid())
+
+        w.clear()
+        self.assertEqual(len(valid_spy), 2)
+        self.assertEqual(len(changed_spy), 2)
+        self.assertFalse(w.isValid())
+        self.assertTrue(w.outputExtent().isNull())
+        w.clear()
+        self.assertEqual(len(valid_spy), 2)
+        self.assertEqual(len(changed_spy), 2)
+        self.assertTrue(w.outputExtent().isNull())
+        w.setOutputExtentFromOriginal()
+        self.assertEqual(len(valid_spy), 3)
+        self.assertEqual(len(changed_spy), 3)
+        self.assertTrue(w.isValid())
+        self.assertEqual(w.outputExtent(), QgsRectangle(1, 2, 3, 4))
+
 
 if __name__ == '__main__':
     unittest.main()