Allow a "no projection" option in projection selection widget/dialog

This option allows users to select "no projection", when
there's no suitable projection to select...

python/gui/qgsprojectionselectiondialog.sip

@@ -18,6 +18,10 @@ class QgsProjectionSelectionDialog : QDialog //, private Ui::QgsGenericProjectio
 
     void setMessage( const QString& message );
 
+    void setShowNoProjection( bool show );
+
+    bool showNoProjection() const;
+
   public slots:
 
 

python/gui/qgsprojectionselectiontreewidget.sip

@@ -5,12 +5,18 @@ class QgsProjectionSelectionTreeWidget : QWidget
 %End
 
   public:
-    QgsProjectionSelectionTreeWidget( QWidget* parent /TransferThis/ );
+    QgsProjectionSelectionTreeWidget( QWidget* parent /TransferThis/ = 0 );
 
     ~QgsProjectionSelectionTreeWidget();
 
     QgsCoordinateReferenceSystem crs() const;
 
+    void setShowNoProjection( bool show );
+
+    bool showNoProjection() const;
+
+    bool hasValidSelection() const;
+
   public slots:
 
     void setCrs( const QgsCoordinateReferenceSystem& crs );

src/gui/qgsprojectionselectiondialog.cpp

@@ -59,6 +59,16 @@ void QgsProjectionSelectionDialog::setMessage( const QString& message )
   textEdit->show();
 }
 
+void QgsProjectionSelectionDialog::setShowNoProjection( bool show )
+{
+  projectionSelector->setShowNoProjection( show );
+}
+
+bool QgsProjectionSelectionDialog::showNoProjection() const
+{
+  return projectionSelector->showNoProjection();
+}
+
 QgsProjectionSelectionDialog::~QgsProjectionSelectionDialog()
 {
   QSettings settings;

src/gui/qgsprojectionselectiondialog.h

@@ -76,6 +76,22 @@ class GUI_EXPORT QgsProjectionSelectionDialog : public QDialog, private Ui::QgsG
      */
     void setMessage( const QString& message );
 
+    /**
+     * Sets whether a "no/invalid" projection option should be shown. If this
+     * option is selected, calling crs() will return an invalid QgsCoordinateReferenceSystem.
+     * @see showNoProjection()
+     * @note added in QGIS 3.0
+     */
+    void setShowNoProjection( bool show );
+
+    /**
+     * Returns whether the "no/invalid" projection option is shown. If this
+     * option is selected, calling crs() will return an invalid QgsCoordinateReferenceSystem.
+     * @note added in QGIS 3.0
+     * @see setShowNoProjection()
+     */
+    bool showNoProjection() const;
+
   public slots:
 
     /**

src/gui/qgsprojectionselectiontreewidget.cpp

@@ -64,6 +64,9 @@ QgsProjectionSelectionTreeWidget::QgsProjectionSelectionTreeWidget( QWidget* par
   lstRecent->setColumnHidden( QgisCrsIdColumn, true );
 
   mRecentProjections = QgsCoordinateReferenceSystem::recentProjections();
+
+  mNoProjItem = new QTreeWidgetItem( lstCoordinateSystems, QStringList( tr( "No projection" ) ) );
+  mNoProjItem->setHidden( true );
 }
 
 QgsProjectionSelectionTreeWidget::~QgsProjectionSelectionTreeWidget()
@@ -268,7 +271,14 @@ QString QgsProjectionSelectionTreeWidget::selectedName()
 
 void QgsProjectionSelectionTreeWidget::setCrs( const QgsCoordinateReferenceSystem& crs )
 {
-  applySelection( AuthidColumn, crs.authid() );
+  if ( !crs.isValid() )
+  {
+    lstCoordinateSystems->setCurrentItem( mNoProjItem );
+  }
+  else
+  {
+    applySelection( AuthidColumn, crs.authid() );
+  }
 }
 
 // Returns the whole proj4 string for the selected projection node
@@ -414,13 +424,35 @@ QString QgsProjectionSelectionTreeWidget::getSelectedExpression( const QString&
 
 QgsCoordinateReferenceSystem QgsProjectionSelectionTreeWidget::crs() const
 {
+  if ( lstCoordinateSystems->currentItem() == mNoProjItem )
+    return QgsCoordinateReferenceSystem();
+
   int srid = getSelectedExpression( QStringLiteral( "srs_id" ) ).toLong();
   if ( srid >= USER_CRS_START_ID )
     return QgsCoordinateReferenceSystem::fromOgcWmsCrs( QString( "USER:%1" ).arg( srid ) );
   else
     return QgsCoordinateReferenceSystem::fromOgcWmsCrs( getSelectedExpression( QStringLiteral( "upper(auth_name||':'||auth_id)" ) ) );
 }
 
+void QgsProjectionSelectionTreeWidget::setShowNoProjection( bool show )
+{
+  mNoProjItem->setHidden( !show );
+}
+
+bool QgsProjectionSelectionTreeWidget::showNoProjection() const
+{
+  return !mNoProjItem->isHidden();
+}
+
+bool QgsProjectionSelectionTreeWidget::hasValidSelection() const
+{
+  QTreeWidgetItem* item = lstCoordinateSystems->currentItem();
+  if ( item == mNoProjItem )
+    return true;
+  else
+    return item && !item->text( QgisCrsIdColumn ).isEmpty();
+}
+
 long QgsProjectionSelectionTreeWidget::selectedCrsId()
 {
   QTreeWidgetItem* item = lstCoordinateSystems->currentItem();

src/gui/qgsprojectionselectiontreewidget.h

@@ -56,6 +56,30 @@ class GUI_EXPORT QgsProjectionSelectionTreeWidget : public QWidget, private Ui::
      */
     QgsCoordinateReferenceSystem crs() const;
 
+    /**
+     * Sets whether a "no/invalid" projection option should be shown. If this
+     * option is selected, calling crs() will return an invalid QgsCoordinateReferenceSystem.
+     * @see showNoProjection()
+     * @note added in QGIS 3.0
+     */
+    void setShowNoProjection( bool show );
+
+    /**
+     * Returns whether the "no/invalid" projection option is shown. If this
+     * option is selected, calling crs() will return an invalid QgsCoordinateReferenceSystem.
+     * @note added in QGIS 3.0
+     * @see setShowNoProjection()
+     */
+    bool showNoProjection() const;
+
+    /**
+     * Returns true if the current selection in the widget is a valid choice. Valid
+     * selections include any projection and also the "no/invalid projection" option
+     * (if setShowNoProjection() was called). Invalid selections are the group
+     * headers (such as "Geographic Coordinate Systems"
+     */
+    bool hasValidSelection() const;
+
   public slots:
 
     /**
@@ -189,6 +213,8 @@ class GUI_EXPORT QgsProjectionSelectionTreeWidget : public QWidget, private Ui::
     QTreeWidgetItem *mGeoList = nullptr;
     //! PROJCS node
     QTreeWidgetItem *mProjList = nullptr;
+    //! "No projection" item
+    QTreeWidgetItem* mNoProjItem = nullptr;
 
     //! Users custom coordinate system file
     QString mCustomCsFile;

tests/src/python/CMakeLists.txt

@@ -90,7 +90,7 @@ ADD_PYTHON_TEST(PyQgsPanelWidgetStack test_qgspanelwidgetstack.py)
 ADD_PYTHON_TEST(PyQgsPoint test_qgspoint.py)
 ADD_PYTHON_TEST(PyQgsPointClusterRenderer test_qgspointclusterrenderer.py)
 ADD_PYTHON_TEST(PyQgsPointDisplacementRenderer test_qgspointdisplacementrenderer.py)
-ADD_PYTHON_TEST(PyQgsProjectionSelectionWidget test_qgsprojectionselectionwidget.py)
+ADD_PYTHON_TEST(PyQgsProjectionSelectionWidgets test_qgsprojectionselectionwidgets.py)
 ADD_PYTHON_TEST(PyQgsRangeWidgets test_qgsrangewidgets.py)
 ADD_PYTHON_TEST(PyQgsRasterFileWriter test_qgsrasterfilewriter.py)
 ADD_PYTHON_TEST(PyQgsRasterLayer test_qgsrasterlayer.py)

tests/src/python/test_qgsprojectionselectionwidget.py → tests/src/python/test_qgsprojectionselectionwidgets.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-"""QGIS Unit tests for QgsProjectionSelectionWidget.
+"""QGIS Unit tests for various projection selection widgets.
 
 .. note:: This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -14,14 +14,16 @@
 
 import qgis  # NOQA
 
-from qgis.gui import QgsProjectionSelectionWidget
+from qgis.gui import (QgsProjectionSelectionWidget,
+QgsProjectionSelectionTreeWidget,
+                      QgsProjectionSelectionDialog)
 from qgis.core import QgsCoordinateReferenceSystem, QgsProject
 from qgis.testing import start_app, unittest
 from qgis.PyQt.QtGui import QColor
 start_app()
 
 
-class TestQgsProjectionSelectionWidget(unittest.TestCase):
+class TestQgsProjectionSelectionWidgets(unittest.TestCase):
 
     def testShowingHiding(self):
         """ test showing and hiding options """
@@ -112,6 +114,53 @@ def testShowingNotSetOption(self):
         self.assertTrue(w.optionVisible(QgsProjectionSelectionWidget.CurrentCrs))
         self.assertTrue(w.optionVisible(QgsProjectionSelectionWidget.CrsNotSet))
 
+    def testTreeWidgetGettersSetters(self):
+        """ basic tests for QgsProjectionSelectionTreeWidget """
+        w = QgsProjectionSelectionTreeWidget()
+        w.show()
+        self.assertFalse(w.hasValidSelection())
+        w.setCrs(QgsCoordinateReferenceSystem('EPSG:3111'))
+        self.assertEqual(w.crs().authid(),'EPSG:3111')
+        self.assertTrue(w.hasValidSelection())
+
+
+    def testTreeWidgetNotSetOption(self):
+        """ test allowing no projection option for QgsProjectionSelectionTreeWidget """
+        w = QgsProjectionSelectionTreeWidget()
+        w.show()
+        w.setShowNoProjection(True)
+        self.assertTrue(w.showNoProjection())
+        w.setShowNoProjection(False)
+        self.assertFalse(w.showNoProjection())
+
+        w.setShowNoProjection(True)
+        # no projection should be a valid selection
+        w.setCrs(QgsCoordinateReferenceSystem())
+        self.assertTrue(w.hasValidSelection())
+        self.assertFalse(w.crs().isValid())
+
+    def testDialogGettersSetters(self):
+        """ basic tests for QgsProjectionSelectionTreeWidget """
+        w = QgsProjectionSelectionDialog()
+        w.show()
+        w.setCrs(QgsCoordinateReferenceSystem('EPSG:3111'))
+        self.assertEqual(w.crs().authid(),'EPSG:3111')
+
+    def testDialogNotSetOption(self):
+        """ test allowing no projection option for QgsProjectionSelectionTreeWidget """
+        w = QgsProjectionSelectionDialog()
+        w.show()
+        w.setShowNoProjection(True)
+        self.assertTrue(w.showNoProjection())
+        w.setShowNoProjection(False)
+        self.assertFalse(w.showNoProjection())
+
+        w.setShowNoProjection(True)
+        w.setCrs(QgsCoordinateReferenceSystem())
+        self.assertFalse(w.crs().isValid())
+
+
+
 
 if __name__ == '__main__':
     unittest.main()