Synchronize project title field and project metadata title

field in project properties dialog

Since these two are equivalent, we automatically keep them
in sync.

python/gui/qgsmetadatawidget.sip.in

@@ -139,6 +139,43 @@ Returns a list of types available by default in the wizard.
     void setMapCanvas( QgsMapCanvas *canvas );
 %Docstring
 Sets a map ``canvas`` associated with the widget.
+%End
+
+    QString title() const;
+%Docstring
+Returns the current title field for the metadata.
+
+.. seealso:: :py:func:`setTitle`
+
+.. seealso:: :py:func:`titleChanged`
+
+.. versionadded:: 3.2
+%End
+
+  public slots:
+
+    void setTitle( const QString &title );
+%Docstring
+Sets the ``title`` field for the metadata.
+
+.. seealso:: :py:func:`title`
+
+.. seealso:: :py:func:`titleChanged`
+
+.. versionadded:: 3.2
+%End
+
+  signals:
+
+    void titleChanged( const QString &title );
+%Docstring
+Emitted when the ``title`` field is changed.
+
+.. seealso:: :py:func:`title`
+
+.. seealso:: :py:func:`setTitle`
+
+.. versionadded:: 3.2
 %End
 
 };

src/app/qgsprojectproperties.cpp

@@ -826,6 +826,10 @@ QgsProjectProperties::QgsProjectProperties( QgsMapCanvas *mapCanvas, QWidget *pa
   mMetadataWidget->setMode( QgsMetadataWidget::ProjectMetadata );
   mMetadataWidget->setMetadata( &QgsProject::instance()->metadata() );
 
+  // sync metadata title and project title fields
+  connect( mMetadataWidget, &QgsMetadataWidget::titleChanged, titleEdit, &QLineEdit::setText );
+  connect( titleEdit, &QLineEdit::textChanged, mMetadataWidget, &QgsMetadataWidget::setTitle );
+
   projectionSelectorInitialized();
   restoreOptionsBaseUi();
   restoreState();

src/gui/qgsmetadatawidget.cpp

@@ -121,6 +121,8 @@ QgsMetadataWidget::QgsMetadataWidget( QWidget *parent, QgsMapLayer *layer )
     setMode( LayerMetadata );
     setUiFromMetadata();
   }
+
+  connect( lineEditTitle, &QLineEdit::textChanged, this, &QgsMetadataWidget::titleChanged );
 }
 
 void QgsMetadataWidget::setMode( QgsMetadataWidget::Mode mode )
@@ -462,7 +464,7 @@ void QgsMetadataWidget::setUiFromMetadata()
   // Title
   if ( ! mMetadata->title().isEmpty() )
   {
-    lineEditTitle->setText( mMetadata->title() );
+    whileBlocking( lineEditTitle )->setText( mMetadata->title() );
   }
 
   // Type
@@ -949,6 +951,20 @@ void QgsMetadataWidget::setMapCanvas( QgsMapCanvas *canvas )
     spatialExtentSelector->setCurrentExtent( canvas->extent(), canvas->mapSettings().destinationCrs() );
 }
 
+QString QgsMetadataWidget::title() const
+{
+  return lineEditTitle->text();
+}
+
+void QgsMetadataWidget::setTitle( const QString &title )
+{
+  if ( title != lineEditTitle->text() )
+  {
+    whileBlocking( lineEditTitle )->setText( title );
+    emit titleChanged( title );
+  }
+}
+
 void QgsMetadataWidget::acceptMetadata()
 {
   saveMetadata( mMetadata.get() );

src/gui/qgsmetadatawidget.h

@@ -38,6 +38,7 @@
 class GUI_EXPORT QgsMetadataWidget : public QWidget, private Ui::QgsMetadataWidgetBase
 {
     Q_OBJECT
+    Q_PROPERTY( QString title READ title WRITE setTitle NOTIFY titleChanged )
 
   public:
 
@@ -153,6 +154,40 @@ class GUI_EXPORT QgsMetadataWidget : public QWidget, private Ui::QgsMetadataWidg
      */
     void setMapCanvas( QgsMapCanvas *canvas );
 
+    /**
+     * Returns the current title field for the metadata.
+     *
+     * \see setTitle()
+     * \see titleChanged()
+     *
+     * \since QGIS 3.2
+     */
+    QString title() const;
+
+  public slots:
+
+    /**
+     * Sets the \a title field for the metadata.
+     *
+     * \see title()
+     * \see titleChanged()
+     *
+     * \since QGIS 3.2
+     */
+    void setTitle( const QString &title );
+
+  signals:
+
+    /**
+     * Emitted when the \a title field is changed.
+     *
+     * \see title()
+     * \see setTitle()
+     *
+     * \since QGIS 3.2
+     */
+    void titleChanged( const QString &title );
+
   private slots:
     void removeSelectedCategories();
     void updatePanel();