Added QgsLayerMetadata logic to QgsDataProvider. Added setMetadata in QgsVector/RasterLayer::setDataProvider. Corrections in QgsMetadataWidget with added get/setMetadata and hasChanged functions plus checking for set mLayer pointer before use.

python/core/metadata/qgslayermetadata.sip.in

@@ -618,6 +618,7 @@ Stores state in Dom node
 :return: true if successful
 %End
 
+
 };
 
 

python/core/qgsdataprovider.sip.in

@@ -362,6 +362,27 @@ The default implementation does nothing.
 %End
 
 
+    virtual QgsLayerMetadata layerMetadata() const;
+%Docstring
+Retrieve collected Metadata from the Provider source
+ A structured metadata store for a map layer.
+\note
+
+.. seealso:: :py:func:`setLayerMetadata`
+
+.. versionadded:: 3.0
+%End
+    virtual bool setLayerMetadata( const QgsLayerMetadata &layerMetadata );
+%Docstring
+Set collected Metadata from the Provider source
+ A structured metadata store for a map layer.
+\note
+
+.. seealso:: :py:func:`layerMetadata`
+
+.. versionadded:: 3.0
+%End
+
   signals:
 
     void fullExtentCalculated();

python/gui/qgsmetadatawidget.sip.in

@@ -26,16 +26,52 @@ class QgsMetadataWidget : QWidget
     QgsMetadataWidget( QWidget *parent, QgsMapLayer *layer = 0 );
 %Docstring
 Constructor for the wizard.
+\note
+For use with a source \layer. This constructor automatically sets the widget's metadata() if the ``layer`` pointer is valid.
+calls setMetadata, using mMetadata
+
+:param layer: to set the main QgsLayerMetadata with mLayer->metadata() when not None
+
+.. seealso:: :py:func:`setMetadata`
+%End
+
+    void setMetadata( const QgsLayerMetadata &layerMetadata );
+%Docstring
+Sets the ``metadata`` to display in the widget
+\note
+Called from constructor and initializes child widget on first use
+Can be called from outside to change the QgsLayerMetadata object.
+
+.. seealso:: :py:func:`metadata`
+%End
+
+    QgsLayerMetadata metadata();
+%Docstring
+Retrieves a QgsLayerMetadata object representing the current state of the widget.
+\note
+saveMetdata is called before returning :py:class:`QgsLayerMetadata`
+
+.. seealso:: :py:func:`saveMetadata`
 %End
 
     void saveMetadata( QgsLayerMetadata &layerMetadata );
 %Docstring
 Save all fields in a QgsLayerMetadata object.
+
+.. seealso:: :py:func:`getMetadata`
+
+.. seealso:: :py:func:`acceptMetadata`
+
+.. seealso:: :py:func:`checkMetadata`
 %End
 
     bool checkMetadata();
 %Docstring
 Check if values in the wizard are correct.
+
+.. seealso:: :py:func:`updatePanel`
+
+.. seealso:: :py:func:`saveMetadata`
 %End
 
     void crsChanged();

src/core/metadata/qgslayermetadata.cpp

@@ -767,3 +767,26 @@ void QgsLayerMetadata::Extent::setTemporalExtents( const QList<QgsDateTimeRange>
 {
   mTemporalExtents = temporalExtents;
 }
+
+bool QgsLayerMetadata::operator==( const QgsLayerMetadata &metadataOther )  const
+{
+  return ( ( parentIdentifier() == metadataOther.parentIdentifier() ) &&
+           ( identifier() == metadataOther.identifier() ) &&
+           ( language() == metadataOther.language() ) &&
+           ( type() == metadataOther.type() ) &&
+           ( title() == metadataOther.title() ) &&
+           ( abstract() == metadataOther.abstract() ) &&
+           ( fees() == metadataOther.fees() ) &&
+           ( rights() == metadataOther.rights() ) &&
+           ( licenses() == metadataOther.licenses() ) &&
+           ( history() == metadataOther.history() ) &&
+           ( encoding() == metadataOther.encoding() ) &&
+           ( crs() == metadataOther.crs() ) &&
+           ( keywords() == metadataOther.keywords() ) &&
+           ( categories() == metadataOther.categories() ) &&
+           // QgsLayerMetadata::ConstraintList, LinkList, Extent, ContactList need to be delt with properly
+           ( constraints().count() == metadataOther.constraints().count() ) &&
+           ( extent().spatialExtents().count() == metadataOther.extent().spatialExtents().count() ) &&
+           ( contacts().count() == metadataOther.contacts().count() ) &&
+           ( links().count() == metadataOther.links().count() ) );
+}

src/core/metadata/qgslayermetadata.h

@@ -726,6 +726,11 @@ class CORE_EXPORT QgsLayerMetadata
      */
     bool writeMetadataXml( QDomElement &metadataElement, QDomDocument &document ) const;
 
+    /**
+     * Compares two features
+     */
+    bool operator==( const QgsLayerMetadata &metadataOther ) const SIP_SKIP;
+
   private:
 
     /*

src/core/qgsdataprovider.h

@@ -24,6 +24,7 @@
 
 //#include "qgsdataitem.h"
 #include "qgsdatasourceuri.h"
+#include "qgslayermetadata.h"
 #include "qgserror.h"
 
 typedef int dataCapabilities_t(); // SIP_SKIP
@@ -492,6 +493,24 @@ class CORE_EXPORT QgsDataProvider : public QObject
      */
     virtual bool renderInPreview( const QgsDataProvider::PreviewContext &context ); // SIP_SKIP
 
+    /**
+     * Retrieve collected Metadata from the Provider source
+     * \brief A structured metadata store for a map layer.
+     * \note
+     * \see setLayerMetadata
+    * \since QGIS 3.0
+    */
+    virtual QgsLayerMetadata layerMetadata() const { return QgsLayerMetadata(); };
+
+    /**
+     * Set collected Metadata from the Provider source
+     * \brief A structured metadata store for a map layer.
+     * \note
+     * \see layerMetadata
+    * \since QGIS 3.0
+    */
+    virtual bool setLayerMetadata( const QgsLayerMetadata &layerMetadata ) { Q_UNUSED( layerMetadata ); return false; }
+
   signals:
 
     /**

src/core/qgsvectorlayer.cpp

@@ -1526,6 +1526,9 @@ bool QgsVectorLayer::setDataProvider( QString const &provider )
     return false;
   }
 
+  setMetadata( mDataProvider->layerMetadata() );
+  QgsDebugMsgLevel( QString( "Set Data provider QgsLayerMetadata identifier[%1]" ).arg( metadata().identifier() ), 4 );
+
   // TODO: Check if the provider has the capability to send fullExtentCalculated
   connect( mDataProvider, &QgsVectorDataProvider::fullExtentCalculated, this, [ = ] { updateExtents(); } );
 

src/core/raster/qgsrasterlayer.cpp

@@ -625,6 +625,9 @@ void QgsRasterLayer::setDataProvider( QString const &provider )
     return;
   }
 
+  setMetadata( mDataProvider->layerMetadata() );
+  QgsDebugMsgLevel( QString( "Set Data provider QgsLayerMetadata identifier[%1]" ).arg( metadata().identifier() ), 4 );
+
   if ( provider == QLatin1String( "gdal" ) )
   {
     // make sure that the /vsigzip or /vsizip is added to uri, if applicable

src/gui/qgsmetadatawidget.cpp

@@ -35,7 +35,10 @@ QgsMetadataWidget::QgsMetadataWidget( QWidget *parent, QgsMapLayer *layer )
     mLayer( layer )
 {
   setupUi( this );
-  mMetadata = layer->metadata();
+  if ( mLayer )
+  {
+    mMetadata = mLayer->metadata();
+  }
   tabWidget->setCurrentIndex( 0 );
 
   // Disable the encoding
@@ -107,15 +110,36 @@ QgsMetadataWidget::QgsMetadataWidget( QWidget *parent, QgsMapLayer *layer )
   connect( btnRemoveCategory, &QPushButton::clicked, this, &QgsMetadataWidget::removeSelectedCategories );
 
   fillComboBox();
+  if ( !mLayer )
+  {
+    btnAutoSource->setEnabled( false );
+    btnAutoEncoding->setEnabled( false );
+    btnAutoCrs->setEnabled( false );
+  }
+  setMetadata( mMetadata );
+}
+
+void QgsMetadataWidget::setMetadata( const QgsLayerMetadata &layerMetadata )
+{
+  mMetadata = layerMetadata;
   setPropertiesFromLayer();
 }
 
-void QgsMetadataWidget::fillSourceFromLayer()
+QgsLayerMetadata QgsMetadataWidget::metadata()
 {
-  lineEditIdentifier->setText( mLayer->publicSource() );
+  saveMetadata( mMetadata );
+  return mMetadata;
 }
 
-void QgsMetadataWidget::addVocabulary()
+void QgsMetadataWidget::fillSourceFromLayer() const
+{
+  if ( mLayer )
+  {
+    lineEditIdentifier->setText( mLayer->publicSource() );
+  }
+}
+
+void QgsMetadataWidget::addVocabulary() const
 {
   int row = tabKeywords->rowCount();
   tabKeywords->setRowCount( row + 1 );
@@ -130,7 +154,7 @@ void QgsMetadataWidget::addVocabulary()
   tabKeywords->setItem( row, 1, pCell );
 }
 
-void QgsMetadataWidget::removeSelectedVocabulary()
+void QgsMetadataWidget::removeSelectedVocabulary() const
 {
   QItemSelectionModel *selectionModel = tabKeywords->selectionModel();
   const QModelIndexList selectedRows = selectionModel->selectedRows();
@@ -152,7 +176,7 @@ void QgsMetadataWidget::addLicence()
   }
 }
 
-void QgsMetadataWidget::removeSelectedLicence()
+void QgsMetadataWidget::removeSelectedLicence() const
 {
   QItemSelectionModel *selectionModel = tabLicenses->selectionModel();
   const QModelIndexList selectedRows = selectionModel->selectedRows();
@@ -173,7 +197,7 @@ void QgsMetadataWidget::addRight()
   }
 }
 
-void QgsMetadataWidget::removeSelectedRight()
+void QgsMetadataWidget::removeSelectedRight() const
 {
   QItemSelectionModel *selection = listRights->selectionModel();
   if ( selection->hasSelection() )
@@ -187,22 +211,22 @@ void QgsMetadataWidget::removeSelectedRight()
   }
 }
 
-void QgsMetadataWidget::addConstraint()
+void QgsMetadataWidget::addConstraint() const
 {
   int row = mConstraintsModel->rowCount();
   mConstraintsModel->setItem( row, 0, new QStandardItem( QString( tr( "undefined %1" ) ).arg( row + 1 ) ) );
   mConstraintsModel->setItem( row, 1, new QStandardItem( QString( tr( "undefined %1" ) ).arg( row + 1 ) ) );
 }
 
-void QgsMetadataWidget::removeSelectedConstraint()
+void QgsMetadataWidget::removeSelectedConstraint() const
 {
   const QModelIndexList selectedRows = tabConstraints->selectionModel()->selectedRows();
   mConstraintsModel->removeRow( selectedRows[0].row() );
 }
 
-void QgsMetadataWidget::crsChanged()
+void QgsMetadataWidget::crsChanged() const
 {
-  if ( mCrs.isValid() )
+  if ( ( mCrs.isValid() ) && ( mLayer ) )
   {
     lblCurrentCrs->setText( tr( "CRS: %1 - %2" ).arg( mCrs.authid(), mCrs.description() ) );
     spatialExtentSelector->setEnabled( true );
@@ -233,7 +257,7 @@ void QgsMetadataWidget::crsChanged()
   }
 }
 
-void QgsMetadataWidget::addAddress()
+void QgsMetadataWidget::addAddress() const
 {
   int row = tabAddresses->rowCount();
   tabAddresses->setRowCount( row + 1 );
@@ -259,7 +283,7 @@ void QgsMetadataWidget::addAddress()
   tabAddresses->setItem( row, 5, new QTableWidgetItem() );
 }
 
-void QgsMetadataWidget::removeSelectedAddress()
+void QgsMetadataWidget::removeSelectedAddress() const
 {
   QItemSelectionModel *selectionModel = tabAddresses->selectionModel();
   const QModelIndexList selectedRows = selectionModel->selectedRows();
@@ -281,7 +305,7 @@ void QgsMetadataWidget::fillCrsFromProvider()
   crsChanged();
 }
 
-void QgsMetadataWidget::addLink()
+void QgsMetadataWidget::addLink() const
 {
   int row = mLinksModel->rowCount();
   mLinksModel->setItem( row, 0, new QStandardItem( QString( tr( "undefined %1" ) ).arg( row + 1 ) ) );
@@ -293,7 +317,7 @@ void QgsMetadataWidget::addLink()
   mLinksModel->setItem( row, 6, new QStandardItem() );
 }
 
-void QgsMetadataWidget::removeSelectedLink()
+void QgsMetadataWidget::removeSelectedLink() const
 {
   const QModelIndexList selectedRows = tabLinks->selectionModel()->selectedRows();
   mLinksModel->removeRow( selectedRows[0].row() );
@@ -310,7 +334,7 @@ void QgsMetadataWidget::addHistory()
   }
 }
 
-void QgsMetadataWidget::removeSelectedHistory()
+void QgsMetadataWidget::removeSelectedHistory() const
 {
   QItemSelectionModel *selection = listHistory->selectionModel();
   if ( selection->hasSelection() )
@@ -324,7 +348,7 @@ void QgsMetadataWidget::removeSelectedHistory()
   }
 }
 
-void QgsMetadataWidget::fillComboBox()
+void QgsMetadataWidget::fillComboBox() const
 {
   // Set default values in type combobox
   // It is advised to use the ISO 19115 MD_ScopeCode values. E.g. 'dataset' or 'series'.
@@ -522,7 +546,7 @@ void QgsMetadataWidget::setPropertiesFromLayer()
   mHistoryModel->setStringList( mMetadata.history() );
 }
 
-void QgsMetadataWidget::saveMetadata( QgsLayerMetadata &layerMetadata )
+void QgsMetadataWidget::saveMetadata( QgsLayerMetadata &layerMetadata ) const
 {
   layerMetadata.setParentIdentifier( lineEditParentId->text() );
   layerMetadata.setIdentifier( lineEditIdentifier->text() );
@@ -635,7 +659,7 @@ void QgsMetadataWidget::saveMetadata( QgsLayerMetadata &layerMetadata )
   layerMetadata.setHistory( mHistoryModel->stringList() );
 }
 
-bool QgsMetadataWidget::checkMetadata()
+bool QgsMetadataWidget::checkMetadata() const
 {
   QgsLayerMetadata metadata = QgsLayerMetadata();
   saveMetadata( metadata );
@@ -815,9 +839,11 @@ void QgsMetadataWidget::setMapCanvas( QgsMapCanvas *canvas )
 void QgsMetadataWidget::acceptMetadata()
 {
   saveMetadata( mMetadata );
-
-  // Save layer metadata properties
-  mLayer->setMetadata( mMetadata );
+  if ( mLayer )
+  {
+    // Save layer metadata properties
+    mLayer->setMetadata( mMetadata );
+  }
 }
 
 void QgsMetadataWidget::setMetadata( const QgsLayerMetadata &metadata )
@@ -826,7 +852,7 @@ void QgsMetadataWidget::setMetadata( const QgsLayerMetadata &metadata )
   setPropertiesFromLayer();
 }
 
-void QgsMetadataWidget::syncFromCategoriesTabToKeywordsTab()
+void QgsMetadataWidget::syncFromCategoriesTabToKeywordsTab() const
 {
   if ( mCategoriesModel->rowCount() > 0 )
   {
@@ -847,7 +873,7 @@ void QgsMetadataWidget::syncFromCategoriesTabToKeywordsTab()
   }
 }
 
-void QgsMetadataWidget::updatePanel()
+void QgsMetadataWidget::updatePanel() const
 {
   int index = tabWidget->currentIndex();
   QString currentTabText = tabWidget->widget( index )->objectName();

src/gui/qgsmetadatawidget.h

@@ -43,16 +43,43 @@ class GUI_EXPORT QgsMetadataWidget : public QWidget, private Ui::QgsMetadataWidg
 
     /**
      * Constructor for the wizard.
+     * \note
+     * For use with a source \layer. This constructor automatically sets the widget's metadata() if the \a layer pointer is valid.
+     *  calls setMetadata, using mMetadata
+     * \param layer to set the main QgsLayerMetadata with mLayer->metadata() when not nullptr
+     * \see setMetadata
      */
     QgsMetadataWidget( QWidget *parent, QgsMapLayer *layer = nullptr );
 
+    /**
+     * Sets the \a metadata to display in the widget
+     * \note
+     * Called from constructor and initializes child widget on first use
+     * Can be called from outside to change the QgsLayerMetadata object.
+     * \see metadata()
+     */
+    void setMetadata( const QgsLayerMetadata &layerMetadata );
+
+    /**
+     * Retrieves a QgsLayerMetadata object representing the current state of the widget.
+     * \note
+     *  saveMetdata is called before returning QgsLayerMetadata
+     * \see saveMetadata
+     */
+    QgsLayerMetadata metadata();
+
     /**
      * Save all fields in a QgsLayerMetadata object.
+     * \see getMetadata
+     * \see acceptMetadata
+     * \see checkMetadata
      */
     void saveMetadata( QgsLayerMetadata &layerMetadata );
 
     /**
      * Check if values in the wizard are correct.
+     * \see updatePanel
+     * \see saveMetadata
      */
     bool checkMetadata();