[FEATURE] Add N:M relation editing possibilities

This adds the possibility to manage data on a normalized relational
database in N:M relations. On the relation editor in a form, the tools
to add, delete, link and unlink work (also) on the linking table if a
relation is visualized as N:M relation.

Configuration is done through the fields tab where on the relation a
second relation can be chosen (if there is a suitable relation in terms
of a second relation on the linking table).

Limitations
===========

QGIS is not a database management system.

It is based on assumptions about the underlying database system. In
particular it expects

 * A `ON DELETE CASCADE` or similar measure on the second relation
 * Does not take care of setting the primary key when adding features.
   Either users need to be instructed to set them manually or - if it's a
   database derived value - the layers need to be in transaction mode
   (currently only activatable through the API)

Author: m-kuhn

ci/travis/linux/before_script.sh

@@ -1,3 +1,4 @@
 printf "[qgis_test]\nhost=localhost\ndbname=qgis_test\nuser=postgres" > ~/.pg_service.conf
 psql -c 'CREATE DATABASE qgis_test;' -U postgres
 psql -f $TRAVIS_BUILD_DIR/tests/testdata/provider/testdata.sql -U postgres -d qgis_test
+psql -f $TRAVIS_BUILD_DIR/tests/testdata/provider/reltests.sql -U postgres -d qgis_test

python/gui/editorwidgets/core/qgswidgetwrapper.sip

@@ -14,6 +14,12 @@
  ***************************************************************************/
 
 
+// This is required for the ConvertToSubClassCode to work properly
+// so RTTI for casting is available in the whole module.
+%ModuleCode
+#include "qgsrelationwidgetwrapper.h"
+%End
+
 /**
  * Manages an editor widget
  * Widget and wrapper share the same parent
@@ -32,9 +38,10 @@ class QgsWidgetWrapper : QObject
 %End
 
 %ConvertToSubClassCode
-  QgsEditorWidgetWrapper* eww = qobject_cast<QgsEditorWidgetWrapper*>( sipCpp );
-  if ( eww )
+  if ( qobject_cast<QgsEditorWidgetWrapper*>( sipCpp ) )
     sipType = sipType_QgsEditorWidgetWrapper;
+  else if ( qobject_cast<QgsRelationWidgetWrapper*>( sipCpp ) )
+    sipType = sipType_QgsRelationWidgetWrapper;
   else
     sipType = 0;
 %End

python/gui/editorwidgets/qgsrelationwidgetwrapper.sip

@@ -0,0 +1,33 @@
+/***************************************************************************
+    qgsrelationwidgetwrapper.h
+     --------------------------------------
+    Date                 : 14.5.2014
+    Copyright            : (C) 2014 Matthias Kuhn
+    Email                : matthias at opengis dot ch
+ ***************************************************************************
+ *                                                                         *
+ *   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  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+
+class QgsRelationWidgetWrapper : QgsWidgetWrapper
+{
+%TypeHeaderCode
+#include <qgsrelationwidgetwrapper.h>
+%End
+
+  public:
+    explicit QgsRelationWidgetWrapper( QgsVectorLayer* vl, const QgsRelation& relation, QWidget* editor = 0, QWidget* parent /TransferThis/ = 0 );
+
+  protected:
+    QWidget* createWidget( QWidget* parent );
+    void initWidget( QWidget* editor );
+    bool valid() const;
+
+  public slots:
+    void setFeature( const QgsFeature& feature );
+};

python/gui/gui.sip

@@ -71,6 +71,7 @@
 %Include qgsfieldvalidator.sip
 %Include qgsfiledropedit.sip
 %Include qgsfilterlineedit.sip
+%Include qgsfeatureselectiondlg.sip
 %Include qgsformannotationitem.sip
 %Include qgsgenericprojectionselector.sip
 %Include qgsgeometryrubberband.sip
@@ -126,6 +127,7 @@
 %Include qgsrasterlayersaveasdialog.sip
 %Include qgsrasterpyramidsoptionswidget.sip
 %Include qgsrubberband.sip
+%Include qgsrelationeditorwidget.sip
 %Include qgsscalecombobox.sip
 %Include qgsscalerangewidget.sip
 %Include qgsscalevisibilitydialog.sip
@@ -231,6 +233,7 @@
 %Include editorwidgets/qgsdoublespinbox.sip
 %Include editorwidgets/qgsrelationreferencewidget.sip
 %Include editorwidgets/qgsrelationreferencewidgetwrapper.sip
+%Include editorwidgets/qgsrelationwidgetwrapper.sip
 %Include editorwidgets/qgsspinbox.sip
 %Include editorwidgets/qgsdatetimeedit.sip
 

python/gui/qgsfeatureselectiondlg.sip

@@ -0,0 +1,50 @@
+/***************************************************************************
+    qgsfeatureselectiondlg.sip
+     --------------------------------------
+    Date                 : 30.11.2015
+    Copyright            : (C) 2015 Matthias Kuhn
+    Email                : matthias at opengis dot ch
+ ***************************************************************************
+ *                                                                         *
+ *   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  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+// This is required for the ConvertToSubClassCode to work properly
+// so RTTI for casting is available in the whole module.
+%ModuleCode
+#include "qgsfeatureselectiondlg.h"
+%End
+
+class QgsFeatureSelectionDlg : QDialog
+{
+%TypeHeaderCode
+#include "qgsfeatureselectiondlg.h"
+%End
+
+%ConvertToSubClassCode
+  if ( qobject_cast<QgsFeatureSelectionDlg*>( sipCpp ) )
+    sipType = sipType_QgsFeatureSelectionDlg;
+  else
+    sipType = 0;
+%End
+
+  public:
+    explicit QgsFeatureSelectionDlg( QgsVectorLayer* vl, QgsAttributeEditorContext &context, QWidget *parent /TransferThis/ = 0 );
+
+    /**
+     * Get the selected features
+     *
+     * @return The selected feature ids
+     */
+    const QgsFeatureIds& selectedFeatures();
+
+    /**
+     * Set the selected features
+     * @param ids The feature ids to select
+     */
+    void setSelectedFeatures( const QgsFeatureIds& ids );
+};

python/gui/qgsrelationeditorwidget.sip

@@ -0,0 +1,68 @@
+/***************************************************************************
+    qgsrelationeditorwidget.sip
+     --------------------------------------
+    Date                 : 28.11.2015
+    Copyright            : (C) 2015 Matthias Kuhn
+    Email                : matthias at opengis dot ch
+ ***************************************************************************
+ *                                                                         *
+ *   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  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+%ModuleCode
+#include "qgsrelationeditorwidget.h"
+%End
+
+class QgsRelationEditorWidget : QgsCollapsibleGroupBox
+{
+%TypeHeaderCode
+#include <qgsrelationeditorwidget.h>
+%End
+
+
+%ConvertToSubClassCode
+  if ( qobject_cast<QgsRelationEditorWidget*>( sipCpp ) )
+    sipType = sipType_QgsRelationEditorWidget;
+  else
+    sipType = 0;
+%End
+
+  public:
+    /**
+     * @param parent parent widget
+     */
+    QgsRelationEditorWidget( QWidget* parent /TransferThis/= 0 );
+
+    //! Define the view mode for the dual view
+    void setViewMode( QgsDualView::ViewMode mode );
+
+    //! Get the view mode for the dual view
+    QgsDualView::ViewMode viewMode();
+
+    void setRelationFeature( const QgsRelation& relation, const QgsFeature& feature );
+
+    /**
+     * Set the relation(s) for this widget
+     * If only one relation is set, it will act as a simple 1:N relation widget
+     * If both relations are set, it will act as an N:M relation widget
+     * inserting and deleting entries on the intermediate table as required.
+     *
+     * @param relation    Relation referencing the edited table
+     * @param nmrelation  Optional reference from the referencing table to a 3rd N:M table
+     */
+    void setRelations( const QgsRelation& relation, const QgsRelation& nmrelation );
+
+    void setFeature( const QgsFeature& feature );
+
+    void setEditorContext( const QgsAttributeEditorContext& context );
+
+    /**
+     * The feature selection manager is responsible for the selected features
+     * which are currently being edited.
+     */
+    QgsIFeatureSelectionManager* featureSelectionManager();
+};

src/core/qgseditformconfig.cpp

@@ -195,6 +195,32 @@ void QgsEditFormConfig::readXml( const QDomNode& node )
     QgsAttributeEditorElement *attributeEditorWidget = attributeEditorElementFromDomElement( elem, this );
     addTab( attributeEditorWidget );
   }
+
+
+  //// TODO: MAKE THIS MORE GENERIC, SO INDIVIDUALL WIDGETS CAN NOT ONLY SAVE STRINGS
+  /// SEE QgsEditorWidgetFactory::writeConfig
+
+  QDomElement widgetsElem = node.namedItem( "widgets" ).toElement();
+
+  QDomNodeList widgetConfigsElems = widgetsElem.childNodes();
+
+  for ( int i = 0; i < widgetConfigsElems.size(); ++i )
+  {
+    QgsEditorWidgetConfig cfg;
+
+    QDomElement wdgElem = widgetConfigsElems.at( i ).toElement();
+
+    QDomElement cfgElem = wdgElem.namedItem( "config" ).toElement();
+
+    for ( int j = 0; j < cfgElem.attributes().size(); ++j )
+    {
+      QDomAttr attr = cfgElem.attributes().item( j ).toAttr();
+      cfg[attr.name()] = attr.value();
+    }
+
+    setWidgetConfig( wdgElem.attribute( "name" ), cfg );
+  }
+  //// END TODO
 }
 
 void QgsEditFormConfig::writeXml( QDomNode& node ) const
@@ -262,6 +288,40 @@ void QgsEditFormConfig::writeXml( QDomNode& node ) const
 
     node.appendChild( tabsElem );
   }
+
+  //// TODO: MAKE THIS MORE GENERIC, SO INDIVIDUALL WIDGETS CAN NOT ONLY SAVE STRINGS
+  /// SEE QgsEditorWidgetFactory::writeConfig
+
+  QDomElement widgetsElem = doc.createElement( "widgets" );
+
+  QMap<QString, QgsEditorWidgetConfig >::ConstIterator configIt( mWidgetConfigs.constBegin() );
+
+  while ( configIt != mWidgetConfigs.constEnd() )
+  {
+    if ( mFields.indexFromName( configIt.key() ) == -1 )
+    {
+      QDomElement widgetElem = doc.createElement( "widget" );
+      widgetElem.setAttribute( "name", configIt.key() );
+
+      QDomElement configElem = doc.createElement( "config" );
+      widgetElem.appendChild( configElem );
+
+      QgsEditorWidgetConfig::ConstIterator cfgIt( configIt.value().constBegin() );
+
+      while ( cfgIt != configIt.value().constEnd() )
+      {
+        configElem.setAttribute( cfgIt.key(), cfgIt.value().toString() );
+        ++cfgIt;
+      }
+
+      widgetsElem.appendChild( widgetElem );
+    }
+    ++configIt;
+  }
+
+  node.appendChild( widgetsElem );
+
+  //// END TODO
 }
 
 QgsAttributeEditorElement* QgsEditFormConfig::attributeEditorElementFromDomElement( QDomElement &elem, QObject* parent )

src/gui/attributetable/qgsattributetablemodel.cpp

@@ -370,6 +370,8 @@ void QgsAttributeTableModel::loadLayer()
   {
     ++i;
 
+    QgsDebugMsg( QString( "Next feature %1" ).arg( i ) );
+
     if ( t.elapsed() > 1000 )
     {
       bool cancel = false;
@@ -486,6 +488,7 @@ int QgsAttributeTableModel::fieldCol( int idx ) const
 
 int QgsAttributeTableModel::rowCount( const QModelIndex &parent ) const
 {
+  QgsDebugMsg( QString( "Row Count %1" ).arg( mRowIdMap.size() ) );
   Q_UNUSED( parent );
   return mRowIdMap.size();
 }

src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp

@@ -17,6 +17,7 @@
 
 #include "qgsrelationeditorwidget.h"
 #include "qgsattributeeditorcontext.h"
+#include "qgsproject.h"
 
 #include <QWidget>
 
@@ -35,7 +36,7 @@ QWidget* QgsRelationWidgetWrapper::createWidget( QWidget* parent )
 void QgsRelationWidgetWrapper::setFeature( const QgsFeature& feature )
 {
   if ( mWidget && mRelation.isValid() )
-    mWidget->setRelationFeature( mRelation, feature );
+    mWidget->setFeature( feature );
 }
 
 void QgsRelationWidgetWrapper::initWidget( QWidget* editor )
@@ -71,6 +72,10 @@ void QgsRelationWidgetWrapper::initWidget( QWidget* editor )
   }
   while ( ctx );
 
+  QgsRelation nmrel = QgsProject::instance()->relationManager()->relation( config( "nm-rel" ).toString() );
+
+  w->setRelations( mRelation, nmrel );
+
   mWidget = w;
 }
 

src/gui/qgsattributeform.cpp

@@ -793,7 +793,7 @@ QWidget* QgsAttributeForm::createWidgetFromDef( const QgsAttributeEditorElement
       }
       QWidget* spacer = new QWidget();
       spacer->setSizePolicy( QSizePolicy::Minimum, QSizePolicy::Preferred );
-      gbLayout->addWidget( spacer, index, 0 );
+      // gbLayout->addWidget( spacer, index, 0 );
 
       labelText = QString::null;
       labelOnTop = true;

src/gui/qgscollapsiblegroupbox.cpp

@@ -89,7 +89,7 @@ void QgsCollapsibleGroupBoxBasic::init()
 
 void QgsCollapsibleGroupBoxBasic::showEvent( QShowEvent * event )
 {
-  //QgsDebugMsg( "Entered" );
+  QgsDebugMsg( "Entered" );
   // initialise widget on first show event only
   if ( mShown )
   {

src/gui/qgsfeatureselectiondlg.cpp

@@ -40,4 +40,9 @@ const QgsFeatureIds& QgsFeatureSelectionDlg::selectedFeatures()
   return mFeatureSelection->selectedFeaturesIds();
 }
 
+void QgsFeatureSelectionDlg::setSelectedFeatures( const QgsFeatureIds& ids )
+{
+  mFeatureSelection->setSelectedFeatures( ids );
+}
+
 

src/gui/qgsfeatureselectiondlg.h

@@ -27,8 +27,19 @@ class GUI_EXPORT QgsFeatureSelectionDlg : public QDialog, private Ui::QgsFeature
   public:
     explicit QgsFeatureSelectionDlg( QgsVectorLayer* vl, QgsAttributeEditorContext &context, QWidget *parent = 0 );
 
+    /**
+     * Get the selected features
+     *
+     * @return The selected feature ids
+     */
     const QgsFeatureIds& selectedFeatures();
 
+    /**
+     * Set the selected features
+     * @param ids The feature ids to select
+     */
+    void setSelectedFeatures( const QgsFeatureIds& ids );
+
   private:
     QgsGenericFeatureSelectionManager* mFeatureSelection;
     QgsVectorLayer* mVectorLayer;