[Feature] conditional visibility for tabs and groupboxes

This adds a new configuration option to conditionally show or hide
tabs and groupboxes in drag and drop designer forms.

Configuration is done via a double click in the designer tree in the
fields configuration interface.

An expression can be entered to control the visibility. The expression
will be re-evaluated everytime values in the form change and the tab or
groupbox shown/hidden accordingly.

src/app/qgsfieldsproperties.cpp

@@ -28,6 +28,7 @@
 #include "qgsrelationmanager.h"
 #include "qgsvectordataprovider.h"
 #include "qgsvectorlayer.h"
+#include "qgsfieldexpressionwidget.h"
 
 #include <QTreeWidgetItem>
 #include <QWidget>
@@ -72,7 +73,7 @@ QgsFieldsProperties::QgsFieldsProperties( QgsVectorLayer *layer, QWidget* parent
   // tab and group display
   mAddItemButton->setEnabled( false );
 
-  mDesignerTree = new DesignerTree( mAttributesTreeFrame );
+  mDesignerTree = new DesignerTree( mLayer, mAttributesTreeFrame );
   mDesignerListLayout->addWidget( mDesignerTree );
   mDesignerTree->setHeaderLabels( QStringList() << tr( "Label" ) );
 
@@ -154,7 +155,7 @@ void QgsFieldsProperties::onAttributeSelectionChanged()
   updateButtons();
 }
 
-QTreeWidgetItem *QgsFieldsProperties::loadAttributeEditorTreeItem( QgsAttributeEditorElement* const widgetDef, QTreeWidgetItem* parent )
+QTreeWidgetItem* QgsFieldsProperties::loadAttributeEditorTreeItem( QgsAttributeEditorElement* const widgetDef, QTreeWidgetItem* parent )
 {
   QTreeWidgetItem* newWidget = nullptr;
   switch ( widgetDef->type() )
@@ -187,6 +188,7 @@ QTreeWidgetItem *QgsFieldsProperties::loadAttributeEditorTreeItem( QgsAttributeE
 
       itemData.setColumnCount( container->columnCount() );
       itemData.setShowAsGroupBox( container->isGroupBox() );
+      itemData.setVisibilityExpression( container->visibilityExpression() );
       newWidget = mDesignerTree->addItem( parent, itemData );
 
       Q_FOREACH ( QgsAttributeEditorElement* wdg, container->children() )
@@ -865,6 +867,7 @@ QgsAttributeEditorElement* QgsFieldsProperties::createAttributeEditorWidget( QTr
       QgsAttributeEditorContainer* container = new QgsAttributeEditorContainer( item->text( 0 ), parent );
       container->setColumnCount( itemData.columnCount() );
       container->setIsGroupBox( forceGroup ? true : itemData.showAsGroupBox() );
+      container->setVisibilityExpression( itemData.visibilityExpression() );
 
       for ( int t = 0; t < item->childCount(); t++ )
       {
@@ -1092,8 +1095,9 @@ QTreeWidgetItem* DesignerTree::addContainer( QTreeWidgetItem* parent, const QStr
   return newItem;
 }
 
-DesignerTree::DesignerTree( QWidget* parent )
+DesignerTree::DesignerTree( QgsVectorLayer* layer, QWidget* parent )
     : QTreeWidget( parent )
+    , mLayer( layer )
 {
   connect( this, SIGNAL( itemDoubleClicked( QTreeWidgetItem*, int ) ), this, SLOT( onItemDoubleClicked( QTreeWidgetItem*, int ) ) );
 }
@@ -1271,11 +1275,22 @@ void DesignerTree::onItemDoubleClicked( QTreeWidgetItem* item, int column )
     QCheckBox* showAsGroupBox = nullptr;
     QLineEdit* title = new QLineEdit( itemData.name() );
     QSpinBox* columnCount = new QSpinBox();
+    QGroupBox* visibilityExpressionGroupBox = new QGroupBox( tr( "Control visibility by expression " ) );
+    visibilityExpressionGroupBox->setCheckable( true );
+    visibilityExpressionGroupBox->setChecked( itemData.visibilityExpression().enabled() );
+    visibilityExpressionGroupBox->setLayout( new QGridLayout );
+    QgsFieldExpressionWidget* visibilityExpressionWidget = new QgsFieldExpressionWidget;
+    visibilityExpressionWidget->setLayer( mLayer );
+    visibilityExpressionWidget->setExpressionDialogTitle( tr( "Visibility expression" ) );
+    visibilityExpressionWidget->setExpression( itemData.visibilityExpression()->expression() );
+    visibilityExpressionGroupBox->layout()->addWidget( visibilityExpressionWidget );
+
     columnCount->setRange( 1, 5 );
     columnCount->setValue( itemData.columnCount() );
 
     layout->addRow( tr( "Title" ), title );
     layout->addRow( tr( "Column count" ), columnCount );
+    layout->addWidget( visibilityExpressionGroupBox );
 
     if ( !item->parent() )
     {
@@ -1299,6 +1314,11 @@ void DesignerTree::onItemDoubleClicked( QTreeWidgetItem* item, int column )
       itemData.setName( title->text() );
       itemData.setShowLabel( showLabelCheckbox->isChecked() );
 
+      QgsOptionalExpression visibilityExpression;
+      visibilityExpression.setData( QgsExpression( visibilityExpressionWidget->expression() ) );
+      visibilityExpression.setEnabled( visibilityExpressionGroupBox->isChecked() );
+      itemData.setVisibilityExpression( visibilityExpression );
+
       item->setData( 0, QgsFieldsProperties::DesignerTreeRole, itemData.asQVariant() );
       item->setText( 0, title->text() );
     }
@@ -1369,3 +1389,13 @@ void QgsFieldsProperties::DesignerTreeItemData::setShowLabel( bool showLabel )
 {
   mShowLabel = showLabel;
 }
+
+QgsOptionalExpression QgsFieldsProperties::DesignerTreeItemData::visibilityExpression() const
+{
+  return mVisibilityExpression;
+}
+
+void QgsFieldsProperties::DesignerTreeItemData::setVisibilityExpression( const QgsOptionalExpression& visibilityExpression )
+{
+  mVisibilityExpression = visibilityExpression;
+}

src/app/qgsfieldsproperties.h

@@ -84,12 +84,16 @@ class APP_EXPORT QgsFieldsProperties : public QWidget, private Ui_QgsFieldsPrope
         bool showLabel() const;
         void setShowLabel( bool showLabel );
 
+        QgsOptionalExpression visibilityExpression() const;
+        void setVisibilityExpression( const QgsOptionalExpression& visibilityExpression );
+
       private:
         Type mType;
         QString mName;
         int mColumnCount;
         bool mShowAsGroupBox;
         bool mShowLabel;
+        QgsOptionalExpression mVisibilityExpression;
     };
 
     /**
@@ -265,7 +269,7 @@ class DesignerTree : public QTreeWidget
     Q_OBJECT
 
   public:
-    explicit DesignerTree( QWidget* parent = nullptr );
+    explicit DesignerTree( QgsVectorLayer* layer, QWidget* parent = nullptr );
     QTreeWidgetItem* addItem( QTreeWidgetItem* parent, QgsFieldsProperties::DesignerTreeItemData data );
     QTreeWidgetItem* addContainer( QTreeWidgetItem* parent, const QString& title , int columnCount );
 
@@ -282,6 +286,9 @@ class DesignerTree : public QTreeWidget
 
   private slots:
     void onItemDoubleClicked( QTreeWidgetItem* item, int column );
+
+  private:
+    QgsVectorLayer* mLayer;
 };
 
 Q_DECLARE_METATYPE( QgsFieldsProperties::FieldConfig )

src/core/qgsattributeeditorelement.cpp

@@ -26,6 +26,19 @@ void QgsAttributeEditorContainer::setName( const QString& name )
   mName = name;
 }
 
+QgsOptionalExpression QgsAttributeEditorContainer::visibilityExpression() const
+{
+  return mVisibilityExpression;
+}
+
+void QgsAttributeEditorContainer::setVisibilityExpression( const QgsOptionalExpression& visibilityExpression )
+{
+  if ( visibilityExpression == mVisibilityExpression )
+    return;
+
+  mVisibilityExpression = visibilityExpression;
+}
+
 QList<QgsAttributeEditorElement*> QgsAttributeEditorContainer::findElements( QgsAttributeEditorElement::AttributeEditorType type ) const
 {
   QList<QgsAttributeEditorElement*> results;

src/core/qgsattributeeditorelement.h

@@ -17,6 +17,7 @@
 #define QGSATTRIBUTEEDITORELEMENT_H
 
 #include "qgsrelation.h"
+#include "qgsoptionalexpression.h"
 
 class QgsRelationManager;
 
@@ -219,6 +220,9 @@ class CORE_EXPORT QgsAttributeEditorContainer : public QgsAttributeEditorElement
      */
     virtual QgsAttributeEditorElement* clone( QgsAttributeEditorElement* parent ) const override;
 
+    QgsOptionalExpression visibilityExpression() const;
+    void setVisibilityExpression( const QgsOptionalExpression& visibilityExpression );
+
   private:
     void saveConfiguration( QDomElement& elem ) const override;
     QString typeIdentifier() const override;
@@ -226,6 +230,7 @@ class CORE_EXPORT QgsAttributeEditorContainer : public QgsAttributeEditorElement
     bool mIsGroupBox;
     QList<QgsAttributeEditorElement*> mChildren;
     int mColumnCount;
+    QgsOptionalExpression mVisibilityExpression;
 };
 
 /** \ingroup core

src/core/qgseditformconfig.cpp

@@ -16,6 +16,7 @@
 #include "qgseditformconfig.h"
 #include "qgsproject.h"
 #include "qgsrelationmanager.h"
+
 //#include "qgseditorwidgetregistry.h"
 
 QgsAttributeEditorContainer::~QgsAttributeEditorContainer()
@@ -573,6 +574,15 @@ QgsAttributeEditorElement* QgsEditFormConfig::attributeEditorElementFromDomEleme
     else
       container->setIsGroupBox( parent );
 
+    bool visibilityExpressionEnabled = elem.attribute( "visibilityExpressionEnabled" ).toInt( &ok );
+    QgsOptionalExpression visibilityExpression;
+    if ( ok )
+    {
+      visibilityExpression.setEnabled( visibilityExpressionEnabled );
+      visibilityExpression.setData( QgsExpression( elem.attribute( "visibilityExpression" ) ) );
+    }
+    container->setVisibilityExpression( visibilityExpression );
+
     QDomNodeList childNodeList = elem.childNodes();
 
     for ( int i = 0; i < childNodeList.size(); i++ )
@@ -627,6 +637,7 @@ QgsAttributeEditorElement* QgsAttributeEditorContainer::clone( QgsAttributeEdito
   }
   element->mIsGroupBox = mIsGroupBox;
   element->mColumnCount = mColumnCount;
+  element->mVisibilityExpression = mVisibilityExpression;
 
   return element;
 }
@@ -635,6 +646,8 @@ void QgsAttributeEditorContainer::saveConfiguration( QDomElement& elem ) const
 {
   elem.setAttribute( "columnCount", mColumnCount );
   elem.setAttribute( "groupBox", mIsGroupBox ? 1 : 0 );
+  elem.setAttribute( "visibilityExpressionEnabled", mVisibilityExpression.enabled() ? 1 : 0 );
+  elem.setAttribute( "visibilityExpression", mVisibilityExpression->expression() );
 
   Q_FOREACH ( QgsAttributeEditorElement* child, mChildren )
   {

src/gui/qgsattributeform.cpp

@@ -30,6 +30,7 @@
 #include "qgseditorwidgetwrapper.h"
 #include "qgsrelationmanager.h"
 #include "qgslogger.h"
+#include "qgstabwidget.h"
 
 #include <QDir>
 #include <QTextStream>
@@ -42,7 +43,6 @@
 #include <QLabel>
 #include <QPushButton>
 #include <QScrollArea>
-#include <QTabWidget>
 #include <QUiLoader>
 #include <QMessageBox>
 #include <QSettings>
@@ -747,6 +747,14 @@ void QgsAttributeForm::updateConstraints( QgsEditorWidgetWrapper *eww )
 
     // sync ok button status
     synchronizeEnabledState();
+
+    mExpressionContext.setFeature( ft );
+
+    // Recheck visibility for all containers which are controlled by this value
+    Q_FOREACH ( ContainerInformation* info, mContainerInformationDependency.value( eww->field().name() ) )
+    {
+      info->apply( &mExpressionContext );
+    }
   }
 }
 
@@ -810,6 +818,15 @@ void QgsAttributeForm::displayInvalidConstraintMessage( const QStringList& f,
   mInvalidConstraintMessage->setStyleSheet( "QLabel { background-color : #ffc800; }" );
 }
 
+void QgsAttributeForm::registerContainerInformation( QgsAttributeForm::ContainerInformation* info )
+{
+  mContainerVisibilityInformation.append( info );
+  Q_FOREACH ( const QString& col, info->expression.referencedColumns() )
+  {
+    mContainerInformationDependency[ col ].append( info );
+  }
+}
+
 bool QgsAttributeForm::currentFormValidConstraints( QStringList &invalidFields,
     QStringList &descriptions )
 {
@@ -1095,7 +1112,7 @@ void QgsAttributeForm::init()
     }
   }
 
-  QTabWidget* tabWidget = nullptr;
+  QgsTabWidget* tabWidget = nullptr;
 
   // Tab layout
   if ( !formWidget && mLayer->editFormConfig().layout() == QgsEditFormConfig::TabLayout )
@@ -1117,13 +1134,14 @@ void QgsAttributeForm::init()
           tabWidget = nullptr;
           WidgetInfo widgetInfo = createWidgetFromDef( widgDef, formWidget, mLayer, mContext );
           layout->addWidget( widgetInfo.widget, row, column, 1, 2 );
+          registerContainerInformation( new ContainerInformation( widgetInfo.widget, containerDef->visibilityExpression().data() ) );
           column += 2;
         }
         else
         {
           if ( !tabWidget )
           {
-            tabWidget = new QTabWidget();
+            tabWidget = new QgsTabWidget();
             layout->addWidget( tabWidget, row, column, 1, 2 );
             column += 2;
           }
@@ -1131,6 +1149,11 @@ void QgsAttributeForm::init()
           QWidget* tabPage = new QWidget( tabWidget );
 
           tabWidget->addTab( tabPage, widgDef->name() );
+
+          if ( containerDef->visibilityExpression().enabled() )
+          {
+            registerContainerInformation( new ContainerInformation( tabWidget, tabPage, containerDef->visibilityExpression().data() ) );
+          }
           QGridLayout* tabPageLayout = new QGridLayout();
           tabPage->setLayout( tabPageLayout );
 
@@ -1595,6 +1618,12 @@ QgsAttributeForm::WidgetInfo QgsAttributeForm::createWidgetFromDef( const QgsAtt
       {
         WidgetInfo widgetInfo = createWidgetFromDef( childDef, myContainer, vl, context );
 
+        if ( childDef->type() == QgsAttributeEditorElement::AeTypeContainer )
+        {
+          QgsAttributeEditorContainer* containerDef = static_cast<QgsAttributeEditorContainer*>( childDef );
+          registerContainerInformation( new ContainerInformation( widgetInfo.widget, containerDef->visibilityExpression().data() ) );
+        }
+
         if ( widgetInfo.labelText.isNull() )
         {
           gbLayout->addWidget( widgetInfo.widget, row, column, 1, 2 );
@@ -1875,3 +1904,22 @@ int QgsAttributeForm::messageTimeout()
   QSettings settings;
   return settings.value( "/qgis/messageTimeout", 5 ).toInt();
 }
+
+void QgsAttributeForm::ContainerInformation::apply( QgsExpressionContext* expressionContext )
+{
+  bool newVisibility = expression.evaluate( expressionContext ).toBool();
+
+  if ( newVisibility != isVisible )
+  {
+    if ( tabWidget )
+    {
+      tabWidget->setTabVisible( widget, newVisibility );
+    }
+    else
+    {
+      widget->setVisible( newVisibility );
+    }
+
+    isVisible = newVisibility;
+  }
+}

src/gui/qgsattributeform.h

@@ -28,6 +28,7 @@ class QgsAttributeFormEditorWidget;
 class QgsMessageBar;
 class QgsMessageBarItem;
 class QgsWidgetWrapper;
+class QgsTabWidget;
 
 /** \ingroup gui
  * \class QgsAttributeForm
@@ -343,6 +344,37 @@ class GUI_EXPORT QgsAttributeForm : public QWidget
     QWidget* mSearchButtonBox;
     QList<QgsAttributeFormInterface*> mInterfaces;
     QMap< int, QgsAttributeFormEditorWidget* > mFormEditorWidgets;
+    QgsExpressionContext mExpressionContext;
+
+    struct ContainerInformation
+    {
+      ContainerInformation( QgsTabWidget* tabWidget, QWidget* widget, QgsExpression expression )
+          : tabWidget( tabWidget )
+          , widget( widget )
+          , expression( expression )
+          , isVisible( true )
+      {}
+
+      ContainerInformation( QWidget* widget, QgsExpression expression )
+          : tabWidget( nullptr )
+          , widget( widget )
+          , expression( expression )
+          , isVisible( true )
+      {}
+
+      QgsTabWidget* tabWidget;
+      QWidget* widget;
+      QgsExpression expression;
+      bool isVisible;
+
+      void apply( QgsExpressionContext* expressionContext );
+    };
+
+    void registerContainerInformation( ContainerInformation* info );
+
+    // Contains information about tabs and groupboxes, their visibility state visibility conditions
+    QVector<ContainerInformation*> mContainerVisibilityInformation;
+    QMap<QString, QVector<ContainerInformation*> > mContainerInformationDependency;
 
     // Variables below are used for python
     static int sFormCounter;

src/gui/qgsfieldexpressionwidget.cpp

@@ -110,6 +110,11 @@ QString QgsFieldExpressionWidget::asExpression() const
   return isExpression() ? currentText() : QgsExpression::quotedColumnRef( currentText() );
 }
 
+QString QgsFieldExpressionWidget::expression() const
+{
+  return asExpression();
+}
+
 bool QgsFieldExpressionWidget::isValidExpression( QString *expressionError ) const
 {
   QString temp;
@@ -200,6 +205,11 @@ void QgsFieldExpressionWidget::setField( const QString &fieldName )
   currentFieldChanged();
 }
 
+void QgsFieldExpressionWidget::setExpression( const QString& expression )
+{
+  setField( expression );
+}
+
 void QgsFieldExpressionWidget::editExpression()
 {
   QString currentExpression = currentText();

src/gui/qgsfieldexpressionwidget.h

@@ -91,13 +91,25 @@ class GUI_EXPORT QgsFieldExpressionWidget : public QWidget
       */
     QString currentText() const;
 
-    /** Returns the currently selected field or expression. If a field is currently selected, the returned
+    /**
+     * Returns the currently selected field or expression. If a field is currently selected, the returned
      * value will be converted to a valid expression referencing this field (ie enclosing the field name with
      * appropriate quotations).
      * @note added in QGIS 2.14
      */
     QString asExpression() const;
 
+    /**
+     * Returns the currently selected field or expression. If a field is currently selected, the returned
+     * value will be converted to a valid expression referencing this field (ie enclosing the field name with
+     * appropriate quotations).
+     *
+     * Alias for asExpression()
+     *
+     * @note added in QGIS 3.0
+     */
+    QString expression() const;
+
     //! Returns the currently used layer
     QgsVectorLayer* layer() const;
 
@@ -132,6 +144,14 @@ class GUI_EXPORT QgsFieldExpressionWidget : public QWidget
     //! sets the current field or expression in the widget
     void setField( const QString &fieldName );
 
+    /**
+     * Sets the current expression text and if applicable also the field.
+     * Alias for setField.
+     *
+     * @note Added in QGIS 3.0
+     */
+    void setExpression( const QString& expression );
+
   protected slots:
     //! open the expression dialog to edit the current or add a new expression
     void editExpression();