Find a suitable editor widget if widget and config mismatch

If a .ui file is specified and the widget specified in the .ui file is not
supported by the widgetwrapper which is configured in the layer properties
the system will automatically try to find a better suitable widgetwrapper.

To do this, widgetwrappers (respectively their factories) can return a map of
supported widget types with priority values.
The widgetwrapper which offers the heighest priority for a certain widget type
will be used in case of a mismatch.

Sponsored by OPENGIS.ch special projects team (aka gis.se troubleshooting
section)

python/gui/editorwidgets/core/qgseditorwidgetwrapper.sip

@@ -88,6 +88,7 @@ class QgsEditorWidgetWrapper : QObject
      */
     void setEnabled( bool enabled );
 
+    virtual bool valid() = 0;
   protected:
     virtual QWidget* createWidget( QWidget* parent ) = 0;
 

python/gui/editorwidgets/core/qgswidgetwrapper.sip

@@ -111,6 +111,17 @@ class QgsWidgetWrapper : QObject
      */
     static QgsWidgetWrapper* fromWidget( QWidget* widget );
 
+    /**
+     * Return true if the widget has been properly initialized.
+     * This acts as hint for the calling party if this wrapper can be used
+     * after initializing it.
+     * If it cannot be used this is a hint tothe caller that he may try to find
+     * another suitable widget type instead.
+     *
+     * @return Validity status of this widget.
+     */
+    virtual bool valid() = 0;
+
   protected:
     /**
      * This method should create a new widget with the provided parent. This will only be called

src/gui/editorwidgets/core/qgseditorwidgetfactory.cpp

@@ -30,8 +30,9 @@ QgsEditorWidgetFactory::~QgsEditorWidgetFactory()
 {
 }
 
-/** Override in own factory to get something different than the default (a simple QgsFilterLineEdit)
- *
+/**
+ * By default a simple QgsFilterLineEdit is returned as search widget.
+ * Override in own factory to get something different than the default.
  */
 QgsSearchWidgetWrapper* QgsEditorWidgetFactory::createSearchWidget( QgsVectorLayer* vl, int fieldIdx, QWidget* parent ) const
 {

src/gui/editorwidgets/core/qgseditorwidgetfactory.h

@@ -115,6 +115,15 @@ class GUI_EXPORT QgsEditorWidgetFactory
      */
     inline bool supportsField( QgsVectorLayer* vl, int fieldIdx ) { return isFieldSupported( vl, fieldIdx ); }
 
+    /**
+     * Returns a list of widget types which this editor widget supports.
+     * Each widget type can have a priority value attached, the factory with the highest one
+     * will be used.
+     *
+     * @return A map of widget type names and weight values
+     */
+    virtual QMap<const char*, int> supportedWidgetTypes() { return QMap<const char*, int>(); }
+
     /**
      * Create a pretty String representation of the value.
      *

src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp

@@ -95,9 +95,21 @@ QgsEditorWidgetWrapper* QgsEditorWidgetRegistry::create( const QString& widgetId
       // Make sure that there is a widget created at this point
       // so setValue() et al won't crash
       ww->widget();
+
+      // If we tried to set a widget which is not supported by this wrapper
+      if ( !ww->valid() )
+      {
+        delete ww;
+        QString wid = findSuitableWrapper( editor );
+        ww = mWidgetFactories[wid]->create( vl, fieldIdx, editor, parent );
+        ww->setConfig( config );
+        ww->setContext( context );
+      }
+
       return ww;
     }
   }
+
   return 0;
 }
 
@@ -164,6 +176,20 @@ bool QgsEditorWidgetRegistry::registerWidget( const QString& widgetId, QgsEditor
   else
   {
     mWidgetFactories.insert( widgetId, widgetFactory );
+
+    // Use this factory as default where it provides the heighest priority
+    QMap<const char*, int> types = widgetFactory->supportedWidgetTypes();
+    QMap<const char*, int>::ConstIterator it;
+    it = types.constBegin();
+
+    for ( ; it != types.constEnd(); ++it )
+    {
+      if ( it.value() > mFactoriesByType[it.key()].first )
+      {
+        mFactoriesByType[it.key()] = qMakePair( it.value(), widgetFactory );
+      }
+    }
+
     return true;
   }
 }
@@ -316,3 +342,32 @@ void QgsEditorWidgetRegistry::writeSymbology( QDomElement& element, QDomDocument
 
   writeMapLayer( vl, element, doc );
 }
+
+QString QgsEditorWidgetRegistry::findSuitableWrapper( QWidget* editor )
+{
+  QMap<const char*, QPair<int, QgsEditorWidgetFactory*> >::ConstIterator it;
+
+  QString widgetid;
+  int weight = 0;
+
+  it = mFactoriesByType.constBegin();
+  for ( ; it != mFactoriesByType.constEnd(); ++it )
+  {
+    if ( editor->staticMetaObject.className() == it.key() )
+    {
+      // if it's a perfect match: return it directly
+      return it.value().second->name();
+    }
+    else if ( editor->inherits( it.key() ) )
+    {
+      // if it's a subclass, continue evaluating, maybe we find a more-specific or one with more weight
+      if ( it.value().first > weight )
+      {
+        weight = it.value().first;
+        widgetid = it.value().second->name();
+      }
+    }
+  }
+
+  return widgetid;
+}

src/gui/editorwidgets/core/qgseditorwidgetregistry.h

@@ -193,7 +193,10 @@ class GUI_EXPORT QgsEditorWidgetRegistry : public QObject
     void writeSymbology( QDomElement& element, QDomDocument& doc, QString& errorMessage );
 
   private:
+    QString findSuitableWrapper( QWidget* editor );
+
     QMap<QString, QgsEditorWidgetFactory*> mWidgetFactories;
+    QMap<const char*, QPair<int, QgsEditorWidgetFactory*> > mFactoriesByType;
 };
 
 #endif // QGSEDITORWIDGETREGISTRY_H

src/gui/editorwidgets/core/qgswidgetwrapper.h

@@ -119,6 +119,17 @@ class GUI_EXPORT QgsWidgetWrapper : public QObject
      */
     static QgsWidgetWrapper* fromWidget( QWidget* widget );
 
+    /**
+     * Return true if the widget has been properly initialized.
+     * This acts as hint for the calling party if this wrapper can be used
+     * after initializing it.
+     * If it cannot be used this is a hint tothe caller that he may try to find
+     * another suitable widget type instead.
+     *
+     * @return Validity status of this widget.
+     */
+    virtual bool valid() = 0;
+
   protected:
     /**
      * This method should create a new widget with the provided parent. This will only be called

src/gui/editorwidgets/qgscheckboxwidgetwrapper.cpp

@@ -53,6 +53,11 @@ void QgsCheckboxWidgetWrapper::initWidget( QWidget* editor )
     connect( mGroupBox, SIGNAL( toggled( bool ) ), this, SLOT( valueChanged( bool ) ) );
 }
 
+bool QgsCheckboxWidgetWrapper::valid()
+{
+  return mCheckBox || mGroupBox;
+}
+
 void QgsCheckboxWidgetWrapper::setValue( const QVariant& value )
 {
   if ( mGroupBox )

src/gui/editorwidgets/qgscheckboxwidgetwrapper.h

@@ -45,6 +45,7 @@ class GUI_EXPORT QgsCheckboxWidgetWrapper : public QgsEditorWidgetWrapper
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
+    bool valid() override;
 
   public slots:
     void setValue( const QVariant& value ) override;

src/gui/editorwidgets/qgsclassificationwidgetwrapper.cpp

@@ -59,6 +59,11 @@ void QgsClassificationWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
+bool QgsClassificationWidgetWrapper::valid()
+{
+  return mComboBox;
+}
+
 void QgsClassificationWidgetWrapper::setValue( const QVariant& value )
 {
   mComboBox->setCurrentIndex( mComboBox->findData( value ) );

src/gui/editorwidgets/qgsclassificationwidgetwrapper.h

@@ -33,6 +33,7 @@ class GUI_EXPORT QgsClassificationWidgetWrapper : public QgsEditorWidgetWrapper
   protected:
     QWidget*createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
+    bool valid() override;
 
   public slots:
     void setValue( const QVariant& value ) override;

src/gui/editorwidgets/qgscolorwidgetwrapper.cpp

@@ -46,6 +46,11 @@ void QgsColorWidgetWrapper::initWidget( QWidget* editor )
   connect( mColorButton, SIGNAL( colorChanged( QColor ) ), this, SLOT( valueChanged() ) );
 }
 
+bool QgsColorWidgetWrapper::valid()
+{
+  return mColorButton;
+}
+
 void QgsColorWidgetWrapper::setValue( const QVariant& value )
 {
   if ( mColorButton )

src/gui/editorwidgets/qgscolorwidgetwrapper.h

@@ -39,6 +39,7 @@ class GUI_EXPORT  QgsColorWidgetWrapper : public QgsEditorWidgetWrapper
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
+    bool valid() override;
 
   public slots:
     void setValue( const QVariant& value ) override;

src/gui/editorwidgets/qgsdatetimeeditwrapper.cpp

@@ -90,6 +90,11 @@ void QgsDateTimeEditWrapper::initWidget( QWidget *editor )
   }
 }
 
+bool QgsDateTimeEditWrapper::valid()
+{
+  return mQgsDateTimeEdit || mQDateTimeEdit;
+}
+
 void QgsDateTimeEditWrapper::dateTimeChanged( const QDateTime& dateTime )
 {
   const QString fieldFormat = config( "field_format", QGSDATETIMEEDIT_DATEFORMAT ).toString();

src/gui/editorwidgets/qgsdatetimeeditwrapper.h

@@ -54,6 +54,7 @@ class GUI_EXPORT QgsDateTimeEditWrapper : public QgsEditorWidgetWrapper
     QVariant value() override;
     QWidget *createWidget( QWidget *parent ) override;
     void initWidget( QWidget *editor ) override;
+    bool valid() override;
 
   public slots:
     void setValue( const QVariant &value ) override;

src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.cpp

@@ -26,7 +26,7 @@ QgsDefaultSearchWidgetWrapper::QgsDefaultSearchWidgetWrapper( QgsVectorLayer* vl
     , mLineEdit( NULL )
     , mCheckbox( NULL )
     , mContainer( NULL )
-    , mCaseString(QString("LIKE"))
+    , mCaseString( QString( "LIKE" ) )
 {
 }
 
@@ -36,67 +36,72 @@ QString QgsDefaultSearchWidgetWrapper::expression()
   return mExpression;
 }
 
-void QgsDefaultSearchWidgetWrapper::setCaseString(int caseSensitiveCheckState)
+void QgsDefaultSearchWidgetWrapper::setCaseString( int caseSensitiveCheckState )
 {
-    if ( caseSensitiveCheckState == Qt::Checked) 
-    {
-        mCaseString = "LIKE";
-    }
-    else
-    {
-        mCaseString = "ILIKE";
-    }
-    // need to update also the line edit 
-    setExpression(mLineEdit->text());
+  if ( caseSensitiveCheckState == Qt::Checked )
+  {
+    mCaseString = "LIKE";
+  }
+  else
+  {
+    mCaseString = "ILIKE";
+  }
+  // need to update also the line edit
+  setExpression( mLineEdit->text() );
 }
 
-void QgsDefaultSearchWidgetWrapper::setExpression(QString exp)
+void QgsDefaultSearchWidgetWrapper::setExpression( QString exp )
 {
-    QVariant::Type fldType = layer()->pendingFields()[mFieldIdx].type();
-    bool numeric = ( fldType == QVariant::Int || fldType == QVariant::Double || fldType == QVariant::LongLong );
-    
-    QSettings settings;
-    QString nullValue = settings.value( "qgis/nullValue", "NULL" ).toString();
-    QString fieldName = layer()->pendingFields()[mFieldIdx].name();
-    QString str;
-    if ( exp == nullValue )
-    {
-      str = QString( "%1 IS NULL" ).arg( QgsExpression::quotedColumnRef( fieldName ) );
-    }
-    else
-    {
-      str = QString( "%1 %2 '%3'" )
-            .arg( QgsExpression::quotedColumnRef( fieldName ) )
-            .arg( numeric ? "=" : mCaseString )
-            .arg( numeric
-                  ? exp.replace( "'", "''" )
-                  :
-                  "%" + exp.replace( "'", "''" ) + "%" ); // escape quotes
-    }
-    mExpression = str;
-    emit expressionChanged(mExpression);
+  QVariant::Type fldType = layer()->pendingFields()[mFieldIdx].type();
+  bool numeric = ( fldType == QVariant::Int || fldType == QVariant::Double || fldType == QVariant::LongLong );
+
+  QSettings settings;
+  QString nullValue = settings.value( "qgis/nullValue", "NULL" ).toString();
+  QString fieldName = layer()->pendingFields()[mFieldIdx].name();
+  QString str;
+  if ( exp == nullValue )
+  {
+    str = QString( "%1 IS NULL" ).arg( QgsExpression::quotedColumnRef( fieldName ) );
+  }
+  else
+  {
+    str = QString( "%1 %2 '%3'" )
+          .arg( QgsExpression::quotedColumnRef( fieldName ) )
+          .arg( numeric ? "=" : mCaseString )
+          .arg( numeric
+                ? exp.replace( "'", "''" )
+                :
+                "%" + exp.replace( "'", "''" ) + "%" ); // escape quotes
+  }
+  mExpression = str;
+  emit expressionChanged( mExpression );
 }
 
 QWidget* QgsDefaultSearchWidgetWrapper::createWidget( QWidget* parent )
 {
   return new QWidget( parent );
 }
 
-bool QgsDefaultSearchWidgetWrapper::applyDirectly() 
+bool QgsDefaultSearchWidgetWrapper::applyDirectly()
 {
-    return false;
+  return false;
 }
 
 void QgsDefaultSearchWidgetWrapper::initWidget( QWidget* widget )
 {
   mContainer = widget;
-  mContainer->setLayout(new QHBoxLayout() );
+  mContainer->setLayout( new QHBoxLayout() );
   mLineEdit = new QgsFilterLineEdit();
-  mCheckbox = new QCheckBox("Case sensitive");
-  mContainer->layout()->addWidget(mLineEdit);
-  mContainer->layout()->addWidget(mCheckbox);
+  mCheckbox = new QCheckBox( "Case sensitive" );
+  mContainer->layout()->addWidget( mLineEdit );
+  mContainer->layout()->addWidget( mCheckbox );
   connect( mLineEdit, SIGNAL( textChanged( QString ) ), this, SLOT( setExpression( QString ) ) );
-  connect( mCheckbox, SIGNAL( stateChanged( int ) ), this, SLOT( setCaseString(int) ) );
-  mCheckbox->setChecked(Qt::Unchecked);
+  connect( mCheckbox, SIGNAL( stateChanged( int ) ), this, SLOT( setCaseString( int ) ) );
+  mCheckbox->setChecked( Qt::Unchecked );
   mCaseString = "ILIKE";
 }
+
+bool QgsDefaultSearchWidgetWrapper::valid()
+{
+  return true;
+}

src/gui/editorwidgets/qgsdefaultsearchwidgetwrapper.h

@@ -37,14 +37,15 @@ class GUI_EXPORT QgsDefaultSearchWidgetWrapper : public QgsSearchWidgetWrapper
     QString expression() override;
     bool applyDirectly() override;
   protected slots:
-    void setExpression(QString exp) override;
+    void setExpression( QString exp ) override;
 
   private slots:
-    void setCaseString(int);
-    
+    void setCaseString( int );
+
   protected:
     QWidget* createWidget( QWidget* parent ) override;
     void initWidget( QWidget* editor ) override;
+    bool valid() override;
 
   private:
     QgsFilterLineEdit* mLineEdit;

src/gui/editorwidgets/qgsenumerationwidgetwrapper.cpp

@@ -57,6 +57,11 @@ void QgsEnumerationWidgetWrapper::initWidget( QWidget* editor )
   }
 }
 
+bool QgsEnumerationWidgetWrapper::valid()
+{
+  return mComboBox;
+}
+
 void QgsEnumerationWidgetWrapper::setValue( const QVariant& value )
 {
   if ( mComboBox )