Add error item to facilitate error handling

Author: wonder-sk

src/core/qgsdataitem.cpp

@@ -565,3 +565,16 @@ void QgsDirectoryParamWidget::showHideColumn()
   }
   settings.setValue( "/dataitem/directoryHiddenColumns", lst );
 }
+
+
+QgsErrorItem::QgsErrorItem( QgsDataItem* parent, QString error, QString path )
+    : QgsDataItem( QgsDataItem::Error, parent, error, path )
+{
+  mIcon = QIcon( getThemePixmap( "/mIconDelete.png" ) );
+
+  mPopulated = true; // no more children
+}
+
+QgsErrorItem::~QgsErrorItem()
+{
+}

src/core/qgsdataitem.h

@@ -46,6 +46,7 @@ class CORE_EXPORT QgsDataItem : public QObject
       Collection,
       Directory,
       Layer,
+      Error,
     };
 
     QgsDataItem( QgsDataItem::Type type, QgsDataItem* parent, QString name, QString path );
@@ -225,6 +226,24 @@ class CORE_EXPORT QgsDirectoryItem : public QgsDataCollectionItem
     static QVector<QLibrary*> mLibraries;
 };
 
+/**
+ Data item that can be used to report problems (e.g. network error)
+ */
+class CORE_EXPORT QgsErrorItem : public QgsDataItem
+{
+    Q_OBJECT
+  public:
+
+    QgsErrorItem( QgsDataItem* parent, QString error, QString path );
+    ~QgsErrorItem();
+
+    //QVector<QgsDataItem*> createChildren();
+    //virtual bool equal( const QgsDataItem *other );
+};
+
+
+// ---------
+
 class QgsDirectoryParamWidget : public QTreeWidget
 {
     Q_OBJECT

src/providers/postgres/qgspostgresdataitems.cpp

@@ -29,7 +29,10 @@ QVector<QgsDataItem*> QgsPGConnectionItem::createChildren()
   QgsDebugMsg( "mConnInfo = " + mConnInfo );
 
   if ( !pgProvider->supportedLayers( mLayerProperties, true, false, false ) )
+  {
+    children.append( new QgsErrorItem( this, tr( "Failed to retrieve layers" ), mPath + "/error" ) );
     return children;
+  }
 
   QMap<QString, QVector<QgsPostgresLayerProperty> > schemasMap;
   foreach( QgsPostgresLayerProperty layerProperty, mLayerProperties )

src/providers/wfs/qgswfsdataitems.cpp

@@ -57,7 +57,7 @@ QVector<QgsDataItem*> QgsWFSConnectionItem::createChildren()
   }
   else
   {
-    // TODO: return an "error" item
+    layers.append( new QgsErrorItem( this, tr( "Failed to retrieve layers" ), mPath + "/error" ) );
   }
 
   mConn->deleteLater();

src/providers/wms/qgswmsdataitems.cpp

@@ -31,7 +31,10 @@ QVector<QgsDataItem*> QgsWMSConnectionItem::createChildren()
 
   // Attention: supportedLayers() gives tree leafes, not top level
   if ( !wmsProvider->supportedLayers( mLayerProperties ) )
+  {
+    children.append( new QgsErrorItem( this, tr( "Failed to retrieve layers" ), mPath + "/error" ) );
     return children;
+  }
 
   QgsWmsCapabilitiesProperty mCapabilitiesProperty = wmsProvider->capabilitiesProperty();
   QgsWmsCapabilityProperty capabilityProperty = mCapabilitiesProperty.capability;