add call to embedded widget provider supportsLayer()

This method was not previously being called anywhere. It is now called in the embedded widget config
just before showing the available providers

src/gui/layertree/qgslayertreeembeddedconfigwidget.cpp

@@ -42,10 +42,13 @@ void QgsLayerTreeEmbeddedConfigWidget::setLayer( QgsMapLayer *layer )
   Q_FOREACH ( const QString &providerId, QgsGui::layerTreeEmbeddedWidgetRegistry()->providers() )
   {
     QgsLayerTreeEmbeddedWidgetProvider *provider = QgsGui::layerTreeEmbeddedWidgetRegistry()->provider( providerId );
-    QStandardItem *item = new QStandardItem( provider->name() );
-    item->setFlags( Qt::ItemIsEnabled | Qt::ItemIsSelectable );
-    item->setData( provider->id(), Qt::UserRole + 1 );
-    modelAvailable->appendRow( item );
+    if ( provider->supportsLayer( mLayer ) )
+    {
+      QStandardItem *item = new QStandardItem( provider->name() );
+      item->setFlags( Qt::ItemIsEnabled | Qt::ItemIsSelectable );
+      item->setData( provider->id(), Qt::UserRole + 1 );
+      modelAvailable->appendRow( item );
+    }
   }
   mListAvailable->setModel( modelAvailable );