annotate document/Document.cpp @ 182:21a76c9ed5c3

* Merge transform directory from sv-match-alignment branch
  (the previous comment included notes for this stuff, but I missed it
  in the actual merge)
* Fix crash when a transform fails to create an output model and the
  thread that created the transform then deletes its input model thinking
  it's no longer needed, even though the transform run thread is still
  using it -- fix is to wait() on the transform before returning the
  null output model

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam and QMUL.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#include "Document.h"

#include "data/model/WaveFileModel.h"
#include "data/model/WritableWaveFileModel.h"
#include "data/model/DenseThreeDimensionalModel.h"
#include "data/model/DenseTimeValueModel.h"
#include "layer/Layer.h"
#include "base/CommandHistory.h"
#include "base/Command.h"
#include "view/View.h"
#include "base/PlayParameterRepository.h"
#include "base/PlayParameters.h"
#include "transform/TransformFactory.h"
#include <QApplication>
#include <iostream>

//!!! still need to handle command history, documentRestored/documentModified

Document::Document() :
    m_mainModel(0)
{
    connect(this, SIGNAL(modelAboutToBeDeleted(Model *)),
            TransformFactory::getInstance(),
            SLOT(modelAboutToBeDeleted(Model *)));
}

Document::~Document()
{
    //!!! Document should really own the command history.  atm we
    //still refer to it in various places that don't have access to
    //the document, be nice to fix that

//    std::cerr << "\n\nDocument::~Document: about to clear command history" << std::endl;
    CommandHistory::getInstance()->clear();
    
//    std::cerr << "Document::~Document: about to delete layers" << std::endl;
    while (!m_layers.empty()) {
	deleteLayer(*m_layers.begin(), true);
    }

    if (!m_models.empty()) {
	std::cerr << "Document::~Document: WARNING: " 
		  << m_models.size() << " model(s) still remain -- "
		  << "should have been garbage collected when deleting layers"
		  << std::endl;
	while (!m_models.empty()) {
	    if (m_models.begin()->first == m_mainModel) {
		// just in case!
		std::cerr << "Document::~Document: WARNING: Main model is also"
			  << " in models list!" << std::endl;
	    } else {
		emit modelAboutToBeDeleted(m_models.begin()->first);
		delete m_models.begin()->first;
	    }
	    m_models.erase(m_models.begin());
	}
    }

//    std::cerr << "Document::~Document: About to get rid of main model"
//	      << std::endl;
    emit modelAboutToBeDeleted(m_mainModel);
    emit mainModelChanged(0);
    delete m_mainModel;

}

Layer *
Document::createLayer(LayerFactory::LayerType type)
{
    Layer *newLayer = LayerFactory::getInstance()->createLayer(type);
    if (!newLayer) return 0;

    newLayer->setObjectName(getUniqueLayerName(newLayer->objectName()));

    m_layers.insert(newLayer);
    emit layerAdded(newLayer);

    return newLayer;
}

Layer *
Document::createMainModelLayer(LayerFactory::LayerType type)
{
    Layer *newLayer = createLayer(type);
    if (!newLayer) return 0;
    setModel(newLayer, m_mainModel);
    return newLayer;
}

Layer *
Document::createImportedLayer(Model *model)
{
    LayerFactory::LayerTypeSet types =
	LayerFactory::getInstance()->getValidLayerTypes(model);

    if (types.empty()) {
	std::cerr << "WARNING: Document::importLayer: no valid display layer for model" << std::endl;
	return 0;
    }

    //!!! for now, just use the first suitable layer type
    LayerFactory::LayerType type = *types.begin();

    Layer *newLayer = LayerFactory::getInstance()->createLayer(type);
    if (!newLayer) return 0;

    newLayer->setObjectName(getUniqueLayerName(newLayer->objectName()));

    addImportedModel(model);
    setModel(newLayer, model);

    //!!! and all channels
    setChannel(newLayer, -1);

    m_layers.insert(newLayer);
    emit layerAdded(newLayer);
    return newLayer;
}

Layer *
Document::createEmptyLayer(LayerFactory::LayerType type)
{
    Model *newModel =
	LayerFactory::getInstance()->createEmptyModel(type, m_mainModel);
    if (!newModel) return 0;

    Layer *newLayer = createLayer(type);
    if (!newLayer) {
	delete newModel;
	return 0;
    }

    addImportedModel(newModel);
    setModel(newLayer, newModel);

    return newLayer;
}

Layer *
Document::createDerivedLayer(LayerFactory::LayerType type,
			     TransformId transform)
{
    Layer *newLayer = createLayer(type);
    if (!newLayer) return 0;

    newLayer->setObjectName(getUniqueLayerName
                            (TransformFactory::getInstance()->
                             getTransformFriendlyName(transform)));

    return newLayer;
}

Layer *
Document::createDerivedLayer(TransformId transform,
                             Model *inputModel, 
                             const PluginTransform::ExecutionContext &context,
                             QString configurationXml)
{
    Model *newModel = addDerivedModel(transform, inputModel,
                                      context, configurationXml);
    if (!newModel) {
        // error already printed to stderr by addDerivedModel
        emit modelGenerationFailed(transform);
        return 0;
    }

    LayerFactory::LayerTypeSet types =
	LayerFactory::getInstance()->getValidLayerTypes(newModel);

    if (types.empty()) {
	std::cerr << "WARNING: Document::createLayerForTransform: no valid display layer for output of transform " << transform.toStdString() << std::endl;
	delete newModel;
	return 0;
    }

    //!!! for now, just use the first suitable layer type

    Layer *newLayer = createLayer(*types.begin());
    setModel(newLayer, newModel);

    //!!! We need to clone the model when adding the layer, so that it
    //can be edited without affecting other layers that are based on
    //the same model.  Unfortunately we can't just clone it now,
    //because it probably hasn't been completed yet -- the transform
    //runs in the background.  Maybe the transform has to handle
    //cloning and cacheing models itself.
    //
    // Once we do clone models here, of course, we'll have to avoid
    // leaking them too.
    //
    // We want the user to be able to add a model to a second layer
    // _while it's still being calculated in the first_ and have it
    // work quickly.  That means we need to put the same physical
    // model pointer in both layers, so they can't actually be cloned.
    
    if (newLayer) {
	newLayer->setObjectName(getUniqueLayerName
                                (TransformFactory::getInstance()->
                                 getTransformFriendlyName(transform)));
    }

    emit layerAdded(newLayer);
    return newLayer;
}

void
Document::setMainModel(WaveFileModel *model)
{
    Model *oldMainModel = m_mainModel;
    m_mainModel = model;

    emit modelAdded(m_mainModel);

    std::vector<Layer *> obsoleteLayers;
    std::set<QString> failedTransforms;

    // We need to ensure that no layer is left using oldMainModel or
    // any of the old derived models as its model.  Either replace the
    // model, or delete the layer for each layer that is currently
    // using one of these.  Carry out this replacement before we
    // delete any of the models.

    for (LayerSet::iterator i = m_layers.begin(); i != m_layers.end(); ++i) {

	Layer *layer = *i;
	Model *model = layer->getModel();

//        std::cerr << "Document::setMainModel: inspecting model "
//                  << (model ? model->objectName().toStdString() : "(null)") << " in layer "
//                  << layer->objectName().toStdString() << std::endl;

	if (model == oldMainModel) {
//            std::cerr << "... it uses the old main model, replacing" << std::endl;
	    LayerFactory::getInstance()->setModel(layer, m_mainModel);
	    continue;
	}

	if (m_models.find(model) == m_models.end()) {
	    std::cerr << "WARNING: Document::setMainModel: Unknown model "
		      << model << " in layer " << layer << std::endl;
	    // get rid of this hideous degenerate
	    obsoleteLayers.push_back(layer);
	    continue;
	}
	    
	if (m_models[model].source == oldMainModel) {

//            std::cerr << "... it uses a model derived from the old main model, regenerating" << std::endl;

	    // This model was derived from the previous main
	    // model: regenerate it.
	    
	    TransformId transform = m_models[model].transform;
            PluginTransform::ExecutionContext context = m_models[model].context;
	    
	    Model *replacementModel =
                addDerivedModel(transform,
                                m_mainModel,
                                context,
                                m_models[model].configurationXml);
	    
	    if (!replacementModel) {
		std::cerr << "WARNING: Document::setMainModel: Failed to regenerate model for transform \""
			  << transform.toStdString() << "\"" << " in layer " << layer << std::endl;
                if (failedTransforms.find(transform) == failedTransforms.end()) {
                    emit modelRegenerationFailed(layer->objectName(),
                                                 transform);
                    failedTransforms.insert(transform);
                }
		obsoleteLayers.push_back(layer);
	    } else {
                std::cerr << "Replacing model " << model << " (type "
                          << typeid(*model).name() << ") with model "
                          << replacementModel << " (type "
                          << typeid(*replacementModel).name() << ") in layer "
                          << layer << " (name " << layer->objectName().toStdString() << ")"
                          << std::endl;
                RangeSummarisableTimeValueModel *rm =
                    dynamic_cast<RangeSummarisableTimeValueModel *>(replacementModel);
                if (rm) {
                    std::cerr << "new model has " << rm->getChannelCount() << " channels " << std::endl;
                } else {
                    std::cerr << "new model is not a RangeSummarisableTimeValueModel!" << std::endl;
                }
		setModel(layer, replacementModel);
	    }
	}	    
    }

    for (size_t k = 0; k < obsoleteLayers.size(); ++k) {
	deleteLayer(obsoleteLayers[k], true);
    }

    emit mainModelChanged(m_mainModel);

    // we already emitted modelAboutToBeDeleted for this
    delete oldMainModel;
}

void
Document::addDerivedModel(TransformId transform,
                          Model *inputModel,
                          const PluginTransform::ExecutionContext &context,
                          Model *outputModelToAdd,
                          QString configurationXml)
{
    if (m_models.find(outputModelToAdd) != m_models.end()) {
	std::cerr << "WARNING: Document::addDerivedModel: Model already added"
		  << std::endl;
	return;
    }

//    std::cerr << "Document::addDerivedModel: source is " << inputModel << " \"" << inputModel->objectName().toStdString() << "\"" << std::endl;

    ModelRecord rec;
    rec.source = inputModel;
    rec.transform = transform;
    rec.context = context;
    rec.configurationXml = configurationXml;
    rec.refcount = 0;

    outputModelToAdd->setSourceModel(inputModel);

    m_models[outputModelToAdd] = rec;

    emit modelAdded(outputModelToAdd);
}


void
Document::addImportedModel(Model *model)
{
    if (m_models.find(model) != m_models.end()) {
	std::cerr << "WARNING: Document::addImportedModel: Model already added"
		  << std::endl;
	return;
    }

    ModelRecord rec;
    rec.source = 0;
    rec.transform = "";
    rec.refcount = 0;

    m_models[model] = rec;

    emit modelAdded(model);
}

Model *
Document::addDerivedModel(TransformId transform,
                          Model *inputModel,
                          const PluginTransform::ExecutionContext &context,
                          QString configurationXml)
{
    Model *model = 0;

    for (ModelMap::iterator i = m_models.begin(); i != m_models.end(); ++i) {
	if (i->second.transform == transform &&
	    i->second.source == inputModel && 
            i->second.context == context &&
            i->second.configurationXml == configurationXml) {
	    return i->first;
	}
    }

    model = TransformFactory::getInstance()->transform
	(transform, inputModel, context, configurationXml);

    if (!model) {
	std::cerr << "WARNING: Document::addDerivedModel: no output model for transform " << transform.toStdString() << std::endl;
    } else {
	addDerivedModel(transform, inputModel, context, model, configurationXml);
    }

    return model;
}

void
Document::releaseModel(Model *model) // Will _not_ release main model!
{
    if (model == 0) {
	return;
    }

    if (model == m_mainModel) {
	return;
    }

    bool toDelete = false;

    if (m_models.find(model) != m_models.end()) {
	
	if (m_models[model].refcount == 0) {
	    std::cerr << "WARNING: Document::releaseModel: model " << model
		      << " reference count is zero already!" << std::endl;
	} else {
	    if (--m_models[model].refcount == 0) {
		toDelete = true;
	    }
	}
    } else { 
	std::cerr << "WARNING: Document::releaseModel: Unfound model "
		  << model << std::endl;
	toDelete = true;
    }

    if (toDelete) {

	int sourceCount = 0;

	for (ModelMap::iterator i = m_models.begin(); i != m_models.end(); ++i) {
	    if (i->second.source == model) {
		++sourceCount;
		i->second.source = 0;
	    }
	}

	if (sourceCount > 0) {
	    std::cerr << "Document::releaseModel: Deleting model "
		      << model << " even though it is source for "
		      << sourceCount << " other derived model(s) -- resetting "
		      << "their source fields appropriately" << std::endl;
	}

	emit modelAboutToBeDeleted(model);
	m_models.erase(model);
	delete model;
    }
}

void
Document::deleteLayer(Layer *layer, bool force)
{
    if (m_layerViewMap.find(layer) != m_layerViewMap.end() &&
	m_layerViewMap[layer].size() > 0) {

	std::cerr << "WARNING: Document::deleteLayer: Layer "
		  << layer << " [" << layer->objectName().toStdString() << "]"
		  << " is still used in " << m_layerViewMap[layer].size()
		  << " views!" << std::endl;

	if (force) {

	    std::cerr << "(force flag set -- deleting from all views)" << std::endl;

	    for (std::set<View *>::iterator j = m_layerViewMap[layer].begin();
		 j != m_layerViewMap[layer].end(); ++j) {
		// don't use removeLayerFromView, as it issues a command
		layer->setLayerDormant(*j, true);
		(*j)->removeLayer(layer);
	    }
	    
	    m_layerViewMap.erase(layer);

	} else {
	    return;
	}
    }

    if (m_layers.find(layer) == m_layers.end()) {
	std::cerr << "Document::deleteLayer: Layer "
		  << layer << " does not exist, or has already been deleted "
		  << "(this may not be as serious as it sounds)" << std::endl;
	return;
    }

    m_layers.erase(layer);

    releaseModel(layer->getModel());
    emit layerRemoved(layer);
    emit layerAboutToBeDeleted(layer);
    delete layer;
}

void
Document::setModel(Layer *layer, Model *model)
{
    if (model && 
	model != m_mainModel &&
	m_models.find(model) == m_models.end()) {
	std::cerr << "ERROR: Document::setModel: Layer " << layer
		  << " (\"" << layer->objectName().toStdString()
                  << "\") wants to use unregistered model " << model
		  << ": register the layer's model before setting it!"
		  << std::endl;
	return;
    }

    Model *previousModel = layer->getModel();

    if (previousModel == model) {
        std::cerr << "WARNING: Document::setModel: Layer " << layer << " (\""
                  << layer->objectName().toStdString()
                  << "\") is already set to model "
                  << model << " (\""
                  << (model ? model->objectName().toStdString() : "(null)")
                  << "\")" << std::endl;
        return;
    }

    if (model && model != m_mainModel) {
	m_models[model].refcount ++;
    }

    if (model && previousModel) {
        PlayParameterRepository::getInstance()->copyParameters
            (previousModel, model);
    }

    LayerFactory::getInstance()->setModel(layer, model);

    if (previousModel) {
        releaseModel(previousModel);
    }
}

void
Document::setChannel(Layer *layer, int channel)
{
    LayerFactory::getInstance()->setChannel(layer, channel);
}

void
Document::addLayerToView(View *view, Layer *layer)
{
    Model *model = layer->getModel();
    if (!model) {
//	std::cerr << "Document::addLayerToView: Layer (\""
//                  << layer->objectName().toStdString()
//                  << "\") with no model being added to view: "
//                  << "normally you want to set the model first" << std::endl;
    } else {
	if (model != m_mainModel &&
	    m_models.find(model) == m_models.end()) {
	    std::cerr << "ERROR: Document::addLayerToView: Layer " << layer
		      << " has unregistered model " << model
		      << " -- register the layer's model before adding the layer!" << std::endl;
	    return;
	}
    }

    CommandHistory::getInstance()->addCommand
	(new Document::AddLayerCommand(this, view, layer));
}

void
Document::removeLayerFromView(View *view, Layer *layer)
{
    CommandHistory::getInstance()->addCommand
	(new Document::RemoveLayerCommand(this, view, layer));
}

void
Document::addToLayerViewMap(Layer *layer, View *view)
{
    bool firstView = (m_layerViewMap.find(layer) == m_layerViewMap.end() ||
                      m_layerViewMap[layer].empty());

    if (m_layerViewMap[layer].find(view) !=
	m_layerViewMap[layer].end()) {
	std::cerr << "WARNING: Document::addToLayerViewMap:"
		  << " Layer " << layer << " -> view " << view << " already in"
		  << " layer view map -- internal inconsistency" << std::endl;
    }

    m_layerViewMap[layer].insert(view);

    if (firstView) emit layerInAView(layer, true);
}
    
void
Document::removeFromLayerViewMap(Layer *layer, View *view)
{
    if (m_layerViewMap[layer].find(view) ==
	m_layerViewMap[layer].end()) {
	std::cerr << "WARNING: Document::removeFromLayerViewMap:"
		  << " Layer " << layer << " -> view " << view << " not in"
		  << " layer view map -- internal inconsistency" << std::endl;
    }

    m_layerViewMap[layer].erase(view);

    if (m_layerViewMap[layer].empty()) {
        m_layerViewMap.erase(layer);
        emit layerInAView(layer, false);
    }
}

QString
Document::getUniqueLayerName(QString candidate)
{
    for (int count = 1; ; ++count) {

        QString adjusted =
            (count > 1 ? QString("%1 <%2>").arg(candidate).arg(count) :
             candidate);
        
        bool duplicate = false;

        for (LayerSet::iterator i = m_layers.begin(); i != m_layers.end(); ++i) {
            if ((*i)->objectName() == adjusted) {
                duplicate = true;
                break;
            }
        }

        if (!duplicate) return adjusted;
    }
}

std::vector<Model *>
Document::getTransformInputModels()
{
    std::vector<Model *> models;

    if (!m_mainModel) return models;

    models.push_back(m_mainModel);

    //!!! This will pick up all models, including those that aren't visible...

    for (ModelMap::iterator i = m_models.begin(); i != m_models.end(); ++i) {

        Model *model = i->first;
        if (!model || model == m_mainModel) continue;
        DenseTimeValueModel *dtvm = dynamic_cast<DenseTimeValueModel *>(model);
        
        if (dtvm) {
            models.push_back(dtvm);
        }
    }

    return models;
}

Document::AddLayerCommand::AddLayerCommand(Document *d,
					   View *view,
					   Layer *layer) :
    m_d(d),
    m_view(view),
    m_layer(layer),
    m_name(qApp->translate("AddLayerCommand", "Add %1 Layer").arg(layer->objectName())),
    m_added(false)
{
}

Document::AddLayerCommand::~AddLayerCommand()
{
//    std::cerr << "Document::AddLayerCommand::~AddLayerCommand" << std::endl;
    if (!m_added) {
	m_d->deleteLayer(m_layer);
    }
}

void
Document::AddLayerCommand::execute()
{
    for (int i = 0; i < m_view->getLayerCount(); ++i) {
	if (m_view->getLayer(i) == m_layer) {
	    // already there
	    m_layer->setLayerDormant(m_view, false);
	    m_added = true;
	    return;
	}
    }

    m_view->addLayer(m_layer);
    m_layer->setLayerDormant(m_view, false);

    m_d->addToLayerViewMap(m_layer, m_view);
    m_added = true;
}

void
Document::AddLayerCommand::unexecute()
{
    m_view->removeLayer(m_layer);
    m_layer->setLayerDormant(m_view, true);

    m_d->removeFromLayerViewMap(m_layer, m_view);
    m_added = false;
}

Document::RemoveLayerCommand::RemoveLayerCommand(Document *d,
						 View *view,
						 Layer *layer) :
    m_d(d),
    m_view(view),
    m_layer(layer),
    m_name(qApp->translate("RemoveLayerCommand", "Delete %1 Layer").arg(layer->objectName())),
    m_added(true)
{
}

Document::RemoveLayerCommand::~RemoveLayerCommand()
{
//    std::cerr << "Document::RemoveLayerCommand::~RemoveLayerCommand" << std::endl;
    if (!m_added) {
	m_d->deleteLayer(m_layer);
    }
}

void
Document::RemoveLayerCommand::execute()
{
    bool have = false;
    for (int i = 0; i < m_view->getLayerCount(); ++i) {
	if (m_view->getLayer(i) == m_layer) {
	    have = true;
	    break;
	}
    }

    if (!have) { // not there!
	m_layer->setLayerDormant(m_view, true);
	m_added = false;
	return;
    }

    m_view->removeLayer(m_layer);
    m_layer->setLayerDormant(m_view, true);

    m_d->removeFromLayerViewMap(m_layer, m_view);
    m_added = false;
}

void
Document::RemoveLayerCommand::unexecute()
{
    m_view->addLayer(m_layer);
    m_layer->setLayerDormant(m_view, false);

    m_d->addToLayerViewMap(m_layer, m_view);
    m_added = true;
}

void
Document::toXml(QTextStream &out, QString indent, QString extraAttributes) const
{
    out << indent + QString("<data%1%2>\n")
        .arg(extraAttributes == "" ? "" : " ").arg(extraAttributes);

    if (m_mainModel) {
	m_mainModel->toXml(out, indent + "  ", "mainModel=\"true\"");
    }

    // Models that are not used in a layer that is in a view should
    // not be written.  Get our list of required models first.

    std::set<const Model *> used;

    for (LayerViewMap::const_iterator i = m_layerViewMap.begin();
         i != m_layerViewMap.end(); ++i) {

        if (i->first && !i->second.empty() && i->first->getModel()) {
            used.insert(i->first->getModel());
        }
    }

    for (ModelMap::const_iterator i = m_models.begin();
	 i != m_models.end(); ++i) {

        const Model *model = i->first;
	const ModelRecord &rec = i->second;

        if (used.find(model) == used.end()) continue;
        
        // We need an intelligent way to determine which models need
        // to be streamed (i.e. have been edited, or are small) and
        // which should not be (i.e. remain as generated by a
        // transform, and are large).
        //
        // At the moment we can get away with deciding not to stream
        // dense 3d models or writable wave file models, provided they
        // were generated from a transform, because at the moment there
        // is no way to edit those model types so it should be safe to
        // regenerate them.  That won't always work in future though.
        // It would be particularly nice to be able to ask the user,
        // as well as making an intelligent guess.

        bool writeModel = true;
        bool haveDerivation = false;

        if (rec.source && rec.transform != "") {
            haveDerivation = true;
        } 

        if (haveDerivation) {
            if (dynamic_cast<const WritableWaveFileModel *>(model)) {
                writeModel = false;
            } else if (dynamic_cast<const DenseThreeDimensionalModel *>(model)) {
                writeModel = false;
            }
        }

        if (writeModel) {
            i->first->toXml(out, indent + "  ");
        }

	if (haveDerivation) {
	    
            //!!! stream the rest of the execution context in both directions (i.e. not just channel)

	    out << indent;
	    out << QString("  <derivation source=\"%1\" model=\"%2\" channel=\"%3\" domain=\"%4\" stepSize=\"%5\" blockSize=\"%6\" windowType=\"%7\" transform=\"%8\"")
		.arg(XmlExportable::getObjectExportId(rec.source))
		.arg(XmlExportable::getObjectExportId(i->first))
                .arg(rec.context.channel)
                .arg(rec.context.domain)
                .arg(rec.context.stepSize)
                .arg(rec.context.blockSize)
                .arg(int(rec.context.windowType))
		.arg(XmlExportable::encodeEntities(rec.transform));

            if (rec.configurationXml != "") {
                out << ">\n    " + indent + rec.configurationXml
                    + "\n" + indent + "  </derivation>\n";
            } else {
                out << "/>\n";
            }
	}

        //!!! We should probably own the PlayParameterRepository
        PlayParameters *playParameters =
            PlayParameterRepository::getInstance()->getPlayParameters(i->first);
        if (playParameters) {
            playParameters->toXml
                (out, indent + "  ",
                 QString("model=\"%1\"")
                 .arg(XmlExportable::getObjectExportId(i->first)));
        }
    }
	    
    for (LayerSet::const_iterator i = m_layers.begin();
	 i != m_layers.end(); ++i) {

	(*i)->toXml(out, indent + "  ");
    }

    out << indent + "</data>\n";
}

QString
Document::toXmlString(QString indent, QString extraAttributes) const
{
    QString s;

    {
        QTextStream out(&s);
        toXml(out, indent, extraAttributes);
    }

    return s;
}