QBarSeries performance when using QVBarModelMapper

wanghl

I paint a barseries on my chart,then using QVBarModelMapper and QStandardItemModel to update data,see below

QAbstractItemModel *m_model = new QStandardItemModel(this);
m_TotalSeriesModel->insertColumns(0, 1);
QVBarModelMapper *mapper = new QVBarModelMapper(this);
mapper->setFirstBarSetColumn(0);
mapper->setLastBarSetColumn(0);
mapper->setFirstRow(0);
mapper->setSeries(m_pBarseries);
mapper->setModel(m_model);

when data is arriving using setdata to update it,liking :
m_model->insertRows(m_model->rowCount(), 1);
m_model->setData(m_model->index(row, 0), value);
if the data is frequently，the series paint is so slow.

is I misstake anyting?

VRonin

Unfortunately it's not a problem of your code but on QChart repainting everything every time you add a data point. What you could try is refreshing only every n number of data points. Let's say value in your code is a double, declare QVector<double> m_dataBuffer; and define the how many points should be painted at once, like enum{BufferSize=100} as a private member then change the receiver to:

m_dataBuffer << value;
if(m_dataBuffer.size()>=BufferSize){
const int startRow= m_model->rowCount();
m_model->insertRows(startRow, m_dataBuffer.size());
for(int i=0;i<m_dataBuffer.size();++i)
m_model->setData(m_model->index(startRow+i, 0), m_dataBuffer.at(i));
m_dataBuffer.clear();
}

wanghl

@VRonin said in QBarSeries performance when using QVBarModelMapper:

m_dataBuffer

Thank you for your reply.

I have done this,but still slow,It seems that setData is slow!

VRonin

@wanghl said in QBarSeries performance when using QVBarModelMapper:

It seems that setData is slow

No, it's the slots QVBarModelMapper connects to dataChanged() that are slow.

try this:

m_dataBuffer << value;
if(m_dataBuffer.size()>=BufferSize){
const int startRow= m_model->rowCount();
m_model->insertRows(startRow, m_dataBuffer.size());
m_model->blockSignals(true);
for(int i=0;i<m_dataBuffer.size();++i){
if(i==m_dataBuffer.size()-1) m_model->blockSignals(false);
m_model->setData(m_model->index(startRow+i, 0), m_dataBuffer.at(i));
}
m_dataBuffer.clear();
}

wanghl

@VRonin said in QBarSeries performance when using QVBarModelMapper:

m_model->blockSignals(true);

I will try it later!

I test if append QList<qreal> valueList to a BarSeries,call pBarSeries->append(valueList),the speed is faster than use setData.

so i read the source code,maybe the reason is append a data into barseries will emit restructuredBars signal
the restructuredBars signal connect slot handleDataStructureChanged,this function will recreate everyting ,so is slow.

so if setData supports add a QList data and emit DataChange once,the speed will faster!!

wanghl

@VRonin

I have test use blockSignal,if add this code,there is nothing to paint ....