How to set labels for items of a KDChart pie diagram? - c++

Question

Is there any way to set text labels for each item of a pie diagram, created using KDChart lib in Qt?
To be more specific, I'm not using the Model/View architecture in this particular case. I create it though KDChart::Widget and merely fill the chart using Widget::setDataCell().
Seemingly there are several ways to set text labels for axis, but I haven't encountered something similar for a pie diagram. Anyway it's not the thing I need. I want to set labels for certain points rather than for its axis. In apply to a pie diagram it would be something like titled sectors.
I thought that maybe with using KDChart::Legend with filled values I can achieve required behavior, but it haven't worked.
Here is a code sample, maybe it will help somewhat. But keep in mind that it's changed (cleared of cluttering lines) and I haven't tested its correctness:
KDChart::Widget* newChart = new KDChart::Widget;
newChart->setType( KDChart::Widget::Pie );
int curColNo = 0; // it's not a size_t 'coz setDataCell requires an int
for( QVector::const_iterator curValueIt = response.begin(); curValueIt != response.end(); ++curValueIt )
{
newChart->setDataCell( 0, curColNo, *curValueIt );
newChart->diagram()->setBrush( curColNo++, QBrush( m_responsesColors[curValueIt] ) );
m_legend->addDiagram( newChart->diagram() );
}
m_mainLayout.addWidget( newChart, m_curLayoutRowNo, m_curLayoutColNo );
One more thing - I tried to fill it with inconsistent column numbers (0,2,5,9,etc) and pie chart was drawn incorrectly - some sectors overlapped others. In other types of charts (bar chart, for example) all data was visualized correctly.
Do you have any ideas about item labels?
P.S. I've figured out what's wrong with filling Pie chart's columns with skipping some of them. If you fill columns inconsistently (skipping some of them), then just set those skipped columns' values to zero explicitly. It will fix problems with wrong pie chart's visualizing.
Probably KDChart should figure out about skipped columns by itself and set it to null automatically, but it won't. So do it yourself.
Hope, this will help someone.

Answer 1

I have found a solution by my own. Considering a small amount of info on KDChart library, I'm posting it here in hope it will help someone with similar problem.
The solution lies quite deeply in the KDChart hierarchy. You need to manually turn on labels display. I've created a separated function for it.
void setValuesVisible( KDChart::AbstractDiagram* diagram, bool visible ) throw()
{
const QFont font( QFont( "Comic", 10 ) ); // the font for all labels
const int colCount = diagram->model()->columnCount();
for ( int iColumn = 0; iColumn < colCount; ++iColumn )
{
//QBrush brush( diagram->brush( iColumn ) ); // here you can get a color of the specified column
KDChart::DataValueAttributes a( diagram->dataValueAttributes( iColumn ) );
KDChart::TextAttributes ta( a.textAttributes() );
ta.setRotation( 0 );
ta.setFont( font );
ta.setAutoRotate( true );
//ta.setPen( QPen( brush.color() ) ); // here you can change a color of the current label's text
ta.setVisible( visible ); // this line turns on labels display
a.setTextAttributes( ta );
a.setVisible( true );
diagram->setDataValueAttributes( iColumn, a);
}
diagram->update();
}
Keep in mind, that there is shorter solution - just set TextAttributes of the "global" DataValueAttributes (there is a method for it in the KDChart::AbstractDiagram class - AbstractDiagram::dataValueAttributes() without any params) if you don't need unique text parameters for each label.