Problem with scale ticks

[gd]

Hi all,

I want to display a plot with a fixed number of major and minor ticks and I don't want to display for each major tick the corresponding label.

This is my code:

void Form1::init()
{
 
    qwtPlot1->setCanvasBackground(Qt::blue);
    QwtPlotGrid *grid=new QwtPlotGrid();
    grid->setPen(QPen(Qt::white,0,DotLine));
    grid->attach(qwtPlot1);
 
 
    QwtValueList xytick[QwtScaleDiv::NTickTypes];
    for (int i=0;i<11;i++)
        xytick[QwtScaleDiv::MajorTick]<<i/10.0;
    for (int i=0;i<61;i++)
        xytick[QwtScaleDiv::MinorTick]<<i/60.0;
 
 
    qwtPlot1->enableAxis(QwtPlot::xTop,true);
    qwtPlot1->enableAxis(QwtPlot::yRight,true);
 
 
    qwtPlot1->setAxisScaleDiv(QwtPlot::xBottom,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::xTop,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::yLeft,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::yRight,QwtScaleDiv(0.0,1.0,xytick));
 
    qwtPlot1->setAxisScaleDraw(QwtPlot::xBottom,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::xTop,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::yLeft,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::yRight,new NullScaleDraw());
}

void Form1::init()
{

    qwtPlot1->setCanvasBackground(Qt::blue);
    QwtPlotGrid *grid=new QwtPlotGrid();
    grid->setPen(QPen(Qt::white,0,DotLine));
    grid->attach(qwtPlot1);


    QwtValueList xytick[QwtScaleDiv::NTickTypes];
    for (int i=0;i<11;i++)
        xytick[QwtScaleDiv::MajorTick]<<i/10.0;
    for (int i=0;i<61;i++)
        xytick[QwtScaleDiv::MinorTick]<<i/60.0;


    qwtPlot1->enableAxis(QwtPlot::xTop,true);
    qwtPlot1->enableAxis(QwtPlot::yRight,true);


    qwtPlot1->setAxisScaleDiv(QwtPlot::xBottom,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::xTop,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::yLeft,QwtScaleDiv(0.0,1.0,xytick));
    qwtPlot1->setAxisScaleDiv(QwtPlot::yRight,QwtScaleDiv(0.0,1.0,xytick));

    qwtPlot1->setAxisScaleDraw(QwtPlot::xBottom,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::xTop,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::yLeft,new NullScaleDraw());
    qwtPlot1->setAxisScaleDraw(QwtPlot::yRight,new NullScaleDraw());
}

To copy to clipboard, switch view to plain text mode 

and

class NullScaleDraw: public QwtScaleDraw
{
public:
  NullScaleDraw()
  {
  }
  virtual QwtText label(double v) const
  {
      return QString("");
  }
};

class NullScaleDraw: public QwtScaleDraw
{
public:
  NullScaleDraw()
  {
  }
  virtual QwtText label(double v) const
  {
      return QString("");
  }
};

To copy to clipboard, switch view to plain text mode 

This gives me the output displayed in the attached file qwtplot.jpg.

My question is why the last major ticks of both xBottom and xTop and the first major ticks of both yLeft and yRight axis disappear when I call qwtPlot1->setAxisScaleDraw(...,new NullScaleDraw)?

Is it possible to avoid the displaying of the tick labels in an easier way?

Thanks a lot for you help.

Best regards

[Uwe]

Is it possible to avoid the displaying of the tick labels in an easier way?

Don't know if this is easier, but you could use medium instead of major ticks. The tick length can be changed using QwtAbstractScaleDraw::setTickLength().

Uwe

[gd]

Dear Uwe,

thanks for the suggestion I will try it.

But anyway why using my code the last and the first major ticks disappear? What is wrong with my code?

Thanks again to be a very helpful person.

Best regards

[Uwe]

I forgot - there is a simple solution:

plot->axisScaleDraw(...)->enableComponent(QwtAbstractScaleDraw::Labels, false);

plot->axisScaleDraw(...)->enableComponent(QwtAbstractScaleDraw::Labels, false);

To copy to clipboard, switch view to plain text mode 

But anyway why using my code the last and the first major ticks disappear?

Looks like a bug in the layout engine of the plot widget- the axis widgets are one pixel too small and the last tick is painted outside. If you can live with a pointless margin a possible workaround is to return a dummy blank for one of your tick labels.

Uwe

[gd]

If you can live with a pointless margin a possible workaround is to return a dummy blank for one of your tick labels.

Really thanks! I have solved in that way!

Best regards