A crosshair which tracks a displayed curve

[wysota]

Can we see some code?

[MrGarbage]

The only code I have is a hacked up version of the Bode plot..

The images I attached are of a different app which I need to emulate.

ie.

d_picker = new QwtPlotPicker(QwtPlot::xBottom, QwtPlot::yLeft,
QwtPicker::PointSelection,
QwtPlotPicker::CrossRubberBand, QwtPicker::AlwaysOn,
d_plot->canvas());
d_picker->setRubberBandPen(QColor(Qt::red));
d_picker->setTrackerMode(QwtPicker::ActiveOnly);

will give me the Cross hair when I left click.

I want this to persist when I release the mouse and then be able to grab it and
move it with it following the displayed curve..

[jacek]

Shouldn't you use QwtPlotMarker instead?

[Uwe]

All type of rubberbands support interactions, but they are not intended to display something persistant on the plot canvas.

So you need to insert a plot item, when your interaction is done. Of course you have to hide this item again, when you restart your interaction. So your code will be a combination of a picker and a plot item.

The plot item, that represents a point ( or a x or a y coordinate ) is indeed a marker, but you can also implement your own type of item. See f.e: http://qwt.svn.sourceforge.net/viewv...pp?view=markup

HTH,
Uwe