How to set a fixed number of ticks on QwtPlot

Question

I'm having some trouble with QwtPlot ticks.

The X axis of my QwtPlot is this:

I'm setting the AxisMaxMajor to 24:

dataPlot->setAxisMaxMajor(QwtPlot::xBottom, 24);

But it does not solve my problem.

I need exactly 23 ticks (1~23) to represent each hour of the day. How can I do that?

Qwt 6.1.0

Qt 5.3.2

Answer 1

When needing date/time related ticks you need to use QwtDateScaleEngine. Scale engines based on the decimal system won't come up if with something in 1-24.

If the QwtDateScale classes does not fit for your use case you have the option to set the ticks manually ( QwtPlot::setAxisScaleDiv() ).

In case you have no control over the axis ranges ( f.e because of zooming ) the final fallback solution is to implement your own type of QwtScaleEngine. This is easier as it sounds, as it simply means returning a tick at every hour for a given range.