qwt5.2 to qt6.0 : waterfall

[janK]

Hello

I has this waterfall running with qwt5.2.
Basically the code (per new line) was (within a derived class from qwtspectrogram):

WaterfallData = new SpectrogramData (plotData,
orig,
width,
Rastersize,
Displaysize,
amp);
this -> detach ();
this -> setData (WaterfallData);
this -> setDisplayMode (QwtPlotSpectrogram::ImageMode,
TRUE);
plotgrid -> setAxisScale (QwtPlot::xBottom,
orig,
orig + width);
plotgrid -> enableAxis (QwtPlot::xBottom);
Marker -> setXValue (marker);
this -> attach (plotgrid);
plotgrid -> replot();

with Spectrogramdata being derived from QwtRasterData.
Plotdata is a vector (array is you wish) containing the data to be printed.

Although exactly the same code worked nicely with qwt5.2, it does not work with qwt6.0. !!!!
No functions are called within the spectrogramdata (just added some print statements for verfication) such as initRaster, interval and value, while
- with the same parametervalues - when using 5.2 bith the Interval and the value functions from the (derived) Qwtrasterdata
is called many, many times.

So, my understanding of either QwtRasterdata, qwtspectrogram or qwtplot (the plotgrid used here) is failing and some semantic
changes occur between 5.2 and 6.0 within either qwtspectrogram or qwtplot. Note that I verified that the replot for the plotgrid (i.e. a QwtPlot)
is called regularly.
Any help would be greatly appreciated

best
jan

'

[Uwe]

With Qwt 6.0 the integer based render engine was replaced by floating point based code, what is the main reason for incompatibilities. I recommend to check all your classes that are overloading methods of Qwt classes if there is a mismatch between int/double, QPoint/QPointF or QRect/QRectF parameters.

Note that QwtRasterData::rasterHint() has been replaced by pixelHint(), with a different semantic. Without implementing pixelHint() the spectrogram doesn't know about the resolution of your data and will call the value() method according to the screen resolution. Also have a look at QwtMatrixRasterData, that had been introduced with Qwt 6.0: it implements a raster data interface for a vector of values ( the rasterview example shows how to use it ).

When migrating to Qwt 6 better start with Qwt 6.1. Only Qwt 6.1 works with Qt5 ( with Qt >= 4.4 ) an of course: http://qwt.sourceforge.net/qwtchangelog.html

Uwe