compatibility problem with a waterfall display

[Uwe]

When forced to use a class qwtmatrixrasterdata ...

QwtMatrixRasterData is for certain situations easier to use, but obviously not in your case. What makes you believe that you are supposed to use it in Qwt 6.0 ?

The difference of QwtRasterData between 5.2 and 6.0 is ( beside trivial renaming ) that you have to return the bounding intervals of the axes by interval(Qt::Axis ) instead of boundingRect() + range(). Also the copy method is gone - instead the pointer to the data object is passed to the spectrogram item taking ownership. Porting your derived class should be a job of 5 minutes.

Performancewise Qwt 6.0 should be significantly faster on multicore systems as you can tell the spectrogram to divide the image into tiles rendering them in different threads ( spectrogram->setRenderThreadCount( 0 ); ) ).

HTH,
Uwe

[janK]

Well, the (my) problem seems to be that whatever I try, there is a crash of the program (segmentation violation) in pixelhint and I do not seem to be able to tell the
qwtrasterdata what the actual data is (a value function is implemented).

>>> instead the pointer to the data object is passed to the spectrogram item taking ownership.<<<< ??????

It might have been solved in 5 minutes by someone understanding the modifications, it takes now three days

best
jan

[Uwe]

Hm, what needs to be done:

• Call YourRasterData::setInterval
  The intervals for the x/y axes are the values you have passed with setBoundingRect before. The interval for z axis is what you have returned as range before.
• Implement the YourRasterData::value method
  Absulutely nothing has changed here.
• Optionally implement YourRasterData::pixelHint(). pixelHint() returns not only the size of a pixel ( rasterHint() returned the number of pixels ! ) but also a position, so that the image can be aligned properly. You can return the geometry of any pixel.
  Note that the pixelHint is not working in Qwt 6.0.1 - you need to use the code from SVN 6.0, or wait for 6.0.2 what will happen the next days.

Then do: spectrogram->setData( new YourRasterData() );

The previous data object gets deleted, when you pass a new data object, but in your case I guess YourRasterData is somehow connected to your vector of doubles and you directly modify this vector behind the back of the spectrogram item. Beside this vector I guess you need to adjust the interval of the y interval and to invalidate the cache ( if QwtPlotRasterItem::PaintCache is enabled ) before you call replot. But this is not different to what you had to do with Qt 5.2.

Uwe