Problem with barchart in Qwt, may be a bug

[kknd1015]

Hi, I am a newer to Qt and Qwt and I got a problem with barchart:

When I set data with function "setSamples( QVector<double> &_data )",
if there is only one data in the QVector (means "_data.size() == 1" is true ) and the orientation is Qt::Horizontal,
charts goes wrong like this:

qwt_problem.png

What did I do is running the example named "distrowatch" and modified the codes like this:

qwt_problem_modify.PNG

This problem appears on both barchart and multi_barchart.

Actually I have try to figure out the problem with debuging the qwt for several hours.

Yet I can not figure out why, but I found the x axis is set wrongly to -0.6 to 0.6 and y axis is set wrongly to 0 to 1200 in this situation so transform and scale works wrongly due to the bad range.

I am working on a project with barchart so I really need your help.

Thanks.

Best regards.

I am using Qwt 6.1

[Uwe]

I tried your modification and ran into an assertion ( debug mode ) because of a bad range check in DistroScaleDraw::label(). After fixing it ( SVN trunk and 6.1 ) the application runs as expected, beside that the mapping between tick labels and bars is not valid anymore. But this is no surprise, as you removed most of the bars without adjusting the tick count.

Uwe

[kknd1015]

Thanks for your help!

Yes there was a range error I forgot to mention that.

But did you try the combo boxes at the top left of the app window to set the chart orientation to "horizon"?

[Uwe]

This is indeed a bug that happens when using the auto scaler for a horizontal barchart with exactly one bar.

Fixed in SVN ( trunk and 6.1 branch ),

Uwe

[kknd1015]

Got it, thanks very much~

Best regards.