How could I display the pos(x,y) of the axis designed by QwtPlot under the mouse ?

Hello, I want to display the pos(x,y) of the Axis draw by the class QwtPlot when my mouse drags, which works only when the mouse is in the axis area . My code is as follow:
QwtPlotCanvas *canva = new QwtPlotCanvas(this);
picker = new QwtPlotPicker(QwtPlot::xBottom,QwtPlot::yLeft,canv a);
picker->setStateMachine(new QwtPickerTrackerMachine);
picker->setTrackerMode(QwtPicker::AlwaysOn);
But in fact, only a small area on the top left corner can display the pos(x,y) of the window instead of the axis which is really I want. Who can tell me what is wrong with my code? Thank you ！

When using Qwt from SVN trunk you have to insert the local canvas into a plot widget.

For all other versions of Qwt the code above makes no sense, because you can't insert a local canvas - instead plot->canvas() needs to be the parent of your picker.

Uwe

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Originally Posted by Uwe

When using Qwt from SVN trunk you have to insert the local canvas into a plot widget.

For all other versions of Qwt the code above makes no sense, because you can't insert a local canvas - instead plot->canvas() needs to be the parent of your picker.

Uwe

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I used qwt6.0,How can I judge whether it is from SVN trunk?And how to insert the local canvas into a plot widget? I tried to insert a line of code"picker->setParent(this->canvas());",it worked worse, I can't get the pos(x,y)even on the left top corner. Thank You!

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I used qwt6.0,How can I judge whether it is from SVN trunk?

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SVN trunk = Qwt 6.1.

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And how to insert the local canvas into a plot widget?

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You can't. Instead your code has to be:

Code:

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QwtPlotPicker *picker = new QwtPlotPicker( plot->canvas() );

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Check the examples how to use picker/zoomer objects.

Quote:

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I tried to insert a line of code"picker->setParent(this->canvas());",it worked worse, ...

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Of course - a second canvas not known by any layout and completely unrelated to the plot coordinate system ...

Uwe

I get it ! Thank you very much!

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Added after 39 minutes:

Quote:

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Originally Posted by Uwe

SVN trunk = Qwt 6.1.


You can't. Instead your code has to be:

Code:

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QwtPlotPicker *picker = new QwtPlotPicker( plot->canvas() );

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Check the examples how to use picker/zoomer objects.


Of course - a second canvas not known by any layout and completely unrelated to the plot coordinate system ...

Uwe

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Then how can I just display the integer ones of x axis？For I want to draw some histograms on the plot,and then display the value of the histograms.