how to scroll qwtplot?

[alizadeh91]

Hello everybody...
I have a little problem with qwtplot.
I've written a plot such a cpuplot(Qwt examples). How can i make it to scroll with time. For example suppose that it's been two hours which it runs, i want to let user go back with scroll to zero.
How can i do that??? (Don't say look at realtime example, cuase it's different approach; i want to scroll with time not when zooming)
Thanks everybody

[desantossierra]

you could try moving plot axis scale like this

plot->setAxisScale(QwtPlot::xBottom,from,to);

where from is x start value and to is de x end value

[alizadeh91]

Thanks for reply...
So how can i attach a scroll to QwtPlot???

[desantossierra]

you can use a Qt Scroll Widget, but you can't attach to your plot.
or you could implement a drag and drop function with a QwtPlotPicket or something like that

[Uwe]

you can use a Qt Scroll Widget, ...

There are many different ways to implement "scrolling". Basically it is not more than translating some sort of user input to changes of the current scale.

Qwt offers a couple of ways how to navigate by user inputs on the plot canvas. But of course you could also use any type of QAbstractSlider ( like a scroll bar ) or QwtAbstractSlider. But when using some sort of slider the application has to implement the layout code - the realtime example shows it for scroll bars, the eventFilter examples for a wheel.

The interesting thing about using a wheel is, that you don't need to have a reference interval ( min, max ) and you can scroll up/down without limits relative to the current scale interval.

Uwe

[alizadeh91]

Thanks Uwe for replying..
can u explain more? I want to scroll back to previous times not when user zooms.

[Neekeetos]

Thanks Uwe for replying..
can u explain more? I want to scroll back to previous times not when user zooms.

How do you assign data to your plot? If say you have an array with full data which is constantly growing and
from time to time you pass it to curve object. Suppose you have X as a number of seconds from start.
Then every time, after updating data to curve you do
plot->setAxisScale(QwtPlot::xBottom,lastSecondOfData - intervalToDisplayInSeconds , lastSecondOfData );
which will show you last (intervalToDisplayInSeconds) seconds of data, not all of them.

Other way is to use piece of full array(say last several elements), and assign this piece to plot curve, it will be
showing updating data.

[Uwe]

Thanks Uwe for replying..
can u explain more? I want to scroll back to previous times not when user zooms.

zooming != scrolling - don't expect any useful answer as long as there is no reasonable question.

Uwe

[alizadeh91]

Thanks. I have a full array of data that only a part of it (last interval) will plot. So i want to go back to previous data by scrolling. All of data are growing

[Uwe]

Thanks. I have a full array of data that only a part of it (last interval) will plot. So i want to go back to previous data by scrolling. All of data are growing

Pagewise by forward/backward buttons - or what type of user interaction do you have in mind ?

Uwe

[alizadeh91]

I want (if possible) full option of scrolling along time axis!!

[Uwe]

I want (if possible) full option of scrolling along time axis!!

You can always modify the scales using QwtPlot::setAxisScale, but when you want to have some sort of user interaction you have to tell us which one.
If you can't - or don't want to - don't expect any further answers.

Uwe

[liversedge]

zooming != scrolling - don't expect any useful answer as long as there is no reasonable question.

Interestingly, we scroll AND zoom via a separate plot in GoldenCheetah and using a qxtspanslider.

Attached is a screenshot. Screenshot at 2012-02-17 22:08:36.jpg

[alizadeh91]

Thanks liversedge...
Can u explain more about GoldenCheetah?? Is it a Qt component or something like that??

[sonulohani]

Use

(void) new QwtPlotPanner(plot->canvas());
(void) new QwtPlotMagnifier(plot->canvas());

and dont forget to include qwt_plot_magnifier.h and qwt_plot_panner.h

you will able to zoom in or zoom out through mouse scroll.
and you can able to move your curve.

[alizadeh91]

That is a good way sonulohani Thanks