Draw a circle or sequare/rectange by mouse on qwtpolt???

[jesse_mark]

Hello,
I want to draw a circle/square/rectangle on qwtpolt using the mouse, so the user can draw it anywhere on the polt with any size he wants.

is there any way or idea of how can i do it ???

Thank you,

Jesse

[Uwe]

Maybe you are looking for QwtPlotPicker.

Uwe

[jesse_mark]

I am still learning about qwt, do you know any example or could you explain more of how can i use the PoltPicker ??
I know it gives the mouse pos for me, but how i show a square that gets bigger as the user drag the mouse more??

just the like the way when u draw a square in the painter.

thank you

[Uwe]

F.e every QwtPlotZoomer is a picker that draws a rectangle.

Uwe

[jesse_mark]

i was looking at the bode example, it does has a piker with zoomer.
which is using (QwtPicker::RectRubberBand) .. // "d_zoomer[0]->setRubberBand(QwtPicker::RectRubberBand);"
but i dont need the zoomer and i want the rect to stay on the canvas when i draw it.
so i think i need a piker and set its rubber band to rect rubberband, but how i make the rect stays on the plot ??
thank you so much

Added after 13 minutes:

I use a piker to give me the the mouse position




QwtPlotPicker *picker = new QwtPlotPicker(QwtPlot::xBottom,QwtPlot::yLeft,this->canvas());
picker->setStateMachine(new QwtPickerTrackerMachine);
picker->setTrackerMode(QwtPicker::AlwaysOn);

// i added these lines not sure if this is the way tho ???
picker->setRubberBand(QwtPicker::RectRubberBand);
picker->setRubberBandPen(QColor(Qt::green));




i have this piker and set the rubberband to rect rubber
how i active it or disactive it ?? i mean make show and stay on the polt? and how i get its points ?

Thank you

[jesse_mark]

i edite my code and i was able to see the rect on my plot, but when i finisd the rect disappear , i would like to keep it shown and have access to its valus(points)



picker = new QwtPlotPicker(QwtPlot::xBottom,QwtPlot::yLeft,this->canvas());
// picker->setStateMachine(new QwtPickerTrackerMachine);
picker->setStateMachine(new QwtPickerClickRectMachine);
picker->setTrackerMode(QwtPicker::ActiveOnly);
picker->setTrackerPen(QColor(Qt::white));

picker->setRubberBand(QwtPicker::RectRubberBand);
picker->setRubberBandPen(QColor(Qt::green));

[wysota]

Implement a custom QwtPlotItem that will represent your rectangle. Use a QwtPlotPicker (or QwtPicker) to allow the user to choose a rectangle. Once the selection is complete, create an instance of your plot item and place it on the plot.

[jesse_mark]

Thank Wysota,

I used QwtPlotPicker and as i read from the qwtplotpicker a selected signal we be emitted once the selection is done.

so i connected it like:




// this is the MainWin
connect(plot->picker,SIGNAL(selected(QVector<QPointF>)),this,SLOT(DrawSelection(QVector<QPointF> SelectionPoints)));


and i have the slot on the mainwindow


void MainWin::DrawSelection(QVector<QPointF> SelectionPoints)
{
/// draw the points
}



but im the single is not emitted
and when i run it can see the slot saying >>
object::connect: No such slot MainWin::DrawSelection(QVector<QPointF> SelectionPoints)

so can u please let me know what is the mistake im making ??

Thanks

[wysota]

I think the message is pretty much self explanatory -- you don't have a slot called "DrawSelection" in your "MainWin" class. Usually this means you either forgot the Q_OBJECT macro or you didn't declare the method as a slot.

[jesse_mark]

I do have this method in the MainWin header under

public slots:
void DrawSelection( QVector<QPointF> SelectionPoints);


and i do have other methods using them as slots and i have no problem.

but what do u exactly mean by Q_OBJECT macro ? I have have Q_OBJECT in header, but to be honest i don't really know exactly what its for .

[wysota]

Ah, I read the error message again and I noticed what was wrong. Remove the variable name from the slot signature in the connect() statement.

[jesse_mark]

Thanks the error message not there, but the signal is not triggred , after i do my selection the rect and every thing but the signal is not triggered??

OK i found in the bode example that come with the qwt library

used a picker and the selected signal

this way :



// mainwindow header
private Q_SLOTS:
void selected(const QPolygon &);

//mainwindow cpp
...
connect(d_picker, SIGNAL(selected(const QPolygon &)),SLOT(selected(const QPolygon &)));
....
....
void MainWindow::selected(const QPolygon & )
{

qDebug()<<" I got triggred ";
................
}




this signal was triggered fine, but why the

connect(picker, SIGNAL(selected(const QVector<QPointF> &)), SLOT(DrawSelection(const QVector<QPointF> &)));
was not triggered ???

[wysota]

You probably have a Rect picker, not a Point picker machine attached to the picker.

[jesse_mark]

yes i have a rect picker, put i though the


selected(const QVector<QPointF> &)

will return a vector with all the points that represent the rect.
i tried to use the

selected( const polygon &p) ,

but when i print the first point in the pollygon

Qdebug() << p.at(0)
it gave me different points than the qwt points where i made the selection.

Do the points in the return polygon in the selected signal, has the same points in qwt ?? and if so how i can access all the points that are returned in the polygon ??

Thank you

Added after 28 minutes:

Thank you Wysota and Uwe so much,

I used selected(QRectF) and got all my points
thanks again