Getting the the curser position in plot coordinates after specific interval

[zaidi1212]

Hello,

I am developing an application using qwtplot to continuiously take the coordinates from the curser position and then plot the amplitude of the sine curve.

T get the cursor position, I am using :

QCursor *mycurser = new QCursor;
pos_global = mycurser->pos();
pos_local = this->mapFromGlobal(pos_global);

Pos_local gives me the coordinates in integers, I dont know if they are called pixel coordinates. I wanted to get the coordinates with reference to myplot, so thats why I used following function:
QPointF plot::myinvTransform( const QPoint &pos ) const
{
QwtScaleMap xMap = this->canvasMap( this->xBottom );
QwtScaleMap yMap = this->canvasMap( this->yLeft );

return QPointF(
xMap.invTransform( pos.x() ),
yMap.invTransform( pos.y() )

);
}
and I call the function after specific interval with my curserposition as:

QPoint pointPlot = myinvTransform( pos_local);
I am getting the mapped coordinates but they are not accurate. There is a little offset in both the x and y positions.

Anyone have any idea please help me. Or if you don;t understand my problem, just ask me, i will reply very fast.

[Uwe]

Widget coordinates are in integers and because of this mapping a plot coordinate into widget coordinates is not reversible without rounding errors.

Uwe

PS: the curvetracker example might be related