Hi,
It is my very first post in the Qt center I'll try to be clear.
I have 3 questions.

First question:
My plot represents a sky view of a map XY. I would like to create a ruler to compute distance between to points a(x1,y1) and b(x2,y2).
And I need also a way to draw one line from point a to point b when the ruler is activated.
I was hesitating between 2 possibilities:
- First way: use a QwtPlotPicker in polygon state machine. But I couldn't find a good example of how to manage the appended and selected signals. And in my case I don't really need several lines but just ONE line.
- Second way: Create my own QwtPlotItem that use a QwtPlotPicker with click machine and manage first and second click to compute distances and draw the line.

If their is a smarter way to do this I would like to know.
Hoping a ruler tool could be provided by default in qwt library.


Second question:
Is there a way to change the mouse shape or color? I would like to make it a little bit transparent.


Last question:
This is a general question since I'm new in Qt.
When we do something like:
setStateMachine(new QwtPickerTrackerMachine());
or
setSymbol(ptr_symbol);
or
setValidator(new QDoubleValidator()); (for a QLineEdit)

who is in charge of deleting the pointers?
Thanks by advance.