How to paint a constellation mapping using Qt.

HYSuperman

Trying to paint a constellation mapping using Qt.
Basiclly, I need to paint a rectangular plane coordinate system, and some dynamicly produced points.
x-coordinate and y-coordinate both range from -1.5 to +1.5.
And the point in the system will be a complex number like: -0.245203354620380 + 0.289405396579750i

I've tried the class QPainter. But I don't know how to paint points anytime and not eliminate the formal points.
It's like I can only paint one point a time using QWidget::paintevent method...

SGaist

Hi and welcome to devnet,

Doesn't QPainter::drawPoints fit ?

HYSuperman

It fits.
But what I want to do is to catch a data stream at anytime and draw the point the data gives me on the widget.
How can I make it happen?

[quote author="SGaist" date="1408432772"]Hi and welcome to devnet,

Doesn't QPainter::drawPoints fit ?[/quote]

HYSuperman

Now I'm using the QWidget::paintevent

But it repaints the whole widget. How can I only update a new point and don't change other points?

[quote author="SGaist" date="1408432772"]Hi and welcome to devnet,

Doesn't QPainter::drawPoints fit ?[/quote]

JohanSolo

IIRC you can give a region argument to the update method, which then triggers the paintEvent calling.

SGaist

There are several possibilities, keep a list of your points, update it and redraw them all. Use a QPixmap, draw each new point on it then just draw this pixmap in your widget.

Or look at e.g. Qwt which provides facilities for that kind of drawing.