RE: plot curve range

[Chad B. <boh...@go...>]

Gianni,
I think you want to derive the QwtPlotCurve class, and overload the
principle draw(painter,...) call. In there you get the maps that
describe the visible area, and you can call the draw(painter, from,to)
yourself. Additionally, if you need to break up the drawing, you can
have your derived class send itself QEvents, which is effectively a form
of pumping messages, but it scales to as many graphs as you want to have
draw at the same time. When you handle your events, the draw(from,to)
call will get a painter for you. I found that about 2000 points per
QEvent looks pretty good on a modern machine.

chad

-----Original Message-----
From: Gianni Ambrosio [mailto:gia...@vi...] 
Sent: Wednesday, November 26, 2008 5:10 AM
To: List for both Qwt users and developers
Subject: Re: plot curve range

Uwe Rathmann ha scritto:
> With QwtPlotCurve::draw(..., from to) you can paint parts of a curve,
but this 
> has no effect on what is painted by QwtPlot::replot().
>   
In fact, I implemented this way forcing a replot() but I understand 
there could be a better way.

> I guess what you want to do is to derive from QwtData.
>   

I deviced from QwtData but could you please tell me how should I 
implement it in a class derived from QwtData? I mean where could I skip 
data plotting? Maybe adding a from/to local variable of the derived 
class and reimplement x(size_t) and y(size_t)? But what should I return 
for indexes outside the from/to range?

Regards
Gianni

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