[Fwd: Re: [guppi-list] strip charts]

[Steven Jenkins <steven jenkins ieee org>]

Oops, forgot to cc: the list.

-------- Original Message --------
Subject: Re: [guppi-list] strip charts
Date: Sun, 08 Sep 2002 10:01:49 -0700
From: Steven Jenkins <steven jenkins ieee org>
To: eennjp leeds ac uk
References: <3D7AE9F5 5090104 ieee org> 
<1031494861 3d7b5ccd92be1 webmail4 leeds ac uk>

eennjp leeds ac uk wrote:

>>Can guppi make strip charts?

[snip]

> I've definitely seen an app do this recently; it was only one graph 
at a time,
> but I'm sure it shouldn't be a problem to be able to nest them. IIRC 
it was a
> demo app that came with the source. Just to check: you basically want
> 'real-time' plotting, with the graphic continually updating, sort-of 
like on an
> oscilloscope?

More like a strip chart than an oscilloscope :-). A strip chart slides,
while an oscilloscope wraps. A strip chart is a standard x-y plot, but
when you try to plot points beyond the rightmost x-axis limit, the graph
slides to the left to make enough room for the new points. In a more
modern threaded implementation, the chart would slide continuously like
the old paper recorders. It's sufficient for my purposes to update the
display only when there's new data. The key is that the latest data is
always at the rightmost edge.

You can, of course, accomplish the "sliding" by just redrawing the
entire graph with recalculated axes. But that seems like a waste of
effort because the rectangle you want to move is already displayed--you
just want to move it over. Doing it on the X server would be fast.

> But I can't remember if that demo app was based on guppi, or whether 
it was from
> scigraphica/gtkextra. So my advice would probably be to look at 
either of those
> two, since I'm fairly sure that its possible with one of them! 
Scigraphica is
> not on the 'other plotting programs' link on the guppi homepage, but 
can be
> found at scigraphica.sf.net

Was it plplot
(http://plplot.sourceforge.net/examples/demo17/index.html)? Plplot can
make a stripchart, but not apparently more than one of arbitrary size,
shape and position. I inquired on the plplot list but didn't hear
anything very encouraging.

The scigraphica package looks intriguing, but I can't tell at first
glance whether it has a library that I can link in with my application.
But I'll ask over there. This is turning into a scavenger hunt!

Steve