Re: graphics issues (was: Re: moving toward a 3.0 release)

[Paul Kienzle]

On Sep 29, 2006, at 3:16 PM, John W. Eaton wrote:

> On 29-Sep-2006, Sebastien Loisel wrote:
> > Even if you didn't use Bill's code, there's an advantage to
> > having the tick and label placement logic in .m files. You're
> > the one who kept asking me for the least amount of stuff to
> > be done in C++ as possible, and the most possible in .m files.
>
> Sure, it's a reasonable goal, but if some code already exists
> to do the job and there's a way for us to use it, there's no
> point in reinventing it as a .m file.  So does OpenGL have
> good routines for autoplacement of tic marks and axis labels
> given data ranges and font metrics?

OpenGL does not have good routines for autoplacement of tics.

I wrote Tcl code which would be easy to translate.  I address
a number of annoyances such as numbers squished too close
or entirely missing, particularly for log scales.

Linear scale tics are always placed at 'nice' numbers ending
in 1, 2 or 5 (with subtics at .2 .5 or 1 respectively).

Logarithmic scale tics also use 'nice' numbers. Depending on
the available space:
  every n decades for really wide ranges
  every decade, with minor tics at 2 and 5
  every decade, 2 and 5, with minor tics at 4,3,6,7,8,9
  every decade,2,3,4,5,6,7,8,9, with no minor tics

Autoscaling pushes the graph range one tic beyond the data.

I do not handle very small linear ranges or very large
log ranges nicely (haven't needed to yet).

Note that OpenGL does not have support for text either.
There are a couple of libraries which provide it but I
haven't used them myself.

- Paul