Very first version with logarithmic scales

[Roland Bock <box2OO6 eudoxos de>]

Hello everyone,

introducing logarithmic scales proved to be more time consuming than I
thought, but now I have uploaded a very first version for review:

http://www.eudoxos.net/gtk/gtkdatabox/download/gtkdatabox-0.8-alpha.0.0.tar.gz

The code supports both, linear and logarithmic scales. As of now, the
scaling method has to be chosen at compile time of the library (this
will have to change, of course). You can change the scaling method in
the file gtk/gtkdatabox_canvas.c, line 151.

A new example has been added, to show how logarithmic scales work
(examples/logarithmic). It shows a 10^x and a sinus (shifted to positiv
values). If the library is unchanged, the X axis will be linear and the
Y axis will be logarithmic.

The other examples probably look awful, especially if negative Y values
are present (which is kind of uncool for logarithms...).

Of course, this is not completed yet, but it shows the direction of
where I want to go. Any feedback is welcome :-)


Regards,

Roland

PS: I don't think I will be able to work much on this again before Monday.

PPS: The nxprulers seem to be the way to go. Thanks for the comments. A
patch for the alpha version would be nice. It should be working with the
logarithmic example, of course :-)