Re: graphing in gnumeric

On Fri, Apr 25, 2003 at 10:36:31AM -0700, William Skaggs wrote:
  I have been developing a Gtk-2.0 based graphing program, and
it is possible that I could contribute something useful to
gnumeric.  Would it be possible to get a description of what
capabilities gnumeric needs, and what the API should ideally
look like?  Would a good plotting widget meet the needs?

Your timing is excellent.  I've been working on something for
gnumeric for several months and finally started producing usable
code in the last few weeks.  The emphasis is on getting data and
allocation working smoothly within gnumeric, and that is now mostly
done (yay!).  I threw together a cheesy rendering scheme using
FooCanvas and some raw gdk drawing primitives which looks butt ugly.
I'll be replacing it with a libart based approach using something
similar to Jon Trowbridge's libguppi/canvas abstraction later this
week then throwing things into cvs.

A couple of notes.
1) A widget will definitely not work.  We need to render to
  canvasitem, or a pixbuf to support alpha blending of graph elements
  onto the underlying sheet.  I've got a patch to libguppi's canvas
  to ensure feasibility.

2) Getting the data handling reasonable without tying things
  directly to gnumeric was a bit of a pain but seems to work
  reasonably now.  The hard part is providing enough information to
  the allocator for it to make good choices.  I've ignored the
  requirement of allowing a graph to change data in gnumeric
  directly.  We can examine that and selection issues later.

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