Gnumeric, vectorial drawings (and charts)

[Jean Brefort <jean brefort normalesup org>]

Hi,

Currently, svg images are displayed in Gnumeric as bitmaps, which makes
them look weird when resized, and print with only screen resolution. It
appears hat the GOImage API is not well suited for vectorial drawings.
There are several possiblities to improve the situation:
* use librsvg,
* use lasem (we already optionally use it for maths equations in
charts),
* add appropriate code in goffice.

The first solution would just work, and might be the easiest, is
reliable, but we should also support other vectorial drawings types, so
it can only be part of the solution.

The second would avoid to depend on librsvg, but I don't know if
Emmanuel will actively support it in the future, even in the near
future. Actually we might also consider importing the mathml code in
goffice.

The third and most demanding solution would be to import the svg paths
as canvas items. We already have most of what we need in the canvas, and
we should just write the parser. This would also work for wmf files
(Valek wrote some demo code in goffice in mf-demo.c) and might be
extended to emf which we do not support at all for now (as far as I
know). I suppose that OpenDocument graphics (odg) would be a valuable
target too.

About charts, I'm wondering if it would be valuable to rewrite the
rendering part using the canvas items. It would help for user
interactions with the graph elements, but might result in some
performance loss (difficult to know without experimenting).

Waiting for comments.

Cheers,
Jean