Gill, the Canvas, libart...

[Lyndon Drake <lyndon stat auckland ac nz>]

Hi,

I maintain the Gnome interface for R, and in the near future I want to use
the canvas for graphics output.  I have experimented with the canvas
previously, and found that it did most of what I wanted.  Over the next few
weeks, I want to do a proper canvas device for R, which will become the
default graphics device for the Gnome version of R.

My initial attempt at using the canvas involved creating a canvas item for
each graphics element (eg lines, circles, text).  This was a great way to
use up lots of memory :-).  Someone pointed out that the Right Way to do
this sort of thing was to create a new canvas item that used libart to
render each of the elements.  Has anyone else started any work on something
similar to this?  Is any of the stuff in Gill related?

I may use gnome-print for the graphics, and write a gnome-print item (like
the PS one) that displays on the canvas item.  The main reason for this is
that there is a nice PS driver in R, which makes writing a gnome-print
driver a lot easier.  Plotting on the gnome-print driver would display on
the canvas item, and users would then be able to print the completed
output.

Is text fully functional yet on the anti-aliased canvas?  When I looked at
it previously, clipping didn't work very well, and rotation didn't work at
all.

I also noticed a couple of things were graphically incorrect with the
antialiased canvas.  Specifically, horizontal 1 pixel lines, instead of
being 1 black pixel high, ended up being two dark grey pixels high.  This
really sucks for the axes on plots.

I am happy to work on a canvas item for doing the plots and a gnome-print
driver for the canvas item, but it would be great if someone who
understands libart was able to help.

Thanks,
Lyndon