[cairo] cairo/inkscape problems

[Emmanuel Pacaud]

On mer, 2007-02-21 at 12:32 -0500, Behdad Esfahbod wrote:
> > 2. Large paths disappear on close zoom. Carl says it's a precision
> > problem. You'll need to compile and run Inkscape SVN to see that.
> > Switch to Outline mode (View > Display mode), draw a path larger than
> > the page, and zoom into it. At some point it disappears.
> > 
> > 3. This may be related to 2. In a complex drawing with lots of paths,
> > zooming in too closely shows lots of random stray lines all over the
> > screen. Open share/examples/gallardo.svgz from Inkscape distribution,
> > switch to Outline and zoom into an area where many paths are close to
> > each other. At about 5000%, the pandemonium starts. 
> 
> Yes, both are the same issue, XFAIL test long-lines.  We may be
> switching from 16.16 fixed point to 24.8.  That will help here a lot,
> but would not completely fix it.  No idea about the real fix, but it
> shouldn't be that hard.  We just need to detect overflows when
> converting doubles to fixed and act appropriately.  Anyone taking this?

What we do in goffice (http://www.gnumeric.org) is to clamp the
coordinates. It's not an accurate solution, but much faster than trying
to actually clip the lines to cairo space bounds (And more ugly, we also
CLAMP spline coordinates...).

That solved our issues we had when viewing graphs with high zoom values.

	Emmanuel.