2geom infinite loop in bezier root finding

[Gellule]

This affects trunk @ r10867.

Draw a vertical bezier curve with control points in the same vertical. Switch to select and transform tool. Turn snap to path on. Try to move the curve. Inkscape fezzes in an infinite loop, until memory exhaustion.

The infinite loop is in 2geom's solve_bezier_roots. Further analysis shows that the freeze happens when the input bezier is identically zero (coming from the verticality described above).

The minimum suggested fix would be to look for identically zero bezier at the beginning of this method. It is actually better to look for a constant bezier that also has no roots (provides a minor speed-up in borderline cases).

[Gellule (gellule-xg)]

Committed a fix at: http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/10880
Since this is a 2geom change, I also submitted this bug report. I think I remember a requirement to up-port 2geom changes...

[Johan Engelen (johanengelen)]

committed to 2geom.
Forwarded it to Nathan who should know whether this is a proper fix. The roots finding has some more bugs.

[Gellule (gellule-xg)]

Thanks for the forward, and for making me notice lp:lib2geom.

[Johan Engelen (johanengelen)]

Thank you for finding the culprit and posting the fix.
The lib2geom team is small and can use help from smart people :-)

[nightrow (jb-benoit)]

Hi,
Seems like you found the solution and the patch is commited.
Do you want to keep this open waiting for a 2geom update, or can we close this as fix commited ?

[su_v (suv-lp)]

Fix had been committed to lp:lib2geom in r2054:
<http://bazaar.launchpad.net/~lib2geom-hackers/lib2geom/trunk/revision/2054>