Wrong intersection on circles at 45° (rev >= 12594)

[LucaDC]

Draw a circle, drag a 45° guide through the center, activate path intersection snapping and snap another guide to the intersection between the circle and the guide, switch to outline mode and zoom in the intersection: it's wrong.
Tested with Rev 12825 on Windows XP.

[su_v (suv-lp)]

Only reproduced with really small circles (regression in trunk).

See also comments #22-23 in bug #1235504
<https://bugs.launchpad.net/inkscape/+bug/1235504>
and
<http://sourceforge.net/mailarchive/message.php?msg_id=31680243>

[Alvin Penner (apenner)]

- reproduced with Windows XP, Inkscape rev 12792, using the attached svg file

[Alvin Penner (apenner)]

attached is a screenshot showing the discrepancy

[Alvin Penner (apenner)]

- not reproduced after applying rev 2122 of lib2geom to the Inkscape files sbasis-to-bezier.cpp and sbasis-to-bezier.h, new screenshot attached

[Tavmjong Bah (tavmjong-free)]

I've seen a problem with very small ellipses. It exists in 0.48 and trunk. I've traced the problem to lib2geom. See bug 1255446.

[su_v (suv-lp)]

Testing with archived builds on OS X 10.7.5:
- not reproduced with rev <= 12593
- reproduced with rev >= 12594

AFAIU bug #1255446 and this one (bug #1253110) are about the same issue.

[Tavmjong Bah (tavmjong-free)]

Bug #1255446 was traced to a preference setting (Minumum exponent set to -1) thus is not relevant to this bug.

[su_v (suv-lp)]

@Alvin - do you happen to know whether there is an update planned of Inkscape's copy of lib2geom in the near future? Would it be better to keep the 'blocker' tag set, until we can be sure that it will happen in time before a new release branch gets created?

[Johan Engelen (johanengelen)]

Hi ~suv, Alvin,
I've been doing partial 2geom updates recently. I suggest you do the same for now :-) Simply copy the file into Inkscape. Please check the diff and verify that there are no large (breaking) changes other than your change.
Thanks for the fix.

[Johan Engelen (johanengelen)]

synched 2geom in r12921

[Alvin Penner (apenner)]

thanks, Johan!
with rev 12921, I can no longer reproduce the problem (Windows XP).
could someone else test to confirm?

[jazzynico (jazzynico)]

Also confirmed on Windows XP, Inkscape trunk rev 12921.

[LucaDC (lucadc)]

Good, circles are circular again!
I confirm the same as jazzynico.