numerical instability when intersecting a line and a parabola when the line is parallel to the axis of the parabola Reproducible: Sometimes Steps to Reproduce: 1. construct a vertical parabola, 2. then its directrix, 3. a perpendicular line through a point constrained on the directrix, 4. intersect this line with the parabola. Sometimes, moving the constrained point shows garbage in kig window that disappears when motion finishes Actual Results: Sometimes, moving the constrained point shows garbage in kig window that disappears when motion finishes Expected Results: A fluid motion of the involved objects url above provides a save file that produces the issue. After loading the file it is necessary to repeatedly zoom around the origin to actually see the construction. This is a hint that the problem is caused by the existence of the "point at infinity" clearly due to rounding errors.
Thanks for the bug report, I'm taking a look at it now.
Created attachment 78054 [details] possible patch, but little discussion needed Here is a possible patch... However it entails the choice of a threshold, which should be discussed.
Can I (try to) commit the patch for this problem?
Hi, sorry I didn't get back to you earlier. I wanted to propose a different approach to the fix but it won't be possible to implement that until 4.11 at least, so yes, please commit your fix to the 4.10 branch.
committed: http://commits.kde.org/kig/4e5500d9fc188eca2eb00cc102cecdab5b3c4955
Git commit 07d2f651014256d4855d4fcb694ec10028266d2c by David E. Narváez. Committed on 04/04/2013 at 15:45. Pushed by narvaez into branch 'KDE/4.10'. Test for point at infinity Cherry-picked from 4e5500d9fc188eca2eb00cc102cecdab5b3c4955 FIXED-IN: 4.10.3 M +4 -0 misc/conic-common.cpp http://commits.kde.org/kig/07d2f651014256d4855d4fcb694ec10028266d2c