From 7a66e0086525c7b54fc0cbba0b93fb5d94213394 Mon Sep 17 00:00:00 2001
From: Jonathan Westhues <jwesthues@cq.cx>
Date: Sat, 28 Nov 2009 18:42:50 -0800
Subject: [PATCH] Stop the perpendicular signs from flickering between the two
 drawn orientations when u and v are equally good choices.

[git-p4: depot-paths = "//depot/solvespace/": change = 2080]
---
 drawconstraint.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drawconstraint.cpp b/drawconstraint.cpp
index a9b6c26..5486a21 100644
--- a/drawconstraint.cpp
+++ b/drawconstraint.cpp
@@ -655,7 +655,9 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
                     u = e->VectorGetNum();
                     u = u.WithMagnitude(16/SS.GW.scale);
                     v = (rn.Cross(u)).WithMagnitude(16/SS.GW.scale);
-                    if(fabs(u.Dot(ru)) < fabs(v.Dot(ru))) {
+                    // a bit of bias to stop it from flickering between the
+                    // two possibilities
+                    if(fabs(u.Dot(ru)) < fabs(v.Dot(ru)) + LENGTH_EPS) {
                         SWAP(Vector, u, v);
                     }
                     if(u.Dot(ru) < 0) u = u.ScaledBy(-1);