Arc Tool behaves strangely when dragging one end to the other and back again

[Marian-Braendle]

Steps to Reproduce

1. Create Arc
2. Drag one end to the other and back again while holding the left mouse button
3. Move the center of the arc

Context

• Ipe 7.2.27
• Ubuntu 22.04

[Marian-Braendle]

This seems to fix the problem, but I'm not sure it's the right way to go:

diff --git a/src/ipe/lua/main.lua b/src/ipe/lua/main.lua
index 2e9d0da..80be492 100644
--- a/src/ipe/lua/main.lua
+++ b/src/ipe/lua/main.lua
@@ -156,6 +156,7 @@ function recomputeArcMatrix(seg, cpno)
   local p = ipe.Direction(alpha)
   local q = ipe.Direction(beta)
   local cl
+  if (seg[2]-seg[1]):sqLen() == 0 then return end
   if cpno == 1 then
     cl = ipe.LineThrough(V(0,0), q)
     p = seg.arc:matrix():inverse() * seg[cpno]

[otfried]

Fixed in 7.2.28.