Draft: snap intersection hangs indefinitely freecad

[alafr]

Is there an existing issue for this?

• I have searched the existing issues

Problem description

Open attached file
View > Fit All
Enable Draft snap on intersection
Draw a line and approach the shape
Freecad hangs indefinitely

snap intersection bug.zip

Full version info

OS: Windows 10 build 19045
Word size of FreeCAD: 64-bit
Version: 0.22.0dev.37094 (Git)
Build type: Release
Branch: alaf-test
Hash: 779c8949d37ae996cc59a11d373fa518b8a0d094
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: French/France (fr_FR)
Installed mods: 
  * ArchTextures
  * BIM
  * Curves 0.6.14
  * Defeaturing 1.2.1
  * DynamicData 2.60.0
  * Trails 2022.1.0


[code]
OS: Windows 10 build 19045
Word size of FreeCAD: 64-bit
Version: 0.21.2.33771 (Git)
Build type: Release
Branch: releases/FreeCAD-0-21
Hash: b9bfa5c5507506e4515816414cd27f4851d00489
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: French/France (fr_FR)
Installed mods: 
  * ArchTextures
  * BIM
  * Curves 0.6.14
  * Defeaturing 1.2.1
  * DynamicData 2.60.0
  * Trails 2022.1.0
[/code]

Subproject(s) affected?

Draft

Anything else?

The problem happens in edge1.distToShape(edge2) here
Snap works fine if I replace

        dist, pts, geom = edge1.distToShape(edge2)
        sol = []
        if round(dist, precision()) == 0:
            for p in pts:
                if p[0] not in sol:
                    sol.append(p[0])
        return sol

with

        sol = []
        section = edge1.section(edge2)
        for vertex in section.Vertexes:
            sol.append(vertex.Point)
        return sol

Of course fixing distToShape would be better

Code of Conduct

• I agree to follow this project's Code of Conduct

[Roy-043]

This is not a Draft issue as such. I suspect it is the degree of the B-splines (the edges are B-splines with a degree of 1) that is the culprit.

[alafr]

Those lines are a section between a plane and a ruled surface. Here is their parametric history:
snap intersection bug history.zip

There is no issue with 1 degree Bsplines created in Draft.

[Roy-043]

You are right. The number of knots is large, that may be the cause instead.
sub.Curve.NbKnots => 947