-------------------------------------------
funct (left-click):
  print_dist_last2_selected
-------------------------------------------
funct (mid-click):
  compute_avg_edgewidth
-------------------------------------------


Detailed Description of "DIST" Button Actions

-------------------------------------------
funct (left-click):
  print_dist_last2_selected
-------------------------------------------

A default left-click on the "DIST" button (lower
middle) prints Euclidean distance in mm between
last two selected surface vertices to the log.

-------------------------------------------
funct (mid-click):
  compute_avg_edgewidth
-------------------------------------------

An alternate middle-click on the "DIST" button
computes the average inter-vertex distance on the
current surface.

The length of each edge coming from a vertex is
measured and averaged.  To obtain the number of
edges (printed to the log), the total number of
measurements is divided by 2, because each edge
is measured twice (from the vertex at each end).

For a triangular mesh, the number of edges can
also be obtained from the number of faces as
follows:

  edges = faces * 3 / 2

We also have to divide by 2 in this case because
each of the 3 edges of a triangular face are
represented twice by the triangle on either side
of the edge.

The Euler equation relating vertices, edges, and
faces for a closed surface without defects is:

  vertices - edges + faces = 2

