plot annotates cell indices incorrectly

[Prof Garth Wells]

Plotting a mesh and using the keyboard shortcut 'c' appears to annotate facets rather than cells. From the documentation, it should annotate cells.

To reproduce:

from dolfin import *
mesh = UnitCubeMesh(1,1,1)
mesh.num_cells()
plot(mesh, interactive=True)

and press 'c' in the plot window. The indices run (0, 11), rather than (0, 5).

Originally reported in https://bitbucket.org/fenics-project/dolfin/issue/439

[Benjamin Dam Kehlet]

The reason, I think, is that the plotter code extracts the boundary mesh (which indeed has 12 cells) and plots it. Does it make sense to annotate indices in 3D when only the boundary is being displayed, or should this perhaps be a "2D only" feature?

[Prof Garth Wells]

To avoid confusion, perhaps it should be a 2D feature only.

[Anders Logg (Chalmers)]

Yes, this is confusing. If one wants to know the indices of the cells of the boundary mesh in 3D, one can just extract the boundary mesh, then plot and press c. So I suggest disabling this features in 3D.

[Johannes Ring]

Fixed in 24265d.

[Prof Garth Wells]

Removing milestone: 1.5 (automated comment)