set_mesh_size_callback does not work with new version of gmsh

[keurfonluu]

Hi @nschloe,

The sample problem in the README file no longer works:

import pygmsh

with pygmsh.geo.Geometry() as geom:
    geom.add_polygon(
        [
            [-1.0, -1.0],
            [+1.0, -1.0],
            [+1.0, +1.0],
            [-1.0, +1.0],
        ]
    )
    geom.set_mesh_size_callback(
        lambda dim, tag, x, y, z: 6.0e-2 + 2.0e-1 * (x**2 + y**2)
    )

    mesh = geom.generate_mesh()

Basically, it seems that gmsh is expecting 5 arguments in the callback functions, but 6 are given. I am using gmsh v4.10.5 and pygmsh v7.1.17. No problem with gmsh v4.8.4, though. The fastest fix would be to add a version requirement in pyproject.toml.

Below the full error:

Exception ignored on calling ctypes callback function: <function model.mesh.setSizeCallback.<locals>.<lambda> at 0x000001E8A714E3A0>
Traceback (most recent call last):
  File "c:\Users\keurf\anaconda3\lib\site-packages\gmsh.py", line 3219, in <lambda>
    api_callback_ = api_callback_type_(lambda dim, tag, x, y, z, lc, _ : callback(dim, tag, x, y, z, lc))
TypeError: <lambda>() takes 5 positional arguments but 6 were given
Output exceeds the [size limit](command:workbench.action.openSettings?[). Open the full output data [in a text editor](command:workbench.action.openLargeOutput?9777202c-aab9-499c-8e72-01d361232c84)
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
Input In [8], in <cell line: 4>()
      5 geom.add_polygon(
      6     [
      7         [-1.0, -1.0],
   (...)
     11     ]
     12 )
     13 geom.set_mesh_size_callback(
     14     lambda dim, tag, x, y, z: 6.0e-2 + 2.0e-1 * (x**2 + y**2)
     15 )
---> 17 mesh = geom.generate_mesh()

File c:\Users\keurf\anaconda3\lib\site-packages\pygmsh\common\geometry.py:374, in CommonGeometry.generate_mesh(self, dim, order, algorithm, verbose)
    [371](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=370) if algorithm:
    [372](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=371)     gmsh.option.setNumber("Mesh.Algorithm", algorithm)
--> [374](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=373) gmsh.model.mesh.generate(dim)
    [376](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=375) # setOrder() after generate(), see
    [377](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=376) # <https://github.com/nschloe/pygmsh/issues/515#issuecomment-1020106499>
    [378](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/pygmsh/common/geometry.py?line=377) if order is not None:

File c:\Users\keurf\anaconda3\lib\site-packages\gmsh.py:1599, in model.mesh.generate(dim)
   [1595](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/gmsh.py?line=1594) lib.gmshModelMeshGenerate(
   [1596](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/gmsh.py?line=1595)     c_int(dim),
...
   [1597](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/gmsh.py?line=1596)     byref(ierr))
   [1598](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/gmsh.py?line=1597) if ierr.value != 0:
-> [1599](file:///c%3A/Users/keurf/anaconda3/lib/site-packages/gmsh.py?line=1598)     raise Exception(logger.getLastError())

Exception: Wrong mesh element size lc = 0 (lcmin = 0, lcmax = 1e+22)