Add progress callback support for all remeshing modules

[kmarchais]

Adds an optional progress callback to mmg3d / mmg2d / mmgs that reports iteration progress and supports cooperative cancellation (return 0 to abort). When unset (the default), the only runtime cost is a NULL check on the existing iterative loops.

Incidental change worth flagging: MMG5_adpdel previously discarded the return value of MMG5_optbad. With this PR a cancellation can originate inside optbad, so the return value is now checked and propagated.

Happy to add a libexamples/<module>/progress_callback/ style example as a follow-up if useful.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.24%. Comparing base (ae7d305) to head (c58ae35).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #324      +/-   ##
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- Coverage    50.31%   50.24%   -0.07%     
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  Files          177      177              
  Lines        47831    47913      +82     
  Branches     10352    10372      +20     
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+ Hits         24065    24073       +8     
- Misses       16037    16099      +62     
- Partials      7729     7741      +12     

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[corentin-prigent]

Hello,

Thank you for your submission. As you suggested, it would be interesting to had an example to illustrate how this option is used, and specifically, how to set the function that goes into mesh.info.progressCb.

Additionnally, this option is currently only available for library usage. Is there a way to extend this option for command line execution ?

Thank you very much in advance for your answers.

[kmarchais]

The latest commit adds the libexamples/mmg3d/progress_callback_example0 example and the -progress CLI option.

To get progress information from the API, create a callback function:

static int progress_cb(void *mesh, int phase, int it, int maxit,
                       int64_t nsplit, int64_t ncollapse,
                       int64_t nswap, int64_t nmove, void *user_data) {
  int pct = maxit > 0 ? 100 * (it + 1) / maxit : 100;
  if ( pct > 100 ) pct = 100;

  printf("\rprogress %3d%%", pct);
  fflush(stdout);
  return 1; /* return 0 to cancel */
}

/* before MMG3D_mmg3dlib */
MMG3D_Set_progressCallback(mmgMesh, progress_cb, NULL);

This progress information can then be used by external tools such as GUIs, Python wrappers, or custom progress bars.

To test the CLI progress bar from the repository root:
mmg3d -progress libexamples\mmg3d\adaptation_example2\2spheres.mesh