MmgTools · kmarchais · May 14, 2026
diff --git a/src/common/libmmgtypes.h b/src/common/libmmgtypes.h
@@ -40,6 +40,50 @@
 #ifndef _LIBMMGTYPES_H
 #define _LIBMMGTYPES_H
 
+/**
+ * \enum MMG5_progressPhase
+ * \brief Phases reported by the progress callback.
+ */
+enum MMG5_progressPhase {
+  MMG5_PHASE_GEOMETRIC_MESH,  /*!< Geometric mesh analysis and splitting */
+  MMG5_PHASE_COMPUTATIONAL_MESH, /*!< Metric definition and gradation */
+  MMG5_PHASE_ADAPTATION,     /*!< Main adaptation loop
+                                (split/collapse/swap/move) */
+  MMG5_PHASE_OPTIMIZATION    /*!< Final quality optimization (swap/move) */
+};
+
+/**
+ * \typedef MMG5_progressCallback
+ * \brief Callback function type for progress reporting.
+ *
+ * Called at each iteration within a phase to report progress.
+ *
+ * \param mesh       pointer to the mesh structure (opaque to caller).
+ * \param phase      current phase (\ref MMG5_progressPhase).
+ * \param iteration  current iteration within the phase (0-based).
+ * \param max_iterations  maximum iterations for this phase.
+ * \param n_split    number of edge splits performed in this iteration.
+ * \param n_collapse number of edge collapses performed in this iteration.
+ * \param n_swap     number of edge swaps performed in this iteration.
+ * \param n_move     number of vertex moves performed in this iteration.
+ * \param user_data  opaque pointer passed by the user.
+ *
+ * \return 1 to continue, 0 to request cancellation.
+ *
+ * \remark The callback is only invoked when set (non-NULL). When not set,
+ * there is zero overhead — no function pointer check occurs in the hot
+ * loops.
+ */
+typedef int (*MMG5_progressCallback)(void *mesh,
+                                     int phase,
+                                     int iteration,
+                                     int max_iterations,
+                                     int64_t n_split,
+                                     int64_t n_collapse,
+                                     int64_t n_swap,
+                                     int64_t n_move,
+                                     void *user_data);
+
 /**
  * \def MMG5_SUCCESS
  *
@@ -561,6 +605,12 @@ typedef struct {
 
   MMG5_pMat     mat;
   MMG5_InvMat   invmat;
+
+  /* Progress callback (optional, NULL by default) */
+  MMG5_progressCallback progressCb;   /**< Progress callback (NULL =
+                                         disabled, zero overhead) */
+  void                 *progressData; /**< Opaque user data forwarded
+                                         to progressCb */
 } MMG5_Info;
 
 /**

diff --git a/src/mmg2d/API_functions_2d.c b/src/mmg2d/API_functions_2d.c
@@ -1950,3 +1950,11 @@ int MMG2D_Free_names(const int starter,...)
 
   return ier;
 }
+
+int MMG2D_Set_progressCallback(MMG5_pMesh mesh,
+                               MMG5_progressCallback callback,
+                               void *user_data) {
+  mesh->info.progressCb   = callback;
+  mesh->info.progressData = user_data;
+  return 1;
+}
diff --git a/src/mmg2d/libmmg2d.h b/src/mmg2d/libmmg2d.h
@@ -2769,6 +2769,21 @@ LIBMMG2D_EXPORT int MMG2D_Free_all(const int starter,...);
  */
   LIBMMG2D_EXPORT int MMG2D_scaleMesh(MMG5_pMesh mesh,MMG5_pSol met,MMG5_pSol ls);
 
+/**
+ * \brief Set a progress callback for the remeshing process.
+ *
+ * \param mesh       pointer to the mesh structure.
+ * \param callback   progress callback function (NULL to disable).
+ * \param user_data  opaque pointer forwarded to every callback invocation.
+ *
+ * \return 1 on success.
+ *
+ * \sa MMG5_progressCallback, MMG3D_Set_progressCallback.
+ */
+  LIBMMG2D_EXPORT int MMG2D_Set_progressCallback(MMG5_pMesh mesh,
+                                                 MMG5_progressCallback callback,
+                                                 void *user_data);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/src/mmg2d/mmg2d1.c b/src/mmg2d/mmg2d1.c
@@ -96,6 +96,25 @@ int MMG2D_anatri(MMG5_pMesh mesh,MMG5_pSol met,int8_t typchk) {
 
     if ( (abs(mesh->info.imprim) > 4 || mesh->info.ddebug) && ns+nc > 0 )
       fprintf(stdout,"     %8" MMG5_PRId " splitted, %8" MMG5_PRId " collapsed, %8" MMG5_PRId " swapped\n",ns,nc,nsw);
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      int phase = (typchk == 1) ?
+        MMG5_PHASE_GEOMETRIC_MESH :
+        MMG5_PHASE_COMPUTATIONAL_MESH;
+      if ( !mesh->info.progressCb(
+             mesh, phase, it, maxit,
+             (int64_t)ns, (int64_t)nc,
+             (int64_t)nsw, 0,
+             mesh->info.progressData) ) {
+        fprintf(stderr,
+          "\n  ## %s cancelled by user callback.\n",
+          (typchk == 1) ?
+          "Geometric mesh" : "Computational mesh");
+        return 0;
+      }
+    }
+
     if ( it > 3 && MMG5_abs(nc-ns) < 0.1 * MG_MAX(nc,ns) )  break;
   }
   while ( ++it < maxit && ns+nc+nsw >0 );
@@ -606,6 +625,17 @@ int MMG2D_adptri(MMG5_pMesh mesh,MMG5_pSol met) {
 
     if ( (abs(mesh->info.imprim) > 4 || mesh->info.ddebug) && ns+nc+nsw+nm > 0 )
       fprintf(stdout,"     %8" MMG5_PRId " splitted, %8" MMG5_PRId " collapsed, %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",ns,nc,nsw,nm);
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_ADAPTATION, it, maxit,
+                                  (int64_t)ns, (int64_t)nc, (int64_t)nsw,
+                                  (int64_t)nm, mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Remeshing cancelled by user callback.\n");
+        return 0;
+      }
+    }
+
     if ( ns < 10 && MMG5_abs(nc-ns) < 3 )  break;
     else if ( it > 3 && MMG5_abs(nc-ns) < 0.3 * MG_MAX(nc,ns) )  break;
   }

diff --git a/src/mmg3d/API_functions_3d.c b/src/mmg3d/API_functions_3d.c
@@ -2585,3 +2585,11 @@ int MMG3D_Free_names(const int starter,...)
 
   return ier;
 }
+
+int MMG3D_Set_progressCallback(MMG5_pMesh mesh,
+                               MMG5_progressCallback callback,
+                               void *user_data) {
+  mesh->info.progressCb   = callback;
+  mesh->info.progressData = user_data;
+  return 1;
+}
diff --git a/src/mmg3d/libmmg3d.h b/src/mmg3d/libmmg3d.h
@@ -3458,6 +3458,31 @@ LIBMMG3D_EXPORT int MMG3D_loadVtuMesh_and_allData(MMG5_pMesh mesh,MMG5_pSol *sol
   * functions.
   */
   LIBMMG3D_EXPORT void MMG3D_Set_commonFunc(void);
+
+/**
+ * \brief Set a progress callback for the remeshing process.
+ *
+ * \param mesh       pointer to the mesh structure.
+ * \param callback   progress callback function (NULL to disable).
+ * \param user_data  opaque pointer forwarded to every callback invocation.
+ *
+ * \return 1 on success.
+ *
+ * The callback is invoked at each iteration of every remeshing phase:
+ * geometric mesh, computational mesh, adaptation loop, and optimization.
+ * Returning 0 from the callback requests graceful cancellation.
+ *
+ * When \a callback is NULL (the default), no function-pointer check is
+ * performed in the hot loops, so there is zero overhead.
+ *
+ * \remark No Fortran interface.
+ *
+ * \sa MMG5_progressCallback for the callback signature.
+ */
+  LIBMMG3D_EXPORT int MMG3D_Set_progressCallback(MMG5_pMesh mesh,
+                                                 MMG5_progressCallback callback,
+                                                 void *user_data);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/src/mmg3d/mmg3d1.c b/src/mmg3d/mmg3d1.c
@@ -3263,6 +3263,24 @@ int MMG5_anatet(MMG5_pMesh mesh,MMG5_pSol met,int8_t typchk, int patternMode) {
       fprintf(stdout,"     %8" MMG5_PRId " splitted, %8" MMG5_PRId " collapsed, %8" MMG5_PRId " swapped\n",ns,nc,nf);
     }
 
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      int phase = (typchk == 1) ?
+        MMG5_PHASE_GEOMETRIC_MESH :
+        MMG5_PHASE_COMPUTATIONAL_MESH;
+      if ( !mesh->info.progressCb(
+             mesh, phase, it, maxit,
+             (int64_t)ns, (int64_t)nc,
+             (int64_t)nf, 0,
+             mesh->info.progressData) ) {
+        fprintf(stderr,
+          "\n  ## %s cancelled by user callback.\n",
+          (typchk == 1) ?
+          "Geometric mesh" : "Computational mesh");
+        return 0;
+      }
+    }
+
     if ( it > minit-1 && ( !(ns+nc) || (MMG5_abs(nc-ns) < 0.1 * MG_MAX(nc,ns)) ) ) {
       ++lastit;
       if ( it > minit && lastit>2 ) break;

diff --git a/src/mmg3d/mmg3d1_delone.c b/src/mmg3d/mmg3d1_delone.c
@@ -614,6 +614,16 @@ int MMG5_optbad(MMG5_pMesh mesh, MMG5_pSol met,MMG3D_pPROctree PROctree) {
       fprintf(stdout,"                                          ");
       fprintf(stdout,"  %8" MMG5_PRId " improved, %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",nw,nf,nm);
     }
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_OPTIMIZATION, it, maxit,
+                                  0, 0, (int64_t)nf, (int64_t)nm,
+                                  mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Optimization cancelled by user callback.\n");
+        return 0;
+      }
+    }
   }
   while( ++it < maxit && nw+nm+nf > 0 );
 
@@ -716,10 +726,22 @@ int MMG5_adpdel(MMG5_pMesh mesh,MMG5_pSol met,MMG3D_pPROctree *PROctree, int* wa
       fprintf(stdout,"     %8"MMG5_PRId" filtered, %8" MMG5_PRId " splitted, %8" MMG5_PRId " collapsed,"
               " %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",ifilt,ns,nc,nf,nm);
 
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_ADAPTATION, it, maxit,
+                                  (int64_t)ns, (int64_t)nc, (int64_t)nf,
+                                  (int64_t)nm, mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Remeshing cancelled by user callback.\n");
+        return 0;
+      }
+    }
+
     /*optimization*/
     dd = MMG5_abs(nc-ns);
     if ( !noptim && (it==5 || ((dd < 5) || (dd < 0.05*MG_MAX(nc,ns)) || !(ns+nc))) ) {
-      MMG5_optbad(mesh,met,*PROctree);
+      if ( !MMG5_optbad(mesh,met,*PROctree) ) {
+        return 0;
+      }
       noptim = 1;
     }
 
@@ -806,6 +828,16 @@ int MMG5_optetLES(MMG5_pMesh mesh, MMG5_pSol met,MMG3D_pPROctree PROctree) {
       fprintf(stdout,"                                          ");
       fprintf(stdout,"  %8" MMG5_PRId " improved, %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",nw,nf,nm);
     }
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_OPTIMIZATION, it, maxit,
+                                  0, 0, (int64_t)nf, (int64_t)nm,
+                                  mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Optimization cancelled by user callback.\n");
+        return 0;
+      }
+    }
   }
   while( ++it < maxit && nw+nm+nf > 0 );
 
@@ -911,6 +943,16 @@ int MMG5_optet(MMG5_pMesh mesh, MMG5_pSol met,MMG3D_pPROctree PROctree) {
       fprintf(stdout,"  %8" MMG5_PRId " improved, %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",nw,nf,nm);
     }
 
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_OPTIMIZATION, it, maxit,
+                                  0, 0, (int64_t)nf, (int64_t)nm,
+                                  mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Optimization cancelled by user callback.\n");
+        return 0;
+      }
+    }
+
     if ( it > 3 ) {
       if ( !nw && (!nm || !nf) )   break;
     }

diff --git a/src/mmg3d/mmg3d1_pattern.c b/src/mmg3d/mmg3d1_pattern.c
@@ -323,6 +323,17 @@ static int MMG5_adptet(MMG5_pMesh mesh,MMG5_pSol met,MMG5_int *permNodGlob) {
 
     if ( (abs(mesh->info.imprim) > 4 || mesh->info.ddebug) && ns+nc > 0 )
       fprintf(stdout,"     %8" MMG5_PRId " splitted, %8" MMG5_PRId " collapsed, %8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",ns,nc,nf,nm);
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_ADAPTATION, it, maxit,
+                                  (int64_t)ns, (int64_t)nc, (int64_t)nf,
+                                  (int64_t)nm, mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Remeshing cancelled by user callback.\n");
+        return 0;
+      }
+    }
+
     if ( ns < 10 && MMG5_abs(nc-ns) < 3 )  break;
     else if ( it > 3 && MMG5_abs(nc-ns) < 0.3 * MG_MAX(nc,ns) )  break;
   }
@@ -387,6 +398,16 @@ static int MMG5_adptet(MMG5_pMesh mesh,MMG5_pSol met,MMG5_int *permNodGlob) {
       fprintf(stdout,"                                            ");
       fprintf(stdout,"%8" MMG5_PRId " swapped, %8" MMG5_PRId " moved\n",nf,nm);
     }
+
+    /* Progress callback */
+    if ( mesh->info.progressCb ) {
+      if ( !mesh->info.progressCb(mesh, MMG5_PHASE_OPTIMIZATION, it, maxit,
+                                  0, 0, (int64_t)nf, (int64_t)nm,
+                                  mesh->info.progressData) ) {
+        fprintf(stderr,"\n  ## Optimization cancelled by user callback.\n");
+        return 0;
+      }
+    }
   }
   while( ++it < maxit && /*nw+*/nm+nf > 0 );
 

diff --git a/src/mmgs/API_functions_s.c b/src/mmgs/API_functions_s.c
@@ -1728,3 +1728,11 @@ int MMGS_Free_names(const int starter,...)
 
   return ier;
 }
+
+int MMGS_Set_progressCallback(MMG5_pMesh mesh,
+                              MMG5_progressCallback callback,
+                              void *user_data) {
+  mesh->info.progressCb   = callback;
+  mesh->info.progressData = user_data;
+  return 1;
+}
diff --git a/src/mmgs/libmmgs.h b/src/mmgs/libmmgs.h
@@ -2576,6 +2576,21 @@ LIBMMGS_EXPORT void MMGS_Free_solutions(MMG5_pMesh mesh,MMG5_pSol sol);
  */
 LIBMMGS_EXPORT void MMGS_Set_commonFunc(void);
 
+/**
+ * \brief Set a progress callback for the remeshing process.
+ *
+ * \param mesh       pointer to the mesh structure.
+ * \param callback   progress callback function (NULL to disable).
+ * \param user_data  opaque pointer forwarded to every callback invocation.
+ *
+ * \return 1 on success.
+ *
+ * \sa MMG5_progressCallback, MMG3D_Set_progressCallback.
+ */
+LIBMMGS_EXPORT int MMGS_Set_progressCallback(MMG5_pMesh mesh,
+                                             MMG5_progressCallback callback,
+                                             void *user_data);
+
 #ifdef __cplusplus
 }
 #endif