From b39d246c27ccbec0a503cd2d5e6dc08762951300 Mon Sep 17 00:00:00 2001
From: howetuft <howetuft@gmail.com>
Date: Tue, 13 Feb 2024 04:38:30 +0100
Subject: [PATCH] Release GIL while meshing in MeshPart.meshFromShape

This commit releases the Global Interpreter Lock around mesher call and
should enable multithreading use when exporting large quantities of
objects (for instance for external rendering).
---
 src/Mod/MeshPart/App/AppMeshPartPy.cpp | 27 +++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/Mod/MeshPart/App/AppMeshPartPy.cpp b/src/Mod/MeshPart/App/AppMeshPartPy.cpp
index 4215369f0c..844058804d 100644
--- a/src/Mod/MeshPart/App/AppMeshPartPy.cpp
+++ b/src/Mod/MeshPart/App/AppMeshPartPy.cpp
@@ -474,6 +474,15 @@ private:
     {
         PyObject *shape;
 
+        auto runMesher = [](const MeshPart::Mesher& mesher) {
+            Mesh::MeshObject* mesh;
+            {
+                Base::PyGILStateRelease releaser{};
+                mesh = mesher.createMesh();
+            }
+            return Py::asObject(new Mesh::MeshPy(mesh));
+        };
+
         static const std::array<const char *, 7> kwds_lindeflection{"Shape", "LinearDeflection", "AngularDeflection",
                                                                     "Relative", "Segments", "GroupColors", nullptr};
         PyErr_Clear();
@@ -509,7 +518,7 @@ private:
                 }
                 mesher.setColors(colors);
             }
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 3> kwds_maxLength{"Shape", "MaxLength", nullptr};
@@ -521,7 +530,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setMaxLength(maxLength);
             mesher.setRegular(true);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 3> kwds_maxArea{"Shape", "MaxArea", nullptr};
@@ -533,7 +542,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setMaxArea(maxArea);
             mesher.setRegular(true);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 3> kwds_localLen{"Shape", "LocalLength", nullptr};
@@ -545,7 +554,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setLocalLength(localLen);
             mesher.setRegular(true);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 3> kwds_deflection{"Shape", "Deflection", nullptr};
@@ -557,7 +566,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setDeflection(deflection);
             mesher.setRegular(true);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 4> kwds_minmaxLen{"Shape", "MinLength", "MaxLength", nullptr};
@@ -569,7 +578,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setMinMaxLengths(minLen, maxLen);
             mesher.setRegular(true);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         static const std::array<const char *, 8> kwds_fineness{"Shape", "Fineness", "SecondOrder", "Optimize",
@@ -587,7 +596,7 @@ private:
             mesher.setOptimize(optimize != 0);
             mesher.setQuadAllowed(allowquad != 0);
             mesher.setMinMaxLengths(minLen, maxLen);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
 #else
             throw Py::RuntimeError("SMESH was built without NETGEN support");
 #endif
@@ -612,7 +621,7 @@ private:
             mesher.setOptimize(optimize != 0);
             mesher.setQuadAllowed(allowquad != 0);
             mesher.setMinMaxLengths(minLen, maxLen);
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
 #else
             throw Py::RuntimeError("SMESH was built without NETGEN support");
 #endif
@@ -627,7 +636,7 @@ private:
             mesher.setMethod(MeshPart::Mesher::Mefisto);
             mesher.setRegular(true);
 #endif
-            return Py::asObject(new Mesh::MeshPy(mesher.createMesh()));
+            return runMesher(mesher);
         }
 
         throw Py::TypeError("Wrong arguments");