From 34dd176116870d24d6a5b93e263e79edad06fd00 Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Fri, 6 Jan 2023 15:11:47 -0500
Subject: [PATCH] gmsh: enable python bindings

---
 .../science/math/gmsh/default.nix             | 18 ++++++-
 .../science/math/gmsh/fix-python.patch        | 50 +++++++++++++++++++
 pkgs/top-level/python-packages.nix            |  4 ++
 3 files changed, 70 insertions(+), 2 deletions(-)
 create mode 100644 pkgs/applications/science/math/gmsh/fix-python.patch

diff --git a/pkgs/applications/science/math/gmsh/default.nix b/pkgs/applications/science/math/gmsh/default.nix
index 3153c128057a..4d9b3afe31ca 100644
--- a/pkgs/applications/science/math/gmsh/default.nix
+++ b/pkgs/applications/science/math/gmsh/default.nix
@@ -1,7 +1,9 @@
 { lib, stdenv, fetchurl, cmake, blas, lapack, gfortran, gmm, fltk, libjpeg
-, zlib, libGL, libGLU, xorg, opencascade-occt }:
+, zlib, libGL, libGLU, xorg, opencascade-occt
+, python ? null, enablePython ? false }:
 
 assert (!blas.isILP64) && (!lapack.isILP64);
+assert enablePython -> (python != null);
 
 stdenv.mkDerivation rec {
   pname = "gmsh";
@@ -18,10 +20,16 @@ stdenv.mkDerivation rec {
     libGL libGLU xorg.libXrender xorg.libXcursor xorg.libXfixes
     xorg.libXext xorg.libXft xorg.libXinerama xorg.libX11 xorg.libSM
     xorg.libICE
-  ];
+  ] ++ lib.optional enablePython python;
 
   enableParallelBuilding = true;
 
+  patches = [ ./fix-python.patch ];
+
+  postPatch = ''
+    substituteInPlace api/gmsh.py --subst-var-by LIBPATH ${placeholder "out"}/lib/libgmsh.so
+  '';
+
   # N.B. the shared object is used by bindings
   cmakeFlags = [
     "-DENABLE_BUILD_SHARED=ON"
@@ -31,6 +39,12 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake gfortran ];
 
+  postFixup = lib.optionalString enablePython ''
+    mkdir -p $out/lib/python${python.pythonVersion}/site-packages
+    mv $out/lib/gmsh.py $out/lib/python${python.pythonVersion}/site-packages
+    mv $out/lib/*.dist-info $out/lib/python${python.pythonVersion}/site-packages
+  '';
+
   doCheck = true;
 
   meta = {
diff --git a/pkgs/applications/science/math/gmsh/fix-python.patch b/pkgs/applications/science/math/gmsh/fix-python.patch
new file mode 100644
index 000000000000..ac07c169c99b
--- /dev/null
+++ b/pkgs/applications/science/math/gmsh/fix-python.patch
@@ -0,0 +1,50 @@
+diff --git a/api/gmsh.py b/api/gmsh.py
+index 747acb203..02004da5d 100644
+--- a/api/gmsh.py
++++ b/api/gmsh.py
+@@ -44,44 +44,7 @@ moduledir = os.path.dirname(os.path.realpath(__file__))
+ parentdir1 = os.path.dirname(moduledir)
+ parentdir2 = os.path.dirname(parentdir1)
+ 
+-if platform.system() == "Windows":
+-    libname = "gmsh-4.11.dll"
+-elif platform.system() == "Darwin":
+-    libname = "libgmsh.4.11.dylib"
+-else:
+-    libname = "libgmsh.so.4.11"
+-
+-# check if the library is in the same directory as the module...
+-libpath = os.path.join(moduledir, libname)
+-
+-# ... or in the parent directory or its lib or Lib subdirectory
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir1, libname)
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir1, "lib", libname)
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir1, "Lib", libname)
+-
+-# ... or in the parent of the parent directory or its lib or Lib subdirectory
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir2, libname)
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir2, "lib", libname)
+-if not os.path.exists(libpath):
+-    libpath = os.path.join(parentdir2, "Lib", libname)
+-
+-# if we couldn't find it, use ctype's find_library utility...
+-if not os.path.exists(libpath):
+-    if platform.system() == "Windows":
+-        libpath = find_library("gmsh-4.11")
+-        if not libpath:
+-            libpath = find_library("gmsh")
+-    else:
+-        libpath = find_library("gmsh")
+-
+-# ... and print a warning if everything failed
+-if not os.path.exists(libpath):
+-    print("Warning: could not find Gmsh shared library " + libname)
++libpath = "@LIBPATH@"
+ 
+ lib = CDLL(libpath)
+ 
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index d47835b1568e..972ae3b4b3df 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -3807,6 +3807,10 @@ self: super: with self; {
 
   gmpy = callPackage ../development/python-modules/gmpy { };
 
+  gmsh = toPythonModule (callPackage ../applications/science/math/gmsh {
+    enablePython = true;
+  });
+
   gntp = callPackage ../development/python-modules/gntp { };
 
   gnureadline = callPackage ../development/python-modules/gnureadline { };