File 0001-Optionally-prefer-system-wide-pybind11.patch of Package netgen.17640

From 3892ddbfa204e61822b87ff2e01ae99035aa09ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <stefan.bruens@rwth-aachen.de>
Date: Thu, 27 Jan 2022 08:45:02 +0100
Subject: [PATCH] Optionally prefer system wide pybind11

Linux distributions typically prefer system provided libraries, so
optionally use it when found.

(This also allows to use the github provided tarball, which omits the
pybind11 submodule).

Fix the PYBIND_INCLUDE_DIR usage:
- remove misleading find_path invocation, which may point to the system
  wide pybind11
- use pybind11_INCLUDE_DIR	which is provided by both find_package(pybind11)
  and bundled pybind11/CMakeLists.txt
- pybind11_INCLUDE_DIR is used by pybind11_add_module, use it also for
  ngcore (core/register_archive.hpp)
---
 CMakeLists.txt | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index dcc24afa..3519d831 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,10 +9,12 @@ else(WIN32)
   cmake_minimum_required(VERSION 3.8)
 endif(WIN32)
 
+include (CMakeDependentOption)
 option( USE_NATIVE_ARCH  "build for native cpu architecture" ON)
 
 option( USE_GUI     "don't build netgen with GUI" ON )
 option( USE_PYTHON  "build with python interface" ON )
+cmake_dependent_option( PREFER_SYSTEM_PYBIND11  "Use system wide PyBind11" ON "USE_PYTHON" OFF)
 option( USE_MPI     "enable mpi parallelization" OFF )
 option( USE_MPI4PY  "enable mpi4py interface" ON )
 option( USE_OCC     "(not supported) compile with OpenCascade geometry kernel" OFF)
@@ -268,23 +270,29 @@ else()
 endif()
 
 if (USE_PYTHON)
-    add_subdirectory(external_dependencies/pybind11)
-    find_path(PYBIND_INCLUDE_DIR pybind11/pybind11.h HINTS ${PYTHON_INCLUDE_DIR})
-    if( PYBIND_INCLUDE_DIR )
-        message(STATUS "Found Pybind11: ${PYBIND_INCLUDE_DIR}")
-    else( PYBIND_INCLUDE_DIR )
+    if (PREFER_SYSTEM_PYBIND11)
+      find_package(pybind11 CONFIG)
+    endif()
+    if (pybind11_FOUND)
+      set(NG_INSTALL_PYBIND OFF)
+    else()
+      add_subdirectory(external_dependencies/pybind11)
+    endif()
+    if (pybind11_INCLUDE_DIR)
+        message(STATUS "Found Pybind11: ${pybind11_INCLUDE_DIR}")
+    else()
         message(FATAL_ERROR "Could NOT find pybind11!")
-    endif( PYBIND_INCLUDE_DIR )
+    endif()
 
-    target_include_directories(netgen_python INTERFACE ${PYBIND_INCLUDE_DIR} ${PYTHON_INCLUDE_DIRS})
+    target_include_directories(netgen_python INTERFACE ${pybind11_INCLUDE_DIR} ${PYTHON_INCLUDE_DIRS})
     if(NOT ${BUILD_FOR_CONDA})
         # Don't link python libraries in conda environments
-        target_link_libraries(netgen_python INTERFACE ${PYTHON_LIBRARIES})
+        target_link_libraries(netgen_python INTERFACE ${PYTHON_LIBRARIES})
     endif()
 
     if(NG_INSTALL_PYBIND)
-      install(DIRECTORY ${PYBIND_INCLUDE_DIR}/pybind11 DESTINATION ${NG_INSTALL_DIR_INCLUDE} COMPONENT netgen_devel)
-      install(FILES ${PYBIND_INCLUDE_DIR}/../LICENSE DESTINATION ${NG_INSTALL_DIR_INCLUDE}/pybind11 COMPONENT netgen_devel)
+      install(DIRECTORY ${pybind11_INCLUDE_DIR}/pybind11 DESTINATION ${NG_INSTALL_DIR_INCLUDE} COMPONENT netgen_devel)
+      install(FILES ${pybind11_INCLUDE_DIR}/../LICENSE DESTINATION ${NG_INSTALL_DIR_INCLUDE}/pybind11 COMPONENT netgen_devel)
     endif(NG_INSTALL_PYBIND)
 endif (USE_PYTHON)
 
-- 
2.34.1