[legacy] geant4: Support brewed GL libs on macOS

cmake/legacy.cmake

@@ -274,9 +274,14 @@ if(PACKAGE_SET STREQUAL full)
     set(mt
       "-DGEANT4_BUILD_MULTITHREADED=OFF")
   endif()
+  if(APPLE)
+    set(patch_support_brewed_gl_macos
+      PATCH_COMMAND ${patch} -p1 -i "${CMAKE_SOURCE_DIR}/legacy/geant4/support_brewed_gl.patch")
+  endif()
   ExternalProject_Add(geant4
     URL https://gitlab.cern.ch/geant4/geant4/-/archive/v${geant4_version}/geant4-v${geant4_version}.tar.gz
     URL_HASH SHA256=e381e04c02aeade1ed8cdd9fdbe7dcf5d6f0f9b3837a417976b839318a005dbd
+    ${patch_support_brewed_gl_macos}
     ${CMAKE_DEFAULT_ARGS} CMAKE_ARGS
       "-DGEANT4_BUILD_CXXSTD=c++${CMAKE_CXX_STANDARD}"
       ${mt}

legacy/geant4/support_brewed_gl.patch

@@ -0,0 +1,39 @@
+commit c4caa66623c7d81d493521d4941498535dc40cd0
+Author: Florian Uhlig <f.uhlig@gsi.de>
+Date:   Fri Jan 15 11:27:17 2021 +0100
+
+    Fix installation error with brew GL package
+
+    The brew package manager for macosx supports meanwhile the installation of
+    x11 and GL and is not longer bound to the usage of the unsupported XQuartz
+    package. Using the brew packages libx11 and mesa-glu the necessary include
+    and library files are ínstalled in /usr/local. Unfortunately this directory
+    is not in the search path such that the configuration of Geant4 fails.
+    The fix add the the missing search path such that GL installation is found
+    and the configuration succeeds.
+
+diff --git a/cmake/Modules/FindXQuartzGL.cmake b/cmake/Modules/FindXQuartzGL.cmake
+index c26754a611..335dc88dc2 100644
+--- a/cmake/Modules/FindXQuartzGL.cmake
++++ b/cmake/Modules/FindXQuartzGL.cmake
+@@ -49,17 +49,17 @@ set(CMAKE_FIND_FRAMEWORK_SAVE ${CMAKE_FIND_FRAMEWORK})
+ set(CMAKE_FIND_FRAMEWORK NEVER)
+
+ find_path(XQuartzGL_INCLUDE_DIR GL/gl.h
+-  PATHS /usr/X11R6/include /opt/X11/include
++  PATHS /usr/X11R6/include /opt/X11/include /usr/local/include
+   NO_DEFAULT_PATH
+   )
+
+ find_library(XQuartzGL_gl_LIBRARY GL
+-  PATHS /usr/X11R6/lib /opt/X11/lib
++  PATHS /usr/X11R6/lib /opt/X11/lib /usr/local/lib
+   NO_DEFAULT_PATH
+   )
+
+ find_library(XQuartzGL_glu_LIBRARY GLU
+-  PATHS /usr/X11R6/lib /opt/X11/lib
++  PATHS /usr/X11R6/lib /opt/X11/lib /usr/local/lib
+   NO_DEFAULT_PATH
+   )
+