From 2b50f4acd2a21e64ac25c4c910c73362c004580f Mon Sep 17 00:00:00 2001
From: Julien Schueller <schueller@phimeca.com>
Date: Wed, 17 Mar 2021 18:37:49 +0100
Subject: [PATCH] CMake: Prefer GLVND if available

---
 .travis.yml                |  7 +++----
 build/cmake/CMakeLists.txt | 23 ++++++++++++++++++++---
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index c427f49..f2424a2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,5 @@
 language: cpp
 dist: trusty
-sudo: false
 install:
 script:
 - make -C auto clobber
@@ -11,9 +10,9 @@ script:
 - make clean && SYSTEM=linux-egl        make
 - make clean && SYSTEM=linux-clang      make
 - make clean && SYSTEM=linux-clang-egl  make
-- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' .                 && make && popd
-- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' -DGLEW_OSMESA=1 . && make && popd
-#- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' -DGLEW_EGL=1 .    && make && popd
+- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' .                              && make && popd
+- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' -DGLEW_OSMESA=ON .             && make && popd
+- pushd build/cmake && git clean -xdf . && cmake -G 'Unix Makefiles' -DGLEW_EGL=ON -DGLEW_X11=OFF . && make && popd
 addons:
   apt:
     packages:
diff --git a/build/cmake/CMakeLists.txt b/build/cmake/CMakeLists.txt
index 9ff5c9f..d04a727 100644
--- a/build/cmake/CMakeLists.txt
+++ b/build/cmake/CMakeLists.txt
@@ -16,6 +16,10 @@ if(POLICY CMP0042)
   cmake_policy (SET CMP0042 NEW)
 endif()
 
+if (POLICY CMP0072)
+  cmake_policy (SET CMP0072 NEW)
+endif(POLICY CMP0072)
+
 set(CMAKE_DEBUG_POSTFIX d)
 
 option (BUILD_UTILS "utilities" ON)
@@ -45,7 +49,20 @@ set (CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 
 find_package (OpenGL REQUIRED)
 
-set (GLEW_LIBRARIES ${OPENGL_LIBRARIES})
+# cmake<3.10 doesnt detect EGL/GLX
+if (CMAKE_VERSION VERSION_LESS 3.10)
+  find_library(OPENGL_egl_LIBRARY NAMES EGL)
+  if (OPENGL_egl_LIBRARY)
+    set (OpenGL_EGL_FOUND TRUE)
+  endif ()
+endif ()
+
+# prefer GLVND
+if (OPENGL_opengl_LIBRARY)
+  set (GLEW_LIBRARIES ${OPENGL_opengl_LIBRARY})
+else ()
+  set (GLEW_LIBRARIES ${OPENGL_gl_LIBRARY})
+endif ()
 
 # X11 required except for Windows and Apple OSX platforms
 if (GLEW_X11 AND NOT WIN32 AND NOT APPLE)
@@ -83,7 +100,7 @@ if (GLEW_OSMESA)
     set (OSMESA_LIB_NAME OSMesa)
   endif ()
   add_definitions (-DGLEW_OSMESA)
-  set (GLEW_LIBRARIES ${OSMESA_LIB_NAME} ${OPENGL_LIBRARIES})
+  list (APPEND GLEW_LIBRARIES ${OSMESA_LIB_NAME})
   set (X11_LIBRARIES)
 endif ()
 
@@ -94,7 +111,7 @@ if (GLEW_EGL AND UNIX)
   if (NOT OpenGL_EGL_FOUND)
     message (FATAL_ERROR "EGL library set but not found.")
   endif ()
-  set (GLEW_LIBRARIES ${OPENGL_LIBRARIES} ${OPENGL_egl_LIBRARY})
+  list (APPEND GLEW_LIBRARIES ${OPENGL_egl_LIBRARY})
 endif ()
 
 #### GLEW ####