From 6940c54fc1ed75531d7fffc2639feaaa607f04a8 Mon Sep 17 00:00:00 2001
From: Gyusun Yeom <omniavinco@gmail.com>
Date: Sun, 22 Aug 2021 21:24:41 +0900
Subject: [PATCH] Support off-screen mode

---
 CMakeLists.txt | 55 ++++++++++++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2b8f367..87e8072 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -31,6 +31,7 @@ include("GeneratePkgConfig.cmake")
 option(glew-cmake_BUILD_SHARED "Build the shared glew library" ON)
 option(glew-cmake_BUILD_STATIC "Build the static glew library" ON)
 option(USE_GLU "Use GLU" OFF)
+option(GLEW_OSMESA "Off-screen Mesa mode" OFF)
 option(PKG_CONFIG_REPRESENTATIVE_TARGET "Generate pc file for specified target as glew. libglew_static|libglew_shared" OFF)
 option(ONLY_LIBS "Do not build executables" OFF)
 
@@ -81,39 +82,41 @@ else()
 endif()
 
 list(APPEND pc_requires gl)
-if(POLICY CMP0072)
-	# GLVND
-	if(USE_NAMESPACED_LIB)
-		list(APPEND LIBRARIES OpenGL::GL)
-		if(NOT (WIN32 OR APPLE))
-			list(APPEND LIBRARIES OpenGL::GLX)
-		endif()
-	else()
-		list(APPEND LIBRARIES ${OPENGL_opengl_LIBRARY})
-		if(NOT (WIN32 OR APPLE))
-			list(APPEND LIBRARIES ${OPENGL_glx_LIBRARY})
-		endif()
-	endif()
+if(USE_NAMESPACED_LIB)
+	list(APPEND LIBRARIES OpenGL::GL)
 else()
-	# Non GLVND
-	if(USE_NAMESPACED_LIB)
-		list(APPEND LIBRARIES OpenGL::OpenGL)
-	else()
-		list(APPEND LIBRARIES ${OPENGL_gl_LIBRARY})
-	endif()
+	list(APPEND LIBRARIES ${OPENGL_opengl_LIBRARY})
 endif()
 
+# OS Specific dependencies
 if(APPLE)
-	find_library(AGL_LIBRARY AGL)
+	find_library(AGL_LIBRARY AGL REQUIRED)
 	list(APPEND LIBRARIES ${AGL_LIBRARY})
 elseif(NOT WIN32)
-	find_package(X11 REQUIRED)
-
-	list(APPEND pc_requires x11 xext)
-	if(USE_NAMESPACED_LIB)
-		list(APPEND LIBRARIES X11::X11 X11::Xext)
+	if(GLEW_OSMESA)
+		find_library(OSMESA_LIBRARY OSMesa REQUIRED)
+		list(APPEND LIBRARIES ${OSMESA_LIBRARY})
+		list(APPEND DEFINITIONS -DGLEW_OSMESA)
+		list(APPEND pc_requires osmesa)
 	else()
-		list(APPEND LIBRARIES ${X11_X11_LIB} ${X11_Xext_LIB})
+		if(NOT OpenGL_GLX_FOUND)
+			message(FATAL_ERROR "GLX is not found. Try with PREFER_GLVND=NO")
+		endif()
+
+		if(USE_NAMESPACED_LIB)
+			list(APPEND LIBRARIES OpenGL::GLX)
+		else()
+			list(APPEND LIBRARIES ${OPENGL_glx_LIBRARY})
+		endif()
+		
+		find_package(X11 REQUIRED)
+
+		list(APPEND pc_requires x11 xext)
+		if(USE_NAMESPACED_LIB)
+			list(APPEND LIBRARIES X11::X11 X11::Xext)
+		else()
+			list(APPEND LIBRARIES ${X11_X11_LIB} ${X11_Xext_LIB})
+		endif()
 	endif()
 endif()