Add an option to link against libepoxy instead of libGL or libGLES*, so we can defer that choice to runtime

CMake/modules/FindEpoxy.cmake

@@ -0,0 +1,16 @@
+# Find libepoxy
+#
+# EPOXY_INCLUDE_DIR
+# EPOXY_LIBRARY
+# EPOXY_FOUND
+
+find_path(EPOXY_INCLUDE_DIR NAMES epoxy/gl.h PATHS /opt/vc/include)
+
+set(EPOXY_NAMES ${EPOXY_NAMES} epoxy)
+find_library(EPOXY_LIBRARY NAMES ${EPOXY_NAMES} PATHS /opt/vc/lib)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(EPOXY DEFAULT_MSG EPOXY_LIBRARY EPOXY_INCLUDE_DIR)
+
+mark_as_advanced(EPOXY_INCLUDE_DIR EPOXY_LIBRARY)
+

CMakeLists.txt

@@ -61,7 +61,7 @@ set(CMAKE_MODULE_PATH "${GLFW_SOURCE_DIR}/CMake/modules")
 
 if (GLFW_USE_EGL)
     set(GLFW_CLIENT_LIBRARY "opengl" CACHE STRING
-        "The client library to use; one of opengl, glesv1 or glesv2")
+        "The client library to use; one of opengl, glesv1, glesv2 or epoxy")
 
     if (${GLFW_CLIENT_LIBRARY} STREQUAL "opengl")
         set(_GLFW_USE_OPENGL 1)
@@ -69,13 +69,15 @@ if (GLFW_USE_EGL)
         set(_GLFW_USE_GLESV1 1)
     elseif (${GLFW_CLIENT_LIBRARY} STREQUAL "glesv2")
         set(_GLFW_USE_GLESV2 1)
+    elseif (${GLFW_CLIENT_LIBRARY} STREQUAL "epoxy")
+        set(_GLFW_USE_EPOXY 1)
     else()
         message(FATAL_ERROR "Unsupported client library")
     endif()
 
     find_package(EGL REQUIRED)
 
-    if (NOT _GLFW_USE_OPENGL)
+    if (NOT _GLFW_USE_OPENGL AND NOT _GLFW_USE_EPOXY)
         set(GLFW_BUILD_EXAMPLES OFF)
         set(GLFW_BUILD_TESTS OFF)
         message(STATUS "NOTE: Examples and tests require OpenGL")
@@ -90,6 +92,8 @@ elseif (_GLFW_USE_GLESV1)
     find_package(GLESv1 REQUIRED)
 elseif (_GLFW_USE_GLESV2)
     find_package(GLESv2 REQUIRED)
+elseif (_GLFW_USE_EPOXY)
+    find_package(Epoxy REQUIRED)
 endif()
 
 find_package(Threads REQUIRED)
@@ -400,6 +404,10 @@ if (_GLFW_EGL)
         list(APPEND glfw_LIBRARIES "${GLESv2_LIBRARY}")
         list(APPEND glfw_INCLUDE_DIRS "${GLESv2_INCLUDE_DIR}")
         list(APPEND glfw_PKG_DEPS "glesv2")
+    elseif (_GLFW_USE_EPOXY)
+        list(APPEND glfw_LIBRARIES "${EPOXY_LIBRARY}")
+        list(APPEND glfw_INCLUDE_DIRS "${EPOXY_INCLUDE_DIR}")
+        list(APPEND glfw_PKG_DEPS "epoxy")
     endif()
 
 endif()

docs/build.dox

@@ -80,6 +80,9 @@ header instead of the regular OpenGL header.
 `GLFW_INCLUDE_ES31` makes the GLFW header include the OpenGL ES 3.1 `GLES3/gl31.h`
 header instead of the regular OpenGL header.
 
+`GLFW_INCLUDE_EPOXY` makes the GLFW header include the libepoxy `epoxy/gl.h`
+header instead of the regular OpenGL header.
+
 `GLFW_INCLUDE_NONE` makes the GLFW header not include any OpenGL or OpenGL ES API
 header.  This is useful in combination with an extension loading library.
 

docs/compile.dox

@@ -281,6 +281,8 @@ through extensions.  The options are:
    OpenGL.framework)
  - `_GLFW_USE_GLESV1` for OpenGL ES 1.x (experimental)
  - `_GLFW_USE_GLESV2` for OpenGL ES 2.x (experimental)
+ - `_GLFW_USE_EPOXY` for libepoxy to resolve which of the three previous ones
+   to use at runtime.
 
 Note that `_GLFW_USE_GLESV1` and `_GLFW_USE_GLESV2` may only be used with EGL,
 as the other context creation APIs do not interface with OpenGL ES client

include/GLFW/glfw3.h

@@ -149,6 +149,8 @@ extern "C" {
   #if defined(GLFW_INCLUDE_GLEXT)
    #include <GLES3/gl2ext.h>
   #endif
+ #elif defined(GLFW_INCLUDE_EPOXY)
+  #include <epoxy/gl.h>
  #elif !defined(GLFW_INCLUDE_NONE)
   #include <GL/gl.h>
   #if defined(GLFW_INCLUDE_GLEXT)

src/glfw_config.h.in

@@ -78,4 +78,6 @@
 #cmakedefine _GLFW_USE_GLESV1
 // Define this to 1 if using OpenGL ES 2.0 as the client library
 #cmakedefine _GLFW_USE_GLESV2
+// Define this to 1 if using libepoxy as the client library
+#cmakedefine _GLFW_USE_EPOXY
 

src/internal.h

@@ -52,6 +52,8 @@
  #define GLFW_INCLUDE_ES1
 #elif defined(_GLFW_USE_GLESV2)
  #define GLFW_INCLUDE_ES2
+#elif defined(_GLFW_USE_EPOXY)
+ #define GLFW_INCLUDE_EPOXY
 #else
  #error "No supported client library selected"
 #endif