-# For glext headers. Needs to be before system includes as often system's GL
-# headers bundle and include glext.h and glxext.h
-include_directories (BEFORE ${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/glext)
-
-# For EGL headers
-include_directories (${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/khr)
+# We use bundled headers for all Khronos APIs, to guarantee support for both
+# OpenGL and OpenGL ES at build time, because the OpenGL and OpenGL ES 1 APIs
+# are so intertwined that conditional compilation extremely difficult. This
+# also avoids missing/inconsistent declarations in system headers.
+include_directories (BEFORE ${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/khronos)