1GL_EXT_x11_sync_object 2http://www.opengl.org/registry/specs/EXT/x11_sync_object.txt 3GL_EXT_x11_sync_object 4 5 GL_SYNC_X11_FENCE_EXT 0x90E1 6 GLsync glImportSyncEXT (GLenum external_sync_type, GLintptr external_sync, GLbitfield flags) 7