-# vi configure
-# add inc_<name> <inc_paths>
-# add add_library name <lib_paths>
-# add probe call if the library may be already in system
-# fix forced_libs list: for lib in $forced_libs; do
-# add dependencies (order matters): for dep in <pairs>; do
+# vi ../configure.ac
+# add PKG_3RD(pkg,<yes/no/auto>, <ver_basename>, <lib_paths>, <inc_paths>)
+# add CHECK_LIB(pkg, <syslib>, <entry_pt>, [opt libs]) if may be in system
+# add CHECK_HEADERS(pkg, <title>, <entry_pt>) to check for devel headers
+# add CHECK_WANT(<want>, <title>, [ checks ]) around tests if conditional
+# see openexr check for example if c++ lib
+# add PKG_PROVIDE(pkg,<cond>) to instance pkg if probe succeeds
+# add to exec > global_config if additional environment needed