Alpar had the key, focus can be set in the window class. But it is not enough, the focused widget has to be activated, as well! Was a hard task to find out... By the way, two compilation warnings are removed.

AM_CPPFLAGS = -I$(top_srcdir)

noinst_HEADERS = bench_tools.h

noinst_PROGRAMS = graph-bench hcube bfs-bench

graph_bench_SOURCES = graph-bench.cc

hcube_SOURCES = hcube.cc

bfs_bench_SOURCES = bfs-bench.cc