Allow to validate the config file without X.

We're going to call parse_configuration() very early if -C is given on
the command line. Instead of the previous "only_check_config", which has
been a global variable, we now simply pass use_nagbar as false if we're
just validating.

This causes the whole parsing to run without X and of course without
starting nagbar and displaying the errors to standard out/error instead.

The return code of parse_configuration() is now a boolean which
represents whether an error occured during parsing and the programs exit
code is returned accordingly.

Although the config parser still has a lot of side-effects, we now can
parse without the need to have an XCB connection. A nicer implementation
would be to just set the new font and load it just after we're done
parsing, but to ensure we don't break functionality we just load a dummy
FONT_TYPE_NONE if XCB isn't available. The main reason for going this
route is that it's a bit difficult to test fonts in a distribution
agnostic way without bundling fonts with i3 (or Xdummy to be more
exact).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

testcases/t/235-check-config-no-x.t

@@ -0,0 +1,60 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Check whether the -C option works without a display and doesn't
+# accidentally start the nagbar.
+#
+use i3test i3_autostart => 0;
+use File::Temp qw(tempfile);
+
+sub check_config {
+    my ($config) = @_;
+    my ($fh, $tmpfile) = tempfile(UNLINK => 1);
+    print $fh $config;
+    my $output = qx(DISPLAY= ../i3 -C -c $tmpfile 2>&1);
+    my $retval = $?;
+    $fh->flush;
+    close($fh);
+    return ($retval >> 8, $output);
+}
+
+################################################################################
+# 1: test with a bogus configuration file
+################################################################################
+
+my $cfg = <<EOT;
+# i3 config file (v4)
+i_am_an_unknown_config option
+EOT
+
+my ($ret, $out) = check_config($cfg);
+is($ret, 1, "exit code == 1");
+like($out, qr/ERROR: *CONFIG: *[Ee]xpected.*tokens/, 'bogus config file');
+
+################################################################################
+# 2: test with a valid configuration file
+################################################################################
+
+my $cfg = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+EOT
+
+my ($ret, $out) = check_config($cfg);
+is($ret, 0, "exit code == 0");
+is($out, "", 'valid config file');
+
+done_testing;