Bugfix: ensure floating windows don’t drop out of fullscreen when restarting

fixes #1263

src/manage.c

@@ -328,8 +328,11 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki
         fs = con_get_fullscreen_con(croot, CF_GLOBAL);
 
     if (xcb_reply_contains_atom(state_reply, A__NET_WM_STATE_FULLSCREEN)) {
-        fs = NULL;
+        /* If this window is already fullscreen (after restarting!), skip
+         * toggling fullscreen, that would drop it out of fullscreen mode. */
+        if (fs != nc)
             con_toggle_fullscreen(nc, CF_OUTPUT);
+        fs = NULL;
     }
 
     bool set_focus = false;

testcases/t/230-floating-fullscreen-restart.t

@@ -0,0 +1,46 @@
+#!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)
+#
+# Ensures floating windows don’t drop out of fullscreen mode when restarting.
+# Ticket: #1263
+# Bug still in: 4.7.2-200-g570b572
+use i3test i3_autostart => 0;
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+for_window [instance=__i3-test-window] floating enable, border pixel 1
+EOT
+
+my $pid = launch_with_config($config);
+my $tmp = fresh_workspace;
+
+my $window = open_window(wm_class => '__i3-test-window');
+
+cmd 'fullscreen';
+
+my ($nodes, $focus) = get_ws($tmp);
+is($nodes->{floating_nodes}->[0]->{nodes}->[0]->{fullscreen_mode}, 1, 'floating window in fullscreen mode');
+
+cmd 'restart';
+
+($nodes, $focus) = get_ws($tmp);
+is($nodes->{floating_nodes}->[0]->{nodes}->[0]->{fullscreen_mode}, 1, 'floating window still in fullscreen mode');
+
+exit_gracefully($pid);
+
+done_testing;