[Pkg-xfce-devel] Bug#776674: xfce4-session: xflock4 does not turn off screen due to xset dpms race condition

[Chris Bainbridge]

Package: xfce4-session
Version: 4.10.1-10
Severity: normal

Dear Maintainer,

/usr/bin/xflock4 does:

for lock_cmd in \
  "xlock -mode blank" \
  "slock"
   set -- $lock_cmd
    if command -v -- $1 >/dev/null 2>&1; then
        $lock_cmd >/dev/null 2>&1 &
        # turn off display backlight:
        xset dpms force off
        exit
    fi
done

But it does not work (presumably xset runs too quickly and slock turns the
monitor back on?)

It appears the xset call should be something like:

        sleep 1; xset dpms force off

Using a hardcoded sleep does not seem elegant, but it is the suggested fix at
http://askubuntu.com/questions/38776/trigger-screensaver-off-monitor and
https://wiki.archlinux.org/index.php/Display_Power_Management_Signaling

(Also, is there a purpose for doing "set -- $lock_cmd" when the process then
immediately calls exit?)



-- System Information:
Debian Release: 8.0
  APT prefers testing-updates
  APT policy: (500, 'testing-updates'), (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages xfce4-session depends on:
ii  libatk1.0-0            2.14.0-1
ii  libc6                  2.19-13
ii  libcairo2              1.14.0-2.1
ii  libdbus-1-3            1.8.12-3
ii  libdbus-glib-1-2       0.102-1
ii  libfontconfig1         2.11.0-6.3
ii  libfreetype6           2.5.2-2
ii  libgdk-pixbuf2.0-0     2.31.1-2+b1
ii  libglib2.0-0           2.42.1-1
ii  libgtk2.0-0            2.24.25-1
ii  libice6                2:1.0.9-1+b1
ii  libpango-1.0-0         1.36.8-3
ii  libpangocairo-1.0-0    1.36.8-3
ii  libpangoft2-1.0-0      1.36.8-3
ii  libpolkit-gobject-1-0  0.105-8
ii  libsm6                 2:1.2.2-1+b1
ii  libwnck22              2.30.7-2
ii  libx11-6               2:1.6.2-3
ii  libxfce4ui-1-0         4.10.0-6
ii  libxfce4util6          4.10.1-2
ii  libxfconf-0-2          4.10.0-3
ii  multiarch-support      2.19-13
ii  xfce4-settings         4.10.1-2
ii  xfconf                 4.10.0-3

Versions of packages xfce4-session recommends:
ii  dbus-x11           1.8.12-3
ii  libpam-systemd     215-10
ii  systemd-shim       9-1
ii  systemd-sysv       215-10
ii  upower             0.99.1-3.1
ii  x11-xserver-utils  7.7+3+b1
ii  xfdesktop4         4.10.2-3
ii  xfwm4              4.10.1-3
pn  xscreensaver       <none>

Versions of packages xfce4-session suggests:
pn  fortunes-mod  <none>
ii  sudo          1.8.10p3-1

-- no debconf information