How to check if Linux console screensaver has blanked screen

is there a way to check programmatically (via ioctl(), etc.) or by reading a file in /sys, /proc or /dev) whether the screen has been blanked by the Linux console screensaver?

Thanks and best regards,

Günter

You can parse the output of xset q with DISPLAY set, but it's not pretty.

$ xset q
Keyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000000
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    off    02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:       off
    06: Suspend:     off    07: Mute:        off    08: Misc:        off
    09: Mail:        off    10: Charging:    off    11: Shift Lock:  off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  250    repeat rate:  30
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  20/10    threshold:  4
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  0    cycle:  600
Colors:
  default colormap:  0x20    BlackPixel:  0    WhitePixel:  16777215
Font Path:
  /usr/share/fonts/misc,/usr/share/fonts/100dpi:unscaled,/usr/share/fonts/75dpi:unscaled,/usr/share/fonts/TTF,/usr/share/fonts/Type1,/usr/share/fonts/misc/,/usr/share/fonts/TTF/,/usr/share/fonts/Type1/,/usr/share/fonts/100dpi/,/usr/share/fonts/75dpi/,built-ins
DPMS (Energy Star):
  Standby: 1200    Suspend: 1800    Off: 0
  DPMS is Enabled
  Monitor is On
Font cache:
  Server does not have the FontCache Extension

Okay, checked the xset source code. The relevant code parts are

#include <X11/extensions/dpms.h>
...
Display* dpy = XOpenDisplay(NULL);
...
int dummy;
CARD16 standby, suspend, off;
BOOL onoff;
CARD16 state;

printf("DPMS (Energy Star):\n");
if (DPMSQueryExtension(dpy, &dummy, &dummy)) 
{
    if (DPMSCapable(dpy)) 
    {
        DPMSGetTimeouts(dpy, &standby, &suspend, &off);
        printf ("  Standby: %d    Suspend: %d    Off: %d\n",
                standby, suspend, off);
        DPMSInfo(dpy, &state, &onoff);
        if (onoff) 
        {
            printf("  DPMS is Enabled\n");
            switch (state) 
            {
            case DPMSModeOn:
                printf("  Monitor is On\n");
                break;
            case DPMSModeStandby:
                printf("  Monitor is in Standby\n");
                break;
            case DPMSModeSuspend:
                printf("  Monitor is in Suspend\n");
                break;
            case DPMSModeOff:
                printf("  Monitor is Off\n");
                break;
            default:
                printf("  Unrecognized response from server\n");
            }
        }
    }
}

Just in case anyone else needs this ;-)

I made an equivalent implementation of Günter's code in Python with ctypes.

import ctypes
import struct

ctypes.cdll.LoadLibrary('libXext.so')
libXext = ctypes.CDLL('libXext.so')

DPMSFAIL = -1
DPMSModeOn = 0
DPMSModeStandby = 1
DPMSModeSuspend = 2
DPMSModeOff = 3


def get_DPMS_state(display_name_in_byte_string=b':0'):
    state = DPMSFAIL
    if not isinstance(display_name_in_byte_string, bytes):
        raise TypeError
    display_name = ctypes.c_char_p()
    display_name.value = display_name_in_byte_string
    libXext.XOpenDisplay.restype = ctypes.c_void_p
    display = ctypes.c_void_p(libXext.XOpenDisplay(display_name))
    dummy1_i_p = ctypes.create_string_buffer(8)
    dummy2_i_p = ctypes.create_string_buffer(8)
    if display.value:
        if libXext.DPMSQueryExtension(display, dummy1_i_p, dummy2_i_p)\
           and libXext.DPMSCapable(display):
            onoff_p = ctypes.create_string_buffer(1)
            state_p = ctypes.create_string_buffer(2)
            if libXext.DPMSInfo(display, state_p, onoff_p):
                onoff = struct.unpack('B', onoff_p.raw)[0]
                if onoff:
                    state = struct.unpack('H', state_p.raw)[0]
        libXext.XCloseDisplay(display)
    return state

Calling sample is on my github.

I haven't done any desktop development in ages, but memory tells me that most linux screensavers were being executed by xscreensaver - maybe checking whether the process is running, or going through its source-code to see for any system-state being set, or asking on the project maillist would yield some results. Of course KDE and Gnome might have separate screensaver implementations by now - there is very little uniformity when it comes to linux GUIs, unfortunately...

I'm using this script to read DPMS info. It works great! Its written in PHP, but you can see the idea how it works.

<?php
if ( !$pid = exec('pidof X') )
    return !trigger_error(E_USER_WARNING,'Could not find pid of X');

if ( !$data = file_get_contents("/proc/$pid/cmdline") )
    return !trigger_error(E_USER_WARNING,"Cound not read pid info (/proc/$pid/cmdline)");

$data = explode(chr(0),$data);
foreach($data as $key => $line) {
    if ( $line == "-auth" ) {
        $auth = $data[$key+1];
        break;
    }
}

if ( !isset($auth) )
    return !trigger_error(E_USER_WARNING,'Could not find XAUTHORITY in xinit process environment');

echo exec("export DISPLAY=:0; export XAUTHORITY={$auth}; export PATH=\${PATH}:/usr/X11R6/bin; xset -q | grep \"Monitor is\" | awk '{print $3}'");
?>

来源：https://stackoverflow.com/questions/3819255/how-to-check-if-linux-console-screensaver-has-blanked-screen

标签

Linux

console

screensaver