如何检查 Linux 控制台屏幕保护程序是否黑屏

Question

有没有办法以编程方式（通过 ioctl() 等）或通过读取 /sys、/proc 或 /dev 中的文件）检查屏幕是否已被 Linux 控制台屏幕保护程序清空？

谢谢并致以最诚挚的问候，

冈特

Answer 1

好的，检查了 xset 源代码。相关的代码部分是

#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");
            }
        }
    }
}

为了以防万一其他人需要这个;-)

Answer 2

您可以使用 DISPLAY 设置来解析 xset q 的输出，但这并不漂亮。

$ 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

Answer 3

我使用 ctypes 在 Python 中对 Günter 的代码进行了等效实现。

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

调用示例位于我的github上。

Answer 4

我已经很久没有做过任何桌面开发了，但记忆告诉我，大多数 Linux 屏幕保护程序都是由 xscreensaver 执行的 - 可能会检查进程是否正在运行，或者检查其源代码以查看是否设置了任何系统状态，或者在项目邮件列表上询问会产生一些结果。
当然，KDE 和 Gnome 现在可能有单独的屏幕保护程序实现 - 不幸的是，Linux GUI 几乎没有统一性......

Answer 5

我正在使用此脚本来读取 DPMS 信息。效果很好！它是用 PHP 编写的，但您可以看到它是如何工作的。

<?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}'");
?>