X Display Power Management Signaling (DPMS) Extension

X Consortium Standard

Rob Lembree

   Digital Equipment Corporation
   <lembree@zk3.dec.com>

   X Version 11, Release 7.7

   Version 1.0

   Copyright © 1996 Digital Equipment Corporation

   Permission to use, copy, modify, distribute, and sell this
   documentation for any purpose is hereby granted without fee,
   provided that the above copyright notice and this permission
   notice appear in all copies. Digital Equipment Corporation
   makes no representations about the suitability for any purpose
   of the information in this document. This documentation is
   provided "as is" without express or implied warranty.

   X Window System is a trademark of The Open Group.
     __________________________________________________________

   Table of Contents

   1. Overview
   2. DPMS Functions

Chapter 1. Overview

   This extension provides X Protocol control over the VESA
   Display Power Management Signaling (DPMS) characteristics of
   video boards under control of the X Window System.

   Traditionally, the X Window System has provided for both
   blanking and non-blanking screen savers. Timeouts associated
   with these built-in screen saver mechanisms are limited to idle
   (dwell) time, and a change timeout that specifies the change
   interval for non-blanking screen savers.

   The United States' Environmental Protection Agency (EPA) Energy
   Star program requires that monitors power down after some idle
   time by default. While it is possible to simply overload the
   existing screen saver timeouts, this solution leaves the
   non-privileged user little to no control over the DPMS
   characteristics of his or her system. For example, disabling
   DPMS would require some unintended side effect in the core
   screen saver, such as disabling the changing of a non-blanking
   screen saver. Providing clients with this control requires an
   extension to the core X Window System Protocol, and this
   extension seeks to fill this gap.

   There are four power levels specified by the Video Electronics
   Standards Association (VESA) Display Power Management Signaling
   (DPMS) standard. These are mapped onto the X DPMS Extension
   like this:

   DPMS Extension Power Levels
        0     DPMSModeOn               In use
        1     DPMSModeStandby          Blanked, low power
        2     DPMSModeSuspend          Blanked, lower power
        3     DPMSModeOff               Shut off, awaiting activit
   y

Chapter 2. DPMS Functions

   Bool DPMSQueryExtention(Display *display, int event_base, int
   error_base);

   *display

   Specifies the connection to the X server.

   event_base

   Specifies the return location for the assigned base event

   error_base

   Specifies the return location for the assigned base error

   The DPMSQueryExtension function queries the X server to
   determine the availability of the DPMS Extension. If the
   extension is available, the return value is TRUE, and
   event_base and error_base are set to the base event number and
   base error number for the extension, respectively. Otherwise,
   the return value is FALSE, and the values of event_base and
   error_base are undefined.

   Status DPMSGetVersion(Display *display, int *major_version, int
   *minor_version);

   display

   Specifies the connection to the X server.

   major_version

   Specifies the return location for the extension major version.

   minor_version

   Specifies the return location for the extension minor version.

   The DPMSGetVersion function returns the version of the DPMS
   extension implemented by the X server. The version is returned
   in major_version and minor_version. The major version and minor
   version for this specification are '1' and '1', respectively.
   The major version will be incremented for protocol incompatible
   changes, and the minor version will be incremented for small,
   upwardly compatible changes.

   Bool DPMSCapable(Display *display);

   display

   Specifies the connection to the X server.

   The DPMSCapable function returns the DPMS capability of the X
   server, either TRUE (capable of DPMS) or FALSE (incapable of
   DPMS). The capability of an X server is implementation defined.
   For example, if a multi-headed X server is capable of DPMS on
   one head, and incapable on another, the truth value of this
   function is defined by the X server implementation.

   Status DPMSSetTimeouts(Display *display, CARD16 standby, CARD16
   suspend, CARD16 off);

   display

   Specifies the connection to the X server.

   standby

   Specifies the new standby timeout in seconds.

   suspend

   Specifies the new suspend timeout in seconds.

   off

   Specifies the new off timeout in seconds.

   The DPMSSetTimeouts function permits applications to set the
   timeout values used by the X server for DPMS timings.

   The value standby is the amount of time of inactivity in
   seconds before standby mode is invoked. The actual effects of
   this mode are implementation defined, but in the case of DPMS
   compliant hardware, it is implemented by shutting off the
   horizontal sync signal, and pulsing the vertical sync signal.
   Standby mode provides the quickest monitor recovery time. Note
   also that many monitors implement this mode identically to
   suspend mode. A value of zero disables this mode.

   The value suspend is the amount of time of inactivity in
   seconds before the second level of power savings is invoked.
   Suspend mode's physical and electrical characteristics are
   implementation defined, but in DPMS compliant hardware, results
   in the pulsing of the horizontal sync signal, and shutting off
   of the vertical sync signal. Suspend mode recovery is
   considered to be slower than standby mode, but faster than off
   mode, however this is monitor dependent. As noted above, many
   monitors implement this mode identically to standby mode. A
   value of zero disables this mode.

   The value off is the amount of time of inactivity in seconds
   before the third and final level of power savings is invoked.
   Off mode's physical and electrical characteristics are
   implementation defined, but in DPMS compliant hardware, is
   implemented by shutting off both horizontal and vertical sync
   signals, resulting in the power-down of the monitor. Recovery
   time is implementation dependant, but frequently is similar to
   the power-up time of the monitor. A value of zero disables this
   mode.

   Chronologically, standby mode occurs before or simultaneously
   with suspend mode, and suspend mode must occur before or
   simultaneously with off mode. Therefore, non-zero mode timeout
   values must be greater than or equal to the timeout values of
   earlier modes. If inconsistent values are supplied, a BadValue
   error will result.

   Status DPMSGetTimeouts(Display *display, CARD16 *standby,
   CARD16 *suspend, CARD16 *off);

   display

   Specifies the connection to the X server.

   standby

   Specifies the new standby timeout in seconds.

   suspend

   Specifies the new suspend timeout in seconds.

   off

   Specifies the new off timeout in seconds.

   The DPMSGetTimeouts function retrieves the timeout values used
   by the X server for DPMS timings.

   The value standby is the amount of time of inactivity in
   seconds before standby mode is invoked. A value of zero
   indicates that this mode has been disabled.

   The value suspend is the amount of time of inactivity in
   seconds before the second level of power savings is invoked. A
   value of zero indicates that this mode has been disabled.

   The value off is the amount of time of inactivity in seconds
   before the third and final level of power savings is invoked. A
   value of zero indicates that this mode has been disabled.

   Status DPMSEnable(Display *display);

   display

   Specifies the connection to the X server.

   The DPMSEnable function enables DPMS on the specified display.
   When enabled, DPMS will use the currently saved timeout values,
   and will invoke the DPMS power mode appropriate for the amount
   of time that the workstation input devices have been idle. If
   DPMSEnable is invoked on a display with DPMS already enabled,
   no change is made, and no error is returned. If DPMSEnable is
   invoked on a display without support for DPMS, no change is
   made and no error is returned.

   Status DPMSDisable(Display *display);

   display

   Specifies the connection to the X server.

   The DPMSDisable function disables DPMS on the specified
   display. When disabled, DPMS returns the display to DPMSModeOn.
   If DPMSDisable is invoked on a display with DPMS already
   disabled, no change is made, and no error is returned. If
   DPMSDisable is invoked on a display without support for DPMS,
   no change is made and no error is returned.

   Status DPMSForceLevel(Display *display, CARD16 level);

   display

   Specifies the connection to the X server.

   level

   Specifies the level to force power to.

   The DPMSForceLevel function forces a DPMS capable display into
   the specified power level. The level must be one of DPMSModeOn,
   DPMSModeStandby, DPMSModeSuspend, or DPMSModeOff. Values other
   than these will result in a BadValue error. If DPMS is disabled
   on the display, a BadMatch protocol error will result.

   Status DPMSInfo(display, power_level, state)

   Status DPMSInfo(Display *display, CARD16 power_level, BOOL
   *state);

   display

   Specifies the connection to the X server.

   power_level

   Specifies the current power level.

   state

   Specifies the current DPMS state.

   The DPMSInfo function returns information about the current
   DPMS state. The state return parameter indicates whether or not
   DPMS is enabled (TRUE) or disabled (FALSE). The power_level
   return parameter indicates the current power level (one of
   DPMSModeOn, DPMSModeStandby, DPMSModeSuspend, or DPMSModeOff.)
