path: root/specs/dpmslib.xml

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<!-- lifted from troff+ms+XMan by doclifter -->
<book id="dpmslib">

<bookinfo>
   <title>X Display Power Management Signaling (DPMS) Extension</title>
   <subtitle>X Consortium Standard</subtitle>
   <releaseinfo>X Version 11, Release &fullrelvers;</releaseinfo>
   <releaseinfo>Version 1.0</releaseinfo>
   <authorgroup>
      <author>
         <firstname>Rob</firstname><surname>Lembree</surname>
         <affiliation><orgname>Digital Equipment Corporation</orgname></affiliation>
         <email>lembree@zk3.dec.com</email>
      </author>
   </authorgroup>
   <copyright><year>1996</year><holder>Digital Equipment Corporation</holder></copyright>

<legalnotice>
<para>
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.
</para>

<para>X Window System is a trademark of The Open Group.</para>
</legalnotice>

</bookinfo>

<chapter id='overview'>
<title>Overview</title>

<para>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.
</para>

<para>
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.
</para>

<para>
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.
</para>

<para>
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:
</para>

<literallayout remap='Ds'>
<function>DPMS Extension Power Levels</function>
     0     DPMSModeOn               In use
     1     DPMSModeStandby          Blanked, low power
     2     DPMSModeSuspend          Blanked, lower power
     3     DPMSModeOff               Shut off, awaiting activity
</literallayout> <!-- remap='De' -->

</chapter>

<chapter id='dpms_functions'>
<title>DPMS Functions</title>


<funcsynopsis id='DPMSQueryExtention'>
<funcprototype>
  <funcdef>Bool <function>DPMSQueryExtention</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>int <parameter>event_base</parameter></paramdef>
    <paramdef>int <parameter>error_base</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>*display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>event_base</emphasis></term>
    <listitem><para>Specifies the return location for the assigned base event</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>error_base</emphasis></term>
    <listitem><para>Specifies the return location for the assigned base error</para></listitem>
  </varlistentry>
</variablelist>

<para>
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 <emphasis remap='I'>event_base</emphasis> and
<emphasis remap='I'>error_base</emphasis> 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
<emphasis remap='I'>event_base</emphasis> and
<emphasis remap='I'>error_base</emphasis> are undefined.
</para>

<funcsynopsis id='DPMSGetVersion'>
<funcprototype>
  <funcdef>Status <function>DPMSGetVersion</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>int <parameter>*major_version</parameter></paramdef>
    <paramdef>int <parameter>*minor_version</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>major_version</emphasis></term>
    <listitem><para>Specifies the return location for the extension major version.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>minor_version</emphasis></term>
    <listitem><para>Specifies the return location for the extension minor version.</para></listitem>
  </varlistentry>
</variablelist>


<para>
The DPMSGetVersion function returns the version of the DPMS extension
implemented by the X server.  The version is returned in
<emphasis remap='I'>major_version</emphasis> and
<emphasis remap='I'>minor_version</emphasis>.
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.
</para>

<funcsynopsis id='DPMSCapable'>
<funcprototype>
  <funcdef>Bool <function>DPMSCapable</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
</variablelist>


<para>
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.
</para>

<funcsynopsis id='DPMSSetTimeouts'>
<funcprototype>
  <funcdef>Status <function>DPMSSetTimeouts</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>CARD16 <parameter>standby</parameter></paramdef>
    <paramdef>CARD16 <parameter>suspend</parameter></paramdef>
    <paramdef>CARD16 <parameter>off</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>standby</emphasis></term>
    <listitem><para>Specifies the new standby timeout in seconds.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>suspend</emphasis></term>
    <listitem><para>Specifies the new suspend timeout in seconds.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>off</emphasis></term>
    <listitem><para>Specifies the new off timeout in seconds.</para></listitem>
  </varlistentry>
</variablelist>

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

<para>
The value <emphasis remap='I'>standby</emphasis> 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.
</para>

<para>
The value <emphasis remap='I'>suspend</emphasis> 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.
</para>

<para>
The value <emphasis remap='I'>off</emphasis> 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 dependent,
but frequently is similar to the power-up time of the monitor.  A value
of zero disables this mode.
</para>

<para>
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.
</para>

<funcsynopsis id='DPMSGetTimeouts'>
<funcprototype>
  <funcdef>Status <function>DPMSGetTimeouts</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>CARD16 <parameter>*standby</parameter></paramdef>
    <paramdef>CARD16 <parameter>*suspend</parameter></paramdef>
    <paramdef>CARD16 <parameter>*off</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>standby</emphasis></term>
    <listitem><para>Specifies the new standby timeout in seconds.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>suspend</emphasis></term>
    <listitem><para>Specifies the new suspend timeout in seconds.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>off</emphasis></term>
    <listitem><para>Specifies the new off timeout in seconds.</para></listitem>
  </varlistentry>
</variablelist>

<para>
The DPMSGetTimeouts function retrieves the timeout values used by the X
server for DPMS timings.
</para>

<para>
The value <emphasis remap='I'>standby</emphasis> 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.
</para>

<para>
The value <emphasis remap='I'>suspend</emphasis> 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.
</para>

<para>
The value <emphasis remap='I'>off</emphasis> 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.
</para>

<funcsynopsis id='DPMSEnable'>
<funcprototype>
  <funcdef>Status <function>DPMSEnable</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
</variablelist>

<para>
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.
</para>

<funcsynopsis id='DPMSDisable'>
<funcprototype>
  <funcdef>Status <function>DPMSDisable</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
</variablelist>

<para>
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.
</para>

<funcsynopsis id='DPMSForceLevel'>
<funcprototype>
  <funcdef>Status <function>DPMSForceLevel</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>CARD16 <parameter>level</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>level</emphasis></term>
    <listitem><para>Specifies the level to force power to.</para></listitem>
  </varlistentry>
</variablelist>

<para>
The DPMSForceLevel function forces a DPMS capable display into the
specified power level.  The <emphasis remap='I'>level</emphasis> 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.
</para>

<para>Status DPMSInfo(<emphasis remap='I'>display, power_level, state</emphasis>)</para>

<funcsynopsis id='DPMSInfo'>
<funcprototype>
  <funcdef>Status <function>DPMSInfo</function></funcdef>
    <paramdef>Display <parameter>*display</parameter></paramdef>
    <paramdef>CARD16 <parameter>power_level</parameter></paramdef>
    <paramdef>BOOL <parameter>*state</parameter></paramdef>
</funcprototype>
</funcsynopsis>

<variablelist remap='IP'>
  <varlistentry>
    <term><emphasis remap='I'>display</emphasis></term>
    <listitem><para>Specifies the connection to the X server.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>power_level</emphasis></term>
    <listitem><para>Specifies the current power level.</para></listitem>
  </varlistentry>
  <varlistentry>
    <term><emphasis remap='I'>state</emphasis></term>
    <listitem><para>Specifies the current DPMS state.</para></listitem>
  </varlistentry>
</variablelist>

<para>
The DPMSInfo function returns information about the current DPMS state.
The <emphasis remap='I'>state</emphasis> return parameter indicates whether
or not DPMS is enabled (TRUE) or disabled (FALSE).  The
<emphasis remap='I'>power_level</emphasis> return parameter indicates the
current power level (one of DPMSModeOn, DPMSModeStandby, DPMSModeSuspend,
or DPMSModeOff.)
</para>

</chapter>
</book>