X11::Protocol::Ext::MIT_SCREEN_SAVER(3)

NAME
X11::Protocol::Ext::MIT_SCREEN_SAVER - external screen saver support

SYNOPSIS
 use X11::Protocol;
 my $X = X11::Protocol->new;
 $X->init_extension('MIT-SCREEN-SAVER')
   or print "MIT-SCREEN-SAVER extension not available";

DESCRIPTION
The MIT-SCREEN-SAVER extension allows a client screen saver program to draw a screen saver. Any client can listen for screen saver activation too.

A screen saver program registers itself and desired window attributes with MitScreenSaverSetAttributes() and selects saver notify events with MitScreenSaverSelectInput(). There can only be one external saver program at any one time.

See examples/mit-screen-saver-external.pl for a complete screen saver program.

See the core SetScreenSaver() for the usual screen idle timeout, saver cycle period, and the "Blank" or "Internal" builtin saver styles. See the core ForceScreenSaver() to forcibly turn on the screen saver.

REQUESTS
The following requests are made available with an init_extension() per "EXTENSIONS" in X11::Protocol.

    my $bool = $X->init_extension('MIT-SCREEN-SAVER');

"($server_major, $server_minor) = $X->MitScreenSaverQueryVersion ($client_major, $client_minor)"
    Negotiate a protocol version with the server. $client_major and $client_minor is what the client would like, the returned $server_major and $server_minor is what the server will do, which will be the closest to the client requested version that the server supports.

    The code in this module supports 1.0. The intention would be to automatically negotiate within init_extension() if/when necessary.

"($state, $window, $til_or_since, $idle, $event_mask, $kind) = $X->MitScreenSaverQueryInfo ($drawable)"
    Return information about the screen saver on the screen of $drawable (an integer XID).

    $state is an enum string "Off", "On", or "Disabled", per "MitScreenSaverState" below.

    $window is the screen saver window, or "None". When this window exists it's an override-redirect child of the root window but it doesn't appear in the QueryTree() children of the root. This window exists when an External saver is activated but might not exist at other times (in which case $window is "None").

    $til_or_since is a period in milliseconds. If $state is "Off" then it's how long until the saver will be activated due to idle. If $state is "On" then it's how long in milliseconds since the saver was activated. But see "BUGS" below.

    $idle is how long in milliseconds the screen has been idle. In the X.org servers this is also available as an "IDLETIME" counter in the SYNC extension (see X11::Protocol::Ext::SYNC).

    $event_mask is the current client's mask as set by MitScreenSaverSelectInput() below.

    $kind is an enum string "Blanked", "Internal" or "External" for how the saver is being done now or how it will be done when next activated, per "MitScreenSaverKind" below.

"$X->MitScreenSaverSelectInput ($drawable, $event_mask)"
    Select "MitScreenSaverNotify" events from the screen of $drawable (an XID). $event_mask has two bits,

                      bitpos  bitval
        NotifyMask      0      0x01
        CycleMask       1      0x02

    There's no pack function for these yet, so just give the integer bitvals, for example 0x03 for both.

"$X->MitScreenSaverSetAttributes ($drawable, $class, $depth, $visual, $x, $y, $width, $height, $border_width, key => value, ...)"
    Setup the screen saver window on the screen of $drawable (an XID).

    The arguments are the same as the core CreateWindow(), except there's no new XID to create and the parent window is always the root window on the screen of $drawable ($drawable could be the root window already).

    This setup makes the saver "External" kind on its next activation. If the saver is currently active then it's not changed. The client can listen for "MitScreenSaverNotify" (see "EVENTS" below) to know when the saver is activated. The saver window XID is reported in that Notify and exposures etc can be selected on it at that time to know when to draw, unless perhaps a background pixel or pixmap in this MitScreenSaverSetAttributes() is enough.

    Only one client at a time can setup a saver window like this. If another has done so then an "Access" error results.

"$X->MitScreenSaverUnsetAttributes ($drawable)"
    Unset the screen saver window. If the client did not set the window then do nothing.

    This changes the saver from "External" kind back to the server builtin. If the screen saver is currently active then that happens immediately.

    At client shutdown an Unset is done automatically, unless "RetainPermanent" closedown mode.

EVENTS
"MitScreenSaverNotify" events are sent to the client when selected by MitScreenSaverSelectInput() above. These events report when the screen saver state changes. The event has the usual fields

    name             "MitScreenSaverNotify"
    synthetic        true if from a SendEvent
    code             integer opcode
    sequence_number  integer

and event-specific fields

    state         "Off", "On", "Cycle"
    time          server timestamp (integer)
    root          root window of affected screen (XID)
    window        the screen saver window (XID)
    kind          "Blanked", "Internal", "External"
    forced        integer 0 or 1

"state" is "Off" if the saver has turned off or "On" if it turned on. "forced" is 1 if the change was due to a ForceScreenSaver() request rather than user activity/inactivity. On/Off events are selected by NotifyMask to MitScreenSaverSelectInput() above.

"state" is "Cycle" if the saver cycling period has expired, which means it's time to show something different. This is selected by CycleMask to MitScreenSaverSelectInput() above.

"kind" is the current saver kind per "MitScreenSaverKind" below.

ENUM TYPES
The following types are available for "$X->interp()" and "$X->num()" after init_extension().

MitScreenSaverKind
        "Blanked"    0     video output turned off
        "Internal"   1     server builtin saver
        "External"   2     external saver client

MitScreenSaverState
    The state of the screen saver, as returned by MitScreenSaverQueryInfo() and in "MitScreenSaverNotify" events.

        "Off"         0
        "On"          1
        "Cycle"       2
        "Disabled"    3

For example,

    my $num = $X->num("MitScreenSaverKind", "External");
    # sets $num to 2

BUGS
In XFree86 and X.org servers through to circa X.org 1.10, if the screen saver is activated with a ForceScreenSaver() request then the $til_or_since from MitScreenSaverQueryInfo() is a big number, apparently being a negative for the future time when it would have activated due to idle. There's no attempt to do anything about that here.

Also in these servers when the saver is "On" the idle timeout apparently continues to fire too, so the "since" of $til_or_since is only since the last firing, as if screen saver was re-activated, not the time since first activated, or something like that.

SEE ALSO
X11::Protocol, X11::Protocol::Ext::DPMS

/usr/share/doc/x11proto-scrnsaver-dev/saver.txt.gz

xset(1), for setting the core screen saver parameters from the command line.

xscreensaver(1), xssstate(1), xprintidle(1), X11::IdleTime

HOME PAGE
<http://user42.tuxfamily.org/x11-protocol-other/index.html>

LICENSE
Copyright 2011, 2012, 2013, 2014, 2016, 2017 Kevin Ryde

X11-Protocol-Other is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

X11-Protocol-Other is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with X11-Protocol-Other. If not, see <http://www.gnu.org/licenses/>.