Ubuntu Manpage: X11::Protocol::Ext::DAMAGE

Provided by: libx11-protocol-other-perl_31-1_all

NAME

       X11::Protocol::Ext::DAMAGE - drawing notifications

SYNOPSIS

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

        my $damage = $X->new_rsrc;
        $X->DamageCreate ($damage, $drawable, 'NonEmpty');

        sub my_event_handler {
          my %h = @_;
          if ($h{'name'} eq 'DamageNotify') {
            my $drawable = $h{'drawable'};
            $X->DamageSubtract ($damage, 'None', $parts_region);
            # do something for $parts_region changed in $drawable
          }
        }

DESCRIPTION

       The DAMAGE extension lets a client listen for changes to drawables (windows, pixmaps, etc) due to drawing
       operations, including drawing into sub-windows which appears in the parent.

       This can be used for various kinds of efficient copying or replicating of window contents, such as
       cloning to another screen, showing a magnified view, etc.  The root window can be monitored to get
       changes on the whole screen.

       Content changes due to drawing are conceived as "damage".  A server-side damage object accumulates areas
       as rectangles to make a server-side "region" per the XFIXES 2.0 extension (see
       X11::Protocol::Ext::XFIXES)

       A DamageNotify event is sent from a damage object.  A reporting level controls the level of detail,
       ranging from just one event on becoming non-empty, up to an event for every drawing operation affecting
       the relevant drawable.

       Fetching an accumulated damage region (or part of it) is reckoned as a "repair".  It doesn't change any
       drawables in any way, just fetches the region from the damage object.  This fetch is atomic, so nothing
       is lost if the listening client is a bit lagged etc.

       See examples/damage-duplicate.pl for one way to use damage to duplicate a window in real-time.

REQUESTS

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

           my $is_available = $X->init_extension('DAMAGE');

   DAMAGE 1.0
       "($server_major, $server_minor) = $X->DamageQueryVersion ($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 might be
           less than requested (but not more).

           The current code supports up to 1.1.  If asking for higher then be careful that it's upwardly
           compatible.  The module code negotiates a version in "init_extension()" so explicit
           "DamageQueryVersion()" is normally not needed.

       "$X->DamageCreate ($damage, $drawable, $level)"
           Create a new damage object in $damage (a new XID) which monitors changes to $drawable.  If $drawable
           is a window then changes to its subwindows are included too.

               # listening to every change on the whole screen
               my $damage = $X->new_rsrc;
               $X->DamageCreate ($damage, $X->root, 'RawRectangles');

           $level is an enum string controlling how often "DamageNotify" events are emitted (see "EVENTS"
           below).

               RawRectangles      every change
               DeltaRectangles    when damage region expands
               BoundingBox        when damage bounding box expands
               NonEmpty           when damage first becomes non-empty

       "$X->DamageDestroy ($damage)"
           Destroy $damage.

       "$X->DamageSubtract ($damage, $repair_region, $parts_region)"
           Move the accumulated region in $damage to $parts_region (a region XID), and clear it from $damage.

           If $parts_region is "None" then $damage is cleared and the region discarded.  This can be used if for
           example the entire $drawable will be copied or re-examined, so the exact parts are not needed.

           $repair_region is what portion of $damage to consider.  "None" means move and clear everything in
           $damage.  Otherwise $repair_region is a region XID and the portion of the damage region within
           $repair_region is moved and cleared.  Anything outside is left in $damage.

           If anything is left in $damage then a new "DamageNotify" event is immediately sent.  This can be good
           for instance if you picked out a $repair_region corresponding to what you thought was the window size
           (perhaps from the "geometry" field of a "DamageNotify" event), but it has grown in the interim.

           Region objects here can be created with the XFIXES 2.0 extension (see X11::Protocol::Ext::XFIXES).
           It should be available whenever DAMAGE is available.  If using "None" and "None" to clear and discard
           then region objects are not required and there's no need for an "init_extension('XFIXES')".

   DAMAGE 1.1
       "$X->DamageAdd ($drawable, $region)"
           Report to any interested damage objects that changes have occurred in $region (a region XID) of
           $drawable.

           This is used by clients which modify a drawable in ways not seen by the normal protocol drawing
           operations.  For example an MIT-SHM shared memory pixmap modified by writing to the memory (see
           X11::Protocol::Ext::MIT_SHM), or the various "direct rendering" to graphics hardware or GL etc.

EVENTS

"DamageNotify" events are sent to the client which created the damage object. These events are always
generated, there's nothing to select or deselect them. The event has the usual fields

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

and event-specific fields

damage XID, damage object
drawable XID, as from DamageCreate
level enum, as from DamageCreate
more boolean, if more DamageNotify on the way
time integer, server timestamp
area arrayref [$x,$y,$width,$height]
geometry arrayref [$rootx,$rooty,$width,$height]

"drawable" and "level" are as from the "DamageCreate()" which made the "damage" object.

"more" is true if there's further "DamageNotify" events on the way for this damage object. This can
happen when the "level" means there's a set of "area" rectangles to report.

"area" is a rectangle within "drawable", as a 4-element arrayref,

[ $x, $y, $width, $height ]

What it covers depends on the reporting level requested,

• "RawRectangles" -- a rectangle around an arc, line, etc, drawing operation which changed "drawable".

• "DeltaRectangles" -- an additional rectangle extending the damage region. Only new rectangles are
reported, not any of the existing damage region. Reporting a region addition may require multiple
"DamageNotify" events.

• "BoundingBox" -- a bounding box around the damage region accumulated, bigger than previously
reported.

• "NonEmpty" -- umm, something, maybe the entire drawable.

"geometry" is the current size and position of the drawable as a 4-element arrayref in root window
coordinates. For a pixmap $root_x and $root_y are 0.

[ $root_x, $root_y, $width, $height ]

ENUM TYPES

       The reporting level above is type "DamageReportLevel".  So for example (after a successful
       "$X->init_extension('DAMAGE')"),

           $number = $X->num('DamageReportLevel', 'RawRectangles');

           $string = $X->interp('DamageReportLevel', 3);

       See "SYMBOLIC CONSTANTS" in X11::Protocol.

ERRORS

       Error type "Damage" is a bad $damage resource XID in a request.

BUGS

       The server extension version number is queried in the "init_extension()", but not yet made available as
       such.  The version determines whether "DamageAdd()" ought to work.  Currently that request is always
       setup, but presumably generates an Opcode error if the server doesn't have it.

HOME PAGE

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

LICENSE

       Copyright 2011, 2012, 2013, 2014, 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/>.