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

Provided by: libx11-protocol-other-perl_28-1_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 in the "X11-Protocol-Other" sources 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 an
           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 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/>.