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<title>X Composite Extension Library</title>
<refentry id='Xcomposite.man'>
<refentryinfo>
<productname>__vendorversion__</productname>
<pubdate>23 April 2007</pubdate>
<authorgroup>
<author><firstname>Keith</firstname><surname>Packard</surname>
<contrib>Extension specification and implementation</contrib>
<email>keithp@keithp.com</email>
</author>
<author><firstname>Deron</firstname><surname>Johnson</surname>
<contrib>Overlay Window specification and implementation</contrib>
<email>deron.johnson@sun.com</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>Xcomposite</refentrytitle>
<manvolnum>__libmansuffix__</manvolnum>
</refmeta>
<refnamediv>
<refname>Xcomposite</refname>
<refpurpose>X Composite Extension library</refpurpose>
</refnamediv>
<refsynopsisdiv><funcsynopsis>
<funcsynopsisinfo>#include <X11/extensions/Xcomposite.h></funcsynopsisinfo>
<funcprototype>
<funcdef>Bool <function>XCompositeQueryExtension</function></funcdef>
<paramdef><type>Display *</type><parameter>dpy</parameter></paramdef>
<paramdef>int *<parameter>event_basep</parameter></paramdef>
<paramdef>int *<parameter>error_basep</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>Status <function>XCompositeQueryVersion</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>int *<parameter>major_versionp</parameter></paramdef>
<paramdef>int *<parameter>minor_versionp</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>XCompositeVersion</function></funcdef>
<void />
</funcprototype>
<funcprototype>
<funcdef>void <function>XCompositeRedirectWindow</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
<paramdef>int <parameter>update</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>XCompositeRedirectSubwindows</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
<paramdef>int <parameter>update</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>XCompositeUnredirectWindow</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
<paramdef>int <parameter>update</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>XCompositeUnredirectSubwindows</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
<paramdef>int <parameter>update</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>XserverRegion <function>XCompositeCreateRegionFromBorderClip</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>Pixmap <function>XCompositeNameWindowPixmap</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>Window <function>XCompositeGetOverlayWindow</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>void <function>XCompositeReleaseOverlayWindow</function></funcdef>
<paramdef>Display *<parameter>dpy</parameter></paramdef>
<paramdef>Window <parameter>window</parameter></paramdef>
</funcprototype>
</funcsynopsis></refsynopsisdiv>
<refsect1><title>Description</title>
<para>
The composite extension provides several related mechanisms:
<variablelist>
<varlistentry>
<term>Per-hierarchy storage</term>
<listitem><para>
The rendering of an entire hierarchy of windows
is redirected to off-screen storage. The pixels of that hierarchy
are available whenever it is viewable. Storage is automatically
reallocated when the top level window changes size. Contents beyond
the geometry of the top window are not preserved.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Automatic shadow update</term>
<listitem><para>
When a hierarchy is rendered off-screen,
the X server provides an automatic mechanism for presenting those
contents within the parent window. The implementation is free to
make this update lag behind actual rendering operations by an
unspecified amount of time. This automatic update mechanism may
be disabled so that the parent window contents can be completely
determined by an external application.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Composite Overlay Window</term>
<listitem><para>
Version 0.3 of the protocol adds the Composite Overlay Window, which
provides compositing managers with a surface on which to draw without
interference. This window is always above normal windows and is always
below the screen saver window. It is an InputOutput window whose width
and height are the screen dimensions. Its visual is the root visual
and its border width is zero. Attempts to redirect it using the
composite extension are ignored. This window does not appear in the
reply of the QueryTree request. It is also an override redirect window.
These last two features make it invisible to window managers and other
X11 clients. The only way to access the XID of this window is via the
CompositeGetOverlayWindow request. Initially, the Composite Overlay
Window is unmapped.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Parent window clipping</term>
<listitem><para>
Version 0.4 of the protocol modifies the semantics of parent window
clipping in the presence of manual redirected children. With this
version, the area in the parent covered by manual redirected
children is left in the parent clip list instead of being removed as
in older versions.
</para></listitem>
</varlistentry>
</variablelist>
</para>
<para>
Per-hierarchy storage may be created for individual windows or for all
children of a window. Manual shadow update may be selected by only a single
application for each window; manual update may also be selected on a
per-window basis or for each child of a window. Detecting when to update
may be done with the Damage extension.
</para>
<para>
The off-screen storage includes the window contents, its borders and the
contents of all descendants.
</para>
</refsect1>
<refsect1><title>Arguments</title>
<para>
<variablelist>
<varlistentry>
<term><parameter>display</parameter></term>
<listitem><para>
Pointer to the <type>Display</type> structure returned from
<function>XOpenDisplay</function> for the connection to the X server.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>event_basep</parameter></term>
<listitem><para>
Pointer to integer where the base value for Composite Extension events
will be stored.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>error_basep</parameter></term>
<listitem><para>
Pointer to integer where the base value for Composite Extension errors
will be stored.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>major_versionp</parameter></term>
<listitem><para>
Pointer to integer where the major version of the Composite Extension
supported by the X server will be stored.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>minor_versionp</parameter></term>
<listitem><para>
Pointer to integer where the minor version of the Composite Extension
supported by the X server will be stored.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>window</parameter></term>
<listitem><para>
Specifies the window ID to operate on.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>update</parameter></term>
<listitem><para>
Specifies the mode for updating the window contents. Must be either
<constant>CompositeRedirectAutomatic</constant> or
<constant>CompositeRedirectManual</constant>.
</para></listitem>
</varlistentry>
</variablelist>
</para></refsect1>
<refsect1><title>Functions</title>
<para>
<variablelist>
<varlistentry>
<term><function>XCompositeQueryExtension</function></term>
<listitem><para>
<function>XCompositeQueryExtension</function> determines if the
Composite Extension is available on the given display. It returns
<constant>True</constant> if the extension is supported, otherwise
<constant>False</constant>. If the extension is present, the base
values for events and errors are returned, and can be used to
decode incoming event and error values.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeQueryVersion</function></term>
<listitem><para>
<function>XCompositeQueryVersion</function> determines if the X Server
supports a version of the X Composite Extension which is compatible
with the client library. A non-zero Status is returned if a compatible
version of the extension is supported, otherwise a zero Status is returned.
If the extension is supported, the major and minor version numbers are
returned to indicate the level of Composite Extension support.
No other XComposite functions (except XCompositeQueryExtension) may be
called before this function. If a client violates this rule, the
effects of all subsequent XComposite calls that it makes are undefined.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeVersion</function></term>
<listitem><para>
<function>XCompositeVersion</function> returns the version of the
X Composite library. The version number is encoded as:
<blockquote><para><code language="C">
(major * 10000) + (minor * 100) + revision
</code></para></blockquote>
</para>
<para>
For example, version 1.4.6 would be encoded as the integer 10406.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeRedirectWindow</function></term>
<listitem><para>
<function>XCompositeRedirectWindow</function> requests the X server
to direct the hierarchy starting at <parameter>window</parameter> to
off-screen storage.
The <parameter>update</parameter> argument specifies whether
the contents are mirrored to the parent window automatically or not.
Only one client at a time may specify an update type of
<constant>CompositeRedirectManual</constant>, another attempt will
result in a <errorname>BadAccess</errorname> error. When all clients
enabling redirection terminate, the redirection will automatically be
disabled.
</para><para>
The root window may not be redirected. Doing so results in a
<errorname>BadMatch</errorname> error. Specifying an invalid
window id will result in a <errorname>BadWindow</errorname> error.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeRedirectSubwindows</function></term>
<listitem><para>
<function>XCompositeRedirectSubwindows</function> requests the X
server to redirect hierarchies starting at all current and future
children of <parameter>window</parameter> as in
<function>XCompositeRedirectWindow</function>.
If <parameter>update</parameter> is
<constant>CompositeRedirectManual</constant>, then painting of the
window background during window manipulation and ClearArea requests
is inhibited.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeUnredirectWindow</function></term>
<listitem><para>
<function>XCompositeUnredirectWindow</function> requests the X
server to terminate redirection of <parameter>window</parameter>.
If the specified window was not selected for redirection by the
current client, a <errorname>BadValue</errorname> error results.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeUnredirectSubwindows</function></term>
<listitem><para>
<function>XCompositeUnredirectWindow</function> requests the X
server to terminate redirection of all children of
<parameter>window</parameter>.
If the specified window was not selected for sub-redirection by the
current client, a <errorname>BadValue</errorname> error results.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeCreateRegionFromBorderClip</function></term>
<listitem><para>
<function>XCompositeCreateRegionFromBorderClip</function>
creates a region containing the "usual" border clip
value; that is the area of the window clipped against siblings and
the parent. This region can be used to restrict rendering to
suitable areas while updating only a single window. The region
is copied at the moment the request is executed; future changes
to the window hierarchy will not be reflected in this region.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeNameWindowPixmap</function></term>
<listitem><para>
<function>XCompositeNameWindowPixmap</function> creates and returns
a pixmap id that serves as a reference to the off-screen storage for
<parameter>window</parameter>. This pixmap will remain allocated
until freed, even if the window is unmapped, reconfigured or
destroyed. However, the window will get a new pixmap allocated each
time it is mapped or resized, so this function will need to be
reinvoked for the client to continue to refer to the storage holding
the current window contents. Generates a
<errorname>BadMatch</errorname> error if <parameter>window</parameter>
is not redirected or is not visible.
</para><para>
The X server must support at least version 0.2 of the Composite
Extension for <function>XCompositeNameWindowPixmap</function>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeGetOverlayWindow</function></term>
<listitem><para>
<function>XCompositeGetOverlayWindow</function> returns the window ID
of the Composite Overlay Window for
the screen specified by the argument <parameter>window</parameter>.
This function notifies the X server that the client wishes to use
the Composite Overlay Window of this screen. If this
Composite Overlay Window has not yet been mapped, it is mapped by this
request.
</para><para>
The Composite Overlay Window for a particular screen will be
unmapped when all clients who have called this function have
either called <function>XCompositeReleaseOverlayWindow</function>
for that screen, or terminated their connection to the X server.
</para><para>
The X server must support at least version 0.3 of the Composite
Extension for <function>XCompositeGetOverlayWindow</function>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><function>XCompositeReleaseOverlayWindow</function></term>
<listitem><para>
This request specifies that the client is no longer using the
Composite Overlay Window on the screen specified by the
argument <parameter>window</parameter>. A screen's Composite
Overlay Window is unmapped when there are no longer any clients using it.
</para><para>
The X server must support at least version 0.3 of the Composite
Extension for <function>XCompositeReleaseOverlayWindow</function>.
</para></listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
</refentry>
</reference>