XCOMPOSITE(3) X Version 11 XCOMPOSITE(3)
NAME
Xcomposite - X Composite Extension library
SYNOPSIS
#include <X11/extensions/Xcomposite.h>
Bool XCompositeQueryExtension(Display *dpy, int *event_base_return, int *error_base_return);
Status XCompositeQueryVersion(Display *dpy, int *major_version_return, int *minor_version_return);
int XCompositeVersion(void);
void XCompositeRedirectWindow(Display *dpy, Window window, int update);
void XCompositeRedirectSubwindows(Display *dpy, Window window, int update);
void XCompositeUnredirectWindow(Display *dpy, Window window, int update);
void XCompositeUnredirectSubwindows(Display *dpy, Window window, int update);
XserverRegion XCompositeCreateRegionFromBorderClip(Display *dpy, Window window);
Pixmap XCompositeNameWindowPixmap(Display *dpy, Window window);
Window XCompositeGetOverlayWindow(Display *dpy, Window window);
void XCompositeReleaseOverlayWindow(Display *dpy, Window window);
DESCRIPTION
The composite extension provides several related mechanisms:
Per-hierarchy storage
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.
Automatic shadow update
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.
Composite Overlay Window
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.
Parent window clipping
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.
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.
The off-screen storage includes the window contents, its borders and the contents of all descendants.
ARGUMENTS
display
Pointer to the Display structure returned from XOpenDisplay for the connection to the X server.
event_base_return
Pointer to integer where the base value for Composite Extension events will be stored.
error_base_return
Pointer to integer where the base value for Composite Extension errors will be stored.
major_version_return
Pointer to integer where the major version of the Composite Extension supported by the X server will be stored.
minor_version_return
Pointer to integer where the minor version of the Composite Extension supported by the X server will be stored.
window Specifies the window ID to operate on.
update Specifies the mode for updating the window contents. Must be either CompositeRedirectAutomatic or CompositeRedirectManual.
FUNCTIONS
XCompositeQueryExtension
XCompositeQueryExtension determines if the Composite Extension is available on the given display. It returns True if the extension
is supported, otherwise False. 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.
XCompositeQueryVersion
XCompositeQueryVersion 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.
XCompositeVersion
XCompositeVersion returns the version of the X Composite library. The version number is encoded as: (major * 10000) + (minor * 100)
+ revision
For example, version 1.4.6 would be encoded as the integer 10406.
XCompositeRedirectWindow
XCompositeRedirectWindow requests the X server to direct the hierarchy starting at window to off-screen storage. The update 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 CompositeRedirectManual, another attempt will result in a BadAccess error. When all clients enabling redirection
terminate, the redirection will automatically be disabled.
The root window may not be redirected. Doing so results in a BadMatch error. Specifying an invalid window id will result in a
BadWindow error.
XCompositeRedirectSubwindows
XCompositeRedirectSubwindows requests the X server to redirect hierarchies starting at all current and future children of window as
in XCompositeRedirectWindow. If update is CompositeRedirectManual, then painting of the window background during window manipulation
and ClearArea requests is inhibited.
XCompositeUnredirectWindow
XCompositeUnredirectWindow requests the X server to terminate redirection of window. If the specified window was not selected for
redirection by the current client, a BadValue error results.
XCompositeUnredirectSubwindows
XCompositeUnredirectWindow requests the X server to terminate redirection of all children of window. If the specified window was not
selected for sub-redirection by the current client, a BadValue error results.
XCompositeCreateRegionFromBorderClip
XCompositeCreateRegionFromBorderClip 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.
XCompositeNameWindowPixmap
XCompositeNameWindowPixmap creates and returns a pixmap id that serves as a reference to the off-screen storage for window. 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 BadMatch error if window is not redirected or is not visible.
The X server must support at least version 0.2 of the Composite Extension for XCompositeNameWindowPixmap.
XCompositeGetOverlayWindow
XCompositeGetOverlayWindow returns the window ID of the Composite Overlay Window for the screen specified by the argument window.
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.
The Composite Overlay Window for a particular screen will be unmapped when all clients who have called this function have either
called XCompositeReleaseOverlayWindow for that screen, or terminated their connection to the X server.
The X server must support at least version 0.3 of the Composite Extension for XCompositeGetOverlayWindow.
XCompositeReleaseOverlayWindow
This request specifies that the client is no longer using the Composite Overlay Window on the screen specified by the argument
window. A screen's Composite Overlay Window is unmapped when there are no longer any clients using it.
The X server must support at least version 0.3 of the Composite Extension for XCompositeReleaseOverlayWindow.
AUTHOR
Keith Packard <keithp@keithp.com>, Deron Johnson <deron.johnson@sun.com>.
libXcomposite 0.4.1 23 April 2007 XCOMPOSITE(3)