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.
AUTHORS
Keith Packard <keithp@keithp.com>
Extension specification and
implementation
Deron Johnson <deron.johnson@sun.com>
Overlay Window specification and
implementation