XScreenSaver(3) UNIX Programmer's Manual XScreenSaver(3)
NAME
XScreenSaver - X11 Screen Saver extension client library
SYNOPSIS
#include <X11/extension/scrnsaver.h>
typedef struct {
Window window; /* screen saver window */
int state; /* ScreenSaver{Off,On,Disabled} */
int kind; /* ScreenSaver{Blanked,Internal,External} */
unsigned long til_or_since; /* milliseconds */
unsigned long idle; /* milliseconds */
unsigned long event_mask; /* events */
} XScreenSaverInfo;
typedef struct {
int type; /* of event */
unsigned long serial; /* # of last request processed by server */
Bool send_event; /* true if this came frome a SendEvent request */
Display *display; /* Display the event was read from */
Window window; /* screen saver window */
Window root; /* root window of event screen */
int state; /* ScreenSaver{Off,On,Cycle} */
int kind; /* ScreenSaver{Blanked,Internal,External} */
Bool forced; /* extents of new region */
Time time; /* event timestamp */
} XScreenSaverNotifyEvent;
Bool XScreenSaverQueryExtension(Display *dpy, int
*event_basep, int *error_basep);
Status XScreenSaverQueryVersion(Display *dpy, int
*major_versionp, int *minor_versionp);
XScreenSaverInfo *XScreenSaverAllocInfo(void);
Status XScreenSaverQueryInfo(Display *dpy, Drawable draw-
able, XScreenSaverInfo *saver_info);
void XScreenSaverSelectInput(Display *dpy, Drawable draw-
able, unsigned long mask);
void XScreenSaverSetAttributes(Display *dpy, Drawable draw-
able, int x, int y, unsigned int width, unsigned int
height, unsigned int border_width, int depth, unsigned
int class, Visual *visual, unsigned long valuemask,
XSetWindowAttributes *attributes);
void XScreenSaverUnsetAttributes(Display *dpy, Drawable
drawable);
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void XScreenSaverSaverRegister(Display *dpy, int screen, XID
xid, Atom type);
Status XScreenSaverUnregister(Display *dpy, int screen);
Status XScreenSaverGetRegistered(Display *dpy, int screen,
XID *xid, Atom *type);
DESCRIPTION
The X Window System provides support for changing the image
on a display screen after a user-settable period of inac-
tivity to avoid burning the cathode ray tube phosphors. How-
ever, no interfaces are provided for the user to control the
image that is drawn. This extension allows an external
``screen saver'' client to detect when the alternate image
is to be displayed and to provide the graphics.
Current X server implementations typically provide at least
one form of ``screen saver'' image. Historically, this has
been a copy of the X logo drawn against the root background
pattern. However, many users have asked for the mechanism to
allow them to write screen saver programs that provide capa-
bilities similar to those provided by other window systems.
In particular, such users often wish to be able to display
corporate logos, instructions on how to reactivate the
screen, and automatic screen-locking utilities. This exten-
sion provides a means for writing such clients.
Assumptions
This extension exports the notion of a special screen saver
window that is mapped above all other windows on a display.
This window has the override-redirect attribute set so that
it is not subject to manipulation by the window manager.
Furthermore, the X identifier for the window is never
returned by QueryTree requests on the root window, so it is
typically not visible to other clients.
XScreenSaverQueryExtension returns True if the XScreenSaver
extension is available on the given display. A client must
call XScreenSaverQueryExtension before calling any other
XScreenSaver function in order to negotiate a compatible
protocol version; otherwise the client will get undefined
behavior (XScreenSaver may or may not work).
If the extension is supported, the event number for Screen-
SaverNotify events is returned in the value pointed to by
event_base. Since no additional errors are defined by this
extension, the results of error_base are not defined.
XScreenSaverQueryVersion returns True if the request suc-
ceeded; the values of the major and minor protocol versions
supported by the server are returned in major_versionp and
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minor_versionp .
XScreenSaverAllocInfo allocates and returns an XScreenSaver-
Info structure for use in calls to XScreenSaverQueryInfo.
All fields in the structure are initialized to zero. If
insufficient memory is available, NULL is returned. The
results of this routine can be released using XFree.
XScreenSaverQueryInfo returns information about the current
state of the screen server in saver_info and a non-zero
value is returned. If the extension is not supported,
saver_info is not changed and 0 is returned.
The state field specifies whether or not the screen saver is
currently active and how the til-or-since value should be
interpreted:
Off The screen is not currently being saved; til-or-since
specifies the number of milliseconds until the screen
saver is expected to activate.
On The screen is currently being saved; til-or-since speci-
fies the number of milliseconds since the screen saver
activated.
Disabled
The screen saver is currently disabled; til-or-since is
zero.
The kind field specifies the mechanism that either is
currently being used or would have been were the screen
being saved:
Blanked
The video signal to the display monitor was disabled.
Internal
A server-dependent, built-in screen saver image was
displayed; either no client had set the screen saver
window attributes or a different client had the server
grabbed when the screen saver activated.
External
The screen saver window was mapped with attributes set
by a client using the ScreenSaverSetAttributes request.
The idle field specifies the number of milliseconds since
the last input was received from the user on any of the
input devices.
The event-mask field specifies which, if any, screen saver
events this client has requested using ScreenSaverSelectIn-
put.
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XScreenSaverSelectInput asks that events related to the
screen saver be generated for this client. If no bits are
set in event-mask, then no events will be generated. Other-
wise, any combination of the following bits may be set:
ScreenSaverNotify
If this bit is set, ScreenSaverNotify events are
generated whenever the screen saver is activated or
deactivated.
ScreenSaverCycle
If this bit is set, ScreenSaverNotify events are
generated whenever the screen saver cycle interval
passes.
XScreenSaverSetAttributes sets the attributes to be used the
next time the external screen saver is activated. If another
client currently has the attributes set, a BadAccess error
is generated and the request is ignored.
Otherwise, the specified window attributes are checked as if
they were used in a core CreateWindow request whose parent
is the root. The override-redirect field is ignored as it is
implicitly set to True. If the window attributes result in
an error according to the rules for CreateWindow, the
request is ignored.
Otherwise, the attributes are stored and will take effect on
the next activation that occurs when the server is not
grabbed by another client. Any resources specified for the
background-pixmap or cursor attributes may be freed immedi-
ately. The server is free to copy the background-pixmap or
cursor resources or to use them in place; therefore, the
effect of changing the contents of those resources is unde-
fined. If the specified colormap no longer exists when the
screen saver activates, the parent's colormap is used
instead. If no errors are generated by this request, any
previous screen saver window attributes set by this client
are released.
When the screen saver next activates and the server is not
grabbed by another client, the screen saver window is
created, if necessary, and set to the specified attributes
and events are generated as usual. The colormap associated
with the screen saver window is installed. Finally, the
screen saver window is mapped.
The window remains mapped and at the top of the stacking
order until the screen saver is deactivated in response to
activity on any of the user input devices, a ForceScreen-
Saver request with a value of Reset, or any request that
would cause the window to be unmapped.
If the screen saver activates while the server is grabbed by
another client, the internal saver mechanism is used. The
ForceScreenSaver request may be used with a value of Active
to deactivate the internal saver and activate the external
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saver.
If the screen saver client's connection to the server is
broken while the screen saver is activated and the client's
close down mode has not been RetainPermanent or RetainTem-
porary, the current screen saver is deactivated and the
internal screen saver is immediately activated.
When the screen saver deactivates, the screen saver window's
colormap is uninstalled and the window is unmapped (except
as described below). The screen saver XID is disassociated
with the window and the server may, but is not required to,
destroy the window along with any children.
When the screen saver is being deactivated and then immedi-
ately reactivated (such as when switching screen savers),
the server may leave the screen saver window mapped (typi-
cally to avoid generating exposures).
XScreenSaverUnsetAttributes instructs the server to discard
any previous screen saver window attributes set by this
client.
XScreenSaverRegister stores the given XID in the
_SCREEN_SAVER_ID property (of the given type) on the root
window of the specified screen. It returns zero if an error
is encountered and the property is not changed, otherwise it
returns non-zero.
XScreenSaverUnregister removes any _SCREEN_SAVER_ID from the
root window of the specified screen. It returns zero if an
error is encountered and the property is changed, otherwise
it returns non-zero.
XScreenSaverGetRegistered returns the XID and type stored in
the _SCREEN_SAVER_ID property on the root window of the
specified screen. It returns zero if an error is encountered
or if the property does not exist or is not of the correct
format; otherwise it returns non-zero.
ERRORS
XScreenSaverSelectInput, XScreenSaverQueryInfo, XScreen-
SaverSetAttributes and XScreenSaverUnsetAttributes will gen-
erate a BadDrawable error if drawable is not a valid draw-
able identifier. If any undefined bits are set in event-
mask, a BadValue error is generated by XScreenSaverSelectIn-
put .
SEE ALSO
Xlib(1), X(7)
AUTHORS
Jim Fulton and Keith Packard.
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STABILITY
This API is considered as experimental. The Xss library
major revision may be incremented whenever incompatible
changes are done to the API without notice. Use with care.
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