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XScreenSaver(3)						       XScreenSaver(3)

NAME
       XScreenSaver - X11 Screen Saver extension client library

SYNOPSIS
       #include <X11/extensions/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_base_return,
	      int *error_base_return);

       Status	XScreenSaverQueryVersion(Display   *dpy,    int	   *major_ver‐
	      sion_return, int *minor_version_return);

       XScreenSaverInfo *XScreenSaverAllocInfo(void);

       Status  XScreenSaverQueryInfo(Display *dpy, Drawable drawable, XScreen‐
	      SaverInfo *saver_info);

       void XScreenSaverSelectInput(Display *dpy, Drawable drawable,  unsigned
	      long mask);

       void  XScreenSaverSetAttributes(Display *dpy, Drawable drawable, 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);

       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);

       void XScreenSaverSuspend(Display *dpy, Bool suspend);

DESCRIPTION
       The X Window System provides support for changing the image on  a  dis‐
       play screen after a user-settable period of inactivity to avoid burning
       the cathode ray tube phosphors.	However, 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  pro‐
       grams that provide capabilities similar to those provided by other win‐
       dow systems.  In particular, such users often wish to be able  to  dis‐
       play corporate logos, instructions on how to reactivate the screen, and
       automatic screen-locking utilities.  This extension  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 manipula‐
       tion by the window manager.  Furthermore, the X identifier for the win‐
       dow  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 XScreenSaver‐
       QueryExtension 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  ScreenSaverNotify
       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 succeeded; the
       values of the major and minor protocol versions supported by the server
       are returned in major_version_return and minor_version_return .

       XScreenSaverAllocInfo  allocates and returns an XScreenSaverInfo struc‐
       ture for use in calls to	 XScreenSaverQueryInfo.	  All  fields  in  the
       structure  are  initialized  to zero.  If insufficient memory is avail‐
       able, 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	 acti‐
	   vate.

       On  The	screen	is  currently  being saved; til-or-since specifies 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 acti‐
	   vated.

       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 ScreenSaverSelectInput.

       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.  Otherwise, 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 immediately.  The server is free	 to  copy  the
       background-pixmap  or  cursor resources or to use them in place; there‐
       fore, 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 ForceScreenSaver 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 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 RetainTemporary, 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	 chil‐
       dren.
       When the screen saver is being deactivated and then immediately reacti‐
       vated (such as when switching screen savers), the server may leave  the
       screen saver window mapped (typically to avoid generating exposures).

       XScreenSaverUnsetAttributes  instructs the server to discard any previ‐
       ous screen saver window attributes set by this client.

       XScreenSaverRegister stores the given XID in the _SCREEN_SAVER_ID prop‐
       erty  (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 win‐
       dow of the specified screen.  It returns zero if an  error  is  encoun‐
       tered 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.

       XScreenSaverSuspend temporarily suspends the screensaver and DPMS timer
       if suspend is 'True', and restarts the timer if suspend is 'False'.
       This  function  should  be  used	 by  applications  that don't want the
       screensaver or DPMS to become activated while they're  for  example  in
       the  process of playing a media sequence, or are otherwise continuously
       presenting visual information to the user while	in  a  non-interactive
       state.  This  function  is  not	intended  to  be called by an external
       screensaver application.
       If XScreenSaverSuspend is called multiple times	with  suspend  set  to
       'True',	it must be called an equal number of times with suspend set to
       'False' in order for  the  screensaver  timer  to  be  restarted.  This
       request has no affect if a client tries to resume the screensaver with‐
       out first having suspended it.  XScreenSaverSuspend  can	 thus  not  be
       used  by one client to resume the screensaver if it's been suspended by
       another client.
       If a client that has suspended  the  screensaver	 becomes  disconnected
       from  the  X  server,  the  screensaver	timer  will  automatically  be
       restarted, unless it's still suspended by  another  client.  Suspending
       the screensaver timer doesn't prevent the screensaver from being force‐
       ably activated with the ForceScreenSaver request, or a DPMS  mode  from
       being set with the DPMSForceLevel request.
       XScreenSaverSuspend  also doesn't deactivate the screensaver or DPMS if
       either is active at the time the request to suspend them is received by
       the  X  server. But once they've been deactivated, they won't automati‐
       cally be activated again, until the client has canceled the suspension.

ERRORS
       XScreenSaverSelectInput,	  XScreenSaverQueryInfo,    XScreenSaverSetAt‐
       tributes	 and  XScreenSaverUnsetAttributes  will generate a BadDrawable
       error if drawable is not a valid drawable identifier.  If any undefined
       bits are set in event-mask, a BadValue error is generated by XScreenSa‐
       verSelectInput .

AVAILABILITY
       XScreenSaverSuspend is available in version 1.1 and later  versions  of
       the  X  Screen  Saver  Extension.  Version  1.1 was first released with
       X11R7.1.

SEE ALSO
       X(7)

AUTHORS
       Jim Fulton and Keith Packard.

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.

X Version 11		      libXScrnSaver 1.1.3	       XScreenSaver(3)
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