AIXwindows provides support for changing the image on a display screen after a user-defined 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 programs that provide capabilities 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 extension provides a means for writing such clients.
The core SetScreenSaver Protocol Request can be used to set the length of time without activity on any input devices after which the screen saver should ``activate'' and alter the image on the screen. This image periodically ``cycles'' to reduce the length of time that any particular pixel is illuminated. Finally, the screen saver is ``deactivated'' in response to activity on any of the input devices or particular X requests.
Screen saving is typically done by disabling video output to the display tube or by drawing a changing pattern onto the display. If the server chooses the latter approach, a window with a special identifier is created and mapped at the top of the stacking order where it remains until the screen saver deactivates. At this time, the window is unmapped and is not accessible to any client requests.
The server's default mechanism is referred to as the internal screen saver. An external screen saver client requires a means of determining the window identifier for the screen saver window and setting the attributes (that is, size, location, visual, colormap) to be used when the window is mapped. These requirements form the basis of this extension.
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 protocol requests on the root window, so it is typically not visible to other clients.
In addition to the common types described in the core protocol, the following type is used in the request and event definitions in subsequent sections.
| Name | Value |
| SCREENSAVEREVENT | {ScreenSaverNotify, ScreenSaverCycle} |
The Screen Saver extension adds no errors beyond the core protocol.
The Screen Saver extension adds the following requests:
ScreenSaverQueryVersion client-major-version: CARD8 client-minor-version: CARD8 -> server-major-version: CARD8 server-minor-version: CARD8
This request allows the client and server to determine which version of the protocol should be used. The client sends the version that it prefers; if the server understands that version, it returns the same values and interprets subsequent requests for this extension according to the specified version. Otherwise, the server returns the closest version of the protocol that it can support and interprets subsequent requests according to that version. This document describes major version 1, minor version 0; the major and minor revision numbers should only be increased in response to incompatible and compatible changes, respectively.
ScreenSaverQueryInfo
drawable: DRAWABLE
->
saver-window: WINDOW
state: {Disabled, Off, On}
kind: {Blanked, Internal, External}
til-or-since: CARD32
idle: CARD32
event-mask: SETofSCREENSAVEREVENT
Errors: Drawable
This request returns information about the state of the screen saver on the screen associated with drawable. The saver-window is the XID type that is associated with the screen saver window. This window is not guaranteed to exist except when external screen saver is active. Although it is a child of the root, this window is not returned by QueryTree protocol requests on the root. Whenever this window is mapped, it is always above any of its siblings in the stacking order.
The state field specifies whether or not the screen saver is currently active and how the til-or-since value should be interpreted:
The kind field specifies the mechanism that either is currently being used or would have been were the screen being saved:
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 the ScreenSaverSelectInput function.
If drawable is not a valid drawable identifier, a Drawable error is returned and the request is ignored.
ScreenSaverSelectInput drawable: DRAWABLE event-mask: SETofSCREENSAVEREVENT Errors: Drawable, Match
This request specifies which Screen Saver extension events on the screen associated with drawable should be generated for this client. If no bits are set in the eventmask field, then no events are generated. Otherwise, any combination of the following bits may be set:
If drawable is not a valid drawable identifier, a Drawable error is returned. If any undefined bits are set in event-mask field, a Value error is returned. If an error is returned, the request is ignored.
ScreenSaverSetAttributes
drawable: DRAWABLE
class: {InputOutput, InputOnly, CopyFromParent}
depth: CARD8
visual: VISUALID or CopyFromParent
x, y: INT16
width, height, border-width: CARD16
value-mask: BITMASK
value-list: LISTofVALUE
Errors: Access, Window, Pixmap, Colormap, Cursor, Match,
Value, Alloc
This request sets the attributes that this client would like to see used in creating the screen saver window on the screen associated with drawable. If another client currently has the attributes set, an Access error is generated and the request is ignored.
Otherwise, the specified window attributes are checked as if they were used in a core CreateWindow protocol request whose parent is the root. The overrideredirect field is ignored as it is implicitly set to a value of True. If the window attributes result in an error according to the rules for the CreateWindow protocol request, the request is ignored.
Otherwise, the attributes are stored and 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; therefore, the effect of changing the contents of those resources is undefined. 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 protocol 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 Retain Permanent or Retain Temporary, 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 immediately reactivated (such as when switching screen savers), the server may leave the screen saver window mapped (typically to avoid generating exposures).
ScreenSaverUnsetAttributes drawable: DRAWABLE Errors: Drawable
This request notifies the server that this client no longer wishes to control the screen saver window. Any screen saver attributes set by this client and any descendents of the screen saver window created by this client should be released immediately if the screen saver is not active, else upon deactivation.
This request is ignored if the client has not previously set the screen saver window attributes.
The Screen Saver extension adds one event:
ScreenSaverNotify
root: WINDOW
window: WINDOW
state: {Off, On, Cycle}
kind: {Blanked, Internal, External}
forced: BOOL
time: TIMESTAMP
This event is delivered to clients that have requested ScreenSaverNotify events using the ScreenSaverSelectInput protocol request whenever the screen saver activates or deactivates.
The root field specifies root window of the screen for which the event was generated. The window field specifies the value that is returned by the ScreenSaverQueryInfo function as the identifier for the screen saver window. This window is not required to exist if the external screen saver is not active.
The state field specifies the cause of the event:
If the state field is set to On or Off then forced indicates whether or not activation or deactivation was caused by a core ForceScreenSaver protocol request; otherwise, forced is set to a value of False. The kind field specifies mechanism that was used to save the screen when the screen saver was activated, as described in the ScreenSaverQueryInfo function.
The time field indicates the server time when the event was generated.
SETofSCREENSAVEREVENT
#x00000001ScreenSaverNotifyMask
#x00000002ScreenSaverCycleMask
ScreenSaverQueryVersion 1 CARD8 screen saver opcode 1 0 minor opcode 2 2 request length 1 CARD8 client major version 1 CARD8 client minor version 2 unused -> 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 reply length 1 CARD8 server major version 1 CARD8 server minor version 22 unused
ScreenSaverQueryInfo
1 CARD8 screen saver opcode
1 1 minor opcode
2 2 request length
4 DRAWABLE drawable associated with screen
->
1 1 Reply
1 CARD8 state
0 Off
1 On
3 Disabled
2 CARD16 sequence number
4 0 reply length
4 WINDOW saver window
4 CARD32 milliseconds until saver or since saver
4 CARD32 milliseconds since last user device input
4 SETofSCREENSAVEREVENTevent mask
1 CARD8 kind
0 Blanked
1 Internal
2 External
10 unused
ScreenSaverSelectInput 1 CARD8 screen saver opcode 1 2 minor opcode 2 3 request length 4 DRAWABLE drawable associated with screen 4 SETofSCREENSAVEREVENTevent mask
ScreenSaverSetAttributes
1 CARD8 screen saver opcode
1 3 minor opcode
2 6+n request length
4 DRAWABLE drawable associated with screen
2 INT16 x
2 INT16 y
2 CARD16 width
2 CARD16 height
2 CARD16 border-width
1 class
0 CopyFromParent
1 InputOutput
2 InputOnly
1 CARD8 depth
4 VISUALID visual
0 CopyFromParent
4 BITMASK value-mask (has n bits set to 1)
encodings are the same as for core CreateWindow
4n LISTofVALUE value-list
encodings are the same as for core CreateWindow
ScreenSaverUnsetAttributes 1 CARD8 screen saver opcode 1 4 minor opcode 2 3 request length 4 DRAWABLE drawable associated with screen
ScreenSaverNotify
1 CARD8 code assigned by core
1 CARD8 state
0 Off
1 On
2 Cycle
2 CARD16 sequence number
4 TIMESTAMP time
4 WINDOW root
4 WINDOW screen saver window
1 CARD8 kind
0 Blanked
1 Internal
2 External
1 BOOL forced
14 unused
Screen saver clients should create at least one resource value whose identifier can be stored in a property named _SCREEN_SAVER_ID on the root of each screen it is managing. This property should have one 32-bit value corresponding to the resource identifier; the type of the property should indicate the type of the resource and should be one of the following: WINDOW, PIXMAP, CURSOR, FONT, COLORMAP.
The C binding for this extension simply provide access to the protocol; they add no semantics beyond what is described above.
The include file for this extension is X11/extensions/scrnsaver.h .
Bool
XScreenSaverQueryExtension (Display,EventBase,ErrorBase)
Display *display;
int *event_base; /* RETURN */
int *error_base; /* RETURN */
This routine returns a value of True if the specified display supports the SCREEN-SAVER extension; otherwise it returns False value. If the extension is supported, the event number for ScreenSaverNotify event functions is returned in the value pointed to by the EventBase parameter. Since no additional errors are defined by this extension, the results of the ErrorBase parameter are not defined.
Status
XScreenSaverQueryVersion (Display, Major, Minor)
Display *display;
int *major; /* RETURN */
int *minor; /* RETURN */
If the specified display supports the extension, the version numbers of the protocol expected by the server are returned in Major and Minor parameters and a nonzero value is returned. Otherwise, the arguments are not set and 0 (zero) is returned.
XScreenSaverInfo * XScreenSaverAllocInfo ()
This routine allocates and returns an XScreenSaverInfo structure for use in calls to the XScreenSaverQueryInfo Function. All fields in the structure are initialized to zero. If insufficient memory is available, a Null value is returned. The results of this routine can be released using the XFree function.
Status
XScreenSaverQueryInfo (display, drawable, saver_info)
Display *display;
Drawable drawable;
XScreenSaverInfo *saver_info; /* RETURN */
If the specified display supports the extension, information about the current state of the screen server is returned in saver_info and a non-zero value is returned. The XScreenSaverInfo structure is defined as follows:
typedef struct {
Window window; /* screen saver window */
int state; /*
ScreenSaver{Off,On,Disabled} */
int /* ScreenSaver{Blanked,Internal,External} */
unsigned long til_or_since; /* milliseconds */
unsigned long idle; /* milliseconds */
unsigned long event_mask; /* events */
} XScreenSaverInfo;
See the ScreenSaverQueryInfo protocol request for a description of the fields. If the extension is not supported, the saver_info structure variable is not changed and 0 is returned.
void
XScreenSaverSelectInput (display, drawable, event_mask)
Display *display;
Drawable drawable;
unsigned long event_mask;
If the specified display supports the extension, this routine asks that events related to the screen saver be generated for this client. The format of the events generated is:
typedef struct {
int type; /* of event */
unsigned long serial; /* # of last request */
/* processed by server */
Bool send_event; /* true if this came from 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;
See the definition of the ScreenSaverSelectInput protocol request for descriptions of the allowed event masks.
void
XScreenSaverSetAttributes (display, drawable, x, y, width, height, border_width,
depth, class, visual,
valuemask, attributes)
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;
If the specified display supports the extension, this routine sets the attributes to be used the next time the external screen saver is activated. See the definition of the ScreenSaverSetAttributes protocol request for a description of each of the arguments.
void
XScreenSaverUnsetAttributes (display, drawable)
Display *display;
Drawable drawable;
If the specified display supports the extension, this routine instructs the server to discard any previous screen saver window attributes set by this client.
Status
XScreenSaverRegister (display, screen, xid, type)
Display *display;
int screen;
XID xid;
Atom type;
This routine stores the given XID in the _SCREEN_SAVER_ID property (of the given type) on the root window of the specified screen. It returns 0 (zero) if an error is encountered and the property is not changed, otherwise it returns nonzero.
Status
XScreenSaverUnregister (display, screen)
Display *display;
int screen;
This routine removes any _SCREEN_SAVER_ID property from the root window of the specified screen. It returns 0 (zero) if an error is encountered and the property is changed, otherwise it returns nonzero.
Status
XScreenSaverGetRegistered (display, screen, xid, type)
Display *display;
int screen;
XID *xid; /* RETURN */
Atom *type; /* RETURN */
This routine returns the XID and type stored in the _SCREEN_SAVER_ID property on the root window of the specified screen. It returns 0 (zero) if an error is encountered or if the property does not exist or is not of the correct format; otherwise it returns nonzero value.