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 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_versionp and minor_versionp.
XScreenSaverAllocInfo allocates and returns an XScreenSaverInfo 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 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 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 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; 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 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 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).
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.