XSetDeviceFocus(3X11)
NAME
XSetDeviceFocus, XGetDeviceFocus - control extension input
device focus
SYNTAX
XSetDeviceFocus(display, device, focus, revert_to, time)
Display *display;
Display *device;
Window focus;
int revert_to;
Time time;
XGetDeviceFocus(display, device, focus_return,
revert_to_return, time_return)
Display *display;
Display *device;
Window *focus_return;
int *revert_to_return;
int *time_return;
ARGUMENTS
display Specifies the connection to the X server.
device Specifies the device whose focus is to be
queried or changed.
focus Specifies the window, PointerRoot, FollowKey-
board, or None.
focus_return
Returns the focus window, PointerRoot, Fol-
lowKeyboard, or None.
revert_to Specifies where the input focus reverts to if
the window becomes not viewable. You can pass
RevertToParent, RevertToPointerRoot, RevertTo-
FollowKeyboard, or RevertToNone.
revert_to_return
Returns the current focus state RevertToPar-
ent, RevertToPointerRoot, RevertToFollowKey-
board, or RevertToNone.
time_return Returns the last_focus_time for the device.
time Specifies the time. You can pass either a
timestamp or CurrentTime.
DESCRIPTION
The XSetDeviceFocus request changes the focus of the spec-
ified device and its last-focus-change time. It has no
effect if the specified time is earlier than the current
last-focus-change time or is later than the current X
server time. Otherwise, the last-focus-change time is set
to the specified time CurrentTime is replaced by the cur-
rent X server time). XSetDeviceFocus causes the X server
to generate DeviceFocusIn and DeviceFocusOut events.
Depending on the focus argument, the following occurs:
+o If focus is None , all device events are discarded
until a new focus window is set, and the revert_to
argument is ignored.
+o If focus is a window, it becomes the device's focus
window. If a generated device event would normally
be reported to this window or one of its inferiors,
the event is reported as usual. Otherwise, the event
is reported relative to the focus window.
+o If focus is PointerRoot, the focus window is dynami-
cally taken to be the root window of whatever screen
the pointer is on at each event from the specified
device. In this case, the revert_to argument is
ignored.
+o If focus is FollowKeyboard, the focus window is
dynamically taken to be the window to which the X
keyboard focus is set at each input event.
The specified focus window must be viewable at the time
XSetDeviceFocus is called, or a BadMatch error results.
If the focus window later becomes not viewable, the X
server evaluates the revert_to argument to determine the
new focus window as follows:
+o If revert_to is RevertToParent, the focus reverts to
the parent (or the closest viewable ancestor), and
the new revert_to value is taken to be RevertToNone.
+o If revert_to is RevertToPointerRoot, RevertToFol-
lowKeyboard, or RevertToNone, the focus reverts to
PointerRoot, FollowKeyboard, or None, respectively.
When the focus reverts, the X server generates DeviceFo-
cusIn and DeviceFocusOut events, but the last-focus-change
time is not affected.
Input extension devices are not required to support the
ability to be focused. Attempting to set the focus of a
device that does not support this request will result in a
BadMatch error. Whether or not given device can support
this request can be determined by the information returned
by XOpenDevice. For those devices that support focus,
XOpenDevice will return an XInputClassInfo structure with
the input_class field equal to the constant FocusClass
(defined in the file XI.h).
XSetDeviceFocus can generate BadDevice, BadMatch, Bad-
Value, and BadWindow errors.
The XGetDeviceFocus request returns the focus window and
the current focus state.
Not all input extension devices can be focused. Attempt-
ing to query the focus state of a device that can't be
focused results in a BadMatch error. A device that can be
focused returns information for input Class Focus when an
XOpenDevice request is made.
XGetDeviceFocus can generate BadDevice, and BadMatch
errors.
DIAGNOSTICS
BadDevice An invalid device was specified. The speci-
fied device does not exist or has not been
opened by this client via XOpenInputDevice.
This error may also occur if the specified
device is the X keyboard or X pointer device.
BadValue Some numeric value falls outside the range of
values accepted by the request. Unless a spe-
cific range is specified for an argument, the
full range defined by the argument's type is
accepted. Any argument defined as a set of
alternatives can generate this error.
BadWindow A value for a Window argument does not name a
defined Window.
BadMatch This error may occur if an XGetDeviceFocus or
XSetDeviceFocus request was made specifying a
device that the server implementation does not
allow to be focused.
SEE ALSO
Programming with Xlib