XSetDeviceFocus(3X11)XSetDeviceFocus(3X11)NAME
XSetDeviceFocus, XGetDeviceFocus - control extension input device focus
SYNOPSIS
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
Specifies the connection to the X server. Specifies the device whose
focus is to be queried or changed. Specifies the window, PointerRoot,
FollowKeyboard, or None. Returns the focus window, PointerRoot, Fol‐
lowKeyboard, or None. Specifies where the input focus reverts to if
the window becomes not viewable. You can pass RevertToParent, RevertTo‐
PointerRoot, RevertToFollowKeyboard, or RevertToNone. Returns the cur‐
rent focus state RevertToParent, RevertToPointerRoot, RevertToFol‐
lowKeyboard, or RevertToNone. Returns the last_focus_time for the
device. Specifies the time. You can pass either a timestamp or Cur‐
rentTime.
DESCRIPTION
The XSetDeviceFocus request changes the focus of the specified 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 current X server
time). XSetDeviceFocus causes the X server to generate DeviceFocusIn
and DeviceFocusOut events.
Depending on the focus argument, the following occurs: If focus is
None, all device events are discarded until a new focus window is set,
and the revert_to argument is ignored. 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. If focus is PointerRoot, the focus window is dynamically
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 argu‐
ment is ignored. 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: If revert_to is RevertToPar‐
ent, the focus reverts to the parent (or the closest viewable ances‐
tor), and the new revert_to value is taken to be RevertToNone. If
revert_to is RevertToPointerRoot, RevertToFollowKeyboard, or Revert‐
ToNone, the focus reverts to PointerRoot, FollowKeyboard, or None,
respectively.
When the focus reverts, the X server generates DeviceFocusIn 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, XOpenDe‐
vice 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, BadValue, and BadWin‐
dow errors.
The XGetDeviceFocus request returns the focus window and the current
focus state.
Not all input extension devices can be focused. Attempting to query
the focus state of a device that cannot be focused results in a Bad‐
Match 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
An invalid device was specified. The specified 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. Some numeric value falls outside the range of values accepted
by the request. Unless a specific range is specified for an argument,
the full range defined by the argument's type is accepted. Any argu‐
ment defined as a set of alternatives can generate this error. A value
for a Window argument does not name a defined Window. This error may
occur if an XGetDeviceFocus or XSetDeviceFocus request was made speci‐
fying a device that the server implementation does not allow to be
focused.
SEE ALSO
Programming with Xlib
XSetDeviceFocus(3X11)
