XSETDEVICEFOCUS(3)

NAME
XSetDeviceFocus, XGetDeviceFocus - control extension input device focus

SYNOPSIS

#include <X11/extensions/XInput.h>

XSetDeviceFocus( Display *display,
                 XDevice *device,
                 Window focus,
                 int revert_to,
                 Time time);

XGetDeviceFocus( Display *display,
                 XDevice *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, FollowKeyboard, or
       None.

focus_return
       Returns the focus window, PointerRoot, FollowKeyboard, or
       None.

revert_to
       Specifies where the input focus reverts to if the window
       becomes not viewable. You can pass RevertToParent,
       RevertToPointerRoot, RevertToFollowKeyboard, or
       RevertToNone.

revert_to_return
       Returns the current focus state RevertToParent,
       RevertToPointerRoot, RevertToFollowKeyboard, 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 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 argument 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 RevertToParent, the focus reverts to the
        parent (or the closest viewable ancestor), and the new
        revert_to value is taken to be RevertToNone.
      * If revert_to is RevertToPointerRoot,
        RevertToFollowKeyboard, or RevertToNone, 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, 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, BadValue, and
    BadWindow 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 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 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.

    BadValue
           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 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.