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.

                                            09/15/2021                         XSETDEVICEFOCUS(3)