XSetInputFocus man page
XSetInputFocus, XGetInputFocus — control input focus
int XSetInputFocus(Display *display, Window focus, int revert_to, Time time);
int XGetInputFocus(Display *display, Window *focus_return, int *revert_to_return);
Specifies the connection to the X server.
Specifies the window, PointerRoot, or None.
Returns the focus window, PointerRoot, or None.
Specifies where the input focus reverts to if the window becomes not viewable. You can pass RevertToParent, RevertToPointerRoot, or RevertToNone.
Returns the current focus state (RevertToParent, RevertToPointerRoot, or RevertToNone).
Specifies the time. You can pass either a timestamp or CurrentTime.
The XSetInputFocus function changes the input focus and the 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). XSetInputFocus causes the X server to generate FocusIn and FocusOut events.
Depending on the focus argument, the following occurs:
- If focus is None, all keyboard 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 keyboard's focus window. If a generated keyboard 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 keyboard event. In this case, the revert_to argument is ignored.
The specified focus window must be viewable at the time XSetInputFocus 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 or RevertToNone, the focus reverts to PointerRoot or None, respectively. When the focus reverts, the X server generates FocusIn and FocusOut events, but the last-focus-change time is not affected.
XSetInputFocus can generate BadMatch, BadValue, and BadWindow errors.
The XGetInputFocus function returns the focus window and the current focus state.
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.
A value for a Window argument does not name a defined Window.
Xlib - C Language X Interface
The man page XGetInputFocus(3) is an alias of XSetInputFocus(3).