10.7 Input Focus Events

This section describes the processing that occurs for the input focus events FocusIn and FocusOut. The X server can report FocusIn or FocusOut events to clients wanting information about when the input focus changes. The keyboard is always attached to some window (typically, the root window or a top-level window), which is called the focus window. The focus window and the position of the pointer determine the window that receives keyboard input. Clients may need to know when the input focus changes to control highlighting of areas on the screen.

To receive FocusIn or FocusOut events, set the FocusChangeMask bit in the event-mask attribute of the window.

The structure for these event types contains:

typedef struct {
	int type;		/* FocusIn or FocusOut */
	unsigned long serial;	/* # of last request processed by server */
	Bool send_event;	/* true if this came from a SendEvent request */
	Display *display;	/* Display the event was read from */
	Window window;		/* window of event */
	int mode;		/* NotifyNormal, NotifyGrab, NotifyUngrab */
	int detail;
	 	* NotifyAncestor, NotifyVirtual, NotifyInferior, 
	 	* NotifyNonlinear,NotifyNonlinearVirtual, NotifyPointer,
	 	* NotifyPointerRoot, NotifyDetailNone 
} XFocusChangeEvent;
typedef XFocusChangeEvent XFocusInEvent;
typedef XFocusChangeEvent XFocusOutEvent;

The window member is set to the window on which the FocusIn or FocusOut event was generated. This is the window used by the X server to report the event. The mode member is set to indicate whether the focus events are normal focus events, focus events while grabbed, focus events when a grab activates, or focus events when a grab deactivates. The X server can set the mode member to NotifyNormal, NotifyWhileGrabbed, NotifyGrab, or NotifyUngrab.

All FocusOut events caused by a window unmap are generated after any UnmapNotify event; however, the X protocol does not constrain the ordering of FocusOut events with respect to generated EnterNotify, LeaveNotify, VisibilityNotify, and Expose events.

Depending on the event mode, the detail member is set to indicate the notify detail and can be NotifyAncestor, NotifyVirtual, NotifyInferior, NotifyNonlinear, NotifyNonlinearVirtual, NotifyPointer, NotifyPointerRoot, or NotifyDetailNone.

Next: Normal Focus Events and Focus Events While Grabbed

Christophe Tronche, ch@tronche.com