Xlib Focus Management

For each text-entry area in which the XmbLookupString() or XwcLookupString() function is used, there is an associated input context.

When the application focus moves to a text-entry area, the application must set the input context focus to the input context associated with that area. The input context focus is set by calling the XSetICFocus() function with the appropriate input context.

Also, when the application focus moves out of a text-entry area, the application should unset the focus for the associated input context by calling the XUnsetICFocus() function. As an optimization, if the XSetICFocus() function is called successively on two different input contexts, setting the focus on the second automatically unsets the focus on the first.

To set and unset the input context focus correctly, it is necessary to track application-level focus changes. Such focus changes do not necessarily correspond to X server focus changes.

If a single input context is used to do input for multiple text-entry areas, it is also necessary to set the focus window of the input context whenever the focus window changes.