Event Filtering

A filtering mechanism is provided to allow input methods to capture X events transparently to clients. It is expected that toolkits (or clients) using the XmbLookupString() or XwcLookupString() function call this filter at some point in the event processing mechanism to make sure that events needed by an input method can be filtered by that input method. If there is no filter, a client can receive and discard events that are necessary for the proper functioning of an input method. The following provides a few examples of such events:

• Expose events that are on a preedit window in local mode.

• Events can be used by an input method to communicate with an input server. Such input server protocol-related events have to be intercepted if the user does not want to disturb client code.

• Key events can be sent to a filter before they are bound to translations such as Xt provides.

Clients are expected to get the XIC XNFilterEvents value and add to the event mask for the client window with that event mask. This mask can be 0.