Setting Up to Receive Messages

Before your application can receive messages from other applications, you must set up your process to watch for arriving messages. When a message arrives for your application, the file descriptor becomes active. The code you use to alert your application that the file descriptor is active depends on how your application is structured.

For example, a program that uses the XView notifier, through the xv_main_loop or notify_start calls, can have a callback function invoked when the file descriptor becomes active. The following code sample invokes notify_set_input_func with the handle for the message object as a parameter.

    /*
     * Arrange for XView to call receive_tt_message when the
     * ToolTalk file descriptor becomes active.
     */
    notify_set_input_func(base_frame,
                                (Notify_func)receive_tt_message,
                            ttfd);

describes various window toolkits and the call used to watch for arriving messages.

Table 7-2 Code Used to Watch for Arriving Messages

Window Toolkits	Code Used
XView	`notify_set_input_func`()
X Window System Xt (Intrinsics)	`XtAddInput`() or `XtAddAppInput`()
Other toolkits including Xlib structured around `select`(2) or `poll`(2) system calls	The file descriptor returned by `tt_fd`() Note: Once the file descriptor is active and the select call exits, use `tt_message_receive`() to obtain a handle for the incoming message.