Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!earth.cray.COM!jlf
From: jlf@earth.cray.COM (John Freeman)
Newsgroups: comp.windows.x
Subject: Re:  Question on XtAddInput
Message-ID: <8902211641.AA21529@thelake.cray.com>
Date: 21 Feb 89 16:41:22 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 49

> The documentation that I have concerning XtAddInput is not particularly
> clear.  
> 
> XtInputId XtAddInput (source,condition,proc,client_data)
> 	int source;
> 	caddr_t condition;
> 	XtInputCallbackProc proc;
> 	caddr_t client_data;
> 
> What is the condition?  My documentation says "Specifies the mask
> that indicates either a read, write, or exception condition or an operating
> system dependent condition"  Does this mean that it can be of type
> XEventMask (e.g., KeyPressMask)?
> 

No, it can't be an XEventMask, use XtAddEventHandler for that.
According to Intrinsic.h, condition can be one of the following:

typedef unsigned long   XtInputMask;

#define XtInputNoneMask         0L
#define XtInputReadMask         (1L<<0)
#define XtInputWriteMask        (1L<<1)
#define XtInputExceptMask       (1L<<2)

> Secondly, can the source be of type FILE, e.g., stdin? If not, what is passed.
> My documentation says that source "specifies the source file descriptor on a 
> dependent-device specification?"

Source is an ordinary file descriptor, as returned from open() or pipe().

> 
> Thirdly, is there some example code that demonstrates the use of XtAddInput?

int out_fd[2];

int read_dbx_pipe() {}

main()
{
    blah; blah;
    pipe(out_fd);
   /*
    * source is out_fd, condition is XtInputReadMask, proc is read_dbx_pipe 
    */
    XtAddInput(out_fd[0], XtInputReadMask, read_dbx_pipe, NULL);

    more blah;
}