X and Self 2.0.1

J. J. Larrea jjl at Panix.Com
Fri May 7 03:28:14 UTC 1993

>   BTW: with regard to comment of using ':0.0' versus 'hostname:0.0':
>     I would assume that XOpenDisplay considers :0.0 to mean unix:0.0, 
> which usually means to open an AF_UNIX domain socket rather than an
> AF_INET (tcp) socket. This is usually in /tmp/.X11_unix/X? 

'Twas that way, but a later release (I forget which number) improved on
that even further.  In systems which implement shared memory, there is a 
three-level hierarchy:

    host:0.0	- AF_INET socket
    unix:0.0	- AF_UNIX socket, exactly as you described
    :0.0	- Uses shared-memory between client & server, completely
		  bypasses network serialization. Yes, it's a hack which
		  might be construed to violate client/server privacy,
		  but it *is* more efficient.  If this connexion is not
		  available, falls back to unix:0.0 behavior.  In essence,
		  ":0.0" means "local server, fastest possible connexion";
		  I would imagine that mechanisms other than systemV
		  shared-memory have been implemented by various vendors.

And, as described by a previous commentor, X will not flush to the display
until the event queue is polled or an explicit XFlush() given; typically
it is not an issue since an application will alternate output with a
call to XNextEvent() to await further user input.

- JJ Larrea

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