From:	jsturm AT sigma6 DOT com (Jeff Sturm)
Subject:	Re: server X
22 Sep 1998 18:26:47 -0700 :
Message-ID:	<3607A48D.311B41C6.cygnus.gnu-win32@sigma6.com>
References:	<01BDDD75 DOT 00B69600 AT sos>
Mime-Version:	1.0
To:	David Fox <dsfox AT cogsci DOT ucsd DOT edu>
Cc:	gnu-win32 AT cygnus DOT com

David Fox wrote:
> Sergey Okhapkin <sos AT prospect DOT com DOT ru> writes:
> > Porting _Xfree86_ to win32 is a bad idea, because Xfree86 requires direct
> > video hardware access.
> 
> Could you expand on this further?  Why is direct video hardware access
> more of a problem under windows than it is under Unix?

(A small clarification to Sergey's post: XFree86 is designed for video
framebuffer access.  It need not access video registers directly. 
Recent work in Linux for example has moved video drivers out of X and
into the kernel; X opens the display via the /dev/fb device.)

The big difference is that under Unix, the X server controls the entire
display.  Under Win32 however, X has to cooperate with the native window
subsystem.  I think that precludes an X server from accessing video
memory from Win32 (does anyone know otherwise?).  It may be able to
write to backing store... I'm not sure if this is better (easier or more
efficient, that is) than just translating X drawing requests into GDI
requests.

If it turns out that the "virtual framebuffer" technique is feasible,
I'd contend that the XFree86 source is a better starting point than
TOG's X11R6.4, since they have cleaned up and fixed a lot of the cfb
code.

-- 
Jeff Sturm
jsturm AT sigma6 DOT com
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