Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!bellcore!spectral!sjs
From: sjs@spectral.ctt.bellcore.com (Stan Switzer)
Newsgroups: comp.windows.news
Subject: Re: multi-screen programming
Keywords: NeWS multiple monitors frame buffer programming idea
Message-ID: <16948@bellcore.bellcore.com>
Date: 20 Jun 89 14:10:50 GMT
References: <191@m2cs.uu.no>
Sender: news@bellcore.bellcore.com
Reply-To: sjs@ctt.bellcore.com (Stan Switzer)
Organization: Bellcore
Lines: 50

Frode L. Odegard (frode@m2cs.uu.no) writes:

> I've been speculating...maybe framebuffer could become a function
> that actually returns 'currentframebuffer' and maybe 'currentframebuffer'
> could be set when the user moves the cursor from one monitor to another?
> I haven't been really deep into the low-level code for event handling
> but it'd be fun to hear what the NeWS experts have to say on this.

Most of what you need is in WinWin.  It turns out to be a bit
difficult because you have to take care of a number of things:

1) As noted, you have to replace "framebuffer" with something that
returns the current framebuffer.

2) You have to start a new window manager to handle root damage and to
provide a root menu.

3) You have to fork a new server for the new device if you want to be
able to create UNIX-initiated windows in it.

4) You have to replace "forkunix" with something that connects to the
right server.  This is messy because the forkunix primitive has
already been autobound into various things, notably the root menu
procs.  You'll have to undo this.

5) You have to redefine "fboverlay" to correspond to the proper
framebuffer.  

6) Unlike all others canvases, NeWS makes children of "framebuffer"
transparent and, if B&W, retained.  This probably applies to children
of any "device" canvas, but you should check.

7) If you use a window class that shares menus (like, for instance
"neatwin" or "quickwin" you will have to deal with the fact that menus
retain canvases and that the canvases are parented to one framebuffer
or another.  I jammed in some code to reparent them.

8) You'll have to figure out what you want "AllWin" to do.

9) You'll have to figure out where you want to put these changes.
There is no way to replace a process's "systemdict" so you may have to
play games like keeping "framebuffer" as a variable in "userdict" and
aranging to propogate it in the "server" process.

10) You'll have to figure out how to warp the mouse to another
framebuffer.

11) When you get it done, send me a copy!

Stan Switzer  sjs@ctt.bellcore.com