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C00002 00002	Introduction
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Introduction
Welcome to the Common Lisp Window Subgroup.
In order to mail to this group, send to the address:

		CL-Windows@su-ai.arpa

Capitalization is not necessary, and if you are directly on the ARPANET,
you can nickname SU-AI.ARPA as SAIL. An archive of messages is kept on
SAIL in the file:

			   CLWIND.MSG[COM,LSP]

You can read this file or FTP it away without logging in to SAIL.

To communicate with the moderator, send to the address:

		CL-Windows-request@su-ai.arpa

Here is a list of the people who are currently on the mailing list:

Person			Affiliation	Net Address

Kent Pitman		MIT		kmp@mc
Dick Gabriel		Stanford/Lucid	rpg@sail
Carl Hewitt		MIT		hewitt-windows@mc
Don Allen		BBN		allen@bbnf
Dan Oldman		Data General	not established
Larry Stabile		Apollo		not established
Tom Kaczuarek		ISI		kaczuarek@isi
Dave Matthews		HP		matthews.hplabs@csnet-relay (I hope)
Dan Stenger		TI		stenger.ti-csl@csnet-relay
Gary Brown		DEC		gbrown@dec-marlboro
Joe Ginder		PERQ		Joseph.Ginder@cmu-cs-spice
Thomas Gruber		Univ. of Mass.	gruber.UMass-CS@csnet-relay

The first order of business is for each of us to ask people we know who may
be interested in this subgroup if they would like to be added to this list.

Next, we ought to consider who might wish to be the chairman of this subgroup.
Before this happens, I think we ought to wait until the list is more nearly
complete. 

∂23-Sep-84  1610	RPG  	Introduction  
To:   cl-windows@SU-AI.ARPA 
Welcome to the Common Lisp Window Subgroup.
In order to mail to this group, send to the address:

		CL-Windows@su-ai.arpa

Capitalization is not necessary, and if you are directly on the ARPANET,
you can nickname SU-AI.ARPA as SAIL. An archive of messages is kept on
SAIL in the file:

			   CLWIND.MSG[COM,LSP]

You can read this file or FTP it away without logging in to SAIL.

To communicate with the moderator, send to the address:

		CL-Windows-request@su-ai.arpa

Here is a list of the people who are currently on the mailing list:

Person			Affiliation	Net Address

Kent Pitman		MIT		kmp@mc
Dick Gabriel		Stanford/Lucid	rpg@sail
Carl Hewitt		MIT		hewitt-windows@mc
Don Allen		BBN		allen@bbnf
Dan Oldman		Data General	not established
Larry Stabile		Apollo		not established
Tom Kaczuarek		ISI		kaczuarek@isi
Dave Matthews		HP		matthews.hplabs@csnet-relay (I hope)
Dan Stenger		TI		stenger.ti-csl@csnet-relay
Gary Brown		DEC		gbrown@dec-marlboro
Joe Ginder		PERQ		Joseph.Ginder@cmu-cs-spice
Thomas Gruber		Univ. of Mass.	gruber.UMass-CS@csnet-relay

The first order of business is for each of us to ask people we know who may
be interested in this subgroup if they would like to be added to this list.

Next, we ought to consider who might wish to be the chairman of this subgroup.
Before this happens, I think we ought to wait until the list is more nearly
complete. 

∂02-Oct-84  1311	RPG  	Chairman 
To:   cl-windows@SU-AI.ARPA 
Now that we've basically got most everyone who is interested on the mailing
list, let's pick a chairman. I suggest that people volunteer for chairman.

The duties are to keep the discussion going, to gather proposals and review
them, and to otherwise administer the needs of the mailing list. I will
retain the duties of maintaining the list itself and the archives, but
otherwise the chairman will be running the show. 

Any takers?
			-rpg-

∂13-Oct-84  1440	RPG  	Chairman 
To:   cl-windows@SU-AI.ARPA 

No one has been nominated as chairman of the Windows subgroup.  I
suggest Howard Cannon of Symbolics. If he is willing, and no one else
volunteers, he will become chairman. Please respond by October 24. At the
end of this month I want to see some ideas and proposals coming in on this
mailing list.

			-rpg-

∂25-Oct-84  0944	FILE-SERVER%WHITE.SWW.Symbolics@SCRC-RIVERSIDE.ARPA 	Chairman    
Received: from SCRC-QUABBIN.ARPA by SU-AI.ARPA with TCP; 25 Oct 84  09:43:40 PDT
Received: from SWW-WHITE by SCRC-QUABBIN via CHAOS with CHAOS-MAIL id 94510; Tue 23-Oct-84 23:01:25-EDT
Date: Tue, 23 Oct 84 20:06 PDT
From: hic%SWW-WHITE@SCRC-RIVERSIDE.ARPA
Sender: FILE-SERVER%SWW-WHITE@SCRC-RIVERSIDE.ARPA
Subject: Chairman 
To: RPG@SU-AI.ARPA, cl-windows@SU-AI.ARPA
In-reply-to: The message of 13 Oct 84 14:40-PDT from Dick Gabriel <RPG at SU-AI>

    Received: from SCRC-STONY-BROOK by SWW-WHITE via CHAOS with CHAOS-MAIL id 47648; Sat 13-Oct-84 15:37:52-PDT
    Received: from MIT-MC by SCRC-STONY-BROOK via CHAOS with CHAOS-MAIL id 107864; Sat 13-Oct-84 18:32:38-EDT
    Date: 13 Oct 84  1440 PDT
    From: Dick Gabriel <RPG@SU-AI.ARPA>
    Subject: Chairman 
    To:   cl-windows@SU-AI.ARPA 


    No one has been nominated as chairman of the Windows subgroup.  I
    suggest Howard Cannon of Symbolics. If he is willing, and no one else
    volunteers, he will become chairman. Please respond by October 24. At the
    end of this month I want to see some ideas and proposals coming in on this
    mailing list.

			    -rpg-

Ah, I see I received this message.  I was worried that this mail wasn't
getting through, or was stuck at MC, or...

In any case, I respectfully decline the offer, not because I don't want
to do it but because of extensive traveling I don't feel I could be
reliable enough.  I do hope to participate actively, though.

I suggest that DDYER would do a fine job as chairman.

--Howard

∂27-Oct-84  2148	RPG  	Hello folks   
To:   cl-windows@SU-AI.ARPA 

We now have a chairman of the windows subgroup:  Dave Dyer of Symbolics. I
think he will make an excellent chairman.  For your information I am
including the current members of the mailing list.

I will now let Dave Dyer take over responsibility for the discussion.

David Matthews		HP		"hpfclp!windows%hplabs"@csnet-relay,
Jerry Boetje		DEC		Boetje@dec-hudson
John Foderaro		Berkeley	jkf@ucbmike.arpa
Steve Muchnick		SUN		"ucbvax!sun!muchnick"@berkeley
Howard Cannon		Symbolics 	"hic%scrc"@mc
Dave Dyer		Symbolics	ddyer@isib
Skef Wholey		CMU		Wholey@cmuc
Richard Zippel		MIT		rz@mc
Ron MacLachlan		CMU		RAM@cmu-cs-c
John Peterson		Univ of Utah	jw-peterson@utah-20
Kent Pitman		MIT		kmp@mc
Dick Gabriel		Stanford/Lucid	rpg@sail
Carl Hewitt		MIT		hewitt-windows@mc
Don Allen		BBN		allen@bbnf
Dan Oldman		Data General	not established
Larry Stabile		Apollo		not established
Tom Kaczmarek		ISI		kaczmarek@isi
Dan Stenger		TI		stenger.ti-csl@csnet-relay
Gary Brown		DEC		brown@dec-hudson
Joe Ginder		PERQ		Joseph.Ginder@cmu-cs-spice
Thomas Gruber		Univ. of Mass.	gruber.UMass-CS@csnet-relay
Ron Fischer		Rutgers		fischer@rutgers
Dario Giuse		CMU		dzg@cmu-cs-spice
Neal Feinberg		Symbolics	feinberg@scrc-stony-brook

∂28-Oct-84  1054	DDYER@USC-ISIB.ARPA 	Initial questions  
Received: from USC-ISIB.ARPA by SU-AI.ARPA with TCP; 28 Oct 84  10:53:57 PST
Date: 28 Oct 1984 10:52:38 PST
Subject: Initial questions
From: Dave Dyer       <DDYER@USC-ISIB.ARPA>
To: cl-windows@SU-AI.ARPA


Ok, since I have no idea what I'm supposed to do, I'll
just do what comes naturally.   What is the scope of
this discussion?  These questions come to mind:


What kinds of window hardware are we talking about?  Plain
glass ttys?  Bitmapped?  Vector?  Color?

What implementation technology?  Particularly, will we use
whatever the CL standard for objects becomes, or structures.

Fonts?  Text formatting?   What is the boundary between 
this mailing list and what "graphics" will discuss.

What about pointing devices?
-------

∂29-Oct-84  0917	DDYER@USC-ISIB.ARPA 	Initial Answer
Received: from USC-ISIB.ARPA by SU-AI.ARPA with TCP; 29 Oct 84  09:17:19 PST
Date: 29 Oct 1984 09:12:53 PST
Subject: Initial Answer
From: Dave Dyer       <DDYER@USC-ISIB.ARPA>
To: cl-windows@SU-AI.ARPA

[ Editors Note:  Since this reply came to me rather than the mailing list,
  I am reminded of the perpetual question;  "To Digest or not to Digest"
  For now, I will package any replies that come directly to me, and send
  them to the mailing list from time to time.   Messages sent to 
  cl-windows@su-ai will continue to be redistributed immediately.
						DDyer@isib]

Return-Path: <KACZMAREK@USC-ISIF.ARPA>
Date: 29 Oct 1984 07:47:00 PST
Subject: Re: Initial questions
From: Tom Kaczmarek <KACZMAREK@USC-ISIF.ARPA>

Regarding interaction with the graphics group, I think we ought to try to 
build on top of what they supply.  I suspect that there is enough cross-
membership to insure that we have sufficient influence.  (I haven't compared
the mailing lists so I could be wrong about that.)

[ddyer: I tend to look at it the other way; Graphics is an additional
 behavior of windows, and graphics capabilities will be built out of
 whatever we supply.]

As far as display hardware goes there seems to be two interesting classes--
"graphics" and glass ttys.  Color is an orthogonal issue, isn't it?
Number of bit planes for black and white graphics falls in this same
category.  Both graphic devices and ttys come in black and white (with
intensity levels) or color.  Graceful degradation seems to be the
appropriate way to handle these issues.  I believe the graphics people
having been looking at this issue for some time and have solutions for this
problem.  

I would guess that if the graphics group does its job well, vector versus
bitmapped graphics should not be an issue.  The resolution of the graphics
may be an issue however.  Low resolution graphics devices seem a lot like
glass ttys as far as windows go.  Storage vector graphics hardware (ala
old Tektronix stuff) does not lend itself to the kind of interaction one
expects from a window system so I think we can eliminate it.  I believe the
graphics group also should make pointing devices less of a problem since
graphics standards have abstracted actions like "picking."  I believe that
complex mouse buttoning will still be something of a problem.

Structures versus objects seems to be a difficult decision.  Perhaps having
to wait for a object standard will be the best argument for structures.
Conceptually, objects are nice for the kind of interactions that occur in
the window world.  Is efficiency an issue here?  Object-oriented
implementations seems to rely on interpretation rather than compilation.
Is that because nobody has done it differently or is it too hard?  Or
impossible?  Or am I wrong about that?

[ddyer: flavors are compiled]
Tom
-------
-------

∂29-Oct-84  1045	boetje@DEC-HUDSON 	some initial answers(?)   
Received: from DEC-HUDSON.ARPA by SU-AI.ARPA with TCP; 29 Oct 84  10:43:09 PST
Date: Mon, 29 Oct 84 13:39:39 EST
From: boetje@DEC-HUDSON
Subject: some initial answers(?)
To: cl-windows@su-ai.arpa

Ok, it's Monday morning and I'm ready to take on windows. This note is in 
direct reply to Dave Dyer's set of questions over the weekend. 

Let's take the terminology question first. I have a strong feeling that we 
need to get this handled before much else can happen. One of the major 
difficulties in this area is that there seem to be two different views of what 
the term "window" refers to. Most everyone working on bitmapped screens these 
days calls the funny rectangular areas (with borders and labels, in which you 
can put text or draw lines) windows. The graphics community uses "window" in a 
very different way. A window is really a way to specify a set of coordinate 
transformations and a set of bounding coordinates for clipping purposes. You 
can't ever see a graphics window. It takes a viewport to make that happen. 
Viewports are potentially viewable objects. But of course in that graphics 
world, there isn't a firm concept of borders and labels.

I will put forth the following radical suggestion: the graphics folks were 
here first, so their terminology should take precedence. Windows and viewports 
are strictly defined in the world of real graphics. A window is a set of 
limiting coordinates (x-y min and max values) in some arbitrary system
(usually the coordinate system of the data values to be plotted). This defines 
the aspect ratio of the eventual display of data. A viewport is another set of 
limiting coordinates which are used to map the data plotted in coordinates of 
the window to a displayable rectangle (this provides for clipping, 
magnification, and transformation to the physical device).So we won't do 
windows (sorry about the marketing slogan). We need to call those funny 
rectangles on the screen something else.

Before I unveil my terms, let me introduce a concept into this arena. In both 
the graphics world and whatever-we-call-the-current-thing world, there is the 
idea of a displayable object. In the graphics world, viewports can be 
displayable objects (when they map things from NDC space for example). They 
can also be previously created "pictures" which can be used to make composite 
images (for example, the symbol for a NAND gate in a CAD system). The common 
term for this object is "segment". Segments can be replicated and scaled ad 
nauseum to make a larger displayable object. The graphics world thus has a 
model of composition by using displayable objects as well as basic line 
drawing primitives.

In the bitmapped world, "windows"  are considered displayable objects. In the
case of Symbolics, they also  provide the idea of decomposition of their window
into "panes" (which can be  treated as individual windows for many purposes).
Another way of looking at  their system is that they treat their "window" as a
displayable object which can be composed of other windows. Their composition 
process also involves a particular contraint system on the interaction between 
the parts of a composed displayable object (resize one and the others adjust).

With all that said, I now introduce my own terms (liberally borrowed from 
unnamed sources):

1. Virtual Display. This is what most folks think of as a "window" or perhaps
a bitmap (depending on whether it's visible or not). You may see it (touch it
and taste it if it's late enough at night) on the screen. It's a  rectangular
area which may be made to appear on a physical display (hence the term virtual
display) which  can have a border, a label, etc. Primitive operations can put
information into  the display (like writing characters or drawing lines). If
they are not currently visible on the physical display, their current state is
kept and  modified by primitive operations. 

They can also be  composed of other virtual displays with appropriate
constraints at the whim of the implemectation. It may or may not be on the
physical display and it may or  may not be hidden obscured by other visible
displays). It can function as an I/O device for CL streams. And if you're into
the graphics side of the world, viewports map directly into the non-border
portion of virtual displays.  

2. Windows and viewports retain (and will only be used for describing) their 
traditional meanings in the world of graphics (which among other things means 
that windows and viewports operate in coordinate systems other than that of 
the physical display device).

3. Displayable object. Well, I gave the sense of it above. If we want to 
strictly define it for CL, then we'll need to do some work on it. I'm inclined 
to leave it alone for now and just use it by way of introducing concepts of 
composition. We'd need to be very closely tied to the graphics folks if we 
want to define it in the language.

Ok, enough on terms. Hardware... hmm... Curiously, the most limiting hardware 
is the vector drawing equipment, because it's hard to change once you've put 
it on the screen. My thought is that we should at least define operations that 
can be done on a cell-oriented screen. We can define optional capabilities for 
displays, but that gets us into the serious business of specifying how the 
user program determines the capabilities that can be used on the runtime 
device and what the error mechanism is for operations that can't be supported 
on the current device. The GKS graphics folks have done this and the inquiry 
functions outnumber the primitive operations.

On the software implementation, we should go for the least disruptive and 
commonly implemented features (GCLISP has some nice display stuff on a small 
machine). I think this means structures, not objects. We might want to define 
an optional object interface to the displays, but I think we need the simple 
level as well. Also, I don't want to wait around for the religious wars over 
objects. We'll have enough of our own...

Fonts, et al. Ok, we need some optional ways to specify font information and 
it's not clear that font bits are the best way to go. VAX LISP would probably 
have a difficult time handling font information in strings (efficient strings 
for us are one byte per character). Font information should be an ignoreable 
parameter (VT200's don't do well when commanded to go into Times Roman). 
Having a function that computes the actual screen size of a string in a 
specified font is a must.

Text formatting. We need text primitives to write, erase and insert 
characters. But I'm not anxious to get into the business of putting Scribe 
into CL. But there should be enough functionality for the cottage industries 
to write a formatting system on top of the CL primitives.

Boundary between this group and graphics. Ok, I've got a foot in both, so I'll 
jump in. We should stick to the ideas of virtual displays and composition of 
virtual displays. They should always operate in the coordinate system of the 
device. The graphics world should get windows, viewports and segments and 
operate in non-device coordinates. Our major interface then becomes a mapping 
of viewport to virtual display with the graphics side worrying about the 
scaling and clipping into the device (virtual display) coordinates.

Last topic for now... pointing devices. hmmm. They're needed for two purposes,
at least. One is to do operations on entire virtual displays (like popping
them to the surface). They other is to indicate a point or segment within a
virtual display. These operations can be handled with mouses and tablets and
can be simulated with cursor keys. We have to be careful not to get into the
business of defining a user interface to CL (pointing at a label brings a
display to the surface). But it would be nice to have some simple functions to
let users roll their own. 

Indicating a point or segment is a bit more interesting and gets us involved 
with the graphics group. Points within a virtual display need to be returned 
in some coordinate system. Most bitmap systems give back a point in raster 
coordinates. That's probably limiting. The graphics world likes them returned 
in the original coordinates used to draw the picture. And picking graphics 
segments has a close counterpart in defining/selecting a sensitive region.
Topic for next time.

Oh yes, color. Pick and stick to one of the international standards. There's 
RGB (red, green, blue) and HLS (hue, lightness and saturation). Any of you 
VideoText folks probably have yet another way. I have no real preference (just 
a minor leaning to HLS) but I haven't figured out if I should grind an ax on 
this or not. Issue deferred...

	Jerry

∂30-Oct-84  0711	dzg@cmu-cs-spice.arpa 	Terminology, etc.
Received: from CMU-CS-SPICE.ARPA by SU-AI.ARPA with TCP; 30 Oct 84  07:10:20 PST
Date: Tuesday 30 October 1984 09:33:00am-EST
From: dzg@CMU-CS-SPICE.ARPA
To: cl-windows@su-ai.arpa
Subject: Terminology, etc.
Message-ID: <0.0.dzg>

I mostly agree with Jerry Boetje. Let's use "window" for a set of bounding
coordinates; the confusion in the bitmap world is hopeless anyway. As an
example, on the Perq a 'viewport' is a rectangular portion of a display, and
a 'window' is essentially a viewport embellished with borders and a
'title'; on the Symbolics, a 'window' is essentially a viewport that may or
may not have borders and a 'label' (title).

I have a little problem with the term "segment", just because it is so
overloaded. I would try and suggest "symbol", a' la Newman & Sproull, just
because it's nice to talk about a symbol and a symbol instance. I realize,
though, that the word "symbol" is also overloaded...
One related question is transformations: can you only specify a
transformation (rotation, scale, offset) for symbols|segments, or can you
transform any graphical object in place?  Do you want to be able to say
"This is an arc of a circle, center and radius such and such, and by the
way it is scaled up 3.2 and rotated pi radians"?  Or do you always have to
wrap the arc in a symbol|segment to achieve the same effect? 

I also agree that we should use the universally available Structures for
the software implementation, given that no universally accepted (or
implemented!) notion of object seems to be around the corner. The BIG
problem, here, is that if you are not very careful your structures turn out
to be a "display list" that the system maintains, and so you have to
duplicate them all to put the interesting stuff you want to deal with. One
of the ideas I am trying to work on is to SHARE your data structures with
the system, so that you can have all the nice slots you want in there that
are not graphical at all, while the system can store all its internal cute
optimization things in it. This is unfortunately difficult to do with
structures a' la DefStruct, since the slots are defined once and for all.
An object system would be much nicer, since the system can define all its
nasty things and you never need to know about them.

Fonts: the "best approximation" paradigm should apply. My approach would be
to have a very generic font definition (family name, face, size, rotation)
which would be mapped into whatever the system provides. Font names are
totally hopeless (What's a CPT10? Is it 10 points or 10 pixels? Or is it
the 10th font in the file CPT? And what's a CPT anyway?), so I think one
would end up having a device-dependent mapping between an "abstract font"
and whatever the system provides. The mapping would be very dull on the
VT200, for instance, but one should use an abstract specification
nonetheless.

I very strongly oppose any notion of text formatting. Only the very minimal
level of support, including obviously the ability to get device-dependent
font information (IN WORLD COORDINATES, not in device coordinates!), should
be present. More complex text formatting is A) highly dependent on personal
taste, and B) extremely difficult to do right for sophisticated
applications. I certainly don't want a window system at this level to have
to deal with kerning and italic corrections.

  - Dario -

∂31-Oct-84  0723	STENGER%ti-csl.csnet@csnet-relay.arpa 	re: inital answers   
Received: from CSNET-RELAY.ARPA by SU-AI.ARPA with TCP; 31 Oct 84  07:23:51 PST
Received: from ti-csl by csnet-relay.csnet id ad00735; 31 Oct 84 10:18 EST
Date: 31 Oct 1984 0625-CST
From: Dan Stenger <STENGER%ti-csl.csnet@csnet-relay.arpa>
Subject: re: inital answers
To: cl-windows%su-ai.arpa@csnet-relay.arpa
Received: from csl60 by ti-csl; Wed, 31 Oct 84 09:13 CST

On terminology:
I agree with Jerry Boetje's proposal on the terminology that we should use.
We should settle on something so that we all understand each other.  The
main problem I see with this is that the terms "windows" and "panes" are
well established in the Lisp community and we may just cause confusion.

On bounds of this group:
I am also in the graphics group.  My view is that we should limit the
efforts of the windows group to virtual displays and other things that
need to work in device coordinates.  The graphics group should handle
what is shown in the virtual displays.

On the software implementation:
I agree that structures are the way to go.  Some implementations may not
want the object oriented programming system but may want windows.  Also
the wait may just put us too far behind.

On display hardware:
It would be nice if what we come up with is compatible with vector refresh
and storage tube hardware but I do not think that we should concern ourselves
with it.  The types of hardware which we do need to address are black/white
and color bitmaped terminals, and text only terminals.

In general I think we should try to design something that is concise, simple,
but very general.  It should be implementable on small machines but be easily
extended (not restrictive) for larger machines.

		Dan Stenger
-------

∂02-Nov-84  2330	DDYER@USC-ISIB.ARPA 	Real devices (mainly)   
Received: from USC-ISIB.ARPA by SU-AI.ARPA with TCP; 2 Nov 84  23:30:41 PST
Date:  2 Nov 1984 23:26:10 PST
Subject: Real devices (mainly)
From: Dave Dyer       <DDYER@USC-ISIB.ARPA>
To: cl-windows@SU-AI.ARPA


There seems to be consensus that vector displays are outside
our domain.  If there are no devotees of vector displays out
out there, I'll consider it official.

I liked "virtual display", but one term isn't a complete glossary.


  Several messages have cast a word in favor of supporting ordinary
terminals; but I wonder just how much one can do, especially if
"virtual display" is taken to imply "multiple virtual displays".
In practice, won't terminals be restricted to one or two virtual
displays, all the same width as the screen?   I've done quite
a bit of display hacking on ordinary terminals, and found anything
fancier to be aesthtically awful, even if technically possible.

  There simply isn't enough real estate to distinguish more than
a few windows, aren't display capabilities to provide margins
and borders, and the devices themselves don't operate fast or
reliably enough to allow manipulation of arbitrary blocks of
characters in a way that is acceptable to users.   Shouldn't we
take this ugly bit of reality into account? 

  I'm not necessarily proposing we punt terminals entirely, but
we should at least consider defining a limited set of primitives 
for terminals sufficient for input editing and (maybe) emacs style
editing.




  I also have doubts about several mentions of "device coordinates"
as the appropriate substrate for virtual displays.   One at least
needs to be able to speak of either "characters" or "pixels", to
accommodate ordinary terminals and bitmaps, but once pixels are
introduced, a whole nest of other problems surface; such as
aspect ratio, variable width and height of fonts, and the variable
size of pixels on different displays.  

  For a particular display, one could of course tweak things into
the right device coordinates to give the desired effect, but we
are speaking "portable" here, so need to at least address the question
of transmitting the author's intent to foreign systems.   

  Just to finish on a concrete point, consider Symbolic's color
displays, where the "same size" characters (in device coordinates)
border on unreadable compared to the same text on the B&W screen.   
Also, consider that a single pixel height horizontal line on a
noninterlaced screen is fine, but on an interlaced screen it is
probably unacceptable due to excess flicker.

  No program that operates in "device" coordinates can ignore facts
of life such as these.  We need to strike a balance between providing 
access to the raw facts, and hoping programs cope with all the possible
implications, and attempting to abstract intent into our specs and letting
the implementation cope with the ramifications.



-------

∂03-Nov-84  0747	FAHLMAN@CMU-CS-C.ARPA 	Goals  
Received: from CMU-CS-C.ARPA by SU-AI.ARPA with TCP; 3 Nov 84  07:47:49 PST
Received: ID <FAHLMAN@CMU-CS-C.ARPA>; Sat 3 Nov 84 10:47:55-EST
Date: Sat, 3 Nov 1984  10:47 EST
Message-ID: <FAHLMAN.12060631562.BABYL@CMU-CS-C.ARPA>
Sender: FAHLMAN@CMU-CS-C.ARPA
From: "Scott E. Fahlman" <Fahlman@CMU-CS-C.ARPA>
To:   cl-windows@SU-AI.ARPA
Subject: Goals


In my opinion, the window group is really in the business of developing
one or more optional semi-standards.  What I mean by that is that I
don't think that the Common Lisp specification should require any
particular sort of display or window system in order for something to be
called Common Lisp.  Display technology is moving pretty fast, and we
wouldn't want to rule out a Common Lisp in a wristwatch or a Common Lisp
running on a brute-force machine with no display of its own.
Furthermore, each machine running Common Lisp will have a few
specialized high-performance tricks available that users will want to
access for the most demanding applications: one machine might have a
hardware font and vector generator, another might have an incredibly
smart rasterop, and so on.  

But what we can and should do is to develop one or more clean interfaces
for doing some collection of popular things on certain popular families
of display technologies.  Implementors will be encouraged to provide
these standard interfaces on their machines wherever they make sense,
and people developing display-oriented code will then have the option of
writing it using the portable interface, for easy portability across a
class of machines, or of writing it to make the best possible use of a
given machine using whatever tense non-standard mechanisms may be
available.

It seems to me that three families of display device are going to be
important in the near future: 24x80 character terminals with varying
degrees of crude graphics support, high-resolution (at least 600 x
800) monochrome bit-mapped displays with some sort of pointing device,
and high-res bit-mapped displays with color.  Rather than ruin the
interface we develop for bit-mapped displays by trying too hard to make
it all work on ASCII terminals, I propose that we define three separate
interfaces:

Level 1: Can be implemented on the majority of ASCII termianls.
Level 2: Assumes bit-mapped graphics, reasonable resolution, and a
         pointer.
Level 3: Same as above, but with color.

Software developers can target their software to raw common Lisp or to
any of these levels, depending on the capability they need and the
market they wish to address, or they can go native on a single
machine/system.  Maybe levels 2 and 3 can be collapsed into one.
This is set up as a sort of hierarchy, since I am assuming that any
machine providing level 2 support will also provide level 1 support and
so on.  But the situation is really not hierarchical -- one might
imagine vector displays as wanting a different kind of interface
altogether.

The most important need right now is to come up with something for level
2, since the vast majority of Common Lisp implementations (not weighted
by number of users) is on machines of this class.

-- Scott

∂04-Nov-84  1816	JW-PETERSON@UTAH-20.ARPA 	Some responses...  
Received: from UTAH-20.ARPA by SU-AI.ARPA with TCP; 4 Nov 84  18:16:37 PST
Date: Sun 4 Nov 84 19:16:54-MST
From: John W. Peterson <JW-Peterson@UTAH-20.ARPA>
Subject: Some responses...
To: cl-windows@SU-AI.ARPA


VT100's.  The 24x80 terminal may not be dead, but is quickly dying.  A
reasonably intelligent bitmapped terminal with a mouse runs around $2K, and
will shortly drop to the VT100 [& clones] price range - this seems like a
good "lowest common denominator" level.

Fonts.  The discussion of fonts and formatting brings up an interesting
analogy: When the world migrated from TTY's to CRT's, many programs broke
(or just "looked ugly") because they couldn't deal with lower case input or
output.  The same sort of thing appears to be happening again, only this
time things are breaking (or just not looking right) because they can't deal
with multiple fonts - particularly ones with proportional spacing.  Having
at least some formatting facilities inherent in the window system (e.g., tab
stops that work correctly with proportional spaced fonts) would make the
programmer's life noticeably easier.

Units of measure.  Is anything wrong with measuring things in Pixels?  It
makes life much, much simpler (both conceptually and pragmatically) to
define screen coordinates in pixel units.  There is nothing very "display
specific" about pixel units of measure, particularly when you consider
"Virtual Displays" are usually of various sizes on the same screen.  As long
as we use digital computers, screens will be measured in discrete units -
both graphics and window packages might as well behave the same way.
(An interesting discussion of this is presented in "A Language for Bitmap
Manipulation" by Guibas & Stolfi in the July '82 Transactions on Graphics.)
-------