Path: utzoo!attcan!uunet!samsung!usc!snorkelwacker!bloom-beacon!SHAMASH.MCRCIM.MCGILL.EDU!mouse
From: mouse@SHAMASH.MCRCIM.MCGILL.EDU (der Mouse)
Newsgroups: comp.windows.x
Subject: Re: what's most important to you for R5?
Message-ID: <9007070058.AA02122@shamash.McRCIM.McGill.EDU>
Date: 7 Jul 90 00:58:35 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 71

>>> The reason for incorporating something like Display PostScript into
>>> X is to remove any dependence on the display resolution.
>> And it would do that tolerably well.  But I argue that this is not
>> something you want to do.  Not until we have displays whose pixels
>> are too small to see.  (Current displays don't begin to approach
>> this; even laser printers aren't that good yet.)
> Perhaps you haven't used the NEXT Machine?   The characters on that
> machine seem to be at least as good as any I've seen on any
> monochrome monitor.

It's a two-bit grayscale display, not truly monochrome.  But that's
irrelevant, because the characters are usually displayed in a
two-gray-level way, typically full-black on full-white.

Yes, I have tried to use a NeXT.  (I found it unusable, because the
user interface is so incredibly expert-hostile.  But that's not the
point.)

The characters look reasonable, yes - provided you use one of the
standard fonts at one of the standard resolutions.  While this could be
done in X as well (and indeed, at the moment that's effectively all you
*can* do), that's not my point.  I was referring less to characters
than to other graphics.  I have had occasion to try to do graphics on a
PostScript 300dpi printer, and getting the results to look good is very
difficult, precisely because it is hard-to-impossible to specify things
at the pixel level.  For example, if I specify a line width that isn't
an exact number of pixels wide, and then draw a horizontal or vertical
line of this width, it will come out in different widths depending on
where within the pixels the endpoints fall.  As another example, I drew
a grid of equilateral triangles.  When the triangles were small (say,
ten pixels high), the mesh was visibly irregular because the triangle
corners were not positioned regularly.

I suppose my point can be summed up as "as long as you can see the
pixels, you have to draw in pixel terms to get high-quality results".
And PostScript makes it somewhere between difficult and impossible to
draw in pixel terms.  Indeed, on the 300dpi printer I mentioned above
it may be that it's *impossible* to draw in pixel terms because of
floating-point problems (1/300 is not exactly representable on most
machines).  But I can't even find out whether this is true or not.

>>> The usefulness of a real PostScript Interpreter cannot be
>>> overstated.  I would rank this as one of the most important
>>> possible features for X11R5.
>> Please, Consortium...if you do decide to include this, make it
>> configurable out.
> A feature doesn't have to be in the X Server to be a part of X11.

A very good point.  Thank you.  If it does not impose a significant
overhead on users that don't use it, I withdraw my objections.  (All
I'm left with then is balancing the possible usefulness of having it
available against the possible siphoning off of X staff time from other
tasks, and I have no grounds to judge either way on that.)

> Not to belabor the point about PostScript fonts, but one should
> realize that there is already a sizable amount of code and memory in
> the X server and Xlib devoted to rendering text.

Well, most of the hair is devoted not to rendering text so much as to
rendering text *fast*.

It may turn out that enough code is eliminated or simplified that it
isn't a big overhead.  In that case, by all means please go ahead.  My
main worry is that it not make things worse for someone who doesn't
touch it, "worse" including memory use, speed, complexity of client
code, etc.

					der Mouse

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