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Re: [Groff] Groff general image feature requirement specification

From: Werner LEMBERG
Subject: Re: [Groff] Groff general image feature requirement specification
Date: Sun, 17 Nov 2002 11:50:34 +0100 (CET)

> 1. It should be an escape sequence, so that it can be placed
> "anywhere".


> 2. As well as being usable by gpic and in macros, the escape
> sequence must also be suitable for use in strings (or directly in a
> text for that matter).  This will allow small images to be used as
> user-defined glyphs/characters.

In general, I see no problem here, but extra glyphs should be defined
with .char and its variants.

> 3. The current point should be the lower left corner of the image.
> This for compatibility with the existing PostScipt image import, but
> also to facilitate using tiny images as characters/glyphs, where
> they should by default rise from the baseline.


> 4. Due to 2., the escape sequence must have the right width, so that
> it will do the right thing within a \w'', for instance.

I still think that \X is sufficient, so you don't have this
possibility -- and I think you don't need it.  Your suggestion implies
that the image is read multiple times just to get the bounding box
again and again.  I prefer something different:

  .char foo ....\n[llx]... \n[ury]...

Note that in the definition of `foo' I use \n and not \\n.  Doing
this the dimensions of are directly coded into the definition
of `foo', and is read exactly once.

> 5. The escape sequence should produce a horizontal movement equal to
> its width, but no vertical movement.

I favor a dimensionless escape.  In most cases, the exact bounding box
is useless since you have to add some horizontal and vertical bearing.


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