[XeTeX] :letterspace oddities
Jonathan Kew
jfkthame at gmail.com
Fri Aug 26 11:36:47 CEST 2016
On 25/8/16 18:02, Philip Taylor wrote:
> For some time now I have been partially aware of some oddities in the
> XeTeX implementation of :letterspace, but it was only today that my
> thoughts crystallised sufficiently for me to attempt to record them on-
> list :
>
> 1) Search functionality.
>
> For :
>
> \font \errorfont = "Copperplate Gothic Bold:letterspace=8,color=BF0000"
> scaled 2260
>
> \newbox \errorbox
>
> \setbox \errorbox = \leftline {\errorfont +++ NOT AT TOP OF PAGE +++}
>
>
> Adobe Acrobat 7.1 has no problem locating the string "+++" if the
> contents of \errorbox end up in the PDF file; however, for
>
>
> \font \errorfont = "Copperplate Gothic Bold:letterspace=16,color=BF0000"
> scaled 2260
>
> the same string cannot be found.
Remember that TeX doesn't treat spaces as "characters" but as glue,
which means they don't end up as part of the *text* in the resulting DVI
or PDF file; they are merely implied by the positioning of the visible
glyphs.
As a result, consider what Acrobat must be doing: it can "see" the
visible glyphs and their positions, but it "sees" no <space> characters
separating words. It must be inferring which characters are adjacent in
the text stream, and which are separated by spaces, purely from their
positions. So when you add a substantial amount of letter-spacing, it
seems likely that Acrobat will view the text as being "+ + +" rather
than "+++".
It's possible that \XeTeXgenerateactualtext=1 would help, as I think it
would annotate the letter-spaced "+++" as a unit with its actual text,
allowing Acrobat to find it correctly despite the intervening spaces
that *appear* to be present from just looking at the glyphs.
JK
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