[texhax] TeX Queries (2): Ascenders and Descenders; Kerning and ligatures and PDF Accessibility

[Paul Stanley]

 > Are descenders glyphs that *descend* below the baseline?

 > Parts of glyphs, yes.

Here's an extract on ascenders and descenders from 
http://www.brightlemon.com/blog/typography-01-font-basics-what-is-x-height-leading-kerning-tracking-ascender-de-0 
:

"6. Ascenders (parts of a character which 'ascend' above it's 
x-height - upper staff of a lower case b,d,t etc )"

"7. Descenders (parts of a character which 'descend' below it's 
x-height - lower tail of a g or y etc.)"

Please feel free to plug any gaps in above definitions.

[snip]

 > yes, kerning pairs can be an accessibility pain in the ... They are
 > either invisible to the screen reader or show up as strange control
 > characters (which comes to the same thing).

 > In a PDF, kerning is not denoted differently from interword space; as
 > far as I can tell from text extraction (searching for a string), a space
 > is interpreted as such if it doesn't exceed a certain amount. For
 > instance, with:

 >     ab\kern1pt cd
 >     ab\kern2pt cd

 > both Acrobat and Evince identify ``abcd'' in the first case but not in
 > the second (I haven't looked up the PDF reference to see whether that's
 > expected behavior).

The following LaTeX source:
\documentclass[a4 12pt]{article}

%\usepackage[T1]{fontenc}

\begin {document}

fluffier firefly fisticuffs, flagstaff fireproofing, chiffchaff and riffraff.

\end{document}
Produces the following lines of nonsense in a PDF:

uer re
y sticus,
agsta reproong, chicha and rira.

It's only when the
\usepackage[T1]{fontenc}
declaration is made that the output is readable.

The TeX source:
fluffier firefly fisticuffs, flagstaff fireproofing, chiffchaff and riffraff.
\end

also produces the same thing, although I don't know what remedies 
there are available in Plain TeX.

Many thanks,
Paul