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

[Paul Isambert]

Paul Stanley <paulrichardstanley at gmail.com> a écrit:
> 
>  > 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.

They're ok for me.

> 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 
sticu
s,
> agsta
 
reproo
ng, chi
cha
 and ri
ra
.
> 
> 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.

The problem is with ligatures, not kerns, then. More precisely, the
fonts should be reencoded in the PDF. To do so, ``simply'' use cm-super
fonts rather than the original Computer Modern. They instruct PDFTeX to
reencode the fonts (via pdftex.map). Sorry I can't say much more on
this, but it's not a simple issue, and I'm not extremely competent.

Best,
Paul