[barcode] Lower/upper case

[Alessandro Rubini]

Hello.

> 	Just a quick question for the code39 (that can maybe be extended to 
> 	other encoding). Why a text must be all in lower or upper case?

I chose that rule because there are other encodings (like code128, and
currently none else in the supported set) that can differentiate
between upper and lowercase.

So the rule is "if we need to differentiate we use the more complex
encoding, otherwise code39 is fine". This works with autodetection of
the needed encoding.

> why convert everything in uppercase if necessary?

I've never seen a mixed-case text below a code39 symbol. Actually,
there is no standardization about the text representation of the
symbol, and I confess I'm not completely happy of my choice (that
mimicks ean13/upc). In general, if you need a specific text enconding
you should implement that by yourself in laying out your page.

Hope this helps
/alessandro