item delimiter

[Ben Rubinstein]

on 4/6/02 10:01 pm, J. Landman Gay at jacque at hyperactivesw.com wrote:

> There are some exceptions -- characters that cannot be typed and which a
> user can't enter into the text. I usually use numToChar(8) as a
> delimiter, because that's the Delete key -- and it is impossible for a
> user to type a delete character into the text. Another one I like is
> numToChar(3), which is the Enter key character, which also cannot be
> placed into the text. I've had good success using both of these. Someone

Warning: "impossible to type" is something you can securely guarantee only
if you don't allow pasting.

Never worked out how exactly it happened, but over many years of using
HyperCard in lots of projects, we did occasionally get problems which came
down to users having entered text which accidentally included 127 (the other
delete) - which similarly you'd think would be impossible to enter.
Different clients, on different projects, using different stacks.  My
assumption is that they must have pasted text in containing the dodgy
character - at which point the question of what they'd originally used to
generate that text opens very wide.  (My guess would be a dodgy version of
Word, possibly on Windows.)

I can only type a very limited set of characters into this email client -
but I can paste every character from 0 to 255 inclusive.  If you want to be
really really really sure, you have to test input and be prepared to do
something with it.  (Of course I'm just being picky; it may not be worth
going to this level for your particular app.  Depends how badly it would
mess you up if by some chance the user did accidentally insert the
character.)

This is also when a universally visible character comes in handy.  The
problem with some of the whackier ones including 0 and 127 is that in many
fonts they don't show up - so the users can't see that they've entered it.

  Ben Rubinstein               |  Email: benr_mc at cogapp.com
  Cognitive Applications Ltd   |  Phone: +44 (0)1273-821600
  http://www.cogapp.com        |  Fax  : +44 (0)1273-728866