Icon validation to prevent SPACE

How do you prevent a SPACE being allowed in an input field via the validation string?

A~ 123

The above doesn’t work, neither does:

A~\ 123

Some time ago, the Wimp was changed to convert spaces typed in writable icons into non-breaking spaces to allow users to save files with ‘spaces’ in them, looking for a space in the reject section of the validation string (As "A~ " was the recommended validation string for Save dialogue boxes).

[Edit: If you really don’t want this behaviour, you can add a non-breaking space into the A~ part of the validation string alongside your existing space.

See https://www.riscosopen.org/forum/forums/10/topics/15474

Amusingly, this behaviour doesn’t seem to be documented in the Wiki.]

[Edit #2: Blooming writable. I prefer writeable, but the RISC OS Style Guide consistently uses writable, my paper Chambers only has writable, and the full online OED seems to prefer writable for things to do with computing. So it shall be for RISC OS…]

Obvious when you know!

this behaviour doesn’t seem to be documented in the Wiki

It is now

It is now

Annd tpyo fxied. ;)