bug#42347: Feature request: Visual block attribute for overlays

[Gregory Heytings]

This should be merged with bug #42307.  (It was sent earlier, and for some 
reason stayed in the mail queue during a week.)

> > 1. calculate the overlay it it would have been displayed by Emacs 
> > 21-26.
> >
> > 2. remove all pixel columns on the right *and on the left* of the 
> > overlay which have no "content" (that is, no characters on the right, 
> > and whitespace characters on the left).
>
> What would be the definition of "whitespace" for this purpose?

I think the regexp "[ \t\r\n]*" would be appropriate.

Gregory