Re: Should invisible imply intangible?

[David.Kastrup@t-online.de (David Kastrup)]

"Stefan Monnier" <monnier+gnu/emacs@RUM.cs.yale.edu> writes:

> >     > The scenario is one where message header lines are marked as
> >     > invisible using overlays, the goal being to hide them.
> > 
> >     Any reason why those cannot explicitly use the `intangible'
> >     property ?
> > 
> > Because the invisibility of these lines is controlled
> > buffer-invisibility-spec, and that can't control the intangible
> > property.  This text is visible sometimes and invisible sometimes,
> > and we want to change that *without* changing the text properties
> > directly.
> > 
> > The text should be intangible when it is invisible, and not when
> > it is not.  And none of that should require changing actual text
> > properties.
> 
> Now it all makes a lot more sense, thank you.
> I guess that's the part of the beginning of the discussion that I missed.
> I'll see what code I can come up with,

I don't think it appropriate to hack intangibility into the invisible
property just because intangibility happens to be missing an API that
invisibility has.

It will do no harm if the user gets his cursor moved out of invisible
areas at command completion time (as is done with point adjustment),
but the semantics of the intangibility property are much more
severe.  It violates a lot of assumptions a programmer might make
about how text behaves and should not be applied lightly.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum
Email: David.Kastrup@t-online.de

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