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Re: Should invisible imply intangible?


From: Richard Stallman
Subject: Re: Should invisible imply intangible?
Date: Wed, 13 Mar 2002 03:58:26 -0700 (MST)

    That much I know, but the problem is when there's some other property
    like a `display' property that ends up displaying something.

If the text is invisible, it should not display *anything* no matter
what other properties it has (including `display', `after-string' and
`before-string').  An invisible piece of text should not contribute to
the screen contents (except for the ellipsis, if any).

    It seems not since David uses display+invisible when replacing TeX source
    code with an image of the output in his preview-latex package (the 
`invisible'
    property seems useless at first, but he uses it so he can use the
    isearch-open-invisible hook).

Isn't it the case that specifying an image with a property on some text
replaces the text with the image?  I think so.

If that is so, I don't understand what purpose this invisible property
is supposed to serve.  Can you explain?  I cannot figure out, from the
mere reference to isearch-open-invisible, what he is trying to do.

Anyway, it is clearly a bug if invisible fails to completely suppress
the display of the text it covers.

    > 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.






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