Re: Proposed extension of show-paren-mode: Highlight parens when point is in L or R margin.

[Alan Mackenzie <acm@muc.de>]

Hi, Eli.

On Sun, Oct 12, 2014 at 12:01:58PM +0300, Eli Zaretskii wrote:
> > Date: Sun, 12 Oct 2014 08:39:09 +0000
> > Cc: emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > > Thanks, but PLEASE don't call this a "margin".

[ ... ]

I've now called it "periphery" and for that doc-string first line I've
got:

"If non-nil, show parens when point is in the line's periphery."

[ ... ]

> Now, let me ask something about the feature as designed (sorry, don't
> have time right now to apply the patch and try this myself).  Suppose
> I have this line of C code:

>     FOO = xyz + foobar (a + (b * sqrt (c) - d) * e) - some; /* foo */

> Is the intent to have the parentheses of the call to 'foobar'
> highlighted when point is before "FOO" or inside the comment, but
> _not_ when point is between "xyz" and "foobar"?  If so, this is soooo
> weird!

No.  The only parens that get highlighted are ones at the beginning or
end of the code on the line (together with their partners).

> And what about this part of your description:

> > So: If point is in the LH margin of the code, highlight the first paren
> > on the line and its match, or failing that, the last paren on the line
> > with its match.               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> When would the "first paren and its match" fail?

When the first non-whitespace character on the line isn't a paren.

> Does this mean you are not going to look past the line with point, i.e.
> multi-line parenthesized expressions will not be highlighted?

They will be highlighted when one of the parens touches the line's
periphery; it doesn't matter how far away the matching paren is, it will
get highlighted.

Anyhow, I've just blasted off an amended patch to Stefan.  Maybe it's
almost all right now.

-- 
Alan Mackenzie (Nuremberg, Germany).