M-; : comment-column gets overridden by fill-column. Is this the Right Thing?

M-; : comment-column gets overridden by fill-column. Is this the Right Thing?

[Alan Mackenzie]

Hi, Emacs,

In a recent request for help from Michael Massmann on gnu.emacs.help,
he wants comments to be at column 100, but was unable to make M-; do
this.

He'd set comment column to 100, and had tried playing around with the
comment configuration in CC Mode, all to no avail.

M-; invokes comment-dwim calls comment-indent, which starts by putting
an empty comment at col 100.  It's not finished, though.

comment-indent then calls comment-choose-indent, which returns 72.
comment-indent then repositions the empty comment to col 72.  :-(

comment-choose-indent (which might better be called
comment-chews-indent ;-) makes the comment fit inside fill-column,
despite the fact that auto-fill-mode isn't enabled.  This is surely not
the right thing.  Should c-c-indent use fill-column when auto-fill-mode
is enabled?

Surely the documentation for M-; should mention fill-column?

Why is this comment stuff in such a mess?

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: M-; : comment-column gets overridden by fill-column. Is this the Right Thing?

[Stefan Monnier]

> comment-choose-indent (which might better be called
> comment-chews-indent ;-) makes the comment fit inside fill-column,
> despite the fact that auto-fill-mode isn't enabled.  This is surely not
> the right thing.  Should c-c-indent use fill-column when auto-fill-mode
> is enabled?

We can do two things:
- ignore fill-column if it's smaller than comment-column.
  That's a pretty "obviously safe" choice which would solve the problem
  of the OP.
- only obey fill-column if auto-fill-mode is enabled.

The second choice is an incompatible change and would force me to enable
auto-fill-mode in my programming modes (and then set
comment-auto-fill-only-comments to avoid the annoying "fill code"
behavior), but it seems reasonable.

> Surely the documentation for M-; should mention fill-column?

As long as it doesn't mention comment-column, I don't see why it should
mention fill-column.

> Why is this comment stuff in such a mess?

What mess?


        Stefan