Re: need option so line-move-to-column ignores fields, plus patch

["Ken Manheimer" <ken.manheimer@gmail.com>]

On 9/25/06, Chong Yidong <cyd@stupidchicken.com> wrote:

> Richard Stallman <rms@gnu.org> writes:
>
> >     > | 1. With the cursor adjacent to the right of any bar,
> >     >  |   if you move forwards a line (^N), the cursor slips to column 0.
> >     >   | 2. Moving backwards (^P) with the cursor in the same place, however,
> >     >    |   doesn't have this problem - it sticks near the boundary.
> >     >
> >     > #1 is clearly a bug.  C-n should be symmetrical with C-p.
> >
> >     I don't see where else the cursor can possibly go in #1.
> >
> > It can go to after the bar.  That's where it should go.
>
> This logic is wrong.  Consider the case where there is a field' in the
> region denoted XXXXXX; everywhere else, the `field' property is null.
> Point is initially located at the position indicated by `|'.
>
>   |
> XXXXXXXXX
>
> Clearly, pressing C-n should move point to the start of the field.
> The trouble is that the example given by Ken is a particular case
> where it *looks* as though the behavior you describe makes sense; but
> in the more general case, it is wrong.

the difference here is that, in my model for #1, above, the "|" cursor
is starting from within a field marked XXXXXX.  if you implement what
you describe below, column-sticky would be provided, as i wish.

> >       The logic of
> >     line-move is like this: "Try to naively move the cursor vertically
> >     down.  If this moves us into a new field, go instead to the beginning
> >     of the field (if going forward) or the end of the field (if going
> >     backward)."
> >
> > I'm saying we need to change that logic, so that the results
> > will be good.
> >
> > I think we need a concept of temporary goal fields to go with the
> > temporary goal column.  When you type the first line-move command
> > it should record some info about the field you're in when you start.
> > Then if a field with the same property appears on the line you move to,
> > it should be handled as if it were -- in some sense -- "the same".
>
> This is a feature, not a bug.

in the situation as it's been, i was in a bind.  i wanted to use
fields to get ^A to respect the boundary between the content and
structure parts of the item head lines.  i didn't want to sacrifice
column-stickiness when moving between successive head lines.  as far
as i can see, by calling this a feature, you're suggesting that i
should either give up on the ^A functionality or column-stickiness.

i originally suggested a setting that would stop this misbehavior, and
give me both.  it's not an ideal solution, but it stops line moves
from being disruptive without sacrificing the ^A respect for the
boundary.  richard suggested instead seeking refinements to the
fields/line-move model that would extend it to accomodate my concerns.
 i think the model extension that he suggested (and that you are
accepting, below) does that.  moreover, i think this extension fixes a
deficiency in the model.

to me, the bug or feature question is, is my content/structure
demarcation for ^A a misuse of fields?  if so, then i'm asking for a
new fields feature.  if not (and i think not), then i'm asking for a
fix in the fields model.

> But if this behavior (i.e., treating non-contiguous fields as
> identical for the purpose of line-motion) is really the behavior you
> want, and we agree that it will close this bug, I can implement this
> even more simply than that, by comparing `field' properties at the
> relevant places inside line-move-finish.

thanks - i think this will work well for my purposes.

-- 
ken
ken.manheimer@gmail.com
http://myriadicity.net