Re: fill-paragraph ill designed

[Tassilo Horn <tsdh@gnu.org>]

Andreas Röhler <andreas.roehler@online.de> writes:

> There are many issues, uncertain/unsound decisions inside this piece
> of code.
>
> Let's start with fill-paragraph-function.
>
> If fill-paragraph-function is set, it must be assumed a valid function
> and be used.

That's not what the documentation says:

,----[ C-h f fill-paragraph RET ]
| fill-paragraph is an interactive compiled Lisp function in ‘fill.el’.
| 
| [...]
| 
| The REGION argument is non-nil if called interactively; in that
| case, if Transient Mark mode is enabled and the mark is active,
| call ‘fill-region’ to fill each of the paragraphs in the active
| region, instead of just filling the current paragraph.
`----

So if there is an active region, `fill-paragraph' just calls
`fill-region', and then the `fill-paragraph-function' is irrelevant.

> So it must precede that clause:
>
> (and region transient-mark-mode mark-active

If `fill-paragraph' would call `fill-paragraph-function' also in this
case, then there are two options:

  (1) `fill-paragraph's documentation stays what it is, and then every
      `fill-paragraph-function' ever going to be defined has to handle
      the active region case and call `fill-region'.

  (2) `fill-paragraph' can't specify any special behavior for the case
      where the region is active.  It might just say that it itself
      behaves differently with an active region when f-p-f is nil.

Option (1) is useless, and option (2) is confusing and might lead to
inconsistent behavior, e.g., in some modes `M-q' with an active region
fills the region (because f-p-f is nil or a function which considers the
active region case) and in some other modes it just fills the current
paragraph (because f-p-f is set to some function which doesn't consider
the active region case).

Bye,
Tassilo