Re: fill-paragraph ill designed

["Andreas Röhler" <andreas.roehler@online.de>]

Am 25.08.2015 um 11:05 schrieb Tassilo Horn:
> 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.

Yeah, but that's unhappy. Where the global fill-paragraph should know 
from, what's needed in a special mode, what special modes want to do 
with strings?

Other way around: any fill-paragraph-function is free to check for 
region as done here.

>> 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'.

That's completely up to the mode how to proceed then. There too many 
unforseen cases - just keep the way free, keep Emacs expandable.



>    (2) `fill-paragraph' can't specify any special behavior for the case
>        where the region is active.

If it's all up to fill-paragraph-function, global fill-paragraph would 
be out of the way.


>   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
>

Cheers,

Andreas