On Sun, May 28, 2017 at 6:50 AM, Nikolay Aleksandrovich Pavlov
<zyx.vim@gmail.com> wrote:
> 2017-05-28 8:57 GMT+03:00 Bram Moolenaar <Bram@moolenaar.net>:
>>
>> Nikolay Pavlov wrote:
>>
>> [..]
>>
>>> >> Enable, disable, query, execute plus two callbacks. *Four* functions
>>> >> and two callbacks in place of just two simple functions, mostly using
>>> >> the functionality that is already there. Five if you remember about
>>> >> :mkvimrc and that somebody may want to replace that on top of new API:
>>> >> query will need a mirror function for creating a mapping then.
>>> >
>>> > You are completely missing the point: those two functions don't provide
>>> > the functionality we are talking about here.
>>>
>>> Why do you think so? They provide everything what is needed to
>>> implement the functionality we are talking about here in VimL.
>>
>> This whole discussion started about the difficutly of using the result
>> of maparg(). As far as I can see you only provide a function to get more
>> mappings, it doesn't help with disabling and restoring mappings.
>> Dealing with that is not easy at all (dealing with modes,
>> escaping/unescaping, etc). I would not want every plugin writer to
>> re-invent the wheel.
>>
>> The basic discussion first need to be held is whether to refer to a
>> mapping just by its LHS (plus mode) or a unique handle can be used. The
>> latter is useful if we disable a mapping but not delete it, it can then
>> be shadowed by another mapping.
>>
>> We probably also need some kind of re-enable or restore function, that
>> takes the result of maparg() and defines a mapping with it. That avoids
>> string manipulation and using :exe (this is tricky because of the way
>> mappings need some characters to be escaped).
>
> Three functions:
>
> 1. Get mappings: mappings_dump(). Needs to output lhs and rhs in some
> canonical form. Takes an argument which allows some basic filtering:
> e.g. select only mappings belonging to buffer with number N or
> globals, select only mappings with given modes and select only
> mappings starting with some prefix.
> 2. Create mappings: mappings_load(). Takes output from
> mappings_dump(), with the help of mappings_canonicalize() it should be
> possible to create your own mappings.
> 2.1. Something to delete mappings: mappings_load() with missing rhs or
> mappings_clear() which takes output of mappings_dump() and deteletes
> those mappings.
> 3. Create string for lhs or rhs in canonical form given something like
> `"\<F1>"` or `"<F1>"` (not sure what would be better) as the input:
> mappings_canonicalize().
>
> So "disabling" is
>
> let disabled_mappings = mappings_dump(some_filter)
> call filter(disabled_mappings, some_more_complex_filter_if_needed)
> call mappings_load(map(deepcopy(disabled_mappings),
> \'[remove(v:val, "rhs"), v:val][-1]'))
>
> "Enabling" is
>
> call mappings_load(disabled_mappings)
>
> One of the key points is that mappings_dump() and mappings_load() need
> to work with canonical form of lhs and rhs strings and thus
> dictionaries returned by them are not entirely compatible with
> maparg() results. Canonical form needs to be independent of
> &cpoptions, allow distinguishing `<LT>F1>` and `<F1>` and
> `mappings_canonicalize(mappings_canonicalize(x))` should be identical
> to `mappings_canonicalize(x)`.
>
> ---
>
> You may also ask Brett Stahlman whether my proposal is enough, it does
> not look like he thinks it is not, just that it may be less
> convenient.
I believe it would be possible to do pretty much anything with the
functions you propose, though for some common use cases, it puts more of
a burden on the user than may be warranted. Yes,
some_more_complex_filter_if_needed could be a function that tests
canonical lhs for conflict/ambiguity, retaining only the ambiguous maps,
and a subsequent call to mappings_load() (passing the filtered results
with 'rhs' key removed) could be used to delete the conflicting
mappings. But this feels a bit roundabout and error-prone compared to...
let handles = maplist('<F8>', 'nv')
call disable_maps(handles)
Question: Would the map handles be mode-specific? E.g., for a map
defined with :map, would there be 1 or 3 handles? I'm assuming that your
mappings_dump() would return a single dict with a modes flag of 'nvo' or
something like that. It occurs to me that either approach could allow
finer-grained control than the :*map commands provide, and could obviate
the need for kludges like this (from the help on omap-info):
{{{
To enter a mapping for Normal and Visual mode, but not Operator-pending mode,
first define it for all three modes, then unmap it for Operator-pending mode:
:map xx something-difficult
:ounmap xx
Likewise for a mapping for Visual and Operator-pending mode or Normal and
Operator-pending mode.
}}}
Also note that your approach does more than simply *disable*; it
actually *removes* the mappings as far as Vim is concerned. Granted, if
we keep a reference to disabled_mappings, it would be easy enough to
recreate them later, but I would imagine this is significantly less
efficient than simply toggling an internal flag indicating enabled
status. Also, as I mentioned before, I don't think checking for
ambiguity/conflict is something that *should* be done by a plugin
developer. Sure, a plugin developer should be capable of writing an
algorithm to do this (assuming he has access to a canonical lhs), but
forcing each plugin developer to do it just feels wrong to me, even if
it ends up being a smallish predicate function/filter (and I suspect
doing it robustly would end up being more than a one-liner). Thus, at
the very least, I would propose having mappings_dump() accept an input
that requests ambiguous/conflicting maps only, or else a separate
function such as mappings_get_conflicts().
As I see it, your approach gives the plugin developer access to all map
information, and lets him do whatever he wants with it, provided he's
willing to do the work of slicing and dicing the data using Vim's list
and dict manipulation functions. By providing all relevant data, while
making few, if any, assumptions about the things a plugin developer
might want to do with that data, you make nothing particularly easy, but
everything possible. This is not wrong. It's simply a lower-level
approach than what I was originally envisioning. Your argument is
essentially that it's better to re-use existing data structures, in
conjunction with sequence manipulation primitives like map() and
filter(), than to invent a DSL whose purpose is to reduce tedious
boilerplate as well as the potential for error associated with the most
common map-related use cases. The advantage, I suppose, is that your
approach is probably less work for Bram, fewer bugs for him to work
through, and ultimately pretty flexible for a competent plugin developer
who doesn't mind a litle extra data massaging. Whereas creating a DSL
forces you (hopefully only once) to think through the likely use cases
and make decisions about the sorts of things that *should* be done with
the DSL, your approach leaves such decisions to each and every plugin
developer: very flexible, but at the cost of forcing each plugin
developer to reinvent the wheel for the most common cases. Ideal, in my
opinion, would be a DSL that facilitated the common cases, without
precluding resort to the brute-force, low-level primitives for those use
cases not envisioned by the DSL designers...
Though I'm not set on the "handle" abstraction, I do think the fact that
Bram and I were independently thinking about the insulation it would
provide from implementation details is probably an indication that the
advantages are at least worth considering. (OTOH, I can also see a
certain attractive simplicity in the use of maparg-style dictionaries as
"handles".) I do think the prolog/epilog callbacks I mentioned in an
earlier post would be a powerful mechanism for plugin developers. (Of
course, it should be possible to implement these with your approach as
well.)
Idea: It would be even more powerful if there were a way to attach the
callbacks to a *partial* map sequence, or alternatively, a way to
"monitor" an "in-progress" map sequence that hasn't yet triggered: e.g.,
a callback function that fires each time a key is pressed, which
receives not only the last key pressed, but also the entire sequence
entered thus far (and possibly even the time remaining on the map
timeout). The default behavior would be to allow the sequence entry to
continue normally, but the callback function would also have the ability
to change the sequence currently recognized to something completely
different: i.e., the callback would be able to manipulate the typeahead
buffer. I'm thinking this sort of capability could be useful for the
handling of `->' in the transliteration mode you were describing in an
earlier email. In my own case, I'm wanting to implement a temporary
"escape" from the special mode I described earlier: though I'm
overriding builtin maps in special mode, I'd like to allow the user to
execute a builtin (without getting out of special mode) by prefixing it
with some sort of escape (e.g., `\', or `,'). I can achieve something
like what I want by defining maps for things like `\d', and using
feedkeys() or normal! in the map handler to execute builtin d, but this
forces me to define a bunch of maps I don't really need. It would be
nice if I could monitor the progress of a map as it's entered and simply
"lie" to Vim about what's been entered when the callback logic decides
it's appropriate. At any rate, I've digressed from the original topic a
bit...
>
> ---
>
> And why do you think that "do not make plugins reinwent the wheel" is
> the same statement as "write needed functionality in C code"? You can
> always add a new file to `autoload`, writing VimL code is easier then
> writing C code.
You mean implementing a sort of "DSL" layer (using the primitive
functions you've proposed) in Vim script, and including it in the
official distribution as an autoload file? If so, I suppose this could
be done, but as part of the official distribution, it would still need
to be thought through and tested pretty thoroughly, so I don't see much
advantage over implementing it in source, where it would be
significantly more efficient. But perhaps I misunderstood what you were
suggesting...
Sincerely,
Brett Stahlman
>
>>
>> --
>> A village. Sound of chanting of Latin canon, punctuated by short, sharp
>> cracks. It comes nearer. We see it is a line of MONKS ala SEVENTH SEAL
>> flagellation scene, chanting and banging themselves on the foreheads with
>> wooden boards.
>> "Monty Python and the Holy Grail" PYTHON (MONTY) PICTURES LTD
>>
>> /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net \\\
>> /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\
>> \\\ an exciting new programming language -- http://www.Zimbu.org ///
>> \\\ help me help AIDS victims -- http://ICCF-Holland.org ///
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