[xmonad] Two patches related to XMonad.Prompt

[Norbert Zeh]

I also noticed that some prompts don't use the searchPredicate.  In my
setup, I'm using the fuzzy matching for matching windows, Thunar bookmarks,
and xrandr settings.  The first of course already uses searchPredicate and
the latter two are custom prompts in my xmonad.hs that I wrote to use
searchPredicate.

X.P.Shell is a particular example that does not use searchPredicate, if I
recall correctly.  All specific instantiations of X.Prompt essentially
decide individually how to define the completion function passed to
mkXPrompt.  I think most existing prompts can be rewritten to use
searchPredicate, but this of course doesn't prevent anybody from writing
new prompt instances that don't use it.  One (bad) possibility to prevent
this would be to change mkXPrompt so that the "completion function" it
accepts is not actually a completion function that depends on the search
string but simply a function that generates all candidates to be filtered
using searchPredicate.  That's a bad idea, though, because (a) it breaks
the current API and thus any setup that includes custom prompts like mine
and (b) it is possible that there are cases where generating all possible
candidates and then filtering matches is impossible or prohibitively
expensive while generating candidate completions based on the current query
string is possible and efficient (e.g., a prompt to list the top 10 matches
of a Google search).

Cheers,
Norbert

On Wed, Apr 15, 2015 at 10:18 AM Brent Yorgey <byorgey at gmail.com> wrote:

> OK, I've made some progress figuring out what is going on.  In short: the
> searchPredicate field is never used in XMonad.Prompt!  The only place the
> searchPredicate is used is in XMonad.Prompt.Window, in the definition of
> the doPrompt function.  So this will work if you happen to be using a
> prompt to pick a window, but not for any other sort of prompt.
>
> This actually seems like a bug in XMonad.Prompt.  At some point someone
> added a searchPredicate field to the XPConfig, but forgot to actually use
> it to filter completion results.
>
> Norbert, is this something you could look into?  I've looked through
> XMonad.Prompt briefly but not sure where the right place is for this to
> go.  I'll probably get around to it eventually if no one else does.
>
> -Brent
>
> On Fri, Apr 3, 2015 at 6:08 PM Brent Yorgey <byorgey at gmail.com> wrote:
>
>> Hmm, I tried it out but can't seem to get it to work.  Mysterious.  The
>> patches are definitely applied, my xmonad.hs includes definitions for
>> sorter and searchPredicate, it compiles cleanly, but when I open a prompt
>> it has the same behavior as before.
>>
>> I'll try to spend some more time tracking down what is going on but just
>> wanted to briefly report.
>>
>> -Brent
>>
>> On Mon, Mar 23, 2015 at 2:39 PM Brent Yorgey <byorgey at gmail.com> wrote:
>>
>>>
>>>
>>> ---------- Forwarded message ---------
>>> From: Norbert Zeh <nzeh at cs.dal.ca>
>>> Date: 12:59pm, Sat, Mar 14, 2015
>>> Subject: [xmonad] Two patches related to XMonad.Prompt
>>> To: xmonad at haskell.org <xmonad at haskell.org>
>>>
>>>
>>> Hi folks,
>>>
>>> I really got used to using emacs ido mode, which offers a pretty
>>> powerful and intuitive fuzzy matching of completions, so I wanted to port
>>> the same to XMonad.Prompt.  This required two patches, included in the
>>> attached patch bundles:
>>>
>>> (1)  Completions should be sortable by how well they match the current
>>> query string.  This turned out to be a very easy addition of a 'sorter'
>>> function to XPConfig, which is parameterized by the current query string.
>>> The default is 'const id', that is, no sorting is done, which is exactly
>>> the old behaviour of XMonad.Prompt.
>>>
>>> (2)  A new module XMonad.Prompt.FuzzyMatch that implements the fuzzy
>>> matching.  The exact rules for matching and sorting of matches are
>>> explained in its documentation.
>>>
>>> As usual, let me know if anything needs to straightened out before these
>>> patches can be applied.
>>>
>>> Cheers,
>>> Norbert
>>>
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