Re: Stepping Back: A Wealth Of Completion systems Re: [ELPA] New package: vertico

[Daniel Mendler]

On 4/7/21 4:15 PM, Philip Kaludercic wrote:
> I think I've also mentioned that selection can be hierarchical. I think
> this too would be applicable to insert-char, considering how unicode
> divided into groups and subgroups.

I agree that hierarchical selection can be useful when browsing through 
a structure. However when doing a quick selection, I perceive it as 
slower. For example there is imenu, where you have to step through 
multiple layers of the hierarchy to reach the destination. A popular 
demand is for a flattened imenu which allows faster completion, see for 
example the package flimenu or counsel-imenu. But as soon as you flatten 
you certainly use the ability to browse the structure, so you have some 
point.

> All of these features already exist, partially or only to the degree it
> is found to be necessary. Eg. ibuffer has hierarchies and the ability to
> filter by some preconfigured predicates. I think that there is a general
> pattern here that can be exploited to make the overall experience more
> uniform.

I wonder how all these use cases could be unified under a common API. I 
would certainly not want to lose the current fast, flat selection 
mechanism via completion as offered by `completing-read'.

Regarding predicates, there is an idea how this could be integrated with 
completion. One can implement a completion style which support a filter 
language, depending on the completion category. The completion style can 
then execute the filter predicates on the corresponding objects. However 
such an approach certainly takes it a bit far as completion styles are 
concerned. I think Icicles offers options to filter within completion 
based on predicates?

Daniel Mendler