Re: [PATCH] (icomplete-vertical-mode): Add support for affixations and, annotations

[Juri Linkov]

> I also don't understand why :affixation-function is given a full list of
> completions, when it is presumably meant to return a list of exactly the
> same length.

This has the advantage in functions like read-extended-command--affixation,
where minibuffer-selected-window is selected only once with 
with-selected-window,
then all completions are processed in the same buffer, without the need
to switch buffers for every completion in a long list, as annotation-function
would require to do.

> Seems like a potential hazard to allow this function to do filtering.

OTOH, not allowing the function to do filtering is too much hand-holding
for users who want the freedom to transform the completions to their likings.