On Tue, Nov 5, 2019 at 6:51 PM Eli Zaretskii <address@hidden
> The purpose of completion-first-difference is to help the user decide
> what to type next.
Indeed it does that. But there are equally efficient other ways to do the
same, in my opinion. One of them is to highlight the preceding
character. You can experiment by switching the values of the "common"
and "first-difference" faces. Do you think you've lost that help?
> What is the purpose of highlighting other parts of
> the candidates?
For a matching style such as flex or substring (as you would find in
many other editors) it's important to visually explain users to users
why certain strings that don't start with the pattern they entered
are being shown on the screen. I attach an image.
> (If there is no useful purpose, then we might as well
> do nothing and leave completion-first-difference the only important
> highlighting in all kinds of completion.)
completion-first-difference is at the very least a misnomer for
other types of completion, because with flex there can be infinitely
many "first" differences.