* Hongyi Zhao <hongyi.zhao@gmail.com> [2021-06-14 10:04]:
> When I typeset LaTeX source file in Emacs with auctex enabled, I
> want to know if the features like tooltip and incremental drop-down
> menus of automatic completion are available.

I don't know about the tooltip, that usually shortly explains the icon
in the toolbar.

Completion of macros is available with C-M-i, for example you write:

\use and press C-M-i then you get possible completions:

Click on a completion to select it.
In this buffer, type RET to select the completion near point.

Possible completions are:
usebox
usecounter
usepackage

If you write:

\usep

and press C-M-i it completes to \usepackage

Now to get an incremental drop down meny I may recommend using package
`ivy' from GNU ELPA as that would open up the possible completions
when using macro completion key bindings C-M-i 

See screenshot attached, as it shows possible incremental completion
next to the cursor, that is `ivy' package doing it.

-- 
Jean

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