insert a line break.
second state:	  Insert the currently selected match.
third state:	  Use the text as it is and insert a line break.

In other words: If you used the cursor keys to select another entry in the
list of matches then the <Enter> key inserts that match.  If you typed
something else then <Enter> inserts a line break.


The colors of the menu can be changed with these highlight groups:
Pmenu		normal item  |hl-Pmenu|
PmenuSel	selected item  |hl-PmenuSel|
PmenuSbar	scrollbar  |hl-PmenuSbar|
PmenuThumb	thumb of the scrollbar  |hl-PmenuThumb|

There are no special mappings for when the popup menu is visible.  However,
you can use an Insert mode mapping that checks the |pumvisible()| function to
do something different.  Example: >
	:inoremap <Down> <C-R>=pumvisible() ? "\<lt>C-N>" : "\<lt>Down>"<CR>

You can use of <expr> in mapping to have the popup menu used when typing a
character and some condition is met.  For example, for typing a dot: >
	inoremap <expr> . MayComplete()
	func MayComplete()
	    if (can complete)
	      return ".\<C-X>\<C-O>"
	    endif
	    return '.'
	endfunc

See |:map-<expr>| for more info.


FILETYPE-SPECIFIC REMARKS FOR OMNI COMPLETION	    *compl-omni-filetypes*

The file used for {filetype} should be autoload/{filetype}complete.vim
in 'runtimepath'.  Thus for "java" it is autoload/javacomplete.vim.


C							*ft-c-omni*

Completion of C code requires a tags file.  You should use Universal/
Exuberant ctags, because it adds extra information that is needed for
completion.  You can find it here:
	Universal Ctags: https://ctags.io

Universal Ctags is preferred, Exuberant Ctags is no longer maintained.

If you want to complete system functions you can do something like this.  Use
ctags to generate a tags file for all the system header files: >
	% ctags -R -f ~/.config/nvim/systags /usr/include /usr/local/include
In your vimrc file add this tags file to the 'tags' option: >
	set tags+=~/.config/nvim/systags

When using CTRL-X CTRL-O after a name without any "." or "->" it is completed
from the tags file directly.  This works for any identifier, also function
names.  If you want to complete a local variable name, which does not appear
in the tags file, use CTRL-P instead.

When using CTRL-X CTRL-O after something that has "." or "->" Vim will attempt
to recognize the type of the variable and figure out what members it has.
This means only members valid for the variable will be listed.

When a member name already was complete, CTRL-X CTRL-O will add a "." or
"->" for composite types.

Vim doesn't include a C compiler, only the most obviously formatted
declarations are recognized.  Preprocessor stuff may cause confusion.
When the same structure name appears in multiple places all possible members
are included.


CSS							*ft-css-omni*

Complete properties and their appropriate values according to CSS 2.1
specification.


HTML							*ft-html-omni*
XHTML							*ft-xhtml-omni*

CTRL-X CTRL-O provides completion of various elements of (X)HTML files.  It is
designed to support writing of XHTML 1.0 Strict files but will also work for
other versions of HTML. Features:

- after "<" complete tag name depending on context (no div suggestion inside
  of an a tag); '/>' indicates empty tags
- inside of tag complete proper attributes (no width attribute for an a tag);
  show also type of attribute; "*" indicates required attributes
- when attribute has limited number of possible values help to complete them
- complete names of entities
- complete values of "class" and "id" attributes with data obtained from
  <style> tag and included CSS files
- when completing value of "style" attribute or working inside of "style" tag
  switch to |ft-css-omni| completion
- when completing values of events attributes or working inside of "script"
  tag switch to |ft-javascript-omni| completion
- when used after "</" CTRL-X CTRL-O will close the last opened tag

Note: When used first time completion menu will be shown with little