path: root/Doc/Zsh/compwid.yo

texinode(Completion Widgets)(Zsh Modules)(Programmable Completion)(Top)
chapter(Completion Widgets)
cindex(completion, widgets)
cindex(completion, programmable)
cindex(completion, controlling)
sect(Description)
Completion widgets are defined by the tt(-C) option to the tt(zle)
builtin command provided by the tt(zle) module (see
ifzman(zmanref(zshzle))\
ifnzman(noderef(The zle Module))\
). For example,

indent(
nofill(tt(zle -C complete expand-or-complete completer))
)

defines a widget named tt(complete). When this widget is bound to a key
using the tt(bindkey) builtin command defined in the tt(zle) module
(see 
ifzman(zmanref(zshzle))\
ifnzman(noderef(Zsh Line Editor))\
), typing that key will call the shell function tt(completer). This
function is responsible for generating the possible matches using the
builtins described below. Once the function returns, the completion code
takes over control again and treats the matches as the builtin widget
tt(expand-or-complete) would do.  For this second argument, the name of any
of the builtin widgets that handle completions can be given:
tt(complete-word), tt(expand-or-complete),
tt(expand-or-complete-prefix), tt(menu-complete),
tt(menu-expand-or-complete), tt(reverse-menu-complete),
tt(list-choices), or tt(delete-char-or-list).

startmenu()
menu(Special Parameters)
menu(Builtin Commands)
menu(Condition Codes)
menu(Examples)
endmenu()

texinode(Special Parameters)(Builtin Commands)()(Completion Widgets)
sect(Special Parameters)

Inside completion widgets, and any functions called from those, some
parameters have special meaning; outside these function they are not
special to the shell in any way.  These parameters are used to pass
information between the completion code and the completion widget. Some of
the builtin commands and the condition codes use or change the current
values of these parameters.  Any existing values will be hidden during
execution of completion widgets; except for tt(compstate), the parameters
are reset on each function exit (including nested function calls from
within the completion widget) to the values they had when the function was
entered.

startitem()
item(tt(words))(
This array contains the words present on the command line currently being
edited.
)
item(tt(CURRENT))(
This is the number of the current word, i.e. the word the cursor is
currently on in the tt(words) array.  Note that this value is only
correct if the tt(ksharrays) options is not set.
)
item(tt(PREFIX))(
Initially this will be set to the part of the current word from the
beginning of the word up to the position of the cursor; it may be altered
to give a common prefix for all matches.
)
item(tt(IPREFIX))(
Initially this will be set to the empty string.  It functions like
tt(PREFIX), and gives a string which precedes the one in tt(PREFIX) and is
not considered part of the list of matches.  Typically, a string is
transferred from the beginning of tt(PREFIX) to the end of tt(IPREFIX), for
example:

tt(indent(
nofill(IPREFIX=${PREFIX%%\=*}=)
nofill(PREFIX=${PREFIX#*=})
))

causes the part of the prefix up to and including the first equal sign not
to be treated as part of a matched string.
)
item(tt(SUFFIX))(
Initially this will be set to the part of the current word from the
cursor position to the end; it may be altered to give a common suffix for
all matches.  It is most useful when the option tt(COMPLETE_IN_WORD) is
set, as otherwise the whole word on the command line is treated as a
prefix.
)
item(tt(ISUFFIX))(
As tt(IPREFIX), but for a suffix that should not be considered part
of the matches; note that the tt(ISUFFIX) string follows the tt(SUFFIX)
string.
)
item(tt(compstate))(
This is an associative array with various keys and values that the
completion code uses to exchange information with the completion widget.
The keys are:

startitem()
item(tt(context))(
This will be set by the completion code to the overall context
in which completion is attempted. Possible values are:

startitem()
item(tt(command))(
when completing for a normal command (either in a command position or for
an argument of the command).
)
item(tt(redirect))(
when completing after a redirection operator.
)
item(tt(condition))(
when completing inside a `tt([[)...tt(]])' conditional expression; in
this case the tt(words) array contains the words inside the
conditional expression.
)
item(tt(math))(
when completing in a mathematical environment such as a
`tt(LPAR()LPAR())...tt(RPAR()RPAR())' construct.
)
item(tt(value))(
when completing the value of a parameter assignment.
)
item(tt(array_value))(
when completing inside the value of an array parameter assignment; in
this case the tt(words) array contains the words inside the parentheses.
)
item(tt(subscript))(
when completing inside a parameter subscript.
)
item(tt(parameter))(
when completing the name of a parameter in a parameter expansion beginning
with tt($) but not tt(${).
)
item(tt(brace_parameter))(
when completing the name of a parameter in a parameter expansion beginning
with tt(${).
)
enditem()
)
item(tt(parameter))(
The name of the parameter when completing in a subscript or in the
value of a parameter assignment.
)
item(tt(redirect))(
The redirection operator when completing in a redirection position,
i.e. one of tt(<), tt(>), etc.
)
item(tt(quoting))(
When completing inside single quotes, this is set to the string
tt(single); inside double quotes, the string
tt(double); inside backticks, the string tt(backtick).
Otherwise it is unset.
)
item(tt(quote))(
When completing inside quotes, this contains the quotation character
(i.e. either a single quote, a double quote, or a backtick).  Otherwise it
is unset.
)
item(tt(nmatches))(
The number of matches generated and accepted by the completion code so far.
)
item(tt(matcher))(
When completion is performed with a global match specification as defined
by

indent(
nofill(tt(compctl -M) var(spec1 ... specN ...))
)

this gives the number of the specification string currently in use.
In this case, matching is performed with each specification in turn.
)
item(tt(matcher_string))(
The global match specification string var(specN) currently used.
)
item(tt(total_matchers))(
The total number of global match specifications.
)
item(tt(restore))(
This is set to tt(auto) before a function is entered, which forces the
special parameters mentioned above (tt(words), tt(CURRENT), tt(PREFIX),
tt(IPREFIX), tt(SUFFIX), and tt(ISUFFIX)) to be restored to their
previous values when the function exits.   If a function unsets it or
sets it to any other string, they will not be restored.
)
item(tt(list))(
This controls whether or how the list of matches will be displayed.  If it
is unset or empty they will never be listed; if is set to tt(list), they
will always be listed; if tt(autolist) or tt(ambiguous), they will be
listed when the tt(AUTO_LIST) or tt(LIST_AMBIGUOUS) options respectively
would normally cause them to be.  It will be set appropriately on entry to
a completion widget and may be changed there.
)
item(tt(force_list))(
If the value for the tt(list) key is tt(ambiguous), the list will
normally be shown only if there are at least two matches in the
list. Setting tt(force_list) to an non-empty string forces the list to be
shown even if there is only one match.
)
item(tt(list_max))(
Initially this is set to the value of the tt(LISTMAX) parameter.
It may be set to any other numeric value; when the widget exits this value
will be used in the same way as the value of tt(LISTMAX).
)
item(tt(last_prompt))(
If this is set to an non-empty string, the completion code will move
the cursor back to the previous prompt after the list of completions
has been displayed.  Initially this is set or unset according to
the tt(ALWAYS_LAST_PROMPT) option.
)
item(tt(insert))(
This controls the manner in which a match is inserted into the command
line.  On entry to the widget fuction, if it is unset the command line is
not to be changed; if set to tt(unambiguous), any prefix common to all
matches is to be inserted; if set to tt(menu) or tt(automenu) the usual
behaviour of the tt(MENU_COMPLETE) or tt(AUTO_MENU) options, respectively,
is to be used.

On exit it may be set to any of the values above, or to a number, in which
case the match whose number is given will be inserted into the command line.
It may also be set to a string of the form `var(group):var(match)' which
specifies a match from a group of matches to be inserted, counting from 1
upwards (e.g. `tt(2:4)' specifies the fourth match of the second group).
Negative numbers count backward from the last match or group (with `tt(-1)'
selecting the last match or group) and out-of-range values are wrapped
around, so that a value of zero selects the last match or group and a value
one more than the maximum selects the first.
)
item(tt(to_end))(
Specifies the occasions on which the cursor is moved to the end of a string
when a match is inserted.  On entry to a widget function, it may be
tt(single) if this will happen when a single unambiguous match was inserted
or tt(match) if it will happen any time a match is inserted (for example,
by menucompletion; this is likely to be the effect of the tt(ALWAYS_TO_END)
option).

On exit, it may be set to tt(single) as above.  It may also be set to
tt(always), or to the empty string or unset; in those cases the cursor will
be moved to the end of the string always or never respectively.  Any
other string is treated as tt(match).
)
item(tt(old_list))(
This is set to tt(yes) if there is still a valid list of completions
from a previous completion at the time the widget is invoked.  This will
usually be the case if and only if the previous editing operation was a
completion widget or one of the builtin completion fuctions.  If there is a
valid list and it is also currently shown on the screen, the value of this
key is tt(shown).

After the widget has exited the value of this key is only used if it
was set to tt(keep).  In this case the completion code will continue
to use this old list.  If the widget generated new matches, they will
not be used.
)
item(tt(old_insert))(
On entry to the widget this will be set to the number of the match of
an old list of completions that is currently inserted into the command
line. If no match has been inserted, this is unset.

As with tt(old_list), the value of this key will only be used if it is the
string tt(keep). If it was set to this value by the widget and there was an
old match inserted into the command line, this match will be kept and if
the value of the tt(insert) key specifies that another match should be
inserted, this will be inserted after the old one.
)
item(tt(exact))(
Controls the behaviour when the tt(REC_EXACT) option is set.  It will be
set to tt(accept) if an exact match would be accepted, and will be unset
otherwise.
)
item(tt(exact_string))(
The string of an exact match if one was found, otherwise unset.
)
item(tt(pattern_match))(
Locally controls the behaviour given by the tt(GLOB_COMPLETE) option.
Initially it is set to `tt(*)' if and only if the option is set.
The completion widget may set it to either of these two values, or to any
other non-empty string.  If it is non-empty, unquoted metacharacters on the
command line will be treated as patterns; if it is `tt(*)', then
additionally a wildcard `tt(*)' is assumed at the cursor position; if
it is empty or unset, metacharacters will be treated literally.
)
item(tt(pattern_insert))(
Normally this is set to tt(menu), which specifies that menu-completion will
be used whenever the matches were generated using pattern matching. If it
is set to any other non-empty string by the user and menu-completion is
not selected by other option settings, the code will insert an
unambiguous string for the generated matches as with normal completion.
)
item(tt(unambiguous))(
This key is read-only and will always be set to the unambiguous string
the completion code has generated for all matches added so far.
)
item(tt(unambiguous_cursor))(
This gives the position the cursor would be placed at if the
unambiguous string in the tt(unambiguous) key were inserted, relative to
the value of that key. The cursor would be placed before the character
whose index is given by this key.
)
enditem()
)
enditem()

texinode(Builtin Commands)(Condition Codes)(Special Parameters)(Completion Widgets)
sect(Builtin Commands)
startitem()
findex(compgen)
item(tt(compgen) var(flags ...))(

Generate matches according to the given var(flags).  These can be any of 
the normal option flags (not those for extended completion) supported by
the tt(compctl) builtin command (see
ifzman(zmanref(zshcompctl))\
ifnzman(noderef(Programmable Completion))\
) except for the tt(-t) and tt(-l) flags.  However, when using the tt(-K)
flag, the function given as argument to it cannot access the command
line with the tt(read) builtin command.

The matches will be generated in the same way as if the completion code
generated them directly from a tt(compctl)-definition with the same
flags. The completion code will consider only those matches as
possible completions that match the prefix and suffix from the special 
parameters desribed above. These strings will be compared with the
generated matches using the normal matching rules and any matching
specifications given with the tt(-M) flag to tt(compgen) and the
global matching specifications given via the tt(compctl -M )var(spec1 ...)
builtin command.

The return value is zero if at least one match was added and non-zero
otherwise.
)
xitem(tt(compadd) [ tt(-qQfnUam) ] [ tt(-F) var(array) ])
xitem([ tt(-P) var(prefix) ] [ tt(-S) var(suffix) ])
xitem([ tt(-p) var(hidden-prefix) ] [ tt(-s) var(hidden-suffix) ])
xitem([ tt(-i) var(ignored-prefix) ] [ tt(-I) var(ignored-suffix) ])
xitem([ tt(-W) var(file-prefix) ])
xitem([ tt(-J) var(name) ] [ tt(-V) var(name) ] [ tt(-X) var(explanation) ])
xitem([ tt(-r) var(remove-chars) ] [ tt(-R) var(remove-func) ])
xitem([ tt(-M) var(match-spec) ] [ tt(-O) var(array) ] [ tt(-A) var(array) ])
item([ tt(--) ] [ var(words) ... ])(

This builtin command can be used to add matches directly and control
all the information the completion code stores with each possible
match. The return value is zero if at least one match was added and
non-zero if no matches were added.

The completion code breaks the string to complete into seven fields in
the order: 

indent(
var(<ipre><apre><hpre><word><hsuf><asuf><isuf>)
)

The first field
is an ignored prefix taken from the command line, the contents of the
tt(IPREFIX) parameter plus the string given with the tt(-i)
option. With the tt(-U) option, only the string from the tt(-i)
option is used. The field var(<apre>) is an optional prefix string
given with the tt(-P) option.  The var(<hpre>) field is a string
that is considered part of the match but that should not be shown when 
listing completions, given with the tt(-p) option; for example,
functions that do filename generation might specify
a common path prefix this way. var(<word>) is the part of the match that
should appear in the list of completions, one of the tt(words) given at the
end. The suffixes var(<hsuf>), var(<asuf>) and var(<isuf>) correspond to
the prefixes var(<hpre>), var(<apre>) and var(<ipre>) and are given by the
options tt(-s), tt(-S) and tt(-I), respectively.

The supported flags are:

startitem()
item(tt(-P) var(prefix))(
As for tt(compctl) and tt(compgen), it gives a string to
be inserted before the given var(words).  The
string given is not considered as part of the match.
)
item(tt(-S) var(suffix))(
Like tt(-P) but gives a string to be inserted after the match.
)
item(tt(-p) var(hidden-prefix))(
This gives a string that should be inserted into the command line before the
match but that should not appear in the list of matches. Unless the
tt(-U) option is given, this string must be matched as part of the string
on the command line.
)
item(tt(-s) var(hidden-suffix))(
Like `tt(-p)', but gives a string to insert after the match.
)
item(tt(-i) var(ignored-prefix))(
This gives a string to insert into the command line just before any
string given with the `tt(-P)' option.  Without `tt(-P)' the string is
inserted before the string given with `tt(-p)' or directly before the
match.
)
item(tt(-I) var(ignored-suffix))(
Like tt(-i), but gives an ignored suffix.
)
item(tt(-J) var(name))(
As for tt(compctl) and tt(compgen), this gives the name of the group
of matches the words should be stored in.
)
item(tt(-V) var(name))(
Like tt(-J) but naming a unsorted group.
)
item(tt(-X) var(explanation))(
As for tt(compctl) and tt(compgen), the var(explanation) string will be
printed with the list of matches.
)
item(tt(-q))(
As for tt(compctl) and tt(compgen),
the suffix given with tt(-S) will be automatically removed if 
the next character typed is a blank or does not insert anything, or if
the suffix consists of only one character and the next character typed 
is the same character.
)
item(tt(-r) var(remove-chars))(
This is a more versatile form of the tt(-q) option.
The suffix given with tt(-S) will be automatically removed if
the next character typed inserts one of the characters given in the
var(remove-chars).  This string is parsed as a characters class and
understands the backslash sequences used by the tt(print) command.  For
example, `tt(-r "a-z\t")' removes the suffix if the next character typed
inserts a lowercase character or a TAB, and `tt(-r "^0-9")' removes the
suffix if the next character typed inserts anything but a digit. One extra
backslash sequence is understood in this string: `tt(\-)' stands for
all characters that insert nothing. Thus `tt(-S "=" -q)' is the same
as `tt(-S "=" -r "= \t\n\-")'.
)
item(tt(-R) var(remove-func))(
This is another form of the tt(-r) option. When a suffix given with the
tt(-S) option has been inserted and the completion accepted, the function
var(remove-func) will be called after the next character typed.  It is
passed the length of the suffix as an argument and can use the special
parameters available in ordinary (non-completion) zle widgets (see
ifzman(zmanref(zshzle))\
ifnzman(noderef(Zsh Line Editor))\
) to analyse and modify the command line.
)
item(tt(-f))(
If this flag is given, all of the matches built from var(words) are
marked as being the names of files.  They are not required to be actual
filenames, but if they are, and the option tt(LIST_TYPES) is set, the
characters describing the types of the files in the completion lists will
be shown. This also forces a slash to be added when the name of a
directory is completed.
)
item(tt(-W) var(file-prefix))(
This option has the same meaning as for the tt(compctl) and
tt(compgen) builtin commands. Here, however, only one string may be
given, not an array. This string is a pathname that will be
prepended to each of the matches formed by the given var(words) together 
with any prefix specified by the tt(-p) option to form a complete filename
for testing.  Hence it is only useful if combined with the tt(-f) flag, as
the tests will not otherwise be performed.
)
item(tt(-a))(
In the tt(compctl) or tt(compgen) commands, the completion code normally
builds two sets of matches: the normal one where words with one of the 
suffixes in the array parameter tt(fignore) are not considered
possible matches, and the alternate set where the words excluded
from the first set are stored. Normally only the matches in the first
set are used, but if this set is empty, the words from the alternate
set are used.

The tt(compadd) builtin does not use tt(fignore) parameter and
normally stores all words in the first set.  With the tt(-a)-flag
given, however, the given var(words) are stored in the alternate set unless
this flag is overridden by the tt(-F) option.
)
item(tt(-F) var(array))(
Specifies an array containing suffixes in the same form as the
tt(fignore) parameter. Words with one of these suffixes are stored in
the alternate set of matches and words without one of these suffixes
are stored in the normal set.

The var(array) may be the name of an array parameter or a list of
literal suffixes enclosed in parentheses and quoted, as in `tt(-F "(.o
.h)")'. If the name of an array is given, the elements of the array are
taken as the suffixes.
)
item(tt(-Q))(
As for tt(compctl) and tt(compgen), this flag instructs the completion 
code not to quote any metacharacters in the words when inserting them
into the command line.
)
item(tt(-M) var(match-spec))(
As for tt(compctl) and tt(compgen), this gives local match specifications.
Note that they will only be used if the tt(-U) option is not given.
)
item(tt(-n))(
Specifies that the words added are to be used as possible
matches, but are not to appear in the completion listing.
)
item(tt(-U))(
If this flag is given, all words given will be accepted and no matching
will be done by the completion code. Normally this is used in
functions that do the matching themselves.

Note that with tt(compadd) this option does not automatically turn on
menu completion if tt(AUTO_LIST), unlike the corresponding option of
tt(compctl) and tt(compgen) commands.
)
item(tt(-O) var(array))(
If this option is given, the var(words) are em(not) added to the set of
possible completions.  Instead, matching is done as usual and all of the
var(words) given as arguments that match the string on the command line
will be stored in the array parameter whose name is given as var(array).
)
item(tt(-A) var(array))(
As the tt(-O) option, except that instead of those of the var(words) which
match being stored in var(array), the strings generated internally by the
completion code are stored. For example,
with a matching specification of `tt(-M "L:|no=")', the string `tt(nof)'
on the command line and the string `tt(foo)' as one of the var(words), this
option stores the string `tt(nofoo)' in the array, whereas the tt(-O)
option stores the `tt(foo)' originally given.
)
item(tt(-), tt(--))(
This flag ends the list of flags and options. All arguments after it
will be taken as the words to use as matches even if they begin with
hyphens.
)
enditem()
)
xitem(tt(compset -p) var(number))
xitem(tt(compset -P) [ var(number) ] var(pattern))
xitem(tt(compset -s) var(number))
xitem(tt(compset -S) [ var(number) ] var(pattern))
xitem(tt(compset -n) var(begin) [ var(end) ])
item(tt(compset -N) var(beg-pat) [ var(end-pat) ])(
This command simplifies modification of the special parameters,
while its return value allows tests on them to be carried out.

The options are:

startitem()
item(tt(-p) var(number))(
If the contents of the tt(PREFIX) parameter is longer than var(number)
characters, the first var(number) characters are removed from it and
appended to the contents of the tt(IPREFIX) parameter.
)
item(tt(-P) [ var(number) ] var(pattern))(
If the value of the tt(PREFIX) parameter begins with anything that
matches the var(pattern), the matched portion is removed from
tt(PREFIX) and appended to tt(IPREFIX).

Without the optional var(number), the longest match is taken, but
if var(number) is given, anything up to the var(number)'th match is
moved.  If the var(number) is negative, the var(number)'th longest
match is moved. For example, if tt(PREFIX) contains the string
`tt(a=b=c)', then tt(compset -P '*\=') will move the string `tt(a=b=)' 
into the tt(IPREFIX) parameter, but tt(compset -P 1 '*\=') will move only
the string `tt(a=)'.
)
item(tt(-s) var(number))(
As tt(-p), but transfer the last var(number) characters from the
value of tt(SUFFIX) to the front of the value of tt(ISUFFIX).
)
item(tt(-S) [ var(number) ] var(pattern))(
As tt(-P), but match the last portion of tt(SUFFIX) and transfer the
matched portion to the front of the value of tt(ISUFFIX).
)
item(tt(-n) var(begin) [ var(end) ])(
If the current word position as specified by the parameter tt(CURRENT) 
is greater than or equal to var(begin), anything up to the
var(begin)'th word is removed from the tt(words) array and the value
of the parameter tt(CURRENT) is decremented by var(begin).

If the optional var(end) is given, the modification is done only if
the current word position is also less than or equal to var(end). In
this case, the words from position var(end) onwards are also removed from
the tt(words) array.

Both var(begin) and var(end) may be negative to count backwards
from the last element of the tt(words) array.
)
item(tt(-N) var(beg-pat) [ var(end-pat) ])(
If one of the elements of the tt(words) array before the one at the
index given by the value of the parameter tt(CURRENT) matches the
pattern var(beg-pat), all elements up to and including the matching one are
removed from the tt(words) array and the value of tt(CURRENT) is changed to
point to the same word in the changed array.

If the optional pattern var(end-pat) is also given, and there is an
element in the tt(words) array matching this pattern, the parameters
are modified only if the index of this word is higher than the one
given by the tt(CURRENT) parameter (so that the matching word has 
to be after the cursor). In this case, the words starting with the one
matching tt(end-pat) are also removed from the tt(words)
array. If tt(words) contains no word matching var(end-pat), the
testing and modification is performed as if it were not given.
)
enditem()

In all the above cases the return value is zero if the test succeded
and the parameters were modified and non-zero otherwise. This allows
one to use this builtin in tests such as:

indent(
tt(if compset -P '*\='; then ...)
)

This forces anything up to and including the last equal sign to be
ignored by the completion code.
)
item(tt(compcall) [ tt(-TD) ])(

This allows the use of completions defined with the tt(compctl) builtin
from within completion widgets.  The list of matches will be generated as
if one of the non-widget completion function (tt(complete-word), etc.)
had been called, except that only tt(compctl)s given for specific commands
are used. To force the code to try completions defined with the tt(-T)
option of tt(compctl) and/or the default completion (whether defined by
tt(compctl -D) or the builtin default) in the appropriate places, the
tt(-T) and/or tt(-D) flags can be passed to tt(compcall).

The return value can be used to test if a matching tt(compctl)
definition was found. It is non-zero if a tt(compctl) was found and
zero otherwise.
)
enditem()

texinode(Condition Codes)(Examples)(Builtin Commands)(Completion Widgets)
sect(Condition Codes)

The following additional condition codes for use within the tt([[ ... ]])
construct are available in completion widgets.  These work on the special
parameters.  All of these tests can also be performed by the tt(compset)
builtin, but in the case of the condition codes the contents of the special
parameters are not modified.

startitem()
item(tt(-prefix) [ var(number) ] var(pattern))(
true if the test for the tt(-P) option of tt(compset) would succeed.
)
item(tt(-suffix) [ var(number) ] var(pattern))(
true if the test for the tt(-S) option of tt(compset) would succeed.
)
item(tt(-after) var(beg-pat))(
true if the test of the tt(-N) option with only the var(beg-pat) given 
would succeed.
)
item(tt(-between) var(beg-pat end-pat))(
true if the test for the tt(-N) option with both patterns would succeed.
)
enditem()

texinode(Examples)()(Condition Codes)(Completion Widgets)
sect(Examples)

The first step is to define the widget:

indent(nofill(
tt(zle -C complete complete-word complete-history)))

Then the widget can be bound to a key using the tt(bindkey) builtin
command:

indent(nofill(
tt(bindkey '^X\t' complete)))

After that the shell function tt(complete-history) will be invoked
after typing control-X and TAB. The function should then generate the
matches, e.g.:

indent(nofill(
tt(complete-history LPAR()RPAR() { compgen -H 0 '' })))

This function will complete words from the history matching the 
current word.

For a description of the widget-based completion system provided with the
source code distribution, see
ifzman(zmanref(zshcompsys))\
ifnzman(noderef(Completion System))\
.