4.3.1 Group Specifications

The suffix and infix commands of a transient are organized in groups. The grouping controls how the descriptions of the suffixes are outlined visually but also makes it possible to set certain properties for a set of suffixes.

Several group classes exist, some of which organize suffixes in subgroups. In most cases the class does not have to be specified explicitly, but see Group Classes.

Groups are specified in the call to transient-define-prefix, using vectors. Because groups are represented using vectors, we cannot use square brackets to indicate an optional element and instead use curly brackets to do the latter.

Group specifications then have this form:

[{LEVEL} {DESCRIPTION} {KEYWORD VALUE}... ELEMENT...]

The LEVEL is optional and defaults to 4. See Enabling and Disabling Suffixes.

The DESCRIPTION is optional. If present, it is used as the heading of the group.

The KEYWORD-VALUE pairs are optional. Each keyword has to be a keyword symbol, either :class or a keyword argument supported by the constructor of that class.

• One of these keywords, :description, is equivalent to specifying DESCRIPTION at the very beginning of the vector. The recommendation is to use :description if some other keyword is also used, for consistency, or DESCRIPTION otherwise, because it looks better.
• Likewise :level is equivalent to LEVEL.
• Other important keywords include the :if... keywords. These keywords control whether the group is available in a certain situation.

  For example, one group of the magit-rebase transient uses :if magit-rebase-in-progress-p, which contains the suffixes that are useful while rebase is already in progress; and another that uses :if-not magit-rebase-in-progress-p, which contains the suffixes that initiate a rebase.

  These predicates can also be used on individual suffixes and are only documented once, see Predicate Slots.

• The value of :hide, if non-nil, is a predicate that controls whether the group is hidden by default. The key bindings for suffixes of a hidden group should all use the same prefix key. Pressing that prefix key should temporarily show the group and its suffixes, which assumes that a predicate like this is used:

  (lambda ()
    (eq (car transient--redisplay-key)
        ?\C-c)) ; the prefix key shared by all bindings
  

• The value of :setup-children, if non-nil, is a function that takes one argument, a potentially list of children, and must return a list of children or an empty list. This can either be used to somehow transform the group’s children that were defined the normal way, or to dynamically create the children from scratch.

  The returned children must have the same form as stored in the prefix’s transient--layout property, but it is often more convenient to use the same form as understood by transient-define-prefix, described below. If you use the latter approach, you can use the transient-parse-suffixes and transient-parse-suffix functions to transform them from the convenient to the expected form.

  If you explicitly specify children and then transform them using :setup-chilren, then the class of the group is determined as usual, based on explicitly specified children.

  If you do not explicitly specify children and thus rely solely on :setup-children, then you must specify the class using :class. For backward compatibility, if you fail to do so, transient-column is used and a warning is displayed. This warning will eventually be replaced with an error.

• The boolean :pad-keys argument controls whether keys of all suffixes contained in a group are right padded, effectively aligning the descriptions.

The ELEMENTs are either all subgroups, or all suffixes and strings. (At least currently no group type exists that would allow mixing subgroups with commands at the same level, though in principle there is nothing that prevents that.)

If the ELEMENTs are not subgroups, then they can be a mixture of lists, which specify commands, and strings. Strings are inserted verbatim into the buffer. The empty string can be used to insert gaps between suffixes, which is particularly useful if the suffixes are outlined as a table.

Inside group specifications, including inside contained suffix specifications, nothing has to be quoted and quoting anyway is invalid. The value following a keyword, can be explicitly unquoted using ,. This feature is experimental and should be avoided.

The form of suffix specifications is documented in the next node.