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This is transient.info, produced by makeinfo version 6.5 from
transient.texi.
Copyright (C) 2018-2019 Jonas Bernoulli <jonas@bernoul.li>
You can redistribute this document and/or modify it under the terms
of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option)
any later version.
This document is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Transient: (transient). Transient Commands.
END-INFO-DIR-ENTRY

File: transient.info, Node: Top, Next: Introduction, Up: (dir)
Transient User and Developer Manual
***********************************
Taking inspiration from prefix keys and prefix arguments, Transient
implements a similar abstraction involving a prefix command, infix
arguments and suffix commands. We could call this abstraction a
"transient command", but because it always involves at least two
commands (a prefix and a suffix) we prefer to call it just a
"transient".
When the user calls a transient prefix command, then a transient
(temporary) keymap is activated, which binds the transients infix and
suffix commands, and functions that control the transient state are
added to pre-command-hook and post-command-hook. The available
suffix and infix commands and their state are shown in a popup buffer
until the transient is exited by invoking a suffix command.
Calling an infix command causes its value to be changed, possibly by
reading a new value in the minibuffer.
Calling a suffix command usually causes the transient to be exited
but suffix commands can also be configured to not exit the transient.
This manual is for Transient version 0.1.0 (v0.1.0-90-g4ce1868+1).
Copyright (C) 2018-2019 Jonas Bernoulli <jonas@bernoul.li>
You can redistribute this document and/or modify it under the terms
of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option)
any later version.
This document is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
* Menu:
* Introduction::
* Usage::
* Other Options::
* Modifying Existing Transients::
* Defining New Commands::
* Classes and Methods::
* Related Abstractions and Packages::
* FAQ::
* Keystroke Index::
* Command Index::
* Function Index::
* Variable Index::
The Detailed Node Listing
Usage
* Invoking Transients::
* Aborting and Resuming Transients::
* Common Suffix Commands::
* Saving Values::
* Using History::
* Getting Help for Suffix Commands::
* Enabling and Disabling Suffixes::
* Other Commands::
Defining New Commands
* Defining Transients::
* Binding Suffix and Infix Commands::
* Defining Suffix and Infix Commands::
* Using Infix Arguments::
* Transient State::
Binding Suffix and Infix Commands
* Group Specifications::
* Suffix Specifications::
Classes and Methods
* Group Classes::
* Group Methods::
* Prefix Classes::
* Suffix Classes::
* Suffix Methods::
* Prefix Slots::
* Suffix Slots::
* Predicate Slots::
Suffix Methods
* Suffix Value Methods::
* Suffix Format Methods::
Related Abstractions and Packages
* Comparison With Prefix Keys and Prefix Arguments::
* Comparison With Other Packages::

File: transient.info, Node: Introduction, Next: Usage, Prev: Top, Up: Top
1 Introduction
**************
Taking inspiration from prefix keys and prefix arguments, Transient
implements a similar abstraction involving a prefix command, infix
arguments and suffix commands. We could call this abstraction a
"transient command", but because it always involves at least two
commands (a prefix and a suffix) we prefer to call it just a
"transient".
Transient keymaps are a feature provided by Emacs. Transients as
implemented by this package involve the use of transient keymaps.
Emacs provides a feature that it calls "prefix commands". When we
talk about "prefix commands" in this manual, then we mean our own
kind of "prefix commands", unless specified otherwise. To avoid
ambiguity we sometimes use the terms "transient prefix command" for
our kind and "regular prefix command" for Emacs kind.
When the user calls a transient prefix command, then a transient
(temporary) keymap is activated, which binds the transients infix and
suffix commands, and functions that control the transient state are
added to pre-command-hook and post-command-hook. The available
suffix and infix commands and their state are shown in a popup buffer
until the transient state is exited by invoking a suffix command.
Calling an infix command causes its value to be changed. How that is
done depends on the type of the infix command. The simplest case is an
infix command that represents a command-line argument that does not take
a value. Invoking such an infix command causes the switch to be toggled
on or off. More complex infix commands may read a value from the user,
using the minibuffer.
Calling a suffix command usually causes the transient to be exited;
the transient keymaps and hook functions are removed, the popup buffer
no longer shows information about the (no longer bound) suffix commands,
the values of some public global variables are set, while some internal
global variables are unset, and finally the command is actually called.
Suffix commands can also be configured to not exit the transient.
A suffix command can, but does not have to, use the infix arguments
in much the same way it can choose to use or ignore the prefix
arguments. For a suffix command that was invoked from a transient the
variable current-transient-suffixes and the function transient-args
serve about the same purpose as the variables prefix-arg and
current-prefix-arg do for any command that was called after the prefix
arguments have been set using a command such as universal-argument.
The information shown in the popup buffer while a transient is active
looks a bit like this:
,-----------------------------------------
|Arguments
| -f Force (--force)
| -a Annotate (--annotate)
|
|Create
| t tag
| r telease
`-----------------------------------------
This is a simplified version of ‘magit-tag’. Info manuals do not
support images or colored text, so the above "screenshot" lacks
some information; in practice you would be able to tell whether the
arguments ‘--force’ and ‘--annotate’ are enabled or not based on
their color.
Transient can be used to implement simple "command dispatchers". The
main benefit then is that the user can see all the available commands in
a popup buffer. That is useful by itself because it frees the user from
having to remember all the keys that are valid after a certain prefix
key or command. Magit’s ‘magit-dispatch’ command is an example of using
Transient to merely implement a command dispatcher.
In addition to that, Transient also allows users to interactively
pass arguments to commands. These arguments can be much more complex
than what is reasonable when using prefix arguments. There is a limit
to how many aspects of a command can be controlled using prefix
arguments. Furthermore what a certain prefix argument means for
different commands can be completely different, and users have to read
documentation to learn and then commit to memory what a certain prefix
argument means to a certain command.
Transient suffix commands on the other hand can accept dozens of
different arguments without the user having to remember anything. When
using Transient, then one can call a command with arguments that are
just as complex as when calling the same function non-interactively
using code.
Invoking a transient command with arguments is similar to invoking a
command in a shell with command-line completion and history enabled.
One benefit of the Transient interface is that it remembers history not
only on a global level ("this command was invoked using these arguments
and previously it was invoked using those other arguments"), but also
remembers the values of individual arguments independently. See *note
Using History::.
After a transient prefix command is invoked ‘C-h <key>’ can be used
to show the documentation for the infix or suffix command that ‘<key>’
is bound to (see *note Getting Help for Suffix Commands::) and infixes
and suffixes can be removed from the transient using ‘C-x l <key>’.
Infixes and suffixes that are disabled by default can be enabled the
same way. See *note Enabling and Disabling Suffixes::.
Transient ships with support for a few different types of specialized
infix commands. A command that sets a command line option for example
has different needs than a command that merely toggles a boolean flag.
Additionally Transient provides abstractions for defining new types,
which the author of Transient did not anticipate (or didn’t get around
to implementing yet).

File: transient.info, Node: Usage, Next: Other Options, Prev: Introduction, Up: Top
2 Usage
*******
* Menu:
* Invoking Transients::
* Aborting and Resuming Transients::
* Common Suffix Commands::
* Saving Values::
* Using History::
* Getting Help for Suffix Commands::
* Enabling and Disabling Suffixes::
* Other Commands::

File: transient.info, Node: Invoking Transients, Next: Aborting and Resuming Transients, Up: Usage
2.1 Invoking Transients
=======================
A transient prefix command is invoked like any other command by pressing
the key that is bound to that command. The main difference to other
commands is that a transient prefix commands activates a transient
keymap, which temporarily binds the transient’s infix and suffix
commands. Bindings from other keymaps may, or may not, be disabled
while the transient state is in effect.
There are two kinds of commands that are available after invoking a
transient prefix command; infix and suffix commands. Infix commands set
some value (which is then shown in a popup buffer), without leaving the
transient. Suffix commands on the other hand usually quit the transient
and they may use the values set by the infix commands, i.e. the infix
*arguments*.
Instead of setting arguments to be used by a suffix command, infix
commands may also set some value by side-effect.

File: transient.info, Node: Aborting and Resuming Transients, Next: Common Suffix Commands, Prev: Invoking Transients, Up: Usage
2.2 Aborting and Resuming Transients
====================================
To quit the transient without invoking a suffix command press ‘C-g’.
Key bindings in transient keymaps may be longer than a single event.
After pressing a valid prefix key, all commands whose bindings do not
begin with that prefix key are temporarily unavailable and grayed out.
To abort the prefix key press ‘C-g’ (which in this case only quits the
prefix key, but not the complete transient).
A transient prefix command can be bound as a suffix of another
transient. Invoking such a suffix replaces the current transient state
with a new transient state, i.e. the available bindings change and the
information displayed in the popup buffer is updated accordingly.
Pressing ‘C-g’ while a nested transient is active only quits the
innermost transient, causing a return to the previous transient.
‘C-q’ or ‘C-z’ on the other hand always exits all transients. If you
use the latter, then you can later resume the stack of transients using
‘M-x transient-resume’.
‘C-g’ (‘transient-quit-seq’)
‘C-g’ (‘transient-quit-one’)
This key quits the currently active incomplete key sequence, if
any, or else the current transient. When quitting the current
transient, then it returns to the previous transient, if any.
Transient’s predecessor bound ‘q’ instead of ‘C-g’ to the quit
command. To learn how to get that binding back see
‘transient-bind-q-to-quit’’s doc-string.
‘C-q’ (‘transient-quit-all’)
This command quits the currently active incomplete key sequence, if
any, and all transients, including the active transient and all
suspended transients, if any.
‘C-z’ (‘transient-suspend’)
Like ‘transient-quit-all’, this command quits an incomplete key
sequence, if any, and all transients. Additionally it saves the
stack of transients so that it can easily be resumed (which is
particularly useful if you quickly need to do "something else" and
the stack is deeper than a single transient and/or you have already
changed the values of some infix arguments).
Note that only a single stack of transients can be saved at a time.
If another stack is already saved, then saving a new stack discards
the previous stack.
‘M-x transient-resume’ (‘transient-resume’)
This command resumes the previously suspended stack of transients,
if any.

File: transient.info, Node: Common Suffix Commands, Next: Saving Values, Prev: Aborting and Resuming Transients, Up: Usage
2.3 Common Suffix Commands
==========================
A few shared suffix commands are available in all transients. These
suffix commands are not shown in the popup buffer by default.
Most of these commands are bound to ‘C-x <key>’ and after pressing
‘C-x’ a section featuring all common commands is temporarily shown in
the popup buffer. After invoking one of these commands, that section
disappears again. Note however that one of these commands is described
as "Show common permanently"; invoke that if you want the common
commands to always be shown for all transients.
‘C-x t’ (‘transient-toggle-common’)
This command toggles whether the generic commands that are common
to all transients are always displayed or only after typing the
incomplete prefix key sequence ‘C-x’. This only affects the
current Emacs session.
-- User Option: transient-show-common-commands
This option controls whether shared suffix commands are shown
alongside the transient-specific infix and suffix commands. By
default the shared commands are not shown to avoid overwhelming the
user with to many options.
While a transient is active, pressing ‘C-x’ always shows the common
command. The value of this option can be changed for the current
Emacs session by typing ‘C-x t’ while a transient is active.
The other common commands are describe in either the previous node or
in one of the following nodes.
Some of Transient’s key bindings differ from the respective bindings
of Magit-Popup; see *note FAQ:: for more information.

File: transient.info, Node: Saving Values, Next: Using History, Prev: Common Suffix Commands, Up: Usage
2.4 Saving Values
=================
After setting the infix arguments in a transient, the user can save
those arguments for future invocations.
Most transients will start out with the saved arguments when they are
invoked. There are a few exceptions though. Some transients are
designed so that the value that they use is stored externally as the
buffer-local value of some variable. Invoking such a transient again
uses the buffer-local value. (1)
If the user does not save the value and just exits using a regular
suffix command, then the value is merely saved to the transient’s
history. That value won’t be used when the transient is next invoked
but it is easily accessible (see *note Using History::).
‘C-x s’ (‘transient-set’)
This command saves the value of the active transient for this Emacs
session.
‘C-x C-s’ (‘transient-save’)
Save the value of the active transient persistently across Emacs
sessions.
-- User Option: transient-values-file
This file is used to persist the values of transients between Emacs
sessions.
---------- Footnotes ----------
(1) ‘magit-diff’ and ‘magit-log’ are two prominent examples, and
their handling of buffer-local values is actually a bit more complicated
than outlined above and even customizable. This is something I am
rethinking, but I don’t want to rush any changes.)

File: transient.info, Node: Using History, Next: Getting Help for Suffix Commands, Prev: Saving Values, Up: Usage
2.5 Using History
=================
Every time the user invokes a suffix command the transient’s current
value is saved to its history. This values can be cycled through the
same way one can cycle through the history of commands that read
user-input in the minibuffer.
‘M-p’ (‘transient-history-prev’)
This command switches to the previous value used for the active
transient.
‘M-n’ (‘transient-history-next’)
This command switches to the next value used for the active
transient.
In addition to the transient-wide history, Transient of course
supports per-infix history. When an infix reads user-input using the
minibuffer, then the user can use the regular minibuffer history
commands to cycle through previously used values. Usually the same keys
as those mentioned above are bound to those commands.
Authors of transients should arrange for different infix commands
that read the same kind of value to also use the same history key (see
*note Suffix Slots::).
Both kinds of history are saved to a file when Emacs is exited.
-- User Option: transient-history-file
This file is used to persist the history of transients and their
infixes between Emacs sessions.
-- User Option: transient-history-limit
This option controls how many history elements are kept at the time
the history in saved in ‘transient-history-file’.

File: transient.info, Node: Getting Help for Suffix Commands, Next: Enabling and Disabling Suffixes, Prev: Using History, Up: Usage
2.6 Getting Help for Suffix Commands
====================================
Transients can have many suffixes and infixes that the user might not be
familiar with. To make it trivial to get help for these, Transient
provides access to the documentation directly from the active transient.
‘C-h’ (‘transient-help’)
This command enters help mode. When help mode is active, then
typing ‘<key>’ shows information about the suffix command that
‘<key>’ normally is bound to (instead of invoking it). Pressing
‘C-h’ a second time shows information about the _prefix_ command.
After typing ‘<key>’ the stack of transient states is suspended and
information about the suffix command is shown instead. Typing ‘q’
in the help buffer buries that buffer and resumes the transient
state.
What sort of documentation is shown depends on how the transient was
defined. For infix commands that represent command-line arguments this
ideally shows the appropriate manpage. ‘transient-help’ then tries to
jump to the correct location within that. Info manuals are also
supported. The fallback is to show the commands doc-string, for
non-infix suffixes this is usually appropriate.

File: transient.info, Node: Enabling and Disabling Suffixes, Next: Other Commands, Prev: Getting Help for Suffix Commands, Up: Usage
2.7 Enabling and Disabling Suffixes
===================================
The user base of a package that uses transients can be very diverse.
This is certainly the case for Magit; some users have been using it and
Git for a decade, while others are just getting started now.
For that reason a mechanism is needed that authors can use to
classify a transient’s infixes and suffixes along the
essentials...everything spectrum. We use the term "levels" to describe
that mechanism.
Each suffix command is placed on a level and each transient has a
level (called transient-level), which controls which suffix commands are
available. Integers between 1 and 7 (inclusive) are valid levels. For
suffixes, 0 is also valid; it means that the suffix is not displayed at
any level.
The levels of individual transients and/or their individual suffixes
can be changed interactively, by invoking the transient and then
pressing ‘C-x l’ to enter the "edit" mode, see below.
The default level for both transients and their suffixes is 4. The
‘transient-default-level’ option only controls the default for
transients. The default suffix level is always 4. The authors of
transients should place certain suffixes on a higher level, if they
expect that it won’t be of use to most users, and they should place very
important suffixes on a lower level, so that they remain available even
if the user lowers the transient level.
(Magit currently places nearly all suffixes on level 4 and lower
levels are not used at all yet. So for the time being you should not
set a lower default level and using a higher level might not give you as
many additional suffixes as you hoped.)
-- User Option: transient-default-level
This option controls which suffix levels are made available by
default. It sets the transient-level for transients for which the
user has not set that individually.
-- User Option: transient-levels-file
This file is used to persist the levels of transients and their
suffixes between Emacs sessions.
‘C-x l’ (‘transient-set-level’)
This command enters edit mode. When edit mode is active, then all
infixes and suffixes that are currently usable are displayed along
with their levels. The colors of the levels indicate whether they
are enabled or not. The level of the transient is also displayed
along with some usage information.
In edit mode, pressing the key that would usually invoke a certain
suffix does instead prompt the user for the level that that suffix
should be placed on.
Help mode is available in edit mode.
To change the transient level press ‘C-x l’ again.
To exit edit mode press ‘C-g’.
Note that edit mode does not display any suffixes that are not
currently usable. ‘magit-rebase’ for example shows different
suffixes depending on whether a rebase is already in progress or
not. The predicates also apply in edit mode.
Therefore, to control which suffixes are available given a certain
state, you have to make sure that that state is currently active.

File: transient.info, Node: Other Commands, Prev: Enabling and Disabling Suffixes, Up: Usage
2.8 Other Commands
==================
When invoking a transient in a small frame, the transient window may not
show the complete buffer, making it necessary to scroll, using the
following commands. These commands are never shown in the transient
window, and the key bindings are the same as for ‘scroll-up-command’ and
‘scroll-down-command’ in other buffers.
-- Command: transient-scroll-up arg
This command scrolls text of transient popup window upward ARG
lines. If ARG is ‘nil’, then it scrolls near full screen. This is
a wrapper around ‘scroll-up-command’ (which see).
-- Command: transient-scroll-down arg
This command scrolls text of transient popup window down ARG lines.
If ARG is ‘nil’, then it scrolls near full screen. This is a
wrapper around ‘scroll-down-command’ (which see).

File: transient.info, Node: Other Options, Next: Modifying Existing Transients, Prev: Usage, Up: Top
3 Other Options
***************
-- User Option: transient-show-popup
This option controls whether the current transient’s infix and
suffix commands are shown in the popup buffer.
• If ‘t’ (the default) then the popup buffer is shown as soon as
a transient prefix command is invoked.
• If ‘nil’, then the popup buffer is not shown unless the user
explicitly requests it, by pressing an incomplete prefix key
sequence.
• If a number, then the a brief one-line summary is shown
instead of the popup buffer. If zero or negative, then not
even that summary is shown; only the pressed key itself is
shown.
The popup is shown when the user explicitly requests it by
pressing an incomplete prefix key sequence. Unless this is
zero, then the popup is shown after that many seconds of
inactivity (using the absolute value).
-- User Option: transient-enable-popup-navigation
This option controls whether navigation commands are enabled in the
transient popup.
While a transient is active the transient popup buffer is not the
current buffer, making it necesary to use dedicated commands to act
on that buffer itself. This is disabled by default. If this
option is non-nil, then the following features are available:
• ‘<up>’ moves the cursor to the previous suffix. ‘<down>’
moves the cursor to the next suffix. ‘RET’ invokes the suffix
the cursor is on.
• ‘<mouse-1>’ invokes the clicked on suffix.
• ‘C-s’ and ‘C-r’ start isearch in the popup buffer.
-- User Option: transient-display-buffer-action
This option specifies the action used to display the transient
popup buffer. The transient popup buffer is displayed in a window
using ‘(display-buffer buf transient-display-buffer-action)’.
The value of this option has the form ‘(FUNCTION . ALIST)’, where
FUNCTION is a function or a list of functions. Each such function
should accept two arguments: a buffer to display and an alist of
the same form as ALIST. See *note (elisp)Choosing Window::.
The default is ‘(display-buffer-in-side-window (side . bottom))’.
This displays the window at the bottom of the selected frame.
Another useful value is ‘(display-buffer-below-selected)’. This is
what ‘magit-popup’ used by default. For more alternatives see
*note (elisp)Display Action Functions::.
It may be possible to display the window in another frame, but
whether that works in practice depends on the window-manager. If
the window manager selects the new window (Emacs frame), then it
doesn’t work.
If you change the value of this option, then you might also want to
change the value of ‘transient-mode-line-format’.
-- User Option: transient-mode-line-format
This option controls whether the transient popup buffer has a
mode-line, separator line, or neither.
If ‘nil’, then the buffer has no mode-line. If the buffer is not
displayed right above the echo area, then this probably is not a
good value.
If ‘line’ (the default), then the buffer also has no mode-line, but
a thin line is drawn instead, using the background color of the
face ‘transient-separator’.
Otherwise this can be any mode-line format. See ~*note (elisp)Mode
Line Format:: for details.
-- User Option: transient-read-with~initial-input
This option controls whether the last history element is used as
the initial minibuffer input when reading the value of an infix
argument from the user. If ‘nil’, then there is no initial input
and the first element has to be accessed the same way as the older
elements.
-- User Option: transient-highlight-mismatched-keys
This option controls whether key bindings of infix commands that do
not match the respective command-line argument should be
highlighted. For other infix commands this option has no effect.
When this option is non-nil, then the key binding for an infix
argument is highlighted when only a long argument (e.g.
‘--verbose’) is specified but no shorthand (e.g ‘-v’). In the rare
case that a shorthand is specified but the key binding does not
match, then it is highlighted differently.
Highlighting mismatched key bindings is useful when learning the
arguments of the underlying command-line tool; you wouldn’t want to
learn any short-hands that do not actually exist.
The highlighting is done using one of the faces
‘transient-mismatched-key’ and ‘transient-nonstandard-key’.
-- User Option: transient-substitute-key-function
This function is used to modify key bindings. It the value of this
option is nil (the default), then no substitution is performed.
This function is called with one argument, the prefix object, and
must return a key binding description, either the existing key
description it finds in the ‘key’ slot, or key description that
replaces the prefix key. It could be used to make other
substitutions, but that is discouraged.
For example, ‘=’ is hard to reach using my custom keyboard layout,
so I substitute ‘(’ for that, which is easy to reach using a layout
optimized for lisp.
(setq transient-substitute-key-function
(lambda (obj)
(let ((key (oref obj key)))
(if (string-match "\\`\\(=\\)[a-zA-Z]" key)
(replace-match "(" t t key 1)
key))))
-- User Option: transient-detect-key-conflicts
This option controls whether key binding conflicts should be
detected at the time the transient is invoked. If so, then this
results in an error, which prevents the transient from being used.
Because of that, conflicts are ignored by default.
Conflicts cannot be determined earlier, i.e. when the transient is
being defined and when new suffixes are being added, because at
that time there can be false-positives. It is actually valid for
multiple suffixes to share a common key binding, provided the
predicates of those suffixes prevent that more than one of them is
enabled at a time.

File: transient.info, Node: Modifying Existing Transients, Next: Defining New Commands, Prev: Other Options, Up: Top
4 Modifying Existing Transients
*******************************
To an extent transients can be customized interactively, see *note
Enabling and Disabling Suffixes::. This section explains how existing
transients can be further modified non-interactively.
The following functions share a few arguments:
• PREFIX is a transient prefix command, a symbol.
• SUFFIX is a transient infix or suffix specification in the same
form as expected by ‘define-transient-command’. Note that an infix
is a special kind of suffix. Depending on context "suffixes" means
"suffixes (including infixes)" or "non-infix suffixes". Here it
means the former. See *note Suffix Specifications::.
SUFFIX may also be a group in the same form as expected by
‘define-transient-command’. See *note Group Specifications::.
• LOC is a command, a key vector, a key description (a string as
returned by ‘key-description’), or a list specifying coordinates
(the last element may also be a command or key). For example ‘(1 0
-1)’ identifies the last suffix (‘-1’) of the first subgroup (‘0’)
of the second group (‘1’).
If LOC is a list of coordinates, then it can be used to identify a
group, not just an individual suffix command.
The function ‘transient-get-suffix’ can be useful to determine
whether a certain coordination list identifies the suffix or group
that you expect it to identify. In hairy cases it may be necessary
to look at the definition of the transient prefix command.
These functions operate on the information stored in the
‘transient--layout’ property of the PREFIX symbol. Suffix entries in
that tree are not objects but have the form ‘(LEVEL CLASS PLIST)’, where
plist should set at least ‘:key’, ‘:description’ and ‘:command’.
-- Function: transient-insert-suffix prefix loc suffix
This function inserts suffix or group SUFFIX into PREFIX before
LOC.
-- Function: transient-append-suffix prefix loc suffix
This function inserts suffix or group SUFFIX into PREFIX after LOC.
-- Function: transient-replace-suffix prefix loc suffix
This function replaces the suffix or group at LOC in PREFIX with
suffix or group SUFFIX.
-- Function: transient-remove-suffix prefix loc
This function removes the suffix or group at LOC in PREFIX.
-- Function: transient-get-suffix prefix loc
This function returns the suffix or group at LOC in PREFIX. The
returned value has the form mentioned above.
-- Function: transient-suffix-put prefix loc prop value
This function edits the suffix or group at LOC in PREFIX, by
setting the PROP of its plist to VALUE.
Most of these functions do not signal an error if they cannot perform
the requested modification. The functions that insert new suffixes show
a warning if LOC cannot be found in PREFIX, without signaling an error.
The reason for doing it like this is that establishing a key binding
(and that is what we essentially are trying to do here) should not
prevent the rest of the configuration from loading. Among these
functions only ‘transient-get-suffix’ and ‘transient-suffix-put’ may
signal an error.

File: transient.info, Node: Defining New Commands, Next: Classes and Methods, Prev: Modifying Existing Transients, Up: Top
5 Defining New Commands
***********************
* Menu:
* Defining Transients::
* Binding Suffix and Infix Commands::
* Defining Suffix and Infix Commands::
* Using Infix Arguments::
* Transient State::

File: transient.info, Node: Defining Transients, Next: Binding Suffix and Infix Commands, Up: Defining New Commands
5.1 Defining Transients
=======================
A transient consists of a prefix command and at least one suffix
command, though usually a transient has several infix and suffix
commands. The below macro defines the transient prefix command *and* it
binds the transient’s infix and suffix commands. In other words, it
defines the complete transient, not just the transient prefix command
that is used to invoke that transient.
-- Macro: define-transient-command name arglist [docstring] [keyword
value]... group... [body...]
This macro defines NAME as a transient prefix command and binds the
transient’s infix and suffix commands.
ARGLIST are the arguments that the prefix command takes. DOCSTRING
is the documentation string and is optional.
These arguments can optionally be followed by keyword-value pairs.
Each key has to be a keyword symbol, either ‘:class’ or a keyword
argument supported by the constructor of that class. The
‘transient-prefix’ class is used if the class is not specified
explicitly.
GROUPs add key bindings for infix and suffix commands and specify
how these bindings are presented in the popup buffer. At least one
GROUP has to be specified. See *note Binding Suffix and Infix
Commands::.
The BODY is optional. If it is omitted, then ARGLIST is ignored
and the function definition becomes:
(lambda ()
(interactive)
(transient-setup 'NAME))
If BODY is specified, then it must begin with an ‘interactive’ form
that matches ARGLIST, and it must call ‘transient-setup’. It may
however call that function only when some condition is satisfied.
All transients have a (possibly ‘nil’) value, which is exported
when suffix commands are called, so that they can consume that
value. For some transients it might be necessary to have a sort of
secondary value, called a "scope". Such a scope would usually be
set in the command’s ‘interactive’ form and has to be passed to the
setup function:
(transient-setup 'NAME nil nil :scope SCOPE)
For example, the scope of the ‘magit-branch-configure’ transient is
the branch whose variables are being configured.

File: transient.info, Node: Binding Suffix and Infix Commands, Next: Defining Suffix and Infix Commands, Prev: Defining Transients, Up: Defining New Commands
5.2 Binding Suffix and Infix Commands
=====================================
The macro ‘define-transient-command’ is used to define a transient.
This defines the actual transient prefix command (see *note Defining
Transients::) and adds the transient’s infix and suffix bindings, as
described below.
Users and third-party packages can add additional bindings using
functions such as ‘transient-insert-suffix’ (See *note Modifying
Existing Transients::). These functions take a "suffix specification"
as one of their arguments, which has the same form as the specifications
used in ‘define-transient-command’.
* Menu:
* Group Specifications::
* Suffix Specifications::

File: transient.info, Node: Group Specifications, Next: Suffix Specifications, Up: Binding Suffix and Infix Commands
5.2.1 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 *note Group Classes::.
Groups are specified in the call to ‘define-transient-command’, 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 *note 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 *note Predicate Slots::.
• Finally 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 ELEMENTs are either all subgroups (vectors), or all suffixes
(lists) 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 that specify commands and strings. Strings are inserted verbatim.
The empty string can be used to insert gaps between suffixes, which is
particularly useful if the suffixes are outlined as a table.
The form of suffix specifications is documented in the next node.

File: transient.info, Node: Suffix Specifications, Prev: Group Specifications, Up: Binding Suffix and Infix Commands
5.2.2 Suffix Specifications
---------------------------
A transient’s suffix and infix commands are bound when the transient
prefix command is defined using ‘define-transient-command’, see *note
Defining Transients::. The commands are organized into groups, see
*note Group Specifications::. Here we describe the form used to bind an
individual suffix command.
The same form is also used when later binding additional commands
using functions such as ‘transient-insert-suffix’, see *note Modifying
Existing Transients::.
Note that an infix is a special kind of suffix. Depending on context
"suffixes" means "suffixes (including infixes)" or "non-infix suffixes".
Here it means the former.
Suffix specifications have this form:
([LEVEL] [KEY] [DESCRIPTION] COMMAND|ARGUMENT [KEYWORD VALUE]...)
LEVEL, KEY and DESCRIPTION can also be specified using the KEYWORDs
‘:level’, ‘:key’ and ‘:description’. If the object that is associated
with COMMAND sets these properties, then they do not have to be
specified here. You can however specify them here anyway, possibly
overriding the objects value just for the binding inside this transient.
• LEVEL is the suffix level, an integer between 1 and 7. See *note
Enabling and Disabling Suffixes::.
• KEY is the key binding, either a vector or key description string.
• DESCRIPTION is the description, either a string or a function that
returns a string. The function should be a lambda expression to
avoid ambiguity. In some cases a symbol that is bound as a
function would also work but to be safe you should use
‘:description’ in that case.
The next element is either a command or an argument. This is the
only argument that is mandatory in all cases.
• COMMAND is a symbol that is bound as a function, which has to be a
command. Any command will do; it does not need to have an object
associated with it (as would be the case if ‘define-suffix-command’
or ‘define-infix-command’ were used to define it).
As mentioned above the object that is associated with a command can
be used to set the default for certain values that otherwise have
to be set in the suffix specification. Therefore if there is no
object, then you have to make sure to specify the KEY and the
DESCRIPTION.
• The mandatory argument can also be an command-line argument, a
string. In that case an anonymous command is defined and bound.
Instead of a string, this can also be a list of two strings, in
which case the first string is used as the short argument (which
can also be specified using ‘:shortarg’) and the second the long
argument (which can also be specified using ‘:argument’).
Only the long argument is displayed in the popup buffer. See
‘transient-detect-key-conflicts’ for how the short argument may be
used.
Unless the class is specified explicitly, the appropriate class is
guessed based on the long argument. If the argument ends with ""
(e.g. "--format") then ‘transient-option’ is used, otherwise
‘transient-switch’.
Finally details can be specified using optional KEYWORD-VALUE pairs.
Each keyword has to be a keyword symbol, either ‘:class’ or a keyword
argument supported by the constructor of that class. See *note Suffix
Slots::.

File: transient.info, Node: Defining Suffix and Infix Commands, Next: Using Infix Arguments, Prev: Binding Suffix and Infix Commands, Up: Defining New Commands
5.3 Defining Suffix and Infix Commands
======================================
Note that an infix is a special kind of suffix. Depending on context
"suffixes" means "suffixes (including infixes)" or "non-infix suffixes".
-- Macro: define-suffix-command name arglist [docstring] [keyword
value]... body...
This macro defines NAME as a transient suffix command.
ARGLIST are the arguments that the command takes. DOCSTRING is the
documentation string and is optional.
These arguments can optionally be followed by keyword-value pairs.
Each keyword has to be a keyword symbol, either ‘:class’ or a
keyword argument supported by the constructor of that class. The
‘transient-suffix’ class is used if the class is not specified
explicitly.
The BODY must begin with an ‘interactive’ form that matches
ARGLIST. Use the function ‘transient-args’ or the low-level
variable ‘current-transient-suffixes’ if the former does not give
you all the required details. This should, but does not
necessarily have to be, done inside the ‘interactive’ form; just
like for ‘prefix-arg’ and ‘current-prefix-arg’.
-- Macro: define-infix-command name arglist [docstring] [keyword
value]...
This macro defines NAME as a transient infix command.
ARGLIST is always ignored (but mandatory never-the-less) and
reserved for future use. DOCSTRING is the documentation string and
is optional.
The keyword-value pairs are mandatory. All transient infix
commands are ‘equal’ to each other (but not ‘eq’), so it is
meaningless to define an infix command without also setting at
least ‘:class’ and one other keyword (which it is depends on the
used class, usually ‘:argument’ or ‘:variable’).
Each keyword has to be a keyword symbol, either ‘:class’ or a
keyword argument supported by the constructor of that class. The
‘transient-switch’ class is used if the class is not specified
explicitly.
The function definitions is always:
(lambda ()
(interactive)
(let ((obj (transient-suffix-object)))
(transient-infix-set obj (transient-infix-read obj)))
(transient--show))
‘transient-infix-read’ and ‘transient-infix-set’ are generic
functions. Different infix commands behave differently because the
concrete methods are different for different infix command classes.
In rare cases the above command function might not be suitable,
even if you define your own infix command class. In that case you
have to use ‘transient-suffix-command’ to define the infix command
and use ‘t’ as the value of the ‘:transient’ keyword.
-- Macro: define-infix-argument name arglist [docstring] [keyword
value]...
This macro defines NAME as a transient infix command.
It is an alias for ‘define-infix-command’. Only use this alias to
define an infix command that actually sets an infix argument. To
define a infix command that, for example, sets a variable use
‘define-infix-command’ instead.

File: transient.info, Node: Using Infix Arguments, Next: Transient State, Prev: Defining Suffix and Infix Commands, Up: Defining New Commands
5.4 Using Infix Arguments
=========================
The function and the variables described below allow suffix commands to
access the value of the transient from which they were invoked; which is
the value of its infix arguments. These variables are set when the user
invokes a suffix command that exits the transient, but before actually
calling the command.
When returning to the command-loop after calling the suffix command,
the arguments are reset to ‘nil’ (which causes the function to return
‘nil’ too).
Like for Emacs’ prefix arguments it is advisable, but not mandatory,
to access the infix arguments inside the command’s ‘interactive’ form.
The preferred way of doing that is to call the ‘transient-args’
function, which for infix arguments serves about the same purpose as
‘prefix-arg’ serves for prefix arguments.
-- Function: transient-args &optional prefix separate
This function returns the value of the transient from which the
current suffix was called. If the current suffix command was not
called from a transient, then it returns ‘nil’.
If optional PREFIX is non-‘nil’, then it should be a symbol, a
transient prefix command. In that case the value of the transient
is only returned if the suffix was invoked from *that* transient.
Otherwise ‘nil’ is returned. This function is also used
internally, in which PREFIX can also be a ‘transient-prefix’
object.
If optional SEPARATE is non-‘nil’, then the arguments are separated
into two groups. If SEPARATE is ‘t’, they are separated into atoms
and conses (‘nil’ isn’t a valid value, so it doesn’t matter that
that is both an atom and a cons).
SEPARATE can also be a predicate function, in which case the first
element is a list of the values for which it returns non-‘nil’ and
the second element is a list of the values for which it returns
‘nil’.
For transients that are used to pass arguments to a subprocess
(such as ‘git’), ‘stringp’ is a useful value for SEPARATE, it
separates non-positional arguments from positional arguments. The
value of Magit’s file argument (‘"--"’) for example looks like
this: ‘("--" file...)’."
-- Variable: current-transient-suffixes
The suffixes of the transient from which this suffix command was
invoked. This is a list of objects. Usually it is sufficient to
instead use the function transient-args, which returns a list of
values. In complex cases it might be necessary to use this
variable instead, i.e. if you need access to information beside
the value.
-- Variable: current-transient-prefix
The transient from which this suffix command was invoked. The
returned value is a transient-prefix object, which holds
information associated with the transient prefix command.
-- Variable: current-transient-command
The transient from which this suffix command was invoked. The
returned value is a symbol, the transient prefix command.

File: transient.info, Node: Transient State, Prev: Using Infix Arguments, Up: Defining New Commands
5.5 Transient State
===================
Invoking a transient prefix command "activates" the respective
transient, i.e. it puts a transient keymap into effect, which binds the
transients infix and suffix commands.
The default behavior while a transient is active is as follows:
Invoking an infix command does not affect the transient state; the
transient remains active.
Invoking a (non-infix) suffix command "deactivates" the transient
state by removing the transient keymap and performing some
additional cleanup.
Invoking a command that is bound in a keymap other than the
transient keymap is disallowed and trying to do so results in a
warning. This does not "deactivate" the transient.
But these are just the defaults. Whether a certain command
deactivates or "exits" the transient is configurable. There is more
than one way in which a command can be "transient" or "non-transient";
the exact behavior is implemented by calling a so-called "pre-command"
function. Whether non-suffix commands are allowed to be called is
configurable per transient.
The transient-ness of suffix commands (including infix commands) is
controlled by the value of their transient slot, which can be set
either when defining the command or when adding a binding to a
transient while defining the respective transient prefix command.
Valid values are booleans and the pre-commands described below.
t is equivalent to transient--do-stay.
nil is equivalent to transient--do-exit.
If transient is unbound (and that is actually the default
for non-infix suffixes) then the value of the prefixs
transient-suffix slot is used instead. The default value of
that slot is nil, so the suffixs transient slot being
unbound is essentially equivalent to it being nil.
A suffix command can be a prefix command itself, i.e. a
"sub-prefix". While a sub-prefix is active we nearly always want
C-g to take the user back to the "super-prefix". However in rare
cases this may not be desirable, and that makes the following
complication necessary:
For transient-suffix objects the transient slot is unbound. We
can ignore that for the most part because, as stated above, nil
and the slot being unbound are equivalent, and means "do exit".
That isnt actually true for suffixes that are sub-prefixes though.
For such suffixes unbound means "do exit but allow going back",
which is the default, while nil means "do exit permanently",
which requires that slot to be explicitly set to that value.
The transient-ness of certain built-in suffix commands is specified
using transient-predicate-map. This is a special keymap, which
binds commands to pre-commands (as opposed to keys to commands) and
takes precedence over the transient slot.
The available pre-command functions are documented below. They are
called by transient--pre-command, a function on pre-command-hook and
the value that they return determines whether the transient is exited.
To do so the value of one of the constants transient--exit or
transient--stay is used (that way we dont have to remember if t
means "exit" or "stay").
Additionally these functions may change the value of this-command
(which explains why they have to be called using pre-command-hook),
call transient-export, transient--stack-zap or
transient--stack-push; and set the values of transient--exitp,
transient--helpp or transient--editp.
5.5.1 Pre-commands for Infixes
------------------------------
The default for infixes is transient--do-stay. This is also the only
function that makes sense for infixes.
-- Function: transient--do-stay
Call the command without exporting variables and stay transient.
5.5.2 Pre-commands for Suffixes
-------------------------------
The default for suffixes is transient--do-exit.
-- Function: transient--do-exit
Call the command after exporting variables and exit the transient.
-- Function: transient--do-call
Call the command after exporting variables and stay transient.
-- Function: transient--do-replace
Call the transient prefix command, replacing the active transient.
This is used for suffix that are prefixes themselves, i.e. for
sub-prefixes.
5.5.3 Pre-commands for Non-Suffixes
-----------------------------------
The default for non-suffixes, i.e commands that are bound in other
keymaps beside the transient keymap, is transient--do-warn. Silently
ignoring the user-error is also an option, though probably not a good
one.
If you want to let the user invoke non-suffix commands, then use
transient--do-stay as the value of the prefixs transient-non-suffix
slot.
-- Function: transient--do-warn
Call transient-undefined and stay transient.
-- Function: transient--do-noop
Call transient-noop and stay transient.
5.5.4 Special Pre-Commands
--------------------------
-- Function: transient--do-quit-one
If active, quit help or edit mode, else exit the active transient.
This is used when the user pressed C-g.
-- Function: transient--do-quit-all
Exit all transients without saving the transient stack.
This is used when the user pressed C-q.
-- Function: transient--do-suspend
Suspend the active transient, saving the transient stack.
This is used when the user pressed C-z.

File: transient.info, Node: Classes and Methods, Next: Related Abstractions and Packages, Prev: Defining New Commands, Up: Top
6 Classes and Methods
*********************
Transient uses classes and generic functions to make it possible to
define new types of suffix commands that are similar to existing types,
but behave differently in some aspects. It does the same for groups and
prefix commands, though at least for prefix commands that *currently*
appears to be less important.
Every prefix, infix and suffix command is associated with an object,
which holds information that controls certain aspects of its behavior.
This happens in two ways.
Associating a command with a certain class gives the command a
type. This makes it possible to use generic functions to do
certain things that have to be done differently depending on what
type of command it acts on.
That in turn makes it possible for third-parties to add new types
without having to convince the maintainer of Transient that that
new type is important enough to justify adding a special case to a
dozen or so functions.
Associating a command with an object makes it possible to easily
store information that is specific to that particular command.
Two commands may have the same type, but obviously their key
bindings and descriptions still have to be different, for example.
The values of some slots are functions. The reader slot for
example holds a function that is used to read a new value for an
infix command. The values of such slots are regular functions.
Generic functions are used when a function should do something
different based on the type of the command, i.e. when all commands
of a certain type should behave the same way but different from the
behavior for other types. Object slots that hold a regular
function as value are used when the task that they perform is
likely to differ even between different commands of the same type.
* Menu:
* Group Classes::
* Group Methods::
* Prefix Classes::
* Suffix Classes::
* Suffix Methods::
* Prefix Slots::
* Suffix Slots::
* Predicate Slots::

File: transient.info, Node: Group Classes, Next: Group Methods, Up: Classes and Methods
6.1 Group Classes
=================
The type of a group can be specified using the :class property at the
beginning of the class specification, e.g. [:class transient-columns
...] in a call to define-transient-command.
The abstract transient-child class is the base class of both
transient-group (and therefore all groups) as well as of
transient-suffix (and therefore all suffix and infix commands).
This class exists because the elements (aka "children") of certain
groups can be other groups instead of suffix and infix commands.
The abstract transient-group class is the superclass of all other
group classes.
The transient-column class is the simplest group.
This is the default "flat" group. If the class is not specified
explicitly and the first element is not a vector (i.e. not a
group), then this class is used.
This class displays each element on a separate line.
The transient-row class displays all elements on a single line.
The transient-columns class displays commands organized in
columns.
Direct elements have to be groups whose elements have to be
commands or strings. Each subgroup represents a column. This
class takes care of inserting the subgroups elements.
This is the default "nested" group. If the class is not specified
explicitly and the first element is a vector (i.e. a group), then
this class is used.
The transient-subgroups class wraps other groups.
Direct elements have to be groups whose elements have to be
commands or strings. This group inserts an empty line between
subgroups. The subgroups themselves are responsible for displaying
their elements.

File: transient.info, Node: Group Methods, Next: Prefix Classes, Prev: Group Classes, Up: Classes and Methods
6.2 Group Methods
=================
-- Function: transient--insert-group group
This generic function formats the group and its elements and
inserts the result into the current buffer, which is a temporary
buffer. The contents of that buffer are later inserted into the
popup buffer.
Functions that are called by this function may need to operate in
the buffer from which the transient was called. To do so they can
temporally make the transient--source-buffer the current buffer.

File: transient.info, Node: Prefix Classes, Next: Suffix Classes, Prev: Group Methods, Up: Classes and Methods
6.3 Prefix Classes
==================
Currently the transient-prefix class is being used for all prefix
command and there is only a single generic functions that can be
specialized based on the class of a prefix command.
-- Function: transient--history-init obj
This generic function is called while setting up the transient and
is responsible for initializing the history slot. This is the
transient-wide history; many individual infixes also have a history
of their own.
The default (and currently only) method extracts the value from the
global variable transient-history.
A transient prefix commands object is stored in the
transient--prefix property of the command symbol. While a transient
is active, a clone of that object is stored in the variable
transient--prefix. A clone is used because some changes that are made
to the active transients object should not affect later invocations.

File: transient.info, Node: Suffix Classes, Next: Suffix Methods, Prev: Prefix Classes, Up: Classes and Methods
6.4 Suffix Classes
==================
All suffix and infix classes derive from transient-suffix, which
in turn derives from transient-child, from which
transient-group also derives (see *note Group Classes::).
All infix classes derived from the abstract transient-infix
class, which in turn derives from the transient-suffix class.
Infixes are a special type of suffixes. The primary difference is
that infixes always use the transient--do-stay pre-command, while
non-infix suffixes use a variety of pre-commands (see *note
Transient State::). Doing that is most easily achieved by using
this class, though theoretically it would be possible to define an
infix class that does not do so. If you do that then you get to
implement many methods.
Also infixes and non-infix suffixes are usually defined using
different macros (see *note Defining Suffix and Infix Commands::).
Classes used for infix commands that represent arguments should be
derived from the abstract transient-argument class.
The transient-switch class (or a derived class) is used for infix
arguments that represent command-line switches (arguments that do
not take a value).
The transient-option class (or a derived class) is used for infix
arguments that represent command-line options (arguments that do
take a value).
The transient-switches class can be used for a set of mutually
exclusive command-line switches.
The transient-files class can be used for a "–" argument that
indicates that all remaining arguments are files.
Classes used for infix commands that represent variables should
derived from the abstract transient-variables class.
Magit defines additional classes, which can serve as examples for the
fancy things you can do without modifying Transient. Some of these
classes will likely get generalized and added to Transient. For now
they are very much subject to change and not documented.

File: transient.info, Node: Suffix Methods, Next: Prefix Slots, Prev: Suffix Classes, Up: Classes and Methods
6.5 Suffix Methods
==================
To get information about the methods implementing these generic
functions use describe-function.
* Menu:
* Suffix Value Methods::
* Suffix Format Methods::

File: transient.info, Node: Suffix Value Methods, Next: Suffix Format Methods, Up: Suffix Methods
6.5.1 Suffix Value Methods
--------------------------
-- Function: transient-init-value obj
This generic function sets the initial value of the object OBJ.
This function is called for all suffix commands, but unless a
concrete method is implemented this falls through to the default
implementation, which is a noop. In other words this usually only
does something for infix commands, but note that this is not
implemented for the abstract class transient-infix, so if your
class derives from that directly, then you must implement a method.
-- Function: transient-infix-read obj
This generic function determines the new value of the infix object
OBJ.
This function merely determines the value; transient-infix-set is
used to actually store the new value in the object.
For most infix classes this is done by reading a value from the
user using the reader specified by the reader slot (using the
transient-infix-value method described below).
For some infix classes the value is changed without reading
anything in the minibuffer, i.e. the mere act of invoking the
infix command determines what the new value should be, based on the
previous value.
-- Function: transient-prompt obj
This generic function returns the prompt to be used to read infix
object OBJs value.
-- Function: transient-infix-set obj value
This generic function sets the value of infix object OBJ to value.
-- Function: transient-infix-value obj
This generic function returns the value of the suffix object OBJ.
This function is called by transient-args (which see), meaning
this function is how the value of a transient is determined so that
the invoked suffix command can use it.
Currently most values are strings, but that is not set in stone.
nil is not a value, it means "no value".
Usually only infixes have a value, but see the method for
transient-suffix.
-- Function: transient-init-scope obj
This generic function sets the scope of the suffix object OBJ.
The scope is actually a property of the transient prefix, not of
individual suffixes. However it is possible to invoke a suffix
command directly instead of from a transient. In that case, if the
suffix expects a scope, then it has to determine that itself and
store it in its scope slot.
This function is called for all suffix commands, but unless a
concrete method is implemented this falls through to the default
implementation, which is a noop.

File: transient.info, Node: Suffix Format Methods, Prev: Suffix Value Methods, Up: Suffix Methods
6.5.2 Suffix Format Methods
---------------------------
-- Function: transient-format obj
This generic function formats and returns OBJ for display.
When this function is called, then the current buffer is some
temporary buffer. If you need the buffer from which the prefix
command was invoked to be current, then do so by temporarily making
transient--source-buffer current.
-- Function: transient-format-key obj
This generic function formats OBJs key for display and returns
the result.
-- Function: transient-format-description obj
This generic function formats OBJs description for display and
returns the result.
-- Function: transient-format-value obj
This generic function formats OBJs value for display and returns
the result.
-- Function: transient-show-help obj
Show help for the prefix, infix or suffix command represented by
OBJ.
For prefixes show the info manual, if that is specified using the
info-manual slot. Otherwise show the manpage if that is
specified using the man-page slot. Otherwise show the commands
doc-string.
For suffixes show the commands doc-string.
For infixes show the manpage if that is specified. Otherwise show
the commands doc-string.

File: transient.info, Node: Prefix Slots, Next: Suffix Slots, Prev: Suffix Methods, Up: Classes and Methods
6.6 *TODO* Prefix Slots
=======================

File: transient.info, Node: Suffix Slots, Next: Predicate Slots, Prev: Prefix Slots, Up: Classes and Methods
6.7 Suffix Slots
================
Here we document most of the slots that are only available for suffix
objects. Some slots are shared by suffix and group objects, they are
documented in *note Predicate Slots::.
Also see *note Suffix Classes::.
6.7.1 Slots of transient-suffix
---------------------------------
key The key, a key vector or a key description string.
command The command, a symbol.
transient Whether to stay transient. See *note Transient
State::.
format The format used to display the suffix in the popup buffer.
It must contain the following %-placeholders:
%k For the key.
%d For the description.
%v For the infix value. Non-infix suffixes dont have a
value.
description The description, either a string or a function that
is called with no argument and returns a string.
6.7.2 Slots of transient-infix
--------------------------------
Some of these slots are only meaningful for some of the subclasses.
They are defined here anyway to allow sharing certain methods.
argument The long argument, e.g. --verbose.
shortarg The short argument, e.g. -v.
multi-value For options, whether the option can have multiple
values. If non-nil, then default to use
completing-read-multiple.
allow-empty For options, whether the empty string is a valid
value.
history-key The key used to store the history. This defaults to
the command name. This is useful when multiple infixes should
share the same history because their values are of the same kind.
reader The function used to read the value of an infix. Not used
for switches. The function takes three arguments, PROMPT,
INITIAL-INPUT and HISTORY, and must return a string.
prompt The prompt used when reading the value, either a string or
a function that takes the object as the only argument and which
returns a prompt string.
choices A list of valid values. How exactly that is used depends
on the class of the object.
6.7.3 Slots of transient-variable
-----------------------------------
variable The variable.
6.7.4 Slots of transient-switches
-----------------------------------
argument-format The display format. Must contain %s, one of
the choices is substituted for that. E.g. --%s-order.
argument-regexp The regexp used to match any one of the switches.
E.g. \\(--\\(topo\\|author-date\\|date\\)-order\\).

File: transient.info, Node: Predicate Slots, Prev: Suffix Slots, Up: Classes and Methods
6.8 Predicate Slots
===================
Suffix and group objects share some predicate slots that control whether
a group or suffix should be available depending on some state. Only one
of these slots can be used at the same time. It is undefined what
happens if you use more than one.
if Enable if predicate returns non-nil.
if-not Enable if predicate returns nil.
if-non-nil Enable if variables value is non-nil.
if-nil Enable if variables value is nil.
if-mode Enable if major-mode matches value.
if-not-mode Enable if major-mode does not match value.
if-derived Enable if major-mode derives from value.
if-not-derived Enable if major-mode does not derive from value.
One more slot is shared between group and suffix classes, level.
Like the slots documented above it is a predicate, but it is used for a
different purpose. The value has to be an integer between 1 and 7.
level controls whether it should be available depending on whether the
user wants that or not. See *note Enabling and Disabling Suffixes::.

File: transient.info, Node: Related Abstractions and Packages, Next: FAQ, Prev: Classes and Methods, Up: Top
7 Related Abstractions and Packages
***********************************
* Menu:
* Comparison With Prefix Keys and Prefix Arguments::
* Comparison With Other Packages::

File: transient.info, Node: Comparison With Prefix Keys and Prefix Arguments, Next: Comparison With Other Packages, Up: Related Abstractions and Packages
7.1 Comparison With Prefix Keys and Prefix Arguments
====================================================
While transient commands were inspired by regular prefix keys and prefix
arguments, they are also quite different and much more complex.
The following diagrams illustrate some of the differences.
(c) represents a return to the command loop.
(+) represents the users choice to press one key or another.
{WORD} are possible behaviors.
{NUMBER} is a footnote.
7.1.1 Regular Prefix Commands
-----------------------------
See *note (elisp)Prefix Keys::.
,--> command1 --> (c)
|
(c)-(+)-> prefix command or key --+--> command2 --> (c)
|
`--> command3 --> (c)
7.1.2 Regular Prefix Arguments
------------------------------
See *note (elisp)Prefix Command Arguments::.
,----------------------------------,
| |
v |
(c)-(+)---> prefix argument command --(c)-(+)-> any command --> (c)
| ^ |
| | |
`-- sets or changes --, ,-- maybe used --' |
| | |
v | |
prefix argument state |
^ |
| |
`-------- discards --------'
7.1.3 Transients
----------------
(∩`-´)⊃━☆゚.*・。゚
This diagram ignores the infix value and external state:
(c)
| ,- {stay} ------<-,-<------------<-,-<---,
(+) | | | |
| | | | |
| | ,--> infix1 --| | |
| | | | | |
| | |--> infix2 --| | |
v v | | | |
prefix -(c)-(+)-> infix3 --' ^ |
| | |
|---------------> suffix1 -->--| |
| | |
|---------------> suffix2 ----{1}------> {exit} --> (c)
| |
|---------------> suffix3 -------------> {exit} --> (c)
| |
`--> any command --{2}-> {warn} -->--|
| |
|--> {noop} -->--|
| |
|--> {call} -->--'
|
`------------------> {exit} --> (c)
This diagram takes the infix value into account to an extend, while
still ignoring external state:
(c)
| ,- {stay} ------<-,-<------------<-,-<---,
(+) | | | |
| | | | |
| | ,--> infix1 --| | |
| | | | | | |
| | ,--> infix2 --| | |
v v | | | | |
prefix -(c)-(+)-> infix3 --' | |
| | ^ |
| | | |
|---------------> suffix1 -->--| |
| | ^ | |
| | | | |
|---------------> suffix2 ----{1}------> {exit} --> (c)
| | ^ | |
| | | | v
| | | | |
|---------------> suffix3 -------------> {exit} --> (c)
| | ^ | |
| sets | | v
| | maybe | |
| | used | |
| | | | |
| | infix --' | |
| `---> value | |
| ^ | |
| | | |
| hides | |
| | | |
| `--------------------------<---|
| | |
`--> any command --{2}-> {warn} -->--| |
| | |
|--> {noop} -->--| |
| | |
|--> {call} -->--' ^
| |
`------------------> {exit} --> (c)
This diagram provides more information about the infix value and also
takes external state into account.
,----sets--- "anything"
|
v
,---------> external
| state
| | |
| initialized | ☉‿⚆
sets from |
| | maybe
| ,----------' used
| | |
(c) | | v
| ,- {stay} --|---<-,-<------|-----<-,-<---,
(+) | | | | | | |
| | | v | | | |
| | ,--> infix1 --| | | |
| | | | | | | | |
| | | | v | | | |
| | ,--> infix2 --| | | |
| | | | ^ | | | |
v v | | | | | | |
prefix -(c)-(+)-> infix3 --' | | |
| | ^ | ^ |
| | | v | |
|---------------> suffix1 -->--| |
| | | ^ | | |
| | | | v | |
|---------------> suffix2 ----{1}------> {exit} --> (c)
| | | ^ | | |
| | | | | | v
| | | | v | |
|---------------> suffix3 -------------> {exit} --> (c)
| | | ^ | |
| sets | | | v
| | initalized maybe | |
| | from used | |
| | | | | |
| | `-- infix --' | |
| `---> value -----------------------------> persistent
| ^ ^ | | across
| | | | | invocations -,
| hides | | | |
| | `----------------------------------------------'
| | | |
| `--------------------------<---|
| | |
`--> any command --{2}-> {warn} -->--| |
| | |
|--> {noop} -->--| |
| | |
|--> {call} -->--' ^
| |
`------------------> {exit} --> (c)
{1} Transients can be configured to be exited when a suffix
command is invoked. The default is to do so for all suffixes
except for those that are common to all transients and which are
used to perform tasks such as providing help and saving the value
of the infix arguments for future invocations. The behavior can
also be specified for individual suffix commands and may even
depend on state.
{2} Transients can be configured to allow the user to invoke
non-suffix commands. The default is to not allow that and instead
warn the user.
Despite already being rather complex, even the last diagram leaves
out many details. Most importantly it implies that the decision whether
to remain transient is made later than it actually is made (for the most
part a function on pre-command-hook is responsible). But such
implementation details are of little relevance to users and are covered
elsewhere.

File: transient.info, Node: Comparison With Other Packages, Prev: Comparison With Prefix Keys and Prefix Arguments, Up: Related Abstractions and Packages
7.2 Comparison With Other Packages
==================================
7.2.1 Magit-Popup
-----------------
Transient is the successor to Magit-Popup (see *note
(magit-popup)Top::).
One major difference between these two implementations of the same
ideas is that while Transient uses transient keymaps and embraces the
command-loop, Magit-Popup implemented an inferior mechanism that does
not use transient keymaps and that instead of using the command-loop
implements a naive alternative based on read-char.
Magit-Popup does not use classes and generic functions and defining a
new command type is near impossible as it involves adding hard-coded
special-cases to many functions. Because of that only a single new type
was added, which was not already part of Magit-Popups initial release.
A lot of things are hard-coded in Magit-Popup. One random example is
that the key bindings for switches must begin with "-" and those for
options must begin with "=".
7.2.2 Hydra
-----------
Hydra (see <https://github.com/abo-abo/hydra>) is another package that
provides features similar to those of Transient.
Both packages use transient keymaps to make a set of commands
temporarily available and show the available commands in a popup buffer.
A Hydra "body" is equivalent to a Transient "prefix" and a Hydra
"head" is equivalent to a Transient "suffix". Hydra has no equivalent
of a Transient "infix".
Both hydras and transients can be used as simple command dispatchers.
Used like this they are similar to regular prefix commands and prefix
keys, except that the available commands are shown in the popup buffer.
(Another package that does this is which-key. It does so
automatically for any incomplete key sequence. The advantage of that
approach is that no additional work is necessary; the disadvantage is
that the available commands are not organized semantically.)
Both Hydra and Transient provide features that go beyond simple
command dispatchers:
Invoking a command from a hydra does not necessarily exit the
hydra. That makes it possible to invoke the same command again,
but using a shorter key sequence (i.e. the key that was used to
enter the hydra does not have to be pressed again).
Transient supports that too, but for now this feature is not a
focus and the interface is a bit more complicated. A very basic
example using the current interface:
(define-transient-command outline-navigate ()
:transient-suffix 'transient--do-stay
:transient-non-suffix 'transient--do-warn
[("p" "next visible heading" outline-previous-visible-heading)
("n" "next visible heading" outline-next-visible-heading)])
Transient supports infix arguments; values that are set by infix
commands and then consumed by the invoked suffix command(s).
To my knowledge, Hydra does not support that.
Both packages make it possible to specify how exactly the available
commands are outlined:
With Hydra this is often done using an explicit format string,
which gives authors a lot of flexibility and makes it possible to
do fancy things.
The downside of this is that it becomes harder for a user to add
additional commands to an existing hydra and to change key
bindings.
Transient allows the author of a transient to organize the commands
into groups and the use of generic functions allows authors of
transients to control exactly how a certain command type is
displayed.
However while Transient supports giving sections a heading it does
not currently support giving the displayed information more
structure by, for example, using box-drawing characters.
That could be implemented by defining a new group class, which lets
the author specify a format string. It should be possible to
implement that without modifying any existing code, but it does not
currently exist.

File: transient.info, Node: FAQ, Next: Keystroke Index, Prev: Related Abstractions and Packages, Up: Top
Appendix A FAQ
**************
A.1 Can I control how the popup buffer is displayed?
====================================================
Yes, see transient-display-buffer-action in *note Other Options::.
A.2 Why did some of the key bindings change?
============================================
You may have noticed that the bindings for some of the common commands
do *not* have the prefix C-x and that furthermore some of these
commands are grayed out while others are not. That unfortunately is a
bit confusing if the section of common commands is not shown
permanently, making the following explanation necessary.
The purpose of usually hiding that section but showing it after the
user pressed the respective prefix key is to conserve space and not
overwhelm users with too much noise, while allowing the user to quickly
list common bindings on demand.
That however should not keep us from using the best possible key
bindings. The bindings that do use a prefix do so to avoid wasting too
many non-prefix bindings, keeping them available for use in individual
transients. The bindings that do not use a prefix and that are *not*
grayed out are very important bindings that are *always* available, even
when invoking the "common command key prefix" or *any other*
transient-specific prefix. The non-prefix keys that *are* grayed out
however, are not available when any incomplete prefix key sequence is
active. They do not use the "common command key prefix" because it is
likely that users want to invoke them several times in a row and e.g.
M-p M-p M-p is much more convenient than C-x M-p C-x M-p C-x M-p.
You may also have noticed that the "Set" command is bound to C-x s,
while Magit-Popup used to bind C-c C-c instead. I have seen several
users praise the latter binding (sic), so I did not change it
willy-nilly. The reason that I changed it is that using different
prefix keys for different common commands, would have made the temporary
display of the common commands even more confusing, i.e. after pressing
C-c all the C-x ... bindings would be grayed out.
Using a single prefix for common commands key means that all other
potential prefix keys can be used for transient-specific commands
*without* the section of common commands also popping up. C-c in
particular is a prefix that I want (and already do) use for Magit, and
also using that for a common command would prevent me from doing so.
(Also see the next question.)
A.3 Why does q not quit popups anymore?
=========================================
I agree that q is a good binding for commands that quit something.
This includes quitting whatever transient is currently active, but it
also includes quitting whatever it is that some specific transient is
controlling. The transient magit-blame for example binds q to the
command that turns magit-blame-mode off.
So I had to decide if q should quit the active transient (like
Magit-Popup used to) or whether C-g should do that instead, so that
q could be bound in individual transient to whatever commands make
sense for them. Because all other letters are already reserved for use
by individual transients, I have decided to no longer make an exception
for q.
If you want to get qs old binding back then you can do so. Doing
that is a bit more complicated than changing a single key binding, so I
have implemented a function, transient-bind-q-to-quit that makes the
necessary changes. See its doc-string for more information.

File: transient.info, Node: Keystroke Index, Next: Command Index, Prev: FAQ, Up: Top
Appendix B Keystroke Index
**************************
[index]
* Menu:
* C-g: Aborting and Resuming Transients.
(line 25)
* C-g <1>: Aborting and Resuming Transients.
(line 26)
* C-h: Getting Help for Suffix Commands.
(line 10)
* C-q: Aborting and Resuming Transients.
(line 36)
* C-x C-s: Saving Values. (line 25)
* C-x l: Enabling and Disabling Suffixes.
(line 49)
* C-x s: Saving Values. (line 20)
* C-x t: Common Suffix Commands.
(line 16)
* C-z: Aborting and Resuming Transients.
(line 42)
* M-n: Using History. (line 16)
* M-p: Using History. (line 11)
* M-x transient-resume: Aborting and Resuming Transients.
(line 55)

File: transient.info, Node: Command Index, Next: Function Index, Prev: Keystroke Index, Up: Top
Appendix C Command Index
************************
[index]
* Menu:
* transient-help: Getting Help for Suffix Commands.
(line 10)
* transient-history-next: Using History. (line 16)
* transient-history-prev: Using History. (line 11)
* transient-quit-all: Aborting and Resuming Transients.
(line 36)
* transient-quit-one: Aborting and Resuming Transients.
(line 26)
* transient-quit-seq: Aborting and Resuming Transients.
(line 25)
* transient-resume: Aborting and Resuming Transients.
(line 55)
* transient-save: Saving Values. (line 25)
* transient-scroll-down arg: Other Commands. (line 18)
* transient-scroll-up arg: Other Commands. (line 12)
* transient-set: Saving Values. (line 20)
* transient-set-level: Enabling and Disabling Suffixes.
(line 49)
* transient-suspend: Aborting and Resuming Transients.
(line 42)
* transient-toggle-common: Common Suffix Commands.
(line 16)

File: transient.info, Node: Function Index, Next: Variable Index, Prev: Command Index, Up: Top
Appendix D Function Index
*************************
[index]
* Menu:
* define-infix-argument: Defining Suffix and Infix Commands.
(line 66)
* define-infix-command: Defining Suffix and Infix Commands.
(line 30)
* define-suffix-command: Defining Suffix and Infix Commands.
(line 9)
* define-transient-command: Defining Transients. (line 13)
* transient--do-call: Transient State. (line 98)
* transient--do-exit: Transient State. (line 94)
* transient--do-noop: Transient State. (line 125)
* transient--do-quit-all: Transient State. (line 138)
* transient--do-quit-one: Transient State. (line 132)
* transient--do-replace: Transient State. (line 102)
* transient--do-stay: Transient State. (line 85)
* transient--do-suspend: Transient State. (line 144)
* transient--do-warn: Transient State. (line 121)
* transient--history-init: Prefix Classes. (line 10)
* transient--insert-group: Group Methods. (line 6)
* transient-append-suffix: Modifying Existing Transients.
(line 47)
* transient-args: Using Infix Arguments.
(line 22)
* transient-format: Suffix Format Methods.
(line 6)
* transient-format-description: Suffix Format Methods.
(line 20)
* transient-format-key: Suffix Format Methods.
(line 15)
* transient-format-value: Suffix Format Methods.
(line 25)
* transient-get-suffix: Modifying Existing Transients.
(line 60)
* transient-infix-read: Suffix Value Methods.
(line 17)
* transient-infix-set: Suffix Value Methods.
(line 39)
* transient-infix-value: Suffix Value Methods.
(line 43)
* transient-init-scope: Suffix Value Methods.
(line 57)
* transient-init-value: Suffix Value Methods.
(line 6)
* transient-insert-suffix: Modifying Existing Transients.
(line 42)
* transient-prompt: Suffix Value Methods.
(line 34)
* transient-remove-suffix: Modifying Existing Transients.
(line 56)
* transient-replace-suffix: Modifying Existing Transients.
(line 51)
* transient-scroll-down: Other Commands. (line 18)
* transient-scroll-up: Other Commands. (line 12)
* transient-show-help: Suffix Format Methods.
(line 30)
* transient-suffix-put: Modifying Existing Transients.
(line 65)

File: transient.info, Node: Variable Index, Prev: Function Index, Up: Top
Appendix E Variable Index
*************************
[index]
* Menu:
* current-transient-command: Using Infix Arguments.
(line 66)
* current-transient-prefix: Using Infix Arguments.
(line 60)
* current-transient-suffixes: Using Infix Arguments.
(line 51)
* transient-default-level: Enabling and Disabling Suffixes.
(line 38)
* transient-detect-key-conflicts: Other Options. (line 136)
* transient-display-buffer-action: Other Options. (line 46)
* transient-enable-popup-navigation: Other Options. (line 28)
* transient-highlight-mismatched-keys: Other Options. (line 95)
* transient-history-file: Using History. (line 33)
* transient-history-limit: Using History. (line 38)
* transient-levels-file: Enabling and Disabling Suffixes.
(line 44)
* transient-mode-line-format: Other Options. (line 71)
* transient-read-with~initial-input: Other Options. (line 87)
* transient-show-common-commands: Common Suffix Commands.
(line 23)
* transient-show-popup: Other Options. (line 6)
* transient-substitute-key-function: Other Options. (line 114)
* transient-values-file: Saving Values. (line 30)

Tag Table:
Node: Top751
Node: Introduction3674
Node: Usage9461
Node: Invoking Transients9795
Node: Aborting and Resuming Transients10828
Node: Common Suffix Commands13487
Node: Saving Values15240
Ref: Saving Values-Footnote-116498
Node: Using History16768
Node: Getting Help for Suffix Commands18308
Node: Enabling and Disabling Suffixes19698
Node: Other Commands22997
Node: Other Options23953
Node: Modifying Existing Transients30567
Node: Defining New Commands33971
Node: Defining Transients34307
Node: Binding Suffix and Infix Commands36742
Node: Group Specifications37597
Node: Suffix Specifications40930
Node: Defining Suffix and Infix Commands44488
Node: Using Infix Arguments47897
Node: Transient State51181
Node: Classes and Methods57053
Node: Group Classes59267
Node: Group Methods61184
Node: Prefix Classes61829
Node: Suffix Classes62921
Node: Suffix Methods65165
Node: Suffix Value Methods65486
Node: Suffix Format Methods68246
Node: Prefix Slots69695
Node: Suffix Slots69859
Node: Predicate Slots72710
Node: Related Abstractions and Packages73959
Node: Comparison With Prefix Keys and Prefix Arguments74246
Node: Comparison With Other Packages84558
Node: FAQ88745
Node: Keystroke Index92476
Node: Command Index94110
Node: Function Index95897
Node: Variable Index100054

End Tag Table

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