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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 transient’s 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 0.3.4.
Copyright (C) 2018-2021 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.
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 transient’s 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 any command can choose to use or ignore the prefix
arguments. For a suffix command that was invoked from a transient the
variable transient-current-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 release `-----------------------------------------
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
(on C-x M-g
) 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 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 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 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).
Next: Modifying Existing Transients, Previous: Introduction, Up: Top [Contents][Index]
Next: Aborting and Resuming Transients, Up: Usage [Contents][Index]
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 command 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, e.g. by setting the value of some variable.
Next: Common Suffix Commands, Previous: Invoking Transients, Up: Usage [Contents][Index]
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
.
transient-quit-seq
)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.
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.
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.
transient-resume
)This command resumes the previously suspended stack of transients, if any.
Next: Saving Values, Previous: Aborting and Resuming Transients, Up: Usage [Contents][Index]
A few shared suffix commands are available in all transients. These suffix commands are not shown in the popup buffer by default.
This includes the aborting commands mentioned in the previous node as
well as some other commands that are all bound to C-x <key>
. After
C-x
is pressed, a section featuring all these common commands is
temporarily shown in the popup buffer. After invoking one of them,
the 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.
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.
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 described 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 FAQ for more information.
Next: Using History, Previous: Common Suffix Commands, Up: Usage [Contents][Index]
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 Using History).
transient-set
)This command saves the value of the active transient for this Emacs session.
transient-save
)Save the value of the active transient persistently across Emacs sessions.
This file is used to persist the values of transients between Emacs sessions.
Next: Getting Help for Suffix Commands, Previous: Saving Values, Up: Usage [Contents][Index]
Every time the user invokes a suffix command the transient’s current value is saved to its history. These values can be cycled through the same way one can cycle through the history of commands that read user-input in the minibuffer.
transient-history-prev
)transient-history-prev
)This command switches to the previous value used for the active transient.
transient-history-next
)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 Suffix Slots).
Both kinds of history are saved to a file when Emacs is exited.
This file is used to persist the history of transients and their infixes between Emacs sessions.
This option controls how many history elements are kept at the time
the history is saved in transient-history-file
.
Next: Enabling and Disabling Suffixes, Previous: Using History, Up: Usage [Contents][Index]
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.
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 command’s doc string, for
non-infix suffixes this is usually appropriate.
Next: Other Commands, Previous: Getting Help for Suffix Commands, Up: Usage [Contents][Index]
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.
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.
This file is used to persist the levels of transients and their suffixes between Emacs sessions.
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 instead prompts the user for the level 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.
Next: Other Options, Previous: Enabling and Disabling Suffixes, Up: Usage [Contents][Index]
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.
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).
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).
Previous: Other Commands, Up: Usage [Contents][Index]
This option controls whether the current transient’s infix and suffix commands are shown in the popup buffer.
t
(the default) then the popup buffer is shown as soon as a
transient prefix command is invoked.
nil
, then the popup buffer is not shown unless the user
explicitly requests it, by pressing an incomplete prefix key
sequence.
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).
This option controls whether navigation commands are enabled in the transient popup buffer.
While a transient is active the transient popup buffer is not the current buffer, making it necessary 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.
This option specifies the action used to display the transient popup
buffer. The transient popup buffer is displayed in a window using
(display-buffer BUFFER 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 (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
(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
.
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
. Termcap frames cannot display thin lines and
therefore fallback to treating line
like nil
.
Otherwise this can be any mode-line format. See (elisp)Mode Line Format for details.
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.
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
.
This function is used to modify key bindings. If 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 the 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))))
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.
This option controls whether to force the use of a monospaced font
in popup buffer. Even if you use a proportional font for the
default
face, you might still want to use a monospaced font in
transient’s popup buffer. Setting this option to t causes default
to be remapped to fixed-pitch
in that buffer.
Next: Defining New Commands, Previous: Usage, Up: Top [Contents][Index]
To an extent transients can be customized interactively, see Enabling and Disabling Suffixes. This section explains how existing transients can be further modified non-interactively.
The following functions share a few arguments:
transient-define-prefix
. 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 Suffix Specifications.
SUFFIX may also be a group in the same form as expected by
transient-define-prefix
. See Group Specifications.
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
.
This function inserts suffix or group SUFFIX into PREFIX before LOC.
This function inserts suffix or group SUFFIX into PREFIX after LOC.
This function replaces the suffix or group at LOC in PREFIX with suffix or group SUFFIX.
This function removes the suffix or group at LOC in PREFIX.
This function returns the suffix or group at LOC in PREFIX. The returned value has the form mentioned above.
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.
Next: Classes and Methods, Previous: Modifying Existing Transients, Up: Top [Contents][Index]
• Defining Transients: | ||
• Binding Suffix and Infix Commands: | ||
• Defining Suffix and Infix Commands: | ||
• Using Infix Arguments: | ||
• Transient State: |
Next: Binding Suffix and Infix Commands, Up: Defining New Commands [Contents][Index]
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 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.
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 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.
Next: Defining Suffix and Infix Commands, Previous: Defining Transients, Up: Defining New Commands [Contents][Index]
The macro transient-define-prefix
is used to define a transient.
This defines the actual transient prefix command (see 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 Modifying Existing Transients). These functions take a "suffix specification" as one of
their arguments, which has the same form as the specifications used in
transient-define-prefix
.
• Group Specifications: | ||
• Suffix Specifications: |
Next: Suffix Specifications, Up: Binding Suffix and Infix Commands [Contents][Index]
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.
: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.
:level
is equivalent to LEVEL.
: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.
: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
:setup-children
, if non-nil, is a function that takes
two arguments the group object itself and a list of children.
The children are given as a, potentially empty, list consisting
of either group or suffix specifications. It can make arbitrary
changes to the children including constructing new children from
scratch. Also see transient-setup-children
.
: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 (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.
Variables are supported inside group specifications. For example in place of a direct subgroup specification, a variable can be used whose value is a vector that qualifies as a group specification. Likewise a variable can be used where a suffix specification is expected. Lists of group or suffix specifications are also supported. Indirect specifications are resolved when the transient prefix is being defined.
The form of suffix specifications is documented in the next node.
Previous: Group Specifications, Up: Binding Suffix and Infix Commands [Contents][Index]
A transient’s suffix and infix commands are bound when the transient
prefix command is defined using transient-define-prefix
, see
Defining Transients. The commands are organized into groups, see
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 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 object’s values just for the binding inside this transient.
: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.
Any command will do; it does not need to have an object associated
with it (as would be the case if transient-define-suffix
or
transient-define-infix
were used to define it).
The command can also be a closure or lambda expression, but that
should only be used for dynamic transients whose suffixes are
defined when the prefix command is invoked. See information about
the :setup-children
function in Group Specifications.
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.
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 as 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 Suffix Slots.
Next: Using Infix Arguments, Previous: Binding Suffix and Infix Commands, Up: Defining New Commands [Contents][Index]
Note that an infix is a special kind of suffix. Depending on context "suffixes" means "suffixes (including infixes)" or "non-infix suffixes".
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.
The infix arguments are usually accessed by using transient-args
inside interactive
.
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 definition 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.
This macro defines NAME as a transient infix command.
This is an alias for transient-define-infix
. Only use this alias
to define an infix command that actually sets an infix argument.
To define an infix command that, for example, sets a variable, use
transient-define-infix
instead.
Next: Transient State, Previous: Defining Suffix and Infix Commands, Up: Defining New Commands [Contents][Index]
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.
This function returns the value of the transient prefix command PREFIX.
If the current command was invoked from the transient prefix command PREFIX, then it returns the active infix arguments. If the current command was not invoked from PREFIX, then it returns the set, saved or default value for PREFIX.
This function return the value of ARG as it appears in ARGS.
For a switch a boolean is returned. For an option the value is returned as a string, using the empty string for the empty value, or nil if the option does not appear in ARGS.
This function returns the suffixes of the transient prefix command PREFIX. This is a list of objects. This function should only be used if you need the objects (as opposed to just their values) and if the current command is not being invoked from PREFIX.
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.
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.
The transient from which this suffix command was invoked. The returned value is a symbol, the transient prefix command.
Previous: Using Infix Arguments, Up: Defining New Commands [Contents][Index]
Invoking a transient prefix command "activates" the respective transient, i.e. it puts a transient keymap into effect, which binds the transient’s infix and suffix commands.
The default behavior while a transient is active is as follows:
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.
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
.
transient
is unbound (and that is actually the default for
non-infix suffixes) then the value of the prefix’s
transient-suffix
slot is used instead. The default value of that
slot is nil
, so the suffix’s transient
slot being unbound is
essentially equivalent to it being nil
.
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 mean "do exit". That isn’t
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.
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 don’t 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
.
The default for infixes is transient--do-stay
. This is also the only
function that makes sense for infixes.
Call the command without exporting variables and stay transient.
The default for suffixes is transient--do-exit
.
Call the command after exporting variables and exit the transient.
Call the command after exporting variables and stay transient.
Call the transient prefix command, replacing the active transient.
This is used for suffixes that are prefixes themselves, i.e. for sub-prefixes.
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 prefix’s transient-non-suffix
slot.
Call transient-undefined
and stay transient.
Call transient-noop
and stay transient.
If active, quit help or edit mode, else exit the active transient.
This is used when the user pressed C-g
.
Exit all transients without saving the transient stack.
This is used when the user pressed C-q
.
Suspend the active transient, saving the transient stack.
This is used when the user pressed C-z
.
Next: Related Abstractions and Packages, Previous: Defining New Commands, Up: Top [Contents][Index]
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.
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.
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.
• Group Classes: | ||
• Group Methods: | ||
• Prefix Classes: | ||
• Suffix Classes: | ||
• Suffix Methods: | ||
• Prefix Slots: | ||
• Suffix Slots: | ||
• Predicate Slots: |
Next: Group Methods, Up: Classes and Methods [Contents][Index]
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 transient-define-prefix
.
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.
transient-group
class is the superclass of all other
group classes.
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.
transient-row
class displays all elements on a single line.
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.
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.
Next: Prefix Classes, Previous: Group Classes, Up: Classes and Methods [Contents][Index]
This generic function can be used to setup the children or a group.
The default implementation usually just returns the children
unchanged, but if the setup-children
slot of GROUP is non-nil, then
it calls that function with CHILDREN as the only argument and
returns the value.
The children are given as a, potentially empty, list consisting of either group or suffix specifications. These functions can make arbitrary changes to the children including constructing new children from scratch.
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
temporarily make the transient--source-buffer
the current buffer.
Next: Suffix Classes, Previous: Group Methods, Up: Classes and Methods [Contents][Index]
Currently the transient-prefix
class is being used for all prefix
commands and there is only a single generic function that can be
specialized based on the class of a prefix command.
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 command’s 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 transient’s
object should not affect later invocations.
Next: Suffix Methods, Previous: Prefix Classes, Up: Classes and Methods [Contents][Index]
transient-suffix
, which in
turn derives from transient-child
, from which transient-group
also
derives (see Group Classes).
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 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 Defining Suffix and Infix Commands).
transient-argument
class.
transient-switch
class (or a derived class) is used for infix
arguments that represent command-line switches (arguments that do
not take a value).
transient-option
class (or a derived class) is used for infix
arguments that represent command-line options (arguments that do
take a value).
transient-switches
class can be used for a set of mutually
exclusive command-line switches.
transient-files
class can be used for a "–" argument that
indicates that all remaining arguments are files.
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.
Next: Prefix Slots, Previous: Suffix Classes, Up: Classes and Methods [Contents][Index]
To get information about the methods implementing these generic
functions use describe-function
.
• Suffix Value Methods: | ||
• Suffix Format Methods: |
Next: Suffix Format Methods, Up: Suffix Methods [Contents][Index]
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.
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.
This generic function returns the prompt to be used to read infix object OBJ’s value.
This generic function sets the value of infix object OBJ to VALUE.
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
.
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.
Previous: Suffix Value Methods, Up: Suffix Methods [Contents][Index]
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.
This generic function formats OBJ’s key
for display and returns the
result.
This generic function formats OBJ’s description
for display and
returns the result.
This generic function formats OBJ’s value for display and returns the result.
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 command’s doc string.
For suffixes, show the command’s doc string.
For infixes, show the manpage if that is specified. Otherwise show the command’s doc string.
Next: Suffix Slots, Previous: Suffix Methods, Up: Classes and Methods [Contents][Index]
man-page
or info-manual
can be used to specify the documentation for
the prefix and its suffixes. The command transient-help
uses the
method transient-show-help
(which see) to lookup and use these
values.
history-key
If multiple prefix commands should share a single value,
then this slot has to be set to the same value for all of them. You
probably don’t want that.
transient-suffix
and transient-non-suffix
play a part when
determining whether the currently active transient prefix command
remains active/transient when a suffix or abitrary non-suffix
command is invoked. See Transient State.
incompatible
A list of lists. Each sub-list specifies a set of
mutually exclusive arguments. Enabling one of these arguments
causes the others to be disabled.
scope
For some transients it might be necessary to have a sort of
secondary value, called a "scope". See transient-define-prefix
.
These slots are mostly intended for internal use. They should not be
set in calls to transient-define-prefix
.
prototype
When a transient prefix command is invoked, then a clone
of that object is stored in the global variable transient--prefix
and the prototype is stored in the clone’s prototype
slot.
command
The command, a symbol. Each transient prefix command
consists of a command, which is stored in a symbol’s function slot
and an object, which is stored in the transient--prefix
property
of the same symbol.
level
The level of the prefix commands. The suffix commands whose
layer is equal or lower are displayed. See Enabling and Disabling Suffixes.
value
The likely outdated value of the prefix. Instead of accessing
this slot directly you should use the function transient-get-value
,
which is guaranteed to return the up-to-date value.
history
and history-pos
are used to keep track of historic values.
Unless you implement your own transient-infix-read
method you should
not have to deal with these slots.
Next: Predicate Slots, Previous: Prefix Slots, Up: Classes and Methods [Contents][Index]
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 Predicate Slots.
Also see Suffix Classes.
transient-suffix
key
The key, a key vector or a key description string.
command
The command, a symbol.
transient
Whether to stay transient. See 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 don’t have a value.
description
The description, either a string or a function that is
called with no argument and returns a string.
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
.
value
The value. Should not be accessed directly.
init-value
Function that is responsable for setting the object’s
value. If bound, then this is called with the object as the only
argument. Usually this is not bound, in which case the object’s
primary transient-init-value
method is called instead.
unsavable
Whether the value of the suffix is not saved as part of
the prefixes.
multi-value
For options, whether the option can have multiple
values. If non-nil, then default to use completing-read-multiple
.
always-read
For options, whether to read a value on every invocation.
If this is nil, then options that have a value are simply unset and
have to be invoked a second time to set a new value.
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.
transient-variable
variable
The variable.
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\\)
.
Previous: Suffix Slots, Up: Classes and Methods [Contents][Index]
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 variable’s value is non-nil.
if-nil
Enable if variable’s 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 a suffix or a group should be
available depending on user preference.
See Enabling and Disabling Suffixes.
Next: FAQ, Previous: Classes and Methods, Up: Top [Contents][Index]
• Comparison With Prefix Keys and Prefix Arguments: | ||
• Comparison With Other Packages: |
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 user’s choice to press one key or another.
{WORD}
are possible behaviors.
{NUMBER}
is a footnote.
See (elisp)Prefix Keys.
,--> command1 --> (c) | (c)-(+)-> prefix command or key --+--> command2 --> (c) | `--> command3 --> (c)
See (elisp)Prefix Command Arguments.
,----------------------------------, | | v | (c)-(+)---> prefix argument command --(c)-(+)-> any command --> (c) | ^ | | | | `-- sets or changes --, ,-- maybe used --' | | | | v | | prefix argument state | ^ | | | `-------- discards --------'
(∩`-´)⊃━☆゚.*・。゚
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 | | initialized 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.
Previous: Comparison With Prefix Keys and Prefix Arguments, Up: Related Abstractions and Packages [Contents][Index]
Transient is the successor to Magit-Popup (see (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-Popup’s 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 "=".
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:
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:
(transient-define-prefix outline-navigate () :transient-suffix 'transient--do-stay :transient-non-suffix 'transient--do-warn [("p" "previous visible heading" outline-previous-visible-heading) ("n" "next visible heading" outline-next-visible-heading)])
To my knowledge, Hydra does not support that.
Both packages make it possible to specify how exactly the available commands are outlined:
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.
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.
Next: Keystroke Index, Previous: Related Abstractions and Packages, Up: Top [Contents][Index]
Yes, see transient-display-buffer-action
in Other Options.
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 to (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.)
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 q
’s 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.
Next: Command Index, Previous: FAQ, Up: Top [Contents][Index]
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Next: Variable Index, Previous: Command Index, Up: Top [Contents][Index]
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Previous: Function Index, Up: Top [Contents][Index]
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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.