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Transient is the library used to implement the keyboard-driven “menus” in Magit. It is distributed as a separate package, so that it can be used to implement similar menus in other packages.
This manual can be bit hard to digest when getting started. A useful resource to get over that hurdle is Psionic K’s interactive tutorial, available at https://github.com/positron-solutions/transient-showcase.
This manual is for Transient version 0.8.1.
Copyright (C) 2018–2024 Free Software Foundation, Inc.
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.
Next: Usage, Previous: Transient User and Developer Manual, Up: Transient User and Developer Manual [Contents][Index]
Transient is the library used to implement the keyboard-driven menus in Magit. It is distributed as a separate package, so that it can be used to implement similar menus in other packages.
This manual can be bit hard to digest when getting started. A useful resource to get over that hurdle is Psionic K’s interactive tutorial, available at https://github.com/positron-solutions/transient-showcase.
Complexity tends to grow with time. How do you manage the complexity of commands? Consider the humble shell command ‘ls’. It now has over fifty command line options. Some of these are boolean flags (‘ls -l’). Some take arguments (‘ls --sort=s’). Some have no effect unless paired with other flags (‘ls -lh’). Some are mutually exclusive. Some shell commands even have so many options that they introduce subcommands (‘git branch’, ‘git commit’), each with their own rich set of options (‘git branch -f’).
What about Emacs commands used interactively? How do these handle options? One solution is to make many versions of the same command, so you don’t need to! Consider: ‘delete-other-windows’ vs. ‘delete-other-windows-vertically’ (among many similar examples).
Some Emacs commands will simply prompt you for the next "argument" (‘M-x switch-to-buffer’). Another common solution is to use prefix arguments which usually start with ‘C-u’. Sometimes these are sensibly numerical in nature (‘C-u 4 M-x forward-paragraph’ to move forward 4 paragraphs). But sometimes they function instead as boolean "switches" (‘C-u C-SPACE’ to jump to the last mark instead of just setting it, ‘C-u C-u C-SPACE’ to unconditionally set the mark). Since there aren’t many standards for the use of prefix options, you have to read the command’s documentation to find out what the possibilities are.
But when an Emacs command grows to have a truly large set of options and arguments, with dependencies between them, lots of option values, etc., these simple approaches just don’t scale. Transient is designed to solve this issue. Think of it as the humble prefix argument ‘C-u’, raised to the power of 10. Like ‘C-u’, it is key driven. Like the shell, it supports boolean "flag" options, options that take arguments, and even "sub-commands", with their own options. But instead of searching through a man page or command documentation, well-designed transients guide their users to the relevant set of options (and even their possible values!) directly, taking into account any important pre-existing Emacs settings. And while for shell commands like ‘ls’, there is only one way to "execute" (hit ‘Return’!), transients can "execute" using multiple different keys tied to one of many self-documenting actions (imagine having 5 different colored return keys on your keyboard!). Transients make navigating and setting large, complex groups of command options and arguments easy. Fun even. Once you’ve tried it, it’s hard to go back to the ‘C-u what can I do here again?’ way.
Next: Modifying Existing Transients, Previous: Introduction, Up: Transient User and Developer Manual [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, and that those bindings are displayed in a transient menu, displayed in a popup buffer. 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 the 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.
This key quits the currently active incomplete key sequence, if any, or else the current transient. When quitting the current transient, 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
documentation string.
This command quits the currently active incomplete key sequence, if any, and all transients, including the active transient and all suspended transients, if any.
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.
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 section, 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.
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 too many options.
While a transient is active, pressing C-x always shows the common commands. 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 or in one of the following sections.
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).
This command saves the value of the active transient for this Emacs session.
This command saves the value of the active transient persistently across Emacs sessions.
This command clears the set and saved values of the active transient.
This option names the file that 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.
This command switches to the previous value used for the active transient.
This command switches to the next value used for the active transient.
In addition to the transient-wide history, infixes can have their own history. When an infix reads user-input using the minibuffer, 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 option controls whether the history of transient commands is saved when exiting Emacs.
This option names the file that 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.
This command enters help mode. When help mode is active, typing a key shows information about the suffix command that the key normally is bound to (instead of invoking it). Pressing C-h a second time shows information about the prefix command.
After typing a 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 documentation
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 option names the file that is used to persist the levels of transients and their suffixes between Emacs sessions.
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.
This command toggle whether suffixes that are on levels higher than
the level specified by transient-default-level are temporarily
available anyway.
Next: Configuration, 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).
The following commands are not available by default. If you would
like to use them for all menus, bind them in transient-map.
This command copies the contents of the menu buffer to the kill ring.
This command toggle between showing suffix descriptions in the menu (as usual) or showing the first lines of the respective docstrings in their place. For commands that do not have a docstring, always display the suffix description. Because there likely isn’t enough room to display multiple docstrings side-by-side, a single column is used when displaying docstrings.
Previous: Other Commands, Up: Usage [Contents][Index]
More options are described in Common Suffix Commands, in Saving Values, in Using History and in Enabling and Disabling Suffixes.
Also see Common Suffix Commands.
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, the popup is shown after that many seconds of inactivity (using the absolute value).
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 too many options.
While a transient is active, pressing C-x always shows the common commands. The value of this option can be changed for the current Emacs session by typing C-x t while a transient is active.
This option controls whether the transient menu continues to be displayed while the minibuffer is used to read user input.
This is only relevant to commands that do not close the menu, such as commands that set infix arguments. If a command exits the menu, and uses the minibuffer, then the menu is always closed before the minibuffer is entered, irrespective of the value of this option.
When nil (the default), hide the menu while the minibuffer is in use.
When t, keep showing the menu, but allow for the menu window to be
resized, to ensure that completion candidates can be displayed.
When fixed, keep showing the menu and prevent it from being resized,
which may make it impossible to display the completion candidates. If
that ever happens for you, consider using t or an integer, as described
below.
If the value is fixed and the menu window uses the full height of its
frame, then the former is ignored and resizing is allowed anyway. This
is necessary because individual menus may use unusual display actions
different from what transient-display-buffer-action specifies (likely
to display that menu in a side-window).
When using a third-party mode, which automatically resizes windows
(e.g., by calling balance-windows on post-command-hook), then
fixed (or nil) is likely a better choice than t.
The value can also be an integer, in which case the behavior depends on whether at least that many lines are left to display windows other than the menu window. If that is the case, display the menu and preserve the size of that window. Otherwise, allow resizing the menu window if the number is positive, or hide the menu if it is negative.
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, there is no initial input and the first
element has to be accessed the same way as the older elements.
This option controls whether navigation commands are enabled in the
transient popup buffer. If the value is verbose (the default),
brief documentation about the command under point is additionally
show in the echo area.
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. If this option is non-nil, then the
following features are available:
By default M-RET is bound to transient-push-button, instead of
RET, because if a transient allows the invocation of non-suffixes,
then it is likely, that you would want RET to do what it would do
if no transient were active."
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,
for details.
The default is:
(display-buffer-in-side-window (side . bottom) (dedicated . t) (inhibit-same-window . t))
This displays the window at the bottom of the selected frame. For alternatives see (elisp)Buffer Display Action Functions, and (elisp)Buffer Display Action Alists.
Note that the buffer that was current before the transient buffer
is shown should remain the current buffer. Many suffix commands
act on the thing at point, if appropriate, and if the transient
buffer became the current buffer, then that would change what is
at point. To that effect inhibit-same-window ensures that the
selected window is not used to show the transient buffer.
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 that unfortunately changes which buffer is current.
If you change the value of this option, then you might also
want to change the value of transient-mode-line-format.
This user option may be overridden if :display-action is passed
when creating a new prefix with transient-define-prefix.
This option controls whether the use of a single column to display suffixes is enforced. This might be useful for users with low vision who use large text and might otherwise have to scroll in two dimensions.
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) or a natural number, then the buffer has no
mode-line, but a line is drawn in its place. If a number is used,
that specifies the thickness of the line. On termcap frames we
cannot draw lines, so there line and numbers are synonyms for nil.
The color of the line is used to indicate if non-suffixes are
allowed and whether they exit the transient. The foreground
color of transient-key-noop (if non-suffixes are disallowed),
transient-key-stay (if allowed and transient stays active), or
transient-key-exit (if allowed and they exit the transient) is
used to draw the line.
This user option may be overridden if :mode-line-format is passed
when creating a new prefix with transient-define-prefix.
Otherwise this can be any mode-line format. See (elisp)Mode Line Format, for details.
This option controls whether colors are used to indicate the transient behavior of commands.
If non-nil, then the key binding of each suffix is colorized to
indicate whether it exits the transient state or not. The color of
the prefix is indicated using the line that is drawn when the value
of transient-mode-line-format is line.
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, 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 columns are aligned pixel-wise in the popup buffer.
If this is non-nil, then columns are aligned pixel-wise to support
variable-pitch fonts. Keys are not aligned, so you should use a
fixed-pitch font for the transient-key face. Other key faces
inherit from that face unless a theme is used that breaks that
relationship.
This option is intended for users who use a variable-pitch font for
the default face.
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.
These options are mainly intended for developers.
This option controls whether key binding conflicts should be detected at the time the transient is invoked. If so, 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 suffixes that would not be available by default are highlighted.
When non-nil then the descriptions of suffixes are highlighted if
their level is above 4, the default of transient-default-level.
Assuming you have set that variable to 7, this highlights all
suffixes that won’t be available to users without them making the
same customization.
This hook is run after a transient is exited.
This hook is run when the transient buffer is being setup. That buffer is current and empty when this hook is runs.
Next: Defining New Commands, Previous: Usage, Up: Transient User and Developer Manual [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. Let’s begin with an example:
(transient-append-suffix 'magit-patch-apply "-3"
'("-R" "Apply in reverse" "--reverse"))
This inserts a new infix argument to toggle the --reverse argument
after the infix argument that toggles -3 in magit-patch-apply.
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.
These functions insert the suffix or group SUFFIX into PREFIX before or after LOC.
Conceptually adding a binding to a transient prefix is similar to adding a binding to a keymap, but this is complicated by the fact that multiple suffix commands can be bound to the same key, provided they are never active at the same time, see Predicate Slots.
Unfortunately both false-positives and false-negatives are possible.
To deal with the former use non-nil KEEP-OTHER. To deal with the
latter remove the conflicting binding explicitly.
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: Transient User and Developer Manual [Contents][Index]
Next: Defining Transients, Up: Defining New Commands [Contents][Index]
Taking inspiration from prefix keys and prefix arguments, Transient implements a similar abstraction involving a prefix command, infix arguments and suffix commands.
When the user calls a transient prefix command, 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.
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, which can be thought of as a “menu”. 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, one can call a command with arguments that are just as complex as when calling the same function non-interactively from Lisp.
Invoking a transient suffix 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).
Note that suffix commands also support regular prefix arguments. A suffix command may even be called with both infix and prefix arguments at the same time. If you invoke a command as a suffix of a transient prefix command, but also want to pass prefix arguments to it, then first invoke the prefix command, and only after doing that invoke the prefix arguments, before finally invoking the suffix command. If you instead began by providing the prefix arguments, then those would apply to the prefix command, not the suffix command. Likewise, if you want to change infix arguments before invoking a suffix command with prefix arguments, then change the infix arguments before invoking the prefix arguments. In other words, regular prefix arguments always apply to the next command, and since transient prefix, infix and suffix commands are just regular commands, the same applies to them. (Regular prefix keys behave differently because they are not commands at all, instead they are just incomplete key sequences, and those cannot be interrupted with prefix commands.)
Next: Binding Suffix and Infix Commands, Previous: Technical Introduction, 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.
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... and :inapt-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
one argument, a potentially list of children, and must return a list
of children or an empty list. This can either be used to somehow
transform the group’s children that were defined the normal way, or
to dynamically create the children from scratch.
The returned children must have the same form as stored in the
prefix’s transient--layout property, but it is often more convenient
to use the same form as understood by transient-define-prefix,
described below. If you use the latter approach, you can use the
transient-parse-suffixes and transient-parse-suffix functions to
transform them from the convenient to the expected form. Depending
on the used group class, transient-parse-suffixes’s SUFFIXES must be
a list of group vectors (for transient-columns) or a list of suffix
lists (for all other group classes).
If you explicitly specify children and then transform them using
:setup-children, then the class of the group is determined as usual,
based on explicitly specified children.
If you do not explicitly specify children and thus rely solely on
:setup-children, then you must specify the class using :class.
For backward compatibility, if you fail to do so, transient-column
is used and a warning is displayed. This warning will eventually
be replaced with an error.
(transient-define-prefix my-finder-by-keyword ()
"Select a keyword and list matching packages."
;; The real `finder-by-keyword' is more convenient
;; of course, but that is not the point here.
[:class transient-columns
:setup-children
(lambda (_)
(transient-parse-suffixes
'my-finder-by-keyword
(let ((char (1- ?A)))
(mapcar ; a list ...
(lambda (partition)
(vconcat ; of group vectors ...
(mapcar (lambda (elt)
(let ((keyword (symbol-name (car elt))))
; ... where each suffix is a list
(list (format "%c" (cl-incf char))
keyword
(lambda ()
(interactive)
(finder-list-matches keyword)))))
partition)))
(seq-partition finder-known-keywords 7)))))])
:pad-keys argument controls whether keys of all suffixes
contained in a group are right padded, effectively aligning the
descriptions.
The ELEMENTs are either all subgroups, or all suffixes and strings. (At least currently no group type exists that would allow mixing subgroups with commands at the same level, though in principle there is nothing that prevents that.)
If the ELEMENTs are not subgroups, then they can be a mixture of lists, which specify commands, and strings. Strings are inserted verbatim into the buffer. The empty string can be used to insert gaps between suffixes, which is particularly useful if the suffixes are outlined as a table.
Inside group specifications, including inside contained suffix
specifications, nothing has to be quoted and quoting anyway is
invalid. The value following a keyword, can be explicitly unquoted
using ,. This feature is experimental and should be avoided.
The form of suffix specifications is documented in the next node.
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).
COMMAND can also be a lambda expression.
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.
As a special case, if you want to add a command that might be neither defined nor autoloaded, you can use a workaround like:
(transient-insert-suffix 'some-prefix "k"
'("!" "Ceci n'est pas une commande" no-command
:if (lambda () (featurep 'no-library))))
Instead of featurep you could also use require with a non-nil value
for NOERROR.
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.
At least one key-value pair is required. All transient infix
commands are equal to each other (but not eq). It is meaningless
to define an infix command, without providing at least one keyword
argument (usually :argument or :variable, depending on the class).
The suffix class defaults to transient-switch and can be set using
the :class keyword.
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-define-suffix 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: Current Suffix Command, Previous: Defining Suffix and Infix Commands, Up: Defining New Commands [Contents][Index]
The functions 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’s 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 returns the value of the current prefix.
This is mostly intended for internal use, but may also be of use
in transient-set-value and transient-save-value methods. Unlike
transient-args, this does not include the values of suffixes whose
unsavable slot is non-nil.
This function returns 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.
Next: Current Prefix Command, Previous: Using Infix Arguments, Up: Defining New Commands [Contents][Index]
This function returns the object associated with the current suffix command.
Each suffix commands is associated with an object, which holds additional information about the suffix, such as its value (in the case of an infix command, which is a kind of suffix command).
This function is intended to be called by infix commands, which
are usually aliases of transient--default-infix-command, which
is defined like this:
(defun transient--default-infix-command ()
(interactive)
(let ((obj (transient-suffix-object)))
(transient-infix-set obj (transient-infix-read obj)))
(transient--show))
(User input is read outside of interactive to prevent the
command from being added to command-history.)
Such commands need to be able to access their associated object
to guide how transient-infix-read reads the new value and to
store the read value. Other suffix commands (including non-infix
commands) may also need the object to guide their behavior.
This function attempts to return the object associated with the
current suffix command even if the suffix command was not invoked
from a transient. (For some suffix command that is a valid thing
to do, for others it is not.) In that case nil may be returned,
if the command was not defined using one of the macros intended
to define such commands.
The optional argument COMMAND is intended for internal use. If you are contemplating using it in your own code, then you should probably use this instead:
(get COMMAND 'transient--suffix)
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.
Next: Transient State, Previous: Current Suffix Command, Up: Defining New Commands [Contents][Index]
This function returns the current prefix as an object.
While a transient is being setup or refreshed (which involves
preparing its suffixes) the variable transient--prefix can be
used to access the prefix object. Thus this is what has to be
used in suffix methods such as transient-format-description,
and in object-specific functions that are stored in suffix slots
such as description.
When a suffix command is invoked (i.e., in its interactive form
and function body) then the variable transient-current-prefix
has to be used instead.
Two distinct variables are needed, because any prefix may itself be used as a suffix of another prefix, and such sub-prefixes have to be able to tell themselves apart from the prefix they were invoked from.
Regular suffix commands, which are not prefixes, do not have to concern themselves with this distinction, so they can use this function instead. In the context of a plain suffix, it always returns the value of the appropriate variable.
The transient from which this suffix command was invoked. The 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 value is a symbol, the transient prefix command.
This function returns the active transient object. It returns nil
if there is no active transient, if the transient buffer isn’t
shown, and while the active transient is suspended (e.g., while the
minibuffer is in use).
Unlike transient-current-prefix, which is only ever non-nil in code
that is run directly by a command that is invoked while a transient
is current, this function is also suitable for use in asynchronous
code, such as timers and callbacks (this function’s main use-case).
If optional PREFIXES is non-nil, it must be a prefix command symbol
or a list of symbols, in which case the active transient object is
only returned if it matches one of the PREFIXES.
Previous: Current Prefix Command, 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:
The behavior can be changed for all suffixes of a particular prefix
and/or for individual suffixes. The values should nearly always be
booleans, but certain functions, called “pre-commands”, can also be
used. These functions are named transient--do-VERB, and the symbol
VERB can be used as a shorthand.
A boolean is interpreted as answering the question "does the
transient stay active, when this command is invoked?" t means that
the transient stays active, while nil means that invoking the command
exits the transient.
Note that when the suffix is a “sub-prefix”, invoking that command
always activates that sub-prefix, causing the outer prefix to no
longer be active and displayed. Here t means that when you exit the
inner prefix, then the outer prefix becomes active again, while nil
means that all outer prefixes are exited at once.
transient-non-suffix slot to a boolean, a suitable
pre-command function, or a shorthand for such a function. See
Pre-commands for Non-Suffixes.
transient-suffixes slot.
The value specified in this slot does not affect infixes. Because it affects both regular suffixes as well as sub-prefixes, which have different needs, it is best to avoid explicitly specifying a function.
transient slot. While it is usually best to use a boolean, for this
slot it can occasionally make sense to specify a function explicitly.
Note that this slot can be set when defining a suffix command using
transient-define-suffix and/or in the definition of the prefix. If
set in both places, then the latter takes precedence, as usual.
The available pre-command functions are documented in the following
sub-sections. 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.
For completeness sake, some notes about complications:
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 prefix’s transient-suffix slot, but not
the suffix’s transient slot.
For transient-suffix objects the transient slot is unbound. We can
ignore that for the most part because nil and the slot being unbound
are treated as 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.
The default for infixes is transient--do-stay. This is also the only
function that makes sense for infixes, which is why this predicate is
used even if the value of the prefix’s transient-suffix slot is t. In
extremely rare cases, one might want to use something else, which can
be done by setting the infix’s transient slot directly.
Call the command without exporting variables and stay transient.
By default, invoking a suffix causes the transient to be exited.
The behavior for an individual suffix command can be changed by
setting its transient slot to a boolean (which is highly recommended),
or to one of the following pre-commands.
Call the command after exporting variables and exit the transient.
Call the command after exporting variables and return to the parent
prefix. If there is no parent prefix, then call transient--do-exit.
Call the command after exporting variables and stay transient.
The following pre-commands are only suitable for sub-prefixes. It is
not necessary to explicitly use these predicates because the correct
predicate is automatically picked based on the value of the transient
slot for the sub-prefix itself.
Call the transient prefix command, preparing for return to active transient.
Whether we actually return to the parent transient is ultimately
under the control of each invoked suffix. The difference between
this pre-command and transient--do-stack is that it changes the
value of the transient-suffix slot to t.
If there is no parent transient, then only call this command and skip the second step.
Call the transient prefix command, stacking the active transient. Push the active transient to the transient stack.
Unless transient--do-recurse is explicitly used, this pre-command
is automatically used for suffixes that are prefixes themselves,
i.e., for sub-prefixes.
Call the transient prefix command, replacing the active transient. Do not push the active transient to the transient stack.
Unless transient--do-recurse is explicitly used, this pre-command
is automatically used for suffixes that are prefixes themselves,
i.e., for sub-prefixes.
Suspend the active transient, saving the transient stack.
This is used by the command transient-suspend and optionally also by
“external events” such as handle-switch-frame. Such bindings should
be added to transient-predicate-map.
By default, non-suffixes (commands that are bound in other keymaps beside the transient keymap) cannot be invoked. Trying to invoke such a command results in a warning and the transient stays active.
If you want a different behavior, then set the transient-non-suffix
slot of the transient prefix command. The value should be a boolean,
answering the question, "is it allowed to invoke non-suffix commands?,
a pre-command function, or a shorthand for such a function.
If the value is t, then non-suffixes can be invoked, when it is nil
(the default) then they cannot be invoked.
The only other recommended value is leave. If that is used, then
non-suffixes can be invoked, but if one is invoked, then that exits
the transient.
Call transient-undefined and stay transient.
Call the command without exporting variables and stay transient.
Call the command without exporting variables and exit the 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: FAQ, Previous: Defining New Commands, Up: Transient User and Developer Manual [Contents][Index]
Transient uses classes and generic functions to make it possible to define new types of suffix and prefix commands, which are similar to existing types, but behave differently in some respects.
Every prefix, infix and suffix command is associated with an object, which holds information, which 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.
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 (or “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--shadowed-buffer the current buffer.
Next: Suffix Classes, Previous: Group Methods, Up: Classes and Methods [Contents][Index]
Transient itself provides a single class for prefix commands,
transient-prefix, but package authors may wish to define specialized
classes. Doing so makes it possible to change the behavior of the set
of prefix commands that use that class, by implementing specialized
methods for certain generic functions (see Prefix Methods).
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: Prefix 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-variable class.
transient-information and transient-information* classes are
special in that suffixes that use these class are not associated
with a command and thus also not with any key binding. Such
suffixes are only used to display arbitrary information, and that
anywhere a suffix can appear. Display-only suffix specifications
take these form:
([LEVEL] :info DESCRIPTION [KEYWORD VALUE]...) ([LEVEL] :info* DESCRIPTION [KEYWORD VALUE]...)
The :info and :info* keyword arguments replaces the :description
keyword used for other suffix classes. Other keyword arguments that
you might want to set, include :face, predicate keywords (such as
:if and :inapt-if), and :format. By default the value of :format
includes %k, which for this class is replaced with the empty string
or spaces, if keys are being padded in the containing group.
The only difference between these two classes is that :info* aligns
its description with the descriptions of suffix commands, while for
:info the description bleeds into the area where suffixes display
their key bindings.
transient-lisp-variable class can be used to show and change the
value of lisp variables. This class is not fully featured yet and
it is somewhat likely that future improvements won’t be fully
backward compatible.
transient-describe-target class is used by the command
transient-describe.
transient-value-preset class is used to implement the command
transient-preset, which activates a value preset.
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: Suffix Methods, Previous: Suffix Classes, Up: Classes and Methods [Contents][Index]
To get information about the methods implementing these generic
functions use describe-function.
This generic function sets the initial value of the object OBJ. Methods exist for both prefix and suffix objects.
The default method for prefix objects sets the value of OBJ’s value
slot to the set, saved or default value. The value that is set for
the current session is preferred over the saved value, which is
preferred over the default value.
The default value is determined using the generic function
transient-default-value. If you need to change how the value for a
prefix class is determined, its usually sufficient to implement a
method for that function.
This generic function returns the default value of the object OBJ. Methods exist for both prefix and suffix objects.
The default method for prefix objects returns the value of the
default-value slot if that is bound and not a function. If it is a
function, that is called to get the value. If the slot is unbound,
nil is returned.
This generic function returns the value of the prefix object OBJ.
The respective generic function for infix and suffix objects is
named transient-infix-value.
This generic function sets the scope of the object OBJ. Methods exist for both prefix and suffix objects.
This function is called for all prefix and suffix commands, but unless a concrete method is implemented this falls through to the default implementation, which is a noop.
transient-set-value, transient-save-value, transient-reset-value,
transient--history-key, transient--history-push and
transient--history-init are other generic functions dealing with the
value of prefix objects. See their doc-strings for more information.
transient-show-help is another generic function implemented for prefix
commands. The default method effectively describes the command using
describe-function.
Next: Prefix Slots, Previous: Prefix Methods, Up: Classes and Methods [Contents][Index]
To get information about the methods implementing these generic
functions use describe-function.
Next: Suffix Format Methods, Up: Suffix Methods [Contents][Index]
This generic function sets the initial value of the object OBJ. Methods exist for both prefix and suffix objects.
For transient-argument objects this function handles setting the
value by itself.
For other transient-suffix objects (including transient-infix
objects), this calls transient-default-value and uses the value
returned by that, unless it is the special value eieio--unbound,
which indicates that there is no default value. Since that is what
the default method for transient-suffix objects does, both of these
functions effectively are noops for these classes.
If you implement a class that derives from transient-infix directly,
then you must implement a dedicated method for this function and/or
transient-default-value.
This generic function returns the default value of the object OBJ. Methods exist for both prefix and suffix objects.
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 object OBJ. Methods exist for both prefix and suffix objects.
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 prefix and 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.
Regardless of OBJ’s type, if its show-help slot is non-nil, that
must be a function, which takes OBJ is its only argument. It must
prepare, display and return a buffer, and select the window used to
display it. The transient-show-help-window macro is intended for
use in such functions.
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
documentation string.
For suffixes, show the command’s documentation string.
For infixes, show the manpage if that is specified. Otherwise show the command’s documentation string.
Evaluate BODY, send output to *Help* buffer, and display it in a
window. Select the help window, and make the help buffer current
and return it.
This generic function shows or, if optional RETURN is non-nil,
returns a brief summary about the command at point or hovered with
the mouse.
This function is called when the mouse is moved over a command and
(if the value of transient-enable-popup-navigation is verbose) when
the user navigates to a command using the keyboard.
If OBJ’s summary slot is a string, that is used. If summary is a
function, that is called with OBJ as the only argument and the
returned string is used. If summary is or returns something other
than a string or nil, no summary is shown. If summary is or returns
nil, the first line of the documentation string is used, if any.
If RETURN is non-nil, this function returns the summary instead of
showing it. This is used when a tooltip is needed.
Next: Suffix Slots, Previous: Suffix Methods, Up: Classes and Methods [Contents][Index]
default-value The default value of the prefix. Use the keyword
argument :value (sic) to set this slot in the definition of a
prefix.
init-value A function that is responsible 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.
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.
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. An argument may appear in
multiple sub-lists. Arguments must me given in the same form as
used in the argument or argument-format slot of the respective
suffix objects, usually something like --switch or --option=%s. For
options and transient-switches suffixes it is also possible to match
against a specific value, as returned by transient-infix-value,
for example, --option=one.
scope For some transients it might be necessary to have a sort of
secondary value, called a “scope”. See transient-define-prefix.
transient-suffix, transient-non-suffix and transient-switch-frame
play a part when determining whether the currently active transient
prefix command remains active/transient when a suffix or arbitrary
non-suffix command is invoked. See Transient State.
refresh-suffixes Normally suffix objects and keymaps are only setup
once, when the prefix is invoked. Setting this to t, causes them to
be recreated after every command. This is useful when using :if...
predicates, and those need to be rerun for some reason. Doing this
is somewhat costly, and there is a risk of losing state, so this is
disabled by default and still considered experimental.
environment A function used to establish an environment while
initializing, refreshing or redisplaying a transient prefix menu.
This is useful to establish a cache, in case multiple suffixes
require the same expensive work. The provided function is called
with at least one argument, the function for which it establishes
the environment. It must funcall that function with no arguments.
During initialization the second argument is the prefix object
being initialized. This slot is still experimental.
display-action determines how this prefix is displayed, overriding
transient-display-buffer-action. It should have the same type.
mode-line-format is this prefix’s mode line format, overriding
transient-mode-line-format. It should have the same type.
column-width is only respected inside transient-columns groups and
allows aligning columns across separate instances of that.
variable-pitch controls whether alignment is done pixel-wise to
account for use of variable-pitch characters, which is useful, e.g.,
when using emoji.
show-help, man-page or info-manual can be used to specify the
documentation for the prefix and its suffixes. The command
transient-help uses the function transient-show-help (which see) to
lookup and use these values.
suffix-description can be used to specify a function which provides
fallback descriptions for suffixes that lack a description. This
is intended to be temporarily used when implementing of a new prefix
command, at which time transient-command-summary-or-name is a useful
value.
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.
unwind-suffix is used internally to ensure transient state is
properly exited, even in case of an error.
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-childThis is the abstract superclass of transient-suffix and transient-group.
This is where the shared if* and inapt-if* slots (see Predicate Slots)
and the level slot (see Enabling and Disabling Suffixes) are defined.
parent The object for the parent group.
transient-suffixkey 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, which is
called with zero or one argument (the suffix object), and returns a
string.
face Face used for the description. In simple cases it is easier
to use this instead of using a function as description and adding
the styling there. face is appended using add-face-text-property.
show-help A function used to display help for the suffix. If
unspecified, the prefix controls how help is displayed for its
suffixes. See also function transient-show-help.
summary The summary displayed in the echo area, or as a tooltip.
If this is nil, which it usually should be, the first line of the
documentation string is used instead. See transient-show-summary
for details.
definition A command, which is used if the body is omitted when
defining a command using transient-define-suffix.
transient-infixSome 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 responsible 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 this is non-nil, then the values are read using
completing-read-multiple by default and if you specify your own
reader, then it should read the values using that function or
similar.
Supported non-nil values are:
rest for an option that can have multiple values. This is
useful e.g., for an -- argument that indicates that all remaining
arguments are files (such as git log -- file1 file2).
In the list returned by transient-args such an option and its
values are represented by a single list of the form (ARGUMENT
. VALUES).
repeat for an option that can be specified multiple times.
In the list returned by transient-args each instance of the option
and its value appears separately in the usual from, for example:
("--another-argument" "--option=first" "--option=second").
In both cases the option’s values have to be specified in the
default value of a prefix using the same format as returned by
transient-args, e.g., ("--other" "--o=1" "--o=2" ("--" "f1" "f2")).
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, or a function that returns such a
list. The latter is not implemented for transient-switches, because
I couldn’t think of a use-case. How exactly the choices are used
varies depending on the class of the suffix.
transient-variablevariable The variable.
transient-switchesargument-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 two sets of predicate slots that control whether a group or suffix should be available depending on some state. Only one slot from each set can be used at the same time. It is undefined which slot is honored if you use more than one.
Predicates from the first group control whether the suffix is present in the menu at all.
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.
Predicates from the second group control whether the suffix can be invoked. The suffix is shown in the menu regardless, but when it is considered "inapt", then it is grayed out to indicated that it currently cannot be invoked.
inapt-if Inapt if predicate returns non-nil.
inapt-if-not Inapt if predicate returns nil.
inapt-if-non-nil Inapt if variable’s value is non-nil.
inapt-if-nil Inapt if variable’s value is nil.
inapt-if-mode Inapt if major-mode matches value.
inapt-if-not-mode Inapt if major-mode does not match value.
inapt-if-derived Inapt if major-mode derives from value.
inapt-if-not-derived Inapt if major-mode does not derive from value.
By default these predicates run when the prefix command is invoked,
but this can be changes, using the refresh-suffixes prefix slot.
See Prefix Slots.
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: Keystroke Index, Previous: Classes and Methods, Up: Transient User and Developer Manual [Contents][Index]
Yes, see transient-display-buffer-action in Configuration. You can
also control how the popup buffer is displayed on a case-by-case basis
by passing :display-action to transient-define-prefix.
To be able to mark text in Transient’s popup buffer using the mouse, you have to add the below binding. Note that for technical reasons, the region won’t be visualized, while doing so. After you have quit the transient popup, you will be able to yank it in another buffer.
(keymap-set transient-predicate-map
"<mouse-set-region>"
#'transient--do-stay)
If your package only supports Emacs 30, just prefix the definition
with ;;;###autoload. If your package supports released versions of
Emacs, you unfortunately have to use a long form autoload comment
as described in (elisp)Autoload.
;;;###autoload (autoload 'magit-dispatch "magit" nil t) (transient-define-prefix magit-dispatch () ...)
See https://github.com/magit/transient/wiki/Comparison-with-prefix-keys-and-universal-arguments.
See https://github.com/magit/transient/wiki/Comparison-with-other-packages.
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 bindings that begin with the C-x prefix 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.
(See also the next question.)
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 documentation string for more information.
Next: Command and Function Index, Previous: FAQ, Up: Transient User and Developer Manual [Contents][Index]
Next: Variable Index, Previous: Keystroke Index, Up: Transient User and Developer Manual [Contents][Index]
Next: Concept Index, Previous: Command and Function Index, Up: Transient User and Developer Manual [Contents][Index]
Next: GNU General Public License, Previous: Variable Index, Up: Transient User and Developer Manual [Contents][Index]
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If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.
one line to give the program's name and a brief idea of what it does. Copyright (C) year name of author This program is free software: you can redistribute it 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 program 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. You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:
program Copyright (C) year name of author This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’. This is free software, and you are welcome to redistribute it under certain conditions; type ‘show c’ for details.
The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, your program’s commands might be different; for a GUI interface, you would use an “about box”.
You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see https://www.gnu.org/licenses/.
The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read https://www.gnu.org/licenses/why-not-lgpl.html.
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.