The editor command loop sets several Lisp variables to keep status
records for itself and for commands that are run. With the exception of
this-command and last-command it’s generally a bad idea to
change any of these variables in a Lisp program.
This variable records the name of the previous command executed by the command loop (the one before the current command). Normally the value is a symbol with a function definition, but this is not guaranteed.
The value is copied from this-command when a command returns to
the command loop, except when the command has specified a prefix
argument for the following command.
This variable is always local to the current terminal and cannot be buffer-local. See Multiple Terminals.
This variable is set up by Emacs just like last-command,
but never altered by Lisp programs.
This variable stores the most recently executed command that was not
part of an input event. This is the command repeat will try to
repeat, See Repeating in The GNU Emacs Manual.
This variable records the name of the command now being executed by
the editor command loop. Like last-command, it is normally a symbol
with a function definition.
The command loop sets this variable just before running a command, and
copies its value into last-command when the command finishes
(unless the command specified a prefix argument for the following
command).
Some commands set this variable during their execution, as a flag for
whatever command runs next. In particular, the functions for killing text
set this-command to kill-region so that any kill commands
immediately following will know to append the killed text to the
previous kill.
If you do not want a particular command to be recognized as the previous
command in the case where it got an error, you must code that command to
prevent this. One way is to set this-command to t at the
beginning of the command, and set this-command back to its proper
value at the end, like this:
(defun foo (args…)
(interactive …)
(let ((old-this-command this-command))
(setq this-command t)
…do the work…
(setq this-command old-this-command)))
We do not bind this-command with let because that would
restore the old value in case of error—a feature of let which
in this case does precisely what we want to avoid.
This has the same value as this-command except when command
remapping occurs (see Remapping Commands). In that case,
this-command gives the command actually run (the result of
remapping), and this-original-command gives the command that
was specified to run but remapped into another command.
This has the same value as this-command, but is bound
recursively when entering a minibuffer. This variable can be used
from minibuffer hooks and the like to determine what command opened
the current minibuffer session.
This function returns a string or vector containing the key sequence
that invoked the present command. Any events read by the command
using read-event without a timeout get tacked on to the end.
However, if the command has called read-key-sequence, it
returns the last read key sequence. See Key Sequence Input. The
value is a string if all events in the sequence were characters that
fit in a string. See Input Events.
(this-command-keys)
;; Now use C-u C-x C-e to evaluate that.
⇒ "^X^E"
Like this-command-keys, except that it always returns the events
in a vector, so you don’t need to deal with the complexities of storing
input events in a string (see Putting Keyboard Events in Strings).
This function empties out the table of events for
this-command-keys to return. Unless keep-record is
non-nil, it also empties the records that the function
recent-keys (see Recording Input) will subsequently return.
This is useful after reading a password, to prevent the password from
echoing inadvertently as part of the next command in certain cases.
This variable holds the last input event read as part of a key sequence, not counting events resulting from mouse menus.
One use of this variable is for telling x-popup-menu where to pop
up a menu. It is also used internally by y-or-n-p
(see Yes-or-No Queries).
This variable is set to the last input event that was read by the
command loop as part of a command. The principal use of this variable
is in self-insert-command, which uses it to decide which
character to insert, and in post-self-insert-hook
(see User-Level Insertion Commands), which uses it to access the
character that was just inserted.
last-command-event
;; Now use C-u C-x C-e to evaluate that.
⇒ 5
The value is 5 because that is the ASCII code for C-e.
This variable records which frame the last input event was directed to. Usually this is the frame that was selected when the event was generated, but if that frame has redirected input focus to another frame, the value is the frame to which the event was redirected. See Input Focus.
If the last event came from a keyboard macro, the value is macro.
Input events must come from somewhere; sometimes, that is a keyboard macro, a signal, or ‘unread-command-events’, but it is usually a physical input device connected to a computer that is controlled by the user. Those devices are referred to as input devices, and Emacs associates each input event with the input device from which it originated. They are identified by a name that is unique to each input device.
The ability to determine the precise input device used depends on the details of each system. When that information is unavailable, Emacs reports keyboard events as originating from the ‘"Virtual core keyboard"’, and other events as originating from the ‘"Virtual core pointer"’. (These values are used on every platform because the X server reports them when detailed device information is not known.)
This variable records the name of the input device from which the last
input event read was generated. It is nil if no such device
exists, i.e., the last input event was read from
unread-command-events, or it came from a keyboard macro.
When the X Input Extension is being used on X Windows, the device name is a string that is unique to each physical keyboard, pointing device and touchscreen attached to the X server. Otherwise, it is either the string ‘"Virtual core pointer"’ or ‘"Virtual core keyboard"’, depending on whether the event was generated by a pointing device (such as a mouse) or a keyboard.
There are various different types of devices, which can be determined from their names. This function can be used to determined the correct type of the device name for an event originating from frame.
The return value is one of the following symbols (“device classes”):
core-keyboardThe core keyboard; this is means the device is a keyboard-like device, but no other characteristics are unknown.
core-pointerThe core pointer; this means the device is a pointing device, but no other characteristics are known.
mouseA computer mouse.
trackpointA trackpoint or joystick (or other similar control.)
eraserThe other end of a stylus on a graphics tablet, or a standalone eraser.
penThe pointed end of a pen on a graphics tablet, a stylus, or some other similar device.
puckA device that looks like a computer mouse, but reports absolute coordinates relative to some other surface.
power-buttonA power button or volume button (or other similar control.)
keyboardA computer keyboard.
touchscreenA computer touchpad.
padA collection of sensitive buttons, rings, and strips commonly found around a drawing tablet.
touchpadAn indirect touch device such as a touchpad.
pianoA musical instrument such as an electronic keyboard.
testA device used by the XTEST extension to report input.