[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
When you run XEmacs, it enters the editor command loop almost immediately. This loop reads events, executes their definitions, and displays the results. In this chapter, we describe how these things are done, and the subroutines that allow Lisp programs to do them.
25.1 Command Loop Overview | How the command loop reads commands. | |
25.2 Defining Commands | Specifying how a function should read arguments. | |
25.3 Interactive Call | Calling a command, so that it will read arguments. | |
25.4 Information from the Command Loop | Variables set by the command loop for you to examine. | |
25.5 Events | What input looks like when you read it. | |
25.6 Reading Input | How to read input events from the keyboard or mouse. | |
25.7 Waiting for Elapsed Time or Input | Waiting for user input or elapsed time. | |
25.8 Quitting | How C-g works. How to catch or defer quitting. | |
25.9 Prefix Command Arguments | How the commands to set prefix args work. | |
25.10 Recursive Editing | Entering a recursive edit, and why you usually shouldn’t. | |
25.11 Disabling Commands | How the command loop handles disabled commands. | |
25.12 Command History | How the command history is set up, and how accessed. | |
25.13 Keyboard Macros | How keyboard macros are implemented. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The command loop in XEmacs is a standard event loop, reading events
one at a time with next-event
and handling them with
dispatch-event
. An event is typically a single user action, such
as a keypress, mouse movement, or menu selection; but they can also be
notifications from the window system, informing XEmacs that (for
example) part of its window was just uncovered and needs to be redrawn.
See section Events. Pending events are held in a first-in, first-out list
called the event queue: events are read from the head of the list,
and newly arriving events are added to the tail. In this way, events
are always processed in the order in which they arrive.
dispatch-event
does most of the work of handling user actions.
The first thing it must do is put the events together into a key
sequence, which is a sequence of events that translates into a command.
It does this by consulting the active keymaps, which specify what the
valid key sequences are and how to translate them into commands.
See section Key Lookup, for information on how this is done. The result of
the translation should be a keyboard macro or an interactively callable
function. If the key is M-x, then it reads the name of another
command, which it then calls. This is done by the command
execute-extended-command
(see section Interactive Call).
To execute a command requires first reading the arguments for it.
This is done by calling command-execute
(see section Interactive Call). For commands written in Lisp, the interactive
specification says how to read the arguments. This may use the prefix
argument (see section Prefix Command Arguments) or may read with prompting
in the minibuffer (see section Minibuffers). For example, the command
find-file
has an interactive
specification which says to
read a file name using the minibuffer. The command’s function body does
not use the minibuffer; if you call this command from Lisp code as a
function, you must supply the file name string as an ordinary Lisp
function argument.
If the command is a string or vector (i.e., a keyboard macro) then
execute-kbd-macro
is used to execute it. You can call this
function yourself (see section Keyboard Macros).
To terminate the execution of a running command, type C-g. This character causes quitting (see section Quitting).
The editor command loop runs this normal hook before each command. At
that time, this-command
contains the command that is about to
run, and last-command
describes the previous command.
See section Hooks.
The editor command loop runs this normal hook after each command. (In
FSF Emacs, it is also run when the command loop is entered, or
reentered after an error or quit.) At that time,
this-command
describes the command that just ran, and
last-command
describes the command before that. See section Hooks.
Quitting is suppressed while running pre-command-hook
and
post-command-hook
. If an error happens while executing one of
these hooks, it terminates execution of the hook, but that is all it
does.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
A Lisp function becomes a command when its body contains, at top
level, a form that calls the special operator interactive
. This
operator does nothing when actually executed, but its presence serves as a
flag to indicate that interactive calling is permitted. Its argument
controls the reading of arguments for an interactive call.
25.2.1 Using interactive | General rules for interactive .
| |
25.2.2 Code Characters for interactive | The standard letter-codes for reading arguments in various ways. | |
25.2.3 Examples of Using interactive | Examples of how to read interactive arguments. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
interactive
This section describes how to write the interactive
form that
makes a Lisp function an interactively-callable command.
This special operator declares that the function in which it appears is a command, and that it may therefore be called interactively (via M-x or by entering a key sequence bound to it). The argument arg-descriptor declares how to compute the arguments to the command when the command is called interactively.
A command may be called from Lisp programs like any other function, but then the caller supplies the arguments and arg-descriptor has no effect.
The interactive
form has its effect because the command loop
(actually, its subroutine call-interactively
) scans through the
function definition looking for it, before calling the function. Once
the function is called, all its body forms including the
interactive
form are executed, but at this time
interactive
simply returns nil
without even evaluating its
argument.
There are three possibilities for the argument arg-descriptor:
nil
; then the command is called with no
arguments. This leads quickly to an error if the command requires one
or more arguments.
If this expression reads keyboard input (this includes using the minibuffer), keep in mind that the integer value of point or the mark before reading input may be incorrect after reading input. This is because the current buffer may be receiving subprocess output; if subprocess output arrives while the command is waiting for input, it could relocate point and the mark.
Here’s an example of what not to do:
(interactive (list (region-beginning) (region-end) (read-string "Foo: " nil 'my-history))) |
Here’s how to avoid the problem, by examining point and the mark only after reading the keyboard input:
(interactive (let ((string (read-string "Foo: " nil 'my-history))) (list (region-beginning) (region-end) string))) |
(interactive "bFrobnicate buffer: ") |
The code letter ‘b’ says to read the name of an existing buffer, with completion. The buffer name is the sole argument passed to the command. The rest of the string is a prompt.
If there is a newline character in the string, it terminates the prompt. If the string does not end there, then the rest of the string should contain another code character and prompt, specifying another argument. You can specify any number of arguments in this way.
The prompt string can use ‘%’ to include previous argument values
(starting with the first argument) in the prompt. This is done using
format
(see section Formatting Strings). For example, here is how
you could read the name of an existing buffer followed by a new name to
give to that buffer:
(interactive "bBuffer to rename: \nsRename buffer %s to: ") |
If the first character in the string is ‘*’, then an error is signaled if the buffer is read-only.
If the first character in the string is ‘@’, and if the key sequence used to invoke the command includes any mouse events, then the window associated with the first of those events is selected before the command is run.
If the first character in the string is ‘_’, then this command will
not cause the region to be deactivated when it completes; that is,
zmacs-region-stays
will be set to t
when the command exits
successfully.
You can use ‘*’, ‘@’, and ‘_’ together; the order does not matter. Actual reading of arguments is controlled by the rest of the prompt string (starting with the first character that is not ‘*’, ‘@’, or ‘_’).
This function retrieves the interactive specification of function,
which may be any funcallable object. The specification will be returned
as the list of the symbol interactive
and the specs. If
function is not interactive, nil
will be returned.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
interactive
The code character descriptions below contain a number of key words, defined here as follows:
Provide completion. <TAB>, <SPC>, and <RET> perform name
completion because the argument is read using completing-read
(see section Completion). ? displays a list of possible completions.
Require the name of an existing object. An invalid name is not accepted; the commands to exit the minibuffer do not exit if the current input is not valid.
A default value of some sort is used if the user enters no text in the minibuffer. The default depends on the code character.
This code letter computes an argument without reading any input. Therefore, it does not use a prompt string, and any prompt string you supply is ignored.
Even though the code letter doesn’t use a prompt string, you must follow it with a newline if it is not the last code character in the string.
A prompt immediately follows the code character. The prompt ends either with the end of the string or with a newline.
This code character is meaningful only at the beginning of the interactive string, and it does not look for a prompt or a newline. It is a single, isolated character.
Here are the code character descriptions for use with interactive
:
Signal an error if the current buffer is read-only. Special.
Select the window mentioned in the first mouse event in the key sequence that invoked this command. Special.
Do not cause the region to be deactivated when this command completes. Special.
A function name (i.e., a symbol satisfying fboundp
). Existing,
Completion, Prompt.
The name of an existing buffer. By default, uses the name of the current buffer (see section Buffers). Existing, Completion, Default, Prompt.
A buffer name. The buffer need not exist. By default, uses the name of a recently used buffer other than the current buffer. Completion, Default, Prompt.
A character. The cursor does not move into the echo area. Prompt.
A command name (i.e., a symbol satisfying commandp
). Existing,
Completion, Prompt.
The position of point, as an integer (see section Point). No I/O.
A directory name. The default is the current default directory of the
current buffer, default-directory
(see section Operating System Environment).
Existing, Completion, Default, Prompt.
The last mouse-button or misc-user event in the key sequence that invoked the command. No I/O.
You can use ‘e’ more than once in a single command’s interactive specification. If the key sequence that invoked the command has n mouse-button or misc-user events, the nth ‘e’ provides the nth such event.
A file name of an existing file (see section File Names). The default
directory is default-directory
. Existing, Completion, Default,
Prompt.
A file name. The file need not exist. Completion, Default, Prompt.
A key sequence (see section Keymap Terminology). This keeps reading events until a command (or undefined command) is found in the current key maps. The key sequence argument is represented as a vector of events. The cursor does not move into the echo area. Prompt.
This kind of input is used by commands such as describe-key
and
global-set-key
.
A key sequence, whose definition you intend to change. This works like ‘k’, except that it suppresses, for the last input event in the key sequence, the conversions that are normally used (when necessary) to convert an undefined key into a defined one.
The position of the mark, as an integer. No I/O.
A number read with the minibuffer. If the input is not a number, the user is asked to try again. The prefix argument, if any, is not used. Prompt.
The raw prefix argument. If the prefix argument is nil
, then
read a number as with n. Requires a number. See section Prefix Command Arguments. Prompt.
The numeric prefix argument. (Note that this ‘p’ is lower case.) No I/O.
The raw prefix argument. (Note that this ‘P’ is upper case.) No I/O.
Point and the mark, as two numeric arguments, smallest first. This is the only code letter that specifies two successive arguments rather than one. No I/O.
Arbitrary text, read in the minibuffer and returned as a string (see section Reading Text Strings with the Minibuffer). Terminate the input with either <LFD> or <RET>. (C-q may be used to include either of these characters in the input.) Prompt.
An interned symbol whose name is read in the minibuffer. Any whitespace character terminates the input. (Use C-q to include whitespace in the string.) Other characters that normally terminate a symbol (e.g., parentheses and brackets) do not do so here. Prompt.
A variable declared to be a user option (i.e., satisfying the predicate
user-variable-p
). See section High-Level Completion Functions. Existing,
Completion, Prompt.
A Lisp object, specified with its read syntax, terminated with a <LFD> or <RET>. The object is not evaluated. See section Reading Lisp Objects with the Minibuffer. Prompt.
A Lisp form is read as with x, but then evaluated so that its value becomes the argument for the command. Prompt.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
interactive
Here are some examples of interactive
:
(defun foo1 () ; (defun foo2 (n) ; (defun foo3 (n) ; (defun three-b (b1 b2 b3) "Select three existing buffers. Put them into three windows, selecting the last one." (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") (delete-other-windows) (split-window (selected-window) 8) (switch-to-buffer b1) (other-window 1) (split-window (selected-window) 8) (switch-to-buffer b2) (other-window 1) (switch-to-buffer b3)) ⇒ three-b (three-b "*scratch*" "declarations.texi" "*mail*") ⇒ nil |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
After the command loop has translated a key sequence into a
definition, it invokes that definition using the function
command-execute
. If the definition is a function that is a
command, command-execute
calls call-interactively
, which
reads the arguments and calls the command. You can also call these
functions yourself.
Returns t
if function is suitable for calling interactively;
that is, if function is a command. Otherwise, returns nil
.
The interactively callable objects include strings and vectors (treated
as keyboard macros), lambda expressions that contain a top-level call to
interactive
, compiled-function objects made from such lambda
expressions, autoload objects that are declared as interactive
(non-nil
fourth argument to autoload
), and some of the
primitive functions.
A symbol is commandp
if its function definition is
commandp
.
Keys and keymaps are not commands. Rather, they are used to look up commands (see section Keymaps).
See documentation
in Access to Documentation Strings, for a
realistic example of using commandp
.
This function calls the interactively callable function command, reading arguments according to its interactive calling specifications. An error is signaled if command is not a function or if it cannot be called interactively (i.e., is not a command). Note that keyboard macros (strings and vectors) are not accepted, even though they are considered commands, because they are not functions.
If record-flag is the symbol lambda
, the interactive
calling arguments for command are read and returned as a list,
but the function is not called on them.
If record-flag is t
, then this command and its arguments
are unconditionally added to the list command-history
.
Otherwise, the command is added only if it uses the minibuffer to read
an argument. See section Command History.
This function executes command as an editing command. The
argument command must satisfy the commandp
predicate; i.e.,
it must be an interactively callable function or a keyboard macro.
A string or vector as command is executed with
execute-kbd-macro
. A function is passed to
call-interactively
, along with the optional record-flag.
A symbol is handled by using its function definition in its place. A
symbol with an autoload
definition counts as a command if it was
declared to stand for an interactively callable function. Such a
definition is handled by loading the specified library and then
rechecking the definition of the symbol.
This function reads a command name from the minibuffer using
completing-read
(see section Completion). Then it uses
command-execute
to call the specified command. Whatever that
command returns becomes the value of execute-extended-command
.
If the command asks for a prefix argument, it receives the value
prefix-argument. If execute-extended-command
is called
interactively, the current raw prefix argument is used for
prefix-argument, and thus passed on to whatever command is run.
execute-extended-command
is the normal definition of M-x,
so it uses the string ‘M-x ’ as a prompt. (It would be better
to take the prompt from the events used to invoke
execute-extended-command
, but that is painful to implement.) A
description of the value of the prefix argument, if any, also becomes
part of the prompt.
(execute-extended-command 1) ---------- Buffer: Minibuffer ---------- 1 M-x forward-word RET ---------- Buffer: Minibuffer ---------- ⇒ t |
This function returns t
if the containing function (the one that
called interactive-p
) was called interactively, with the function
call-interactively
. (It makes no difference whether
call-interactively
was called from Lisp or directly from the
editor command loop.) If the containing function was called by Lisp
evaluation (or with apply
or funcall
), then it was not
called interactively.
The most common use of interactive-p
is for deciding whether to
print an informative message. As a special exception,
interactive-p
returns nil
whenever a keyboard macro is
being run. This is to suppress the informative messages and speed
execution of the macro.
For example:
(defun foo () (interactive) (and (interactive-p) (message "foo"))) ⇒ foo (defun bar () (interactive) (setq foobar (list (foo) (interactive-p)))) ⇒ bar ;; Type M-x foo.
-| foo
;; Type M-x bar. ;; This does not print anything. foobar ⇒ (nil t) |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The editor command loop sets several Lisp variables to keep status records for itself and for commands that are run.
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 specifies a prefix argument
for the following command.
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 specifies 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)))
|
This function returns a vector containing the key and mouse events that invoked the present command, plus any previous commands that generated the prefix argument for this command. (Note: this is not the same as in FSF Emacs, which can return a string.) See section Events.
This function copies the vector and the events; it is safe to keep and modify them.
(this-command-keys)
;; Now use C-u C-x C-e to evaluate that.
⇒ [#<keypress-event control-U> #<keypress-event control-X> #<keypress-event control-E>]
|
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.
This variable is off limits: you may not set its value or modify the
event that is its value, as it is destructively modified by
read-key-sequence
. If you want to keep a pointer to this value,
you must use copy-event
.
Note that this variable is an alias for last-command-char
in
FSF Emacs.
last-command-event
;; Now type C-u C-x C-e.
⇒ #<keypress-event control-E>
|
If the value of last-command-event
is a keyboard event, then this
is the nearest character equivalent to it (or nil
if there is no
character equivalent). last-command-char
is the character that
self-insert-command
will insert in the buffer. Remember that
there is not a one-to-one mapping between keyboard events and
XEmacs characters: many keyboard events have no corresponding character,
and when the Mule feature is available, most characters can not be input
on standard keyboards, except possibly with help from an input method.
So writing code that examines this variable to determine what key has
been typed is bad practice, unless you are certain that it will be one
of a small set of characters.
This variable exists for compatibility with Emacs version 18.
last-command-char
;; Now use C-u C-x C-e to evaluate that.
⇒ ?\^E
|
This variable holds the mouse-button event which invoked this command,
or nil
. This is what (interactive "e")
returns.
This variable determines how much time should elapse before command characters echo. Its value must be a float or a fixnum, which specifies the number of seconds to wait before echoing. If the user types a prefix key (say C-x) and then delays this many seconds before continuing, the key C-x is echoed in the echo area. Any subsequent characters in the same command will be echoed as well.
If the value is zero, then command input is not echoed.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The XEmacs command loop reads a sequence of events that represent keyboard or mouse activity. Unlike in Emacs 18 and in FSF Emacs, events are a primitive Lisp type that must be manipulated using their own accessor and settor primitives. This section describes the representation and meaning of input events in detail.
A key sequence that starts with a mouse event is read using the keymaps of the buffer in the window that the mouse was in, not the current buffer. This does not imply that clicking in a window selects that window or its buffer—that is entirely under the control of the command binding of the key sequence.
For information about how exactly the XEmacs command loop works, See section Reading Input.
This function returns non-nil
if object is an input event.
25.5.1 Event Types | Events come in different types. | |
25.5.2 Contents of the Different Types of Events | What the contents of each event type are. | |
25.5.3 Event Predicates | Querying whether an event is of a particular type. | |
25.5.4 Accessing the Position of a Mouse Event | Determining where a mouse event occurred, and over what. | |
25.5.5 Accessing the Other Contents of Events | Accessing non-positional event info. | |
25.5.6 Working With Events | Creating, copying, and destroying events. | |
25.5.7 Converting Events | Converting between events, keys, and characters. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Events represent keyboard or mouse activity or status changes of various sorts, such as process input being available or a timeout being triggered. The different event types are as follows:
A key was pressed. Note that modifier keys such as “control”, “shift”, and “alt” do not generate events; instead, they are tracked internally by XEmacs, and non-modifier key presses generate events that specify both the key pressed and the modifiers that were held down at the time.
A button was pressed or released. Along with the button that was pressed or released, button events specify the modifier keys that were held down at the time and the position of the pointer at the time.
The pointer was moved. Along with the position of the pointer, these events also specify the modifier keys that were held down at the time.
A menu item was selected, the scrollbar was used, or a drag or a drop occurred.
Input is available on a process.
A timeout has triggered.
Some window-system-specific action (such as a frame being resized or
a portion of a frame needing to be redrawn) has occurred. The contents
of this event are not accessible at the E-Lisp level, but
dispatch-event
knows what to do with an event of this type.
This is a special kind of event specifying that a particular function
needs to be called when this event is dispatched. An event of this type
is sometimes placed in the event queue when a magic event is processed.
This kind of event should generally just be passed off to
dispatch-event
. See section Dispatching an Event.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Every event, no matter what type it is, contains a timestamp (which is typically an offset in milliseconds from when the X server was started) indicating when the event occurred. In addition, many events contain a channel, which specifies which frame the event occurred on, and/or a value indicating which modifier keys (shift, control, etc.) were held down at the time of the event.
The contents of each event are as follows:
Which key was pressed. This is an integer (in the printing ASCII
range: >32 and <127) or a symbol such as left
or right
.
Note that many physical keys are actually treated as two separate keys,
depending on whether the shift key is pressed; for example, the “a”
key is treated as either “a” or “A” depending on the state of the
shift key, and the “1” key is similarly treated as either “1” or
“!” on most keyboards. In such cases, the shift key does not show up
in the modifier list. For other keys, such as backspace
, the
shift key shows up as a regular modifier.
Which modifier keys were pressed. As mentioned above, the shift key is not treated as a modifier for many keys and will not show up in this list in such cases.
What button went down or up. Buttons are numbered starting at 1.
Which modifier keys were pressed. The special business mentioned above for the shift key does not apply to mouse events.
The position of the pointer (in pixels) at the time of the event.
The position of the pointer (in pixels) after it moved.
Which modifier keys were pressed. The special business mentioned above for the shift key does not apply to mouse events.
The E-Lisp function to call for this event. This is normally either
eval
or call-interactively
.
The object to pass to the function. This is normally the callback that was specified in the menu description.
What button went down or up. Buttons are numbered starting at 1.
Which modifier keys were pressed. The special business mentioned above for the shift key does not apply to mouse events.
The position of the pointer (in pixels) at the time of the event.
The Emacs “process” object in question.
The E-Lisp function to call for this timeout. It is called with one argument, the event.
Some Lisp object associated with this timeout, to make it easier to tell them apart. The function and object for this event were specified when the timeout was set.
(The rest of the information in this event is not user-accessible.)
An E-Lisp function to call when this event is dispatched.
The object to pass to the function. The function and object are set when the event is created.
Return the type of event.
This will be a symbol; one of
key-press
A key was pressed.
button-press
A mouse button was pressed.
button-release
A mouse button was released.
motion
The mouse moved.
misc-user
Some other user action happened; typically, this is a menu selection, scrollbar action, or drag and drop action.
process
Input is available from a subprocess.
timeout
A timeout has expired.
eval
This causes a specified action to occur when dispatched.
magic
Some window-system-specific event has occurred.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following predicates return whether an object is an event of a particular type.
This is true if object is a key-press event.
This is true if object is a mouse button-press or button-release event.
This is true if object is a mouse button-press event.
This is true if object is a mouse button-release event.
This is true if object is a mouse motion event.
This is true if object is a mouse button-press, button-release or motion event.
This is true if object is an eval event.
This is true if object is a misc-user event.
This is true if object is a process event.
This is true if object is a timeout event.
This is true if object is any event that has not been deallocated.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Unlike other events, mouse events (i.e. motion, button-press, button-release, and drag or drop type misc-user events) occur in a particular location on the screen. Many primitives are provided for determining exactly where the event occurred and what is under that location.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following functions return frame-level information about where a mouse event occurred.
This function returns the “channel” or frame that the given mouse
motion, button press, button release, or misc-user event occurred in.
This will be nil
for non-mouse events.
This function returns the X position in pixels of the given mouse event. The value returned is relative to the frame the event occurred in. This will signal an error if the event is not a mouse event.
This function returns the Y position in pixels of the given mouse event. The value returned is relative to the frame the event occurred in. This will signal an error if the event is not a mouse event.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following functions return window-level information about where a mouse event occurred.
Given a mouse motion, button press, button release, or misc-user event, compute and
return the window on which that event occurred. This may be nil
if the event occurred in the border or over a toolbar. The modeline is
considered to be within the window it describes.
Given a mouse motion, button press, button release, or misc-user event, compute and
return the buffer of the window on which that event occurred. This may
be nil
if the event occurred in the border or over a toolbar.
The modeline is considered to be within the window it describes. This is
equivalent to calling event-window
and then calling
window-buffer
on the result if it is a window.
This function returns the X position in pixels of the given mouse event. The value returned is relative to the window the event occurred in. This will signal an error if the event is not a mouse-motion, button-press, button-release, or misc-user event.
This function returns the Y position in pixels of the given mouse event. The value returned is relative to the window the event occurred in. This will signal an error if the event is not a mouse-motion, button-press, button-release, or misc-user event.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following functions return information about the text (including the modeline) that a mouse event occurred over or near.
Given a mouse-motion, button-press, button-release, or misc-user event, this
function returns t
if the event is over the text area of a
window. Otherwise, nil
is returned. The modeline is not
considered to be part of the text area.
Given a mouse-motion, button-press, button-release, or misc-user event, this
function returns t
if the event is over the modeline of a window.
Otherwise, nil
is returned.
This function returns the X position of the given mouse-motion, button-press, button-release, or misc-user event in characters. This is relative to the window the event occurred over.
This function returns the Y position of the given mouse-motion, button-press, button-release, or misc-user event in characters. This is relative to the window the event occurred over.
This function returns the character position of the given mouse-motion,
button-press, button-release, or misc-user event. If the event did not occur over
a window, or did not occur over text, then this returns nil
.
Otherwise, it returns an index into the buffer visible in the event’s
window.
This function returns the character position of the given mouse-motion,
button-press, button-release, or misc-user event. If the event did not occur over
a window or over text, it returns the closest point to the location of
the event. If the Y pixel position overlaps a window and the X pixel
position is to the left of that window, the closest point is the
beginning of the line containing the Y position. If the Y pixel
position overlaps a window and the X pixel position is to the right of
that window, the closest point is the end of the line containing the Y
position. If the Y pixel position is above a window, 0 is returned. If
it is below a window, the value of (window-end)
is returned.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following functions return information about the glyph (if any) that a mouse event occurred over.
Given a mouse-motion, button-press, button-release, or misc-user event, this
function returns t
if the event is over a glyph. Otherwise,
nil
is returned.
If the given mouse-motion, button-press, button-release, or misc-user event happened
on top of a glyph, this returns its extent; else nil
is returned.
Given a mouse-motion, button-press, button-release, or misc-user event over a
glyph, this function returns the X position of the pointer relative to
the upper left of the glyph. If the event is not over a glyph, it returns
nil
.
Given a mouse-motion, button-press, button-release, or misc-user event over a
glyph, this function returns the Y position of the pointer relative to
the upper left of the glyph. If the event is not over a glyph, it returns
nil
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Given a mouse-motion, button-press, button-release, or misc-user event, this
function returns t
if the event is over a toolbar. Otherwise,
nil
is returned.
If the given mouse-motion, button-press, button-release, or misc-user event
happened on top of a toolbar button, this function returns the button.
Otherwise, nil
is returned.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Given a mouse-motion, button-press, button-release, or misc-user event, this
function returns t
if the event is over an internal toolbar.
Otherwise, nil
is returned.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The following functions allow access to the contents of events other than the position info described in the previous section.
This function returns the timestamp of the given event object.
This function returns the device that the given event occurred on.
This function returns the Keysym of the given key-press event. This will be the ASCII code of a printing character, or a symbol.
This function returns the button-number of the given button-press or button-release event.
This function returns a list of symbols, the names of the modifier keys which were down when the given mouse or keyboard event was produced.
This function returns a number representing the modifier keys which were down when the given mouse or keyboard event was produced.
This function returns the callback function of the given timeout, misc-user, or eval event.
This function returns the callback function argument of the given timeout, misc-user, or eval event.
This function returns the process of the given process event.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
XEmacs provides primitives for creating, copying, and destroying event
objects. Many functions that return events take an event object as an
argument and fill in the fields of this event; or they make accept
either an event object or nil
, creating the event object first in
the latter case.
This function creates a new event structure. If no arguments are
specified, the created event will be empty. To specify the event type,
use the type argument. The allowed types are empty
,
key-press
, button-press
, button-release
,
motion
, or misc-user
.
plist is a property list, the properties being compatible to those
returned by event-properties
. For events other than
empty
, it is mandatory to specify certain properties. For
empty
events, plist must be nil
. The list is
canonicalized, which means that if a property keyword is present
more than once, only the first instance is taken into account.
Specifying an unknown or illegal property signals an error.
The following properties are allowed:
channel
The event channel. This is a frame or a console. For mouse events (of
type button-press
, button-release
and motion
), this
must be a frame. For key-press events, it must be a console. If
channel is unspecified by plist, it will be set to the selected
frame or selected console, as appropriate.
key
The event key. This is either a symbol or a character. It is allowed (and required) only for key-press events.
button
The event button. This an integer, either 1, 2 or 3. It is allowed for button-press, button-release and misc-user events.
modifiers
The event modifiers. This is a list of modifier symbols. It is allowed for key-press, button-press, button-release and motion events.
x
The event X coordinate. This is an integer. It is relative to the channel’s root window, and is allowed for button-press, button-release and motion events.
y
The event Y coordinate. This is an integer. It is relative to the
channel’s root window, and is allowed for button-press, button-release
and motion events. This means that, for instance, to access the
toolbar, the y
property will have to be negative.
timestamp
The event timestamp, a non-negative integer. Allowed for all types of events.
WARNING: the event object returned by this function may be a
reused one; see the function deallocate-event
.
The events created by make-event
can be used as non-interactive
arguments to the functions with an (interactive "e")
specification.
Here are some basic examples of usage:
;; Create an empty event.
(make-event)
⇒ #<empty-event>
;; Try creating a key-press event.
(make-event 'key-press)
error--> Undefined key for keypress event
;; Creating a key-press event, try 2
(make-event 'key-press '(key home))
⇒ #<keypress-event home>
;; Create a key-press event of dubious fame.
(make-event 'key-press '(key escape modifiers (meta alt control shift)))
⇒ #<keypress-event control-meta-alt-shift-escape>
;; Create a M-button1 event at coordinates defined by variables ;; x and y. (make-event 'button-press `(button 1 modifiers (meta) x ,x y ,y)) ⇒ #<buttondown-event meta-button1> ;; Create a similar button-release event.
(make-event 'button-release `(button 1 modifiers (meta) x ,x y ,x))
⇒ #<buttonup-event meta-button1up>
;; Create a mouse-motion event.
(make-event 'motion '(x 20 y 30))
⇒ #<motion-event 20, 30>
(event-properties (make-event 'motion '(x 20 y 30)))
⇒ (channel #<x-frame "emacs" 0x8e2> x 20 y 30
modifiers nil timestamp 0)
|
In conjunction with event-properties
, you can use
make-event
to create modified copies of existing events. For
instance, the following code will return an equal
copy of
event:
(make-event (event-type event) (event-properties event)) |
Note, however, that you cannot use make-event
as the generic
replacement for copy-event
, because it does not allow creating
all of the event types.
To create a modified copy of an event, you can use the canonicalization
feature of plist. The following example creates a copy of
event, but with modifiers
reset to nil
.
(make-event (event-type event) (append '(modifiers nil) (event-properties event))) |
This function makes a copy of the event object event1. If a
second event argument event2 is given, event1 is copied into
event2 and event2 is returned. If event2 is not
supplied (or is nil
) then a new event will be made, as with
make-event
.
This function allows the given event structure to be reused. You MUST NOT use this event object after calling this function with it. You will lose. It is not necessary to call this function, as event objects are garbage-collected like all other objects; however, it may be more efficient to explicitly deallocate events when you are sure that it is safe to do so.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
XEmacs provides some auxiliary functions for converting between events and other ways of representing keys. These are useful when working with ASCII strings and with keymaps.
This function converts a keystroke description to an event structure. key-description is the specification of a key stroke, and event is the event object to fill in. This function contains knowledge about what the codes “mean”—for example, the number 9 is converted to the character <Tab>, not the distinct character <Control-I>.
Note that key-description can be an integer, a character, a symbol
such as clear
or a list such as (control backspace)
.
If optional arg event is non-nil
, it is modified;
otherwise, a new event object is created. In both cases, the event is
returned.
Optional third arg console is the console to store in the event, and defaults to the selected console.
If key-description is an integer or character, the high bit may be
interpreted as the meta key. (This is done for backward compatibility in
lots of places.) If use-console-meta-flag is nil
, this
will always be the case. If use-console-meta-flag is
non-nil
, the meta
flag for console affects whether
the high bit is interpreted as a meta key. (See set-input-mode
.)
If you don’t want this silly meta interpretation done, you should pass
in a list containing the character.
Beware that character-to-event
and event-to-character
are
not strictly inverse functions, since events contain much more
information than the XEmacs internal character encoding can store.
This function returns the closest character approximation to
event. If the event isn’t a keypress, this returns nil
.
If allow-extra-modifiers is non-nil
, then this is lenient
in its translation; it will ignore modifier keys other than
<control> and <meta>, and will ignore the <shift> modifier
on those characters which have no shifted ASCII equivalent
(<Control-Shift-A> for example, will be mapped to the same
ASCII code as <Control-A>).
If allow-meta is non-nil
, then the <Meta> modifier will
be represented by turning on the high bit of the byte returned;
otherwise, nil
will be returned for events containing the
<Meta> modifier.
Specifying allow-meta will give ambiguous results—<M-x> and <oslash> will return the same thing, for example—so you should probably not use it.
allow-non-ascii is ignored; in previous versions of XEmacs, it controlled whether one particular type of mapping between X11 keysyms and characters would take place. The intention was that this flag could be clear and you could be sure that if you got a Latin-1 character with the high bit set back, you could assume that the lower seven bits of the character were the ASCII code of the character in question, and that the Meta key was pressed at the same time. This didn’t work in the general case, however, because it left the other type of X11 keysym-to-character mapping in place, ready to give you a Latin-1 character for a Latin-1 key. If you feel the need to use such a flag, sit back and think about abstracting your code, and if you still feel the need, bear in mind that it will be buggy in earlier versions of XEmacs.
Given a vector of event objects, this function returns a vector of key descriptors, or a string (if they all fit in the ASCII range). Optional arg no-mice means that button events are not allowed.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The editor command loop reads keyboard input using the function
next-event
and constructs key sequences out of the events using
dispatch-event
. Lisp programs can also use the function
read-key-sequence
, which reads input a key sequence at a time.
See also momentary-string-display
in Temporary Displays,
and sit-for
in Waiting for Elapsed Time or Input. See section Terminal Input, for
functions and variables for controlling terminal input modes and
debugging terminal input.
For higher-level input facilities, see Minibuffers.
25.6.1 Key Sequence Input | How to read one key sequence. | |
25.6.2 Reading One Event | How to read just one event. | |
25.6.3 Dispatching an Event | What to do with an event once it has been read. | |
25.6.4 Quoted Character Input | Asking the user to specify a character. | |
25.6.5 Miscellaneous Event Input Features | How to reread or throw away input events. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Lisp programs can read input a key sequence at a time by calling
read-key-sequence
; for example, describe-key
uses it to
read the key to describe.
This function reads a sequence of keystrokes or mouse clicks and returns it as a vector of event objects read. It keeps reading events until it has accumulated a full key sequence; that is, enough to specify a non-prefix command using the currently active keymaps.
The vector and the event objects it contains are freshly created (and so will not be side-effected by subsequent calls to this function).
The function read-key-sequence
suppresses quitting: C-g
typed while reading with this function works like any other character,
and does not set quit-flag
. See section Quitting.
The argument prompt is either a string to be displayed in the echo
area as a prompt, or nil
, meaning not to display a prompt.
Second optional arg continue-echo non-nil
means this key
echoes as a continuation of the previous key.
Third optional arg dont-downcase-last non-nil
means do not
convert the last event to lower case. (Normally any upper case event is
converted to lower case if the original event is undefined and the lower
case equivalent is defined.) This argument is provided mostly for
fsf compatibility; the equivalent effect can be achieved more
generally by binding retry-undefined-key-binding-unshifted
to
nil
around the call to read-key-sequence
.
If the user selects a menu item while we are prompting for a key
sequence, the returned value will be a vector of a single menu-selection
event (a misc-user event). An error will be signalled if you pass this
value to lookup-key
or a related function.
In the example below, the prompt ‘?’ is displayed in the echo area, and the user types C-x C-f.
(read-key-sequence "?") ---------- Echo Area ---------- ?C-x C-f ---------- Echo Area ---------- ⇒ [#<keypress-event control-X> #<keypress-event control-F>] |
If an input character is an upper-case letter and has no key binding,
but its lower-case equivalent has one, then read-key-sequence
converts the character to lower case. Note that lookup-key
does
not perform case conversion in this way.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The lowest level functions for command input are those which read a single event. These functions often make a distinction between command events, which are user actions (keystrokes and mouse actions), and other events, which serve as communication between XEmacs and the window system.
This function reads and returns the next available event from the window
system or terminal driver, waiting if necessary until an event is
available. Pass this object to dispatch-event
to handle it. If
an event object is supplied, it is filled in and returned; otherwise a
new event object will be created.
Events can come directly from the user, from a keyboard macro, or from
unread-command-events
.
In most cases, the function next-command-event
is more
appropriate.
This function returns the next available “user” event from the window
system or terminal driver. Pass this object to dispatch-event
to
handle it. If an event object is supplied, it is filled in and
returned, otherwise a new event object will be created.
The event returned will be a keyboard, mouse press, or mouse release
event. If there are non-command events available (mouse motion,
sub-process output, etc) then these will be executed (with
dispatch-event
) and discarded. This function is provided as a
convenience; it is equivalent to the Lisp code
(while (progn (next-event event) (not (or (key-press-event-p event) (button-press-event-p event) (button-release-event-p event) (menu-event-p event)))) (dispatch-event event)) |
Here is what happens if you call next-command-event
and then
press the right-arrow function key:
(next-command-event) ⇒ #<keypress-event right> |
This function reads and returns a character of command input. If a
mouse click is detected, an error is signalled. The character typed is
returned as an ASCII value. This function is retained for
compatibility with Emacs 18, and is most likely the wrong thing for you
to be using: consider using next-command-event
instead.
This function adds an eval event to the back of the queue. The eval event will be the next event read after all pending events.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Given an event object returned by next-event
, this function
executes it. This is the basic function that makes XEmacs respond to
user input; it also deals with notifications from the window system
(such as Expose events).
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
You can use the function read-quoted-char
to ask the user to
specify a character, and allow the user to specify a control or meta
character conveniently, either literally or as an octal character code.
The command quoted-insert
uses this function.
This function is like read-char
, except that if the first
character read is an octal digit (0-7), it reads up to two more octal digits
(but stopping if a non-octal digit is found) and returns the
character represented by those digits in octal.
Quitting is suppressed when the first character is read, so that the user can enter a C-g. See section Quitting.
If prompt is supplied, it specifies a string for prompting the user. The prompt string is always displayed in the echo area, followed by a single ‘-’.
In the following example, the user types in the octal number 177 (which is 127 in decimal).
(read-quoted-char "What character") ---------- Echo Area ---------- What character-177 ---------- Echo Area ---------- ⇒ 127 |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes how to “peek ahead” at events without using them up, how to check for pending input, and how to discard pending input.
See also the variables last-command-event
and last-command-char
(Information from the Command Loop).
This variable holds a list of events waiting to be read as command input. The events are used in the order they appear in the list, and removed one by one as they are used.
The variable is needed because in some cases a function reads an event and then decides not to use it. Storing the event in this variable causes it to be processed normally, by the command loop or by the functions to read command input.
For example, the function that implements numeric prefix arguments reads any number of digits. When it finds a non-digit event, it must unread the event so that it can be read normally by the command loop. Likewise, incremental search uses this feature to unread events with no special meaning in a search, because these events should exit the search and then execute normally.
This variable holds a single event to be read as command input.
This variable is mostly obsolete now that you can use
unread-command-events
instead; it exists only to support programs
written for versions of XEmacs prior to 19.12.
This function determines whether any command input is currently
available to be read. It returns immediately, with value t
if
there is available input, nil
otherwise. On rare occasions it
may return t
when no input is available.
This variable is set to the last keyboard or mouse button event received.
This variable is off limits: you may not set its value or modify the
event that is its value, as it is destructively modified by
read-key-sequence
. If you want to keep a pointer to this value,
you must use copy-event
.
Note that this variable is an alias for last-input-char
in
FSF Emacs.
In the example below, a character is read (the character 1). It
becomes the value of last-input-event
, while C-e (from the
C-x C-e command used to evaluate this expression) remains the
value of last-command-event
.
(progn (print (next-command-event)) (print last-command-event) last-input-event) -| #<keypress-event 1> -| #<keypress-event control-E> ⇒ #<keypress-event 1> |
If the value of last-input-event
is a keyboard event, then this
is the nearest ASCII equivalent to it. Remember that there is
not a 1:1 mapping between keyboard events and ASCII
characters: the set of keyboard events is much larger, so writing code
that examines this variable to determine what key has been typed is bad
practice, unless you are certain that it will be one of a small set of
characters.
This function exists for compatibility with Emacs version 18.
This function discards the contents of the terminal input buffer and
cancels any keyboard macro that might be in the process of definition.
It returns nil
.
In the following example, the user may type a number of characters right
after starting the evaluation of the form. After the sleep-for
finishes sleeping, discard-input
discards any characters typed
during the sleep.
(progn (sleep-for 2) (discard-input)) ⇒ nil |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The wait functions are designed to wait for a certain amount of time
to pass or until there is input. For example, you may wish to pause in
the middle of a computation to allow the user time to view the display.
sit-for
pauses and updates the screen, and returns immediately if
input comes in, while sleep-for
pauses without updating the
screen.
Note that in FSF Emacs, the commands sit-for
and sleep-for
take two arguments to specify the time (one integer and one float
value), instead of a single argument that can be either an integer or a
float.
This function performs redisplay (provided there is no pending input
from the user), then waits seconds seconds, or until input is
available. The result is t
if sit-for
waited the full
time with no input arriving (see input-pending-p
in Miscellaneous Event Input Features). Otherwise, the value is nil
.
The argument seconds need not be an integer. If it is a floating
point number, sit-for
waits for a fractional number of seconds.
Redisplay is normally preempted if input arrives, and does not happen at
all if input is available before it starts. (You can force screen
updating in such a case by using force-redisplay
. See section Refreshing the Screen.) If there is no input pending, you can force an update with no
delay by using (sit-for 0)
.
If nodisplay is non-nil
, then sit-for
does not
redisplay, but it still returns as soon as input is available (or when
the timeout elapses).
The usual purpose of sit-for
is to give the user time to read
text that you display.
This function simply pauses for seconds seconds without updating
the display. This function pays no attention to available input. It
returns nil
.
The argument seconds need not be an integer. If it is a floating
point number, sleep-for
waits for a fractional number of seconds.
Use sleep-for
when you wish to guarantee a delay.
See section Time of Day, for functions to get the current time.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Typing C-g while a Lisp function is running causes XEmacs to quit whatever it is doing. This means that control returns to the innermost active command loop.
Typing C-g while the command loop is waiting for keyboard input
does not cause a quit; it acts as an ordinary input character. In the
simplest case, you cannot tell the difference, because C-g
normally runs the command keyboard-quit
, whose effect is to quit.
However, when C-g follows a prefix key, the result is an undefined
key. The effect is to cancel the prefix key as well as any prefix
argument.
In the minibuffer, C-g has a different definition: it aborts out of the minibuffer. This means, in effect, that it exits the minibuffer and then quits. (Simply quitting would return to the command loop within the minibuffer.) The reason why C-g does not quit directly when the command reader is reading input is so that its meaning can be redefined in the minibuffer in this way. C-g following a prefix key is not redefined in the minibuffer, and it has its normal effect of canceling the prefix key and prefix argument. This too would not be possible if C-g always quit directly.
When C-g does directly quit, it does so by setting the variable
quit-flag
to t
. XEmacs checks this variable at appropriate
times and quits if it is not nil
. Setting quit-flag
non-nil
in any way thus causes a quit.
At the level of C code, quitting cannot happen just anywhere; only at the
special places that check quit-flag
. The reason for this is
that quitting at other places might leave an inconsistency in XEmacs’s
internal state. Because quitting is delayed until a safe place, quitting
cannot make XEmacs crash.
Certain functions such as read-key-sequence
or
read-quoted-char
prevent quitting entirely even though they wait
for input. Instead of quitting, C-g serves as the requested
input. In the case of read-key-sequence
, this serves to bring
about the special behavior of C-g in the command loop. In the
case of read-quoted-char
, this is so that C-q can be used
to quote a C-g.
You can prevent quitting for a portion of a Lisp function by binding
the variable inhibit-quit
to a non-nil
value. Then,
although C-g still sets quit-flag
to t
as usual, the
usual result of this—a quit—is prevented. Eventually,
inhibit-quit
will become nil
again, such as when its
binding is unwound at the end of a let
form. At that time, if
quit-flag
is still non-nil
, the requested quit happens
immediately. This behavior is ideal when you wish to make sure that
quitting does not happen within a “critical section” of the program.
In some functions (such as read-quoted-char
), C-g is
handled in a special way that does not involve quitting. This is done
by reading the input with inhibit-quit
bound to t
, and
setting quit-flag
to nil
before inhibit-quit
becomes nil
again. This excerpt from the definition of
read-quoted-char
shows how this is done; it also shows that
normal quitting is permitted after the first character of input.
(defun read-quoted-char (&optional prompt) "…documentation…" (let ((count 0) (code 0) char) (while (< count 3) (let ((inhibit-quit (zerop count)) (help-form nil)) (and prompt (message "%s-" prompt)) (setq char (read-char)) (if inhibit-quit (setq quit-flag nil))) …) (logand 255 code))) |
If this variable is non-nil
, then XEmacs quits immediately, unless
inhibit-quit
is non-nil
. Typing C-g ordinarily sets
quit-flag
non-nil
, regardless of inhibit-quit
.
This variable determines whether XEmacs should quit when quit-flag
is set to a value other than nil
. If inhibit-quit
is
non-nil
, then quit-flag
has no special effect.
This function signals the quit
condition with (signal 'quit
nil)
. This is the same thing that quitting does. (See signal
in Errors.)
You can specify a character other than C-g to use for quitting.
See the function set-input-mode
in Terminal Input.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Most XEmacs commands can use a prefix argument, a number
specified before the command itself. (Don’t confuse prefix arguments
with prefix keys.) The prefix argument is at all times represented by a
value, which may be nil
, meaning there is currently no prefix
argument. Each command may use the prefix argument or ignore it.
There are two representations of the prefix argument: raw and numeric. The editor command loop uses the raw representation internally, and so do the Lisp variables that store the information, but commands can request either representation.
Here are the possible values of a raw prefix argument:
nil
, meaning there is no prefix argument. Its numeric value is
1, but numerous commands make a distinction between nil
and the
integer 1.
-
. This indicates that M-- or C-u - was
typed, without following digits. The equivalent numeric value is
-1, but some commands make a distinction between the integer
-1 and the symbol -
.
We illustrate these possibilities by calling the following function with various prefixes:
(defun display-prefix (arg) "Display the value of the raw prefix arg." (interactive "P") (message "%s" arg)) |
Here are the results of calling display-prefix
with various
raw prefix arguments:
M-x display-prefix -| nil C-u M-x display-prefix -| (4) C-u C-u M-x display-prefix -| (16) C-u 3 M-x display-prefix -| 3 M-3 M-x display-prefix -| 3 ; (Same as |
XEmacs uses two variables to store the prefix argument:
prefix-arg
and current-prefix-arg
. Commands such as
universal-argument
that set up prefix arguments for other
commands store them in prefix-arg
. In contrast,
current-prefix-arg
conveys the prefix argument to the current
command, so setting it has no effect on the prefix arguments for future
commands.
Normally, commands specify which representation to use for the prefix
argument, either numeric or raw, in the interactive
declaration.
(See section Using interactive
.) Alternatively, functions may look at the
value of the prefix argument directly in the variable
current-prefix-arg
, but this is less clean.
This function returns the numeric meaning of a valid raw prefix argument
value, raw. The argument may be a symbol, a number, or a list.
If it is nil
, the value 1 is returned; if it is -
, the
value -1 is returned; if it is a number, that number is returned;
if it is a list, the CAR of that list (which should be a number) is
returned.
This variable holds the raw prefix argument for the current
command. Commands may examine it directly, but the usual way to access
it is with (interactive "P")
.
The value of this variable is the raw prefix argument for the next editing command. Commands that specify prefix arguments for the following command work by setting this variable.
Do not call the functions universal-argument
,
digit-argument
, or negative-argument
unless you intend to
let the user enter the prefix argument for the next command.
This command reads input and specifies a prefix argument for the following command. Don’t call this command yourself unless you know what you are doing.
This command adds to the prefix argument for the following command. The argument arg is the raw prefix argument as it was before this command; it is used to compute the updated prefix argument. Don’t call this command yourself unless you know what you are doing.
This command adds to the numeric argument for the next command. The argument arg is the raw prefix argument as it was before this command; its value is negated to form the new prefix argument. Don’t call this command yourself unless you know what you are doing.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The XEmacs command loop is entered automatically when XEmacs starts up. This top-level invocation of the command loop never exits; it keeps running as long as XEmacs does. Lisp programs can also invoke the command loop. Since this makes more than one activation of the command loop, we call it recursive editing. A recursive editing level has the effect of suspending whatever command invoked it and permitting the user to do arbitrary editing before resuming that command.
The commands available during recursive editing are the same ones available in the top-level editing loop and defined in the keymaps. Only a few special commands exit the recursive editing level; the others return to the recursive editing level when they finish. (The special commands for exiting are always available, but they do nothing when recursive editing is not in progress.)
All command loops, including recursive ones, set up all-purpose error handlers so that an error in a command run from the command loop will not exit the loop.
Minibuffer input is a special kind of recursive editing. It has a few special wrinkles, such as enabling display of the minibuffer and the minibuffer window, but fewer than you might suppose. Certain keys behave differently in the minibuffer, but that is only because of the minibuffer’s local map; if you switch windows, you get the usual XEmacs commands.
To invoke a recursive editing level, call the function
recursive-edit
. This function contains the command loop; it also
contains a call to catch
with tag exit
, which makes it
possible to exit the recursive editing level by throwing to exit
(see section Explicit Nonlocal Exits: catch
and throw
). If you throw a value other than t
,
then recursive-edit
returns normally to the function that called
it. The command C-M-c (exit-recursive-edit
) does this.
Throwing a t
value causes recursive-edit
to quit, so that
control returns to the command loop one level up. This is called
aborting, and is done by C-] (abort-recursive-edit
).
Most applications should not use recursive editing, except as part of using the minibuffer. Usually it is more convenient for the user if you change the major mode of the current buffer temporarily to a special major mode, which should have a command to go back to the previous mode. (The e command in Rmail uses this technique.) Or, if you wish to give the user different text to edit “recursively”, create and select a new buffer in a special mode. In this mode, define a command to complete the processing and go back to the previous buffer. (The m command in Rmail does this.)
Recursive edits are useful in debugging. You can insert a call to
debug
into a function definition as a sort of breakpoint, so that
you can look around when the function gets there. debug
invokes
a recursive edit but also provides the other features of the debugger.
Recursive editing levels are also used when you type C-r in
query-replace
or use C-x q (kbd-macro-query
).
This function invokes the editor command loop. It is called automatically by the initialization of XEmacs, to let the user begin editing. When called from a Lisp program, it enters a recursive editing level.
In the following example, the function simple-rec
first
advances point one word, then enters a recursive edit, printing out a
message in the echo area. The user can then do any editing desired, and
then type C-M-c to exit and continue executing simple-rec
.
(defun simple-rec () (forward-word 1) (message "Recursive edit in progress") (recursive-edit) (forward-word 1)) ⇒ simple-rec (simple-rec) ⇒ nil |
This function exits from the innermost recursive edit (including
minibuffer input). Its definition is effectively (throw 'exit
nil)
.
This function aborts the command that requested the innermost recursive
edit (including minibuffer input), by signaling quit
after exiting the recursive edit. Its definition is effectively
(throw 'exit t)
. See section Quitting.
This function exits all recursive editing levels; it does not return a value, as it jumps completely out of any computation directly back to the main command loop.
This function returns the current depth of recursive edits. When no recursive edit is active, it returns 0.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Disabling a command marks the command as requiring user confirmation before it can be executed. Disabling is used for commands which might be confusing to beginning users, to prevent them from using the commands by accident.
The low-level mechanism for disabling a command is to put a
non-nil
disabled
property on the Lisp symbol for the
command. These properties are normally set up by the user’s
‘.emacs’ file with Lisp expressions such as this:
(put 'upcase-region 'disabled t) |
For a few commands, these properties are present by default and may be removed by the ‘.emacs’ file.
If the value of the disabled
property is a string, the message
saying the command is disabled includes that string. For example:
(put 'delete-region 'disabled "Text deleted this way cannot be yanked back!\n") |
See (xemacs)Disabling section ‘Disabling’ in The XEmacs User’s Manual, for the details on what happens when a disabled command is invoked interactively. Disabling a command has no effect on calling it as a function from Lisp programs.
Allow command to be executed without special confirmation from now on, and (if the user confirms) alter the user’s ‘.emacs’ file so that this will apply to future sessions.
Require special confirmation to execute command from now on, and (if the user confirms) alter the user’s ‘.emacs’ file so that this will apply to future sessions.
This normal hook is run instead of a disabled command, when the user
invokes the disabled command interactively. The hook functions can use
this-command-keys
to determine what the user typed to run the
command, and thus find the command itself. See section Hooks.
By default, disabled-command-hook
contains a function that asks
the user whether to proceed.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
The command loop keeps a history of the complex commands that have
been executed, to make it convenient to repeat these commands. A
complex command is one for which the interactive argument reading
uses the minibuffer. This includes any M-x command, any
M-: command, and any command whose interactive
specification reads an argument from the minibuffer. Explicit use of
the minibuffer during the execution of the command itself does not cause
the command to be considered complex.
This variable’s value is a list of recent complex commands, each represented as a form to evaluate. It continues to accumulate all complex commands for the duration of the editing session, but all but the first (most recent) thirty elements are deleted when a garbage collection takes place (see section Garbage Collection).
command-history ⇒ ((switch-to-buffer "chistory.texi") (describe-key "^X^[") (visit-tags-table "~/emacs/src/") (find-tag "repeat-complex-command")) |
This history list is actually a special case of minibuffer history (see section Minibuffer History), with one special twist: the elements are expressions rather than strings.
There are a number of commands devoted to the editing and recall of
previous commands. The commands repeat-complex-command
, and
list-command-history
are described in the user manual
(see (xemacs)Repetition section ‘Repetition’ in The XEmacs User’s Manual). Within the
minibuffer, the history commands used are the same ones available in any
minibuffer.
The commands are described in the user’s manual (see (xemacs)Keyboard Macros section ‘Keyboard Macros’ in The XEmacs User’s Manual).
[ << ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This document was generated by Aidan Kehoe on December 27, 2016 using texi2html 1.82.