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This is Info file elisp, produced by Makeinfo-1.55 from the input file elisp.texi. This is edition 2.0 of the GNU Emacs Lisp Reference Manual, for Emacs Version 19. Published by the Free Software Foundation, 675 Massachusetts Avenue, Cambridge, MA 02139 USA Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. File: elisp, Node: Yes-or-No Queries, Next: Multiple Queries, Prev: Completion, Up: Minibuffers Yes-or-No Queries ================= This section describes functions used to ask the user a yes-or-no question. The function `y-or-n-p' can be answered with a single character; it is useful for questions where an inadvertent wrong answer will not have serious consequences. `yes-or-no-p' is suitable for more momentous questions, since it requires three or four characters to answer. Strictly speaking, `yes-or-no-p' uses the minibuffer and `y-or-n-p' does not; but it seems best to describe them together. - Function: y-or-n-p PROMPT This function asks the user a question, expecting input in the echo area. It returns `t' if the user types `y', `nil' if the user types `n'. This function also accepts SPC to mean yes and DEL to mean no. It accepts `C-]' to mean "quit", like `C-g', because the question might look like a minibuffer and for that reason the user might try to use `C-]' to get out. The answer is a single character, with no RET needed to terminate it. Upper and lower case are equivalent. "Asking the question" means printing PROMPT in the echo area, followed by the string `(y or n) '. If the input is not one of the expected answers (`y', `n', `SPC', `DEL', or something that quits), the function responds `Please answer y or n.', and repeats the request. This function does not actually use the minibuffer, since it does not allow editing of the answer. It actually uses the echo area (*note The Echo Area::.), which uses the same screen space as the minibuffer. The cursor moves to the echo area while the question is being asked. The meanings of answers, even `y' and `n', are not hardwired. They are controlled by the keymap `query-replace-map'. *Note Replacement::. In the following example, the user first types `q', which is invalid. At the next prompt the user types `n'. (y-or-n-p "Do you need a lift? ") ;; After evaluating the preceding expression, ;; the following prompt appears in the echo area: ---------- Echo area ---------- Do you need a lift? (y or n) ---------- Echo area ---------- ;; If the user then types `q', the following appears: ---------- Echo area ---------- Please answer y or n. Do you need a lift? (y or n) ---------- Echo area ---------- ;; When the user types a valid answer, ;; it is displayed after the question: ---------- Echo area ---------- Do you need a lift? (y or n) y ---------- Echo area ---------- Note that we show successive lines of echo area messages here. Only one actually appears on the screen at a time. - Function: yes-or-no-p PROMPT This function asks the user a question, expecting input in minibuffer. It returns `t' if the user enters `yes', `nil' if the user types `no'. The user must type RET to finalize the response. Upper and lower case are equivalent. `yes-or-no-p' starts by displaying PROMPT in the echo area, followed by `(yes or no) '. The user must type one of the expected responses; otherwise, the function responds `Please answer yes or no.', waits about two seconds and repeats the request. `yes-or-no-p' requires more work from the user than `y-or-n-p' and is appropriate for more crucial decisions. Here is an example: (yes-or-no-p "Do you really want to remove everything? ") ;; After evaluating the preceding expression, ;; the following prompt appears, ;; with an empty minibuffer: ---------- Buffer: minibuffer ---------- Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ---------- If the user first types `y RET', which is invalid because this function demands the entire word `yes', it responds by displaying these prompts, with a brief pause between them: ---------- Buffer: minibuffer ---------- Please answer yes or no. Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ---------- File: elisp, Node: Multiple Queries, Next: Minibuffer Misc, Prev: Yes-or-No Queries, Up: Minibuffers Asking Multiple Y-or-N Queries ============================== - Function: map-y-or-n-p PROMPTER ACTOR LIST &optional HELP ACTION-ALIST This function, new in Emacs 19, asks the user a series of questions, reading a single-character answer in the echo area for each one. The value of LIST specifies what varies from question to question within the series. It should be either a list of objects or a generator function. If it is a function, it should expect no arguments, and should return either the next object or `nil' meaning there are no more questions. The argument PROMPTER specifies how to ask each question. If PROMPTER is a string, the question text is computed like this: (format PROMPTER OBJECT) where OBJECT is the next object to ask about (as obtained from LIST). If not a string, PROMPTER should be a function of one argument (the next object to ask about) and should return the question text. The argument ACTOR says how to act on the answers that the user gives. It should be a function of one argument, and it is called with each object that the user says yes for. Its argument is always an object obtained from LIST. If the argument HELP is given, it should be a list of this form: (SINGULAR PLURAL ACTION) where SINGULAR is a string containing a singular noun that describes the objects conceptually being acted on, PLURAL is the corresponding plural noun, and ACTION is a transitive verb describing what ACTOR does. If you don't specify HELP, the default is `("object" "objects" "act on")'. Each time a question is asked, the user may enter `y', `Y', or SPC to act on that object; `n', `N', or DEL to skip that object; `!' to act on all following objects; ESC or `q' to exit (skip all following objects); `.' (period) to act on the current object and then exit; or `C-h' to get help. These are the same answers that `query-replace' accepts. The keymap `query-replace-map' defines their meaning for `map-y-or-n-p' as well as for `query-replace'; see *Note Replacement::. You can use ACTION-ALIST to specify additional possible answers and what they mean. It is an alist of elements of the form `(CHAR FUNCTION HELP)', each of which defines one additional answer. In this element, CHAR is a character (the answer); FUNCTION is a function of one argument (an object from LIST); HELP is a string. When the user responds with CHAR, `map-y-or-n-p' calls FUNCTION. If it returns non-`nil', the object is considered "acted upon", and `map-y-or-n-p' advances to the next object in LIST. If it returns `nil', the prompt is repeated for the same object. The return value of `map-y-or-n-p' is the number of objects acted on. File: elisp, Node: Minibuffer Misc, Prev: Multiple Queries, Up: Minibuffers Minibuffer Miscellany ===================== This section describes some basic functions and variables related to minibuffers. - Command: exit-minibuffer This command exits the active minibuffer. It is normally bound to keys in minibuffer local keymaps. - Command: self-insert-and-exit This command exits the active minibuffer after inserting the last character typed on the keyboard (found in `last-command-char'; *note Command Loop Info::.). - Command: previous-history-element N This command replaces the minibuffer contents with the value of the Nth previous (older) history element. - Command: next-history-element N This command replaces the minibuffer contents with the value of the Nth more recent history element. - Command: previous-matching-history-element PATTERN This command replaces the minibuffer contents with the value of the previous (older) history element that matches PATTERN. At the time of printing, we have not made a final decision about how to get the pattern interactively or how to match it against history elements. - Command: next-matching-history-element PATTERN This command replaces the minibuffer contents with the value of the next (newer) history element that matches PATTERN. - Variable: minibuffer-help-form The current value of this variable is used to rebind `help-form' locally inside the minibuffer (*note Help Functions::.). - Function: minibuffer-window &optional FRAME This function returns the window that is used for the minibuffer. In Emacs 18, there is one and only one minibuffer window; this window always exists and cannot be deleted. In Emacs 19, each frame can have its own minibuffer, and this function returns the minibuffer window used for frame FRAME (which defaults to the currently selected frame). - Function: window-minibuffer-p WINDOW This function returns non-`nil' if WINDOW is a minibuffer window. It is not correct to determine whether a given window is a minibuffer by comparing it with the result of `(minibuffer-window)', because there can be more than one minibuffer window there is more than one frame. - Variable: minibuffer-scroll-window If the value of this variable is non-`nil', it should be a window object. When the function `scroll-other-window' is called in the minibuffer, it scrolls this window. Finally, some functions and variables deal with recursive minibuffers (*note Recursive Editing::.): - Function: minibuffer-depth This function returns the current depth of activations of the minibuffer, a nonnegative integer. If no minibuffers are active, it returns zero. - User Option: enable-recursive-minibuffers If this variable is non-`nil', you can invoke commands (such as `find-file') which use minibuffers even while in the minibuffer window. Such invocation produces a recursive editing level for a new minibuffer. The outer-level minibuffer is invisible while you are editing the inner one. This variable only affects invoking the minibuffer while the minibuffer window is selected. If you switch windows while in the minibuffer, you can always invoke minibuffer commands while some other window is selected. If a command name has a property `enable-recursive-minibuffers' which is non-`nil', then the command can use the minibuffer to read arguments even if it is invoked from the minibuffer. The minibuffer command `next-matching-history-element' (normally bound to `M-s' in the minibuffer) uses this feature. File: elisp, Node: Command Loop, Next: Keymaps, Prev: Minibuffers, Up: Top Command Loop ************ When you run Emacs, it enters the "editor command loop" almost immediately. This loop reads key sequences, 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. * Menu: * Command Overview:: How the command loop reads commands. * Defining Commands:: Specifying how a function should read arguments. * Interactive Call:: Calling a command, so that it will read arguments. * Command Loop Info:: Variables set by the command loop for you to examine. * Input Events:: What input looks like when you read it. * Reading Input:: How to read input events from the keyboard or mouse. * Waiting:: Waiting for user input or elapsed time. * Quitting:: How `C-g' works. How to catch or defer quitting. * Prefix Command Arguments:: How the commands to set prefix args work. * Recursive Editing:: Entering a recursive edit, and why you usually shouldn't. * Disabling Commands:: How the command loop handles disabled commands. * Command History:: How the command history is set up, and how accessed. * Keyboard Macros:: How keyboard macros are implemented. File: elisp, Node: Command Overview, Next: Defining Commands, Up: Command Loop Command Loop Overview ===================== The first thing the command loop must do is read a key sequence, which is a sequence of events that translates into a command. It does this by calling the function `read-key-sequence'. Your Lisp code can also call this function (*note Key Sequence Input::.). Lisp programs can also do input at a lower level with `read-event' (*note Reading One Event::.) or discard pending input with `discard-input' (*note Peeking and Discarding::.). The key sequence is translated into a command through the currently active keymaps. *Note Key Lookup::, for information on how this is done. The result 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 is used instead. This is done by the command `execute-extended-command' (*note Interactive Call::.). Once the command is chosen, it must be executed, which includes reading arguments to be given to it. This is done by calling `command-execute' (*note Interactive Call::.). For commands written in Lisp, the `interactive' specification says how to read the arguments. This may use the prefix argument (*note Prefix Command Arguments::.) or may read with prompting in the minibuffer (*note 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 (*note Keyboard Macros::.). If a command runs away, typing `C-g' terminates its execution immediately. This is called "quitting" (*note Quitting::.). - Variable: pre-command-hook The editor command loop runs this normal hook before each command. - Variable: post-command-hook The editor command loop runs this normal hook after each command. File: elisp, Node: Defining Commands, Next: Interactive Call, Prev: Command Overview, Up: Command Loop Defining Commands ================= A Lisp function becomes a command when its body contains, at top level, a form which calls the special form `interactive'. This form 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. * Menu: * Using Interactive:: General rules for `interactive'. * Interactive Codes:: The standard letter-codes for reading arguments in various ways. * Interactive Examples:: Examples of how to read interactive arguments. File: elisp, Node: Using Interactive, Next: Interactive Codes, Up: Defining Commands Using `interactive' ------------------- This section describes how to write the `interactive' form that makes a Lisp function an interactively-callable command. - Special Form: interactive ARG-DESCRIPTOR This special form 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 the way the arguments to the command are to be computed when the command is called interactively. A command may be called from Lisp programs like any other function, but then the arguments are supplied by the caller 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: * It may be omitted or `nil'; then the command is called with no arguments. This leads quickly to an error if the command requires one or more arguments. * It may be a Lisp expression that is not a string; then it should be a form that is evaluated to get a list of arguments to pass to the command. * It may be a string; then its contents should consist of a code character followed by a prompt (which some code characters use and some ignore). The prompt ends either with the end of the string or with a newline. Here is a simple example: (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 in the prompt. This is done using `format' (*note 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. 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 `@'). File: elisp, Node: Interactive Codes, Next: Interactive Examples, Prev: Using Interactive, Up: Defining Commands Code Characters for `interactive' --------------------------------- The code character descriptions below contain a number of key words, defined here as follows: Completion Provide completion. TAB, SPC, and RET perform name completion because the argument is read using `completing-read' (*note Completion::.). `?' displays a list of possible completions. Existing 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. Default A default value of some sort is used if the user enters no text in the minibuffer. The default depends on the code character. No I/O 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. Prompt A prompt immediately follows the code character. The prompt ends either with the end of the string or with a newline. Special 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. `a' A function name (i.e., a symbol which is `fboundp'). Existing, Completion, Prompt. `b' The name of an existing buffer. By default, uses the name of the current buffer (*note Buffers::.). Existing, Completion, Default, Prompt. `B' A buffer name. The buffer need not exist. By default, uses the name of a recently used buffer other than the current buffer. Completion, Prompt. `c' A character. The cursor does not move into the echo area. Prompt. `C' A command name (i.e., a symbol satisfying `commandp'). Existing, Completion, Prompt. `d' The position of point as a number (*note Point::.). No I/O. `D' A directory name. The default is the current default directory of the current buffer, `default-directory' (*note System Environment::.). Existing, Completion, Default, Prompt. `e' The first or next mouse event in the key sequence that invoked the command. More precisely, `e' gets events which are lists, so you can look at the data in the lists. *Note Input Events::. No I/O. You can use `e' more than once in a single command's interactive specification. If the key sequence which invoked the command has N events with parameters, the Nth `e' provides the Nth list event. Events which are not lists, such as function keys and ASCII characters, do not count where `e' is concerned. Even though `e' does not use a prompt string, you must follow it with a newline if it is not the last code character. `f' A file name of an existing file (*note File Names::.). The default directory is `default-directory'. Existing, Completion, Default, Prompt. `F' A file name. The file need not exist. Completion, Default, Prompt. `k' A key sequence (*note 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 string or vector. 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'. `m' The position of the mark as a number. No I/O. `n' 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. `N' The raw prefix argument. If the prefix argument is `nil', then a number is read as with `n'. Requires a number. Prompt. `p' The numeric prefix argument. (Note that this `p' is lower case.) No I/O. `P' The raw prefix argument. (Note that this `P' is upper case.) *Note Prefix Command Arguments::. No I/O. `r' 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. `s' Arbitrary text, read in the minibuffer and returned as a string (*note Text from Minibuffer::.). Terminate the input with either LFD or RET. (`C-q' may be used to include either of these characters in the input.) Prompt. `S' 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. `v' A variable declared to be a user option (i.e., satisfying the predicate `user-variable-p'). *Note High-Level Completion::. Existing, Completion, Prompt. `x' A Lisp object specified in printed representation, terminated with a LFD or RET. The object is not evaluated. *Note Object from Minibuffer::. Prompt. `X' A Lisp form is read as with `x', but then evaluated so that its value becomes the argument for the command. Prompt. File: elisp, Node: Interactive Examples, Prev: Interactive Codes, Up: Defining Commands Examples of Using `interactive' ------------------------------- Here are some examples of `interactive': (defun foo1 () ; `foo1' takes no arguments, (interactive) ; just moves forward two words. (forward-word 2)) => foo1 (defun foo2 (n) ; `foo2' takes one argument, (interactive "p") ; which is the numeric prefix. (forward-word (* 2 n))) => foo2 (defun foo3 (n) ; `foo3' takes one argument, (interactive "nCount:") ; which is read with the Minibuffer. (forward-word (* 2 n))) => foo3 (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 File: elisp, Node: Interactive Call, Next: Command Loop Info, Prev: Defining Commands, Up: Command Loop Interactive Call ================ 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. - Function: commandp OBJECT Returns `t' if OBJECT is suitable for calling interactively; that is, if OBJECT 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', byte-code function objects, 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 (*note Keymaps::.). See `documentation' in *Note Accessing Documentation::, for a realistic example of using `commandp'. - Function: call-interactively COMMAND &optional RECORD-FLAG This function calls the interactively callable function COMMAND, reading arguments according to its interactive calling specifications. An error is signaled if COMMAND cannot be called interactively (i.e., it is not a command). Note that keyboard macros (strings and vectors) are not accepted, even though they are considered commands. If RECORD-FLAG is non-`nil', 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. *Note Command History::. - Function: command-execute COMMAND &optional RECORD-FLAG 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 string. 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. - Command: execute-extended-command PREFIX-ARGUMENT This function reads a command name from the minibuffer using `completing-read' (*note 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, the value PREFIX-ARGUMENT is supplied. 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 ---------- M-x forward-word RET ---------- Buffer: Minibuffer ---------- => t - Function: interactive-p 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.) Note that if the containing function was called by Lisp evaluation (or with `apply' or `funcall'), then it was not called interactively. The usual application 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) File: elisp, Node: Command Loop Info, Next: Input Events, Prev: Interactive Call, Up: Command Loop Information from the Command Loop ================================= The editor command loop sets several Lisp variables to keep status records for itself and for commands that are run. - Variable: last-command 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 set by copying the value of `this-command' when a command returns to the command loop, except when the command specifies a prefix argument for the following command. - Variable: this-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. This variable is set by the command loop just before the command is run, and its value is copied into `last-command' when the command finishes (unless the command specifies a prefix argument for the following command). Some commands change the value of this variable during their execution, simply as a flag for whatever command runs next. In particular, the functions that kill 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. - Function: this-command-keys This function returns a string or vector containing the key sequence that invoked the present command, plus any previous commands that generated the prefix argument for this command. The value is a string if all those events were characters. *Note Input Events::. (this-command-keys) ;; Now type `C-u C-x C-e'. => "^U^X^E" - Variable: last-nonmenu-event This variable holds the last input event read as part of a key sequence, aside from events resulting from mouse menus. One use of this variable is to figure out a good default location to pop up another menu. - Variable: last-command-event - Variable: last-command-char 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. last-command-char ;; Now type `C-u C-x C-e'. => 5 The value is 5 because that is the ASCII code for `C-e'. The alias `last-command-char' exists for compatibility with Emacs version 18. - Variable: last-event-frame 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. *Note Input Focus::. - Variable: echo-keystrokes This variable determines how much time should elapse before command characters echo. Its value must be an integer, 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. File: elisp, Node: Input Events, Next: Reading Input, Prev: Command Loop Info, Up: Command Loop Input Events ============ The Emacs command loop reads a sequence of "input events" that represent keyboard or mouse activity. The events for keyboard activity are characters or symbols; mouse events are always lists. This section describes the representation and meaning of input events in detail. A command invoked using events that are lists can get the full values of these events using the `e' interactive code. *Note Interactive Codes::. 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. - Function: eventp OBJECT This function returns non-`nil' if EVENT is an input event. * Menu: * Keyboard Events:: Ordinary characters-keys with symbols on them. * Function Keys:: Function keys-keys with names, not symbols. * Click Events:: Pushing and releasing a mouse button. * Drag Events:: Moving the mouse before releasing the button. * Button-Down Events:: A button was pushed and not yet released. * Motion Events:: Just moving the mouse, not pushing a button. * Focus Events:: Moving the mouse between frames. * Event Examples:: Examples of the lists for mouse events. * Classifying Events:: Finding the modifier keys in an event symbol. Event types. * Accessing Events:: Functions to extract info from events. * Strings of Events:: Special considerations for putting keyboard character events in a string. File: elisp, Node: Keyboard Events, Next: Function Keys, Up: Input Events Keyboard Events --------------- There are two kinds of input you can get from the keyboard: ordinary keys, and function keys. Ordinary keys correspond to characters; the events they generate are represented in Lisp as characters. In Emacs versions 18 and earlier, characters were the only events. An input character event consists of a "basic code" between 0 and 255, plus any or all of these "modifier bits": meta The 2**23 bit in the character code indicates a character typed with the meta key held down. control The 2**22 bit in the character code indicates a non-ASCII control character. ASCII control characters such as `C-a' have special basic codes of their own, so Emacs needs no special bit to indicate them. Thus, the code for `C-a' is just 1. But if you type a control combination not in ASCII, such as `%' with the control key, the numeric value you get is the code for `%' plus 2**22 (assuming the terminal supports non-ASCII control characters). shift The 2**21 bit in the character code indicates an ASCII control character typed with the shift key held down. For letters, the basic code indicates upper versus lower case; for digits and punctuation, the shift key selects an entirely different character with a different basic code. In order to keep within the ASCII character set whenever possible, Emacs avoids using the 2**21 bit for those characters. However, ASCII provides no way to distinguish `C-A' from `C-A', so Emacs uses the 2**21 bit in `C-A' and not in `C-a'. hyper The 2**20 bit in the character code indicates a character typed with the hyper key held down. super The 2**19 bit in the character code indicates a character typed with the super key held down. alt The 2**18 bit in the character code indicates a character typed with the alt key held down. (On some terminals, the key labeled ALT is actually the meta key.) In the future, Emacs may support a larger range of basic codes. We may also move the modifier bits to larger bit numbers. Therefore, you should avoid mentioning specific bit numbers in your program. Instead, the way to test the modifier bits of a character is with the function `event-modifiers' (*note Classifying Events::.). File: elisp, Node: Function Keys, Next: Click Events, Prev: Keyboard Events, Up: Input Events Function Keys ------------- Most keyboards also have "function keys"--keys which have names or symbols that are not characters. Function keys are represented in Lisp as symbols; the symbol's name is the function key's label. For example, pressing a key labeled F1 places the symbol `f1' in the input stream. For all keyboard events, the event type (which classifies the event for key lookup purposes) is identical to the event--it is the character or the symbol. *Note Classifying Events::. Here are a few special cases in the symbol naming convention for function keys: `backspace', `tab', `newline', `return', `delete' These keys correspond to common ASCII control characters that have special keys on most keyboards. In ASCII, `C-i' and TAB are the same character. Emacs lets you distinguish them if you wish, by returning the former as the integer 9, and the latter as the symbol `tab'. Most of the time, it's not useful to distinguish the two. So normally `function-key-map' is set up to map `tab' into 9. Thus, a key binding for character code 9 also applies to `tab'. Likewise for the other symbols in this group. The function `read-char' also converts these events into characters. In ASCII, BS is really `C-h'. But `backspace' converts into the character code 127 (DEL), not into code 8 (BS). This is what most users prefer. `kp-add', `kp-decimal', `kp-divide', ... Keypad keys (to the right of the regular keyboard). `kp-0', `kp-1', ... Keypad keys with digits. `kp-f1', `kp-f2', `kp-f3', `kp-f4' Keypad PF keys. `left', `up', `right', `down' Cursor arrow keys You can use the modifier keys CTRL, META, HYPER, SUPER, ALT and SHIFT with function keys. The way to represent them is with prefixes in the symbol name: `A-' The alt modifier. `C-' The control modifier. `H-' The hyper modifier. `M-' The meta modifier. `S-' The shift modifier. `s-' The super modifier. Thus, the symbol for the key F3 with META held down is `M-F3'. When you use more than one prefix, we recommend you write them in alphabetical order (though the order does not matter in arguments to the key-binding lookup and modification functions). File: elisp, Node: Click Events, Next: Drag Events, Prev: Function Keys, Up: Input Events Click Events ------------ When the user presses a mouse button and releases it at the same location, that generates a "click" event. Mouse click events have this form: (EVENT-TYPE (WINDOW BUFFER-POS (COLUMN . ROW) TIMESTAMP)) Here is what the elements normally mean: EVENT-TYPE This is a symbol that indicates which mouse button was used. It is one of the symbols `mouse-1', `mouse-2', ..., where the buttons are numbered numbered left to right. You can also use prefixes `A-', `C-', `H-', `M-', `S-' and `s-' for modifiers alt, control, hyper, meta, shift and super, just as you would with function keys. This symbol also serves as the event type of the event. Key bindings describe events by their types; thus, if there is a key binding for `mouse-1', that binding would apply to all events whose EVENT-TYPE is `mouse-1'. WINDOW This is the window in which the click occurred. COLUMN ROW These are the column and row of the click, relative to the top left corner of WINDOW, which is `(0 . 0)'. BUFFER-POS This is the buffer position of the character clicked on. TIMESTAMP This is the time at which the event occurred, in milliseconds. (Since this value wraps around the entire range of Emacs Lisp integers in about five hours, it is useful only for relating the times of nearby events.) The meanings of BUFFER-POS, ROW and COLUMN are somewhat different when the event location is in a special part of the screen, such as the mode line or a scroll bar. If the location is in a scroll bar, then BUFFER-POS is the symbol `vertical-scroll-bar' or `horizontal-scroll-bar', and the pair `(COLUMN . ROW)' is replaced with a pair `(PORTION . WHOLE)', where PORTION is the distance of the click from the top or left end of the scroll bar, and WHOLE is the length of the entire scroll bar. If the position is on a mode line or the vertical line separating WINDOW from its neighbor to the right, then BUFFER-POS is the symbol `mode-line' or `vertical-line'. For the mode line, ROW does not have meaningful data. For the vertical line, COLUMN does not have meaningful data. File: elisp, Node: Drag Events, Next: Button-Down Events, Prev: Click Events, Up: Input Events Drag Events ----------- With Emacs, you can have a drag event without even changing your clothes. A "drag event" happens every time the user presses a mouse button and then moves the mouse to a different character position before releasing the button. Like all mouse events, drag events are represented in Lisp as lists. The lists record both the starting mouse position and the final position, like this: (EVENT-TYPE (WINDOW1 BUFFER-POS1 (COLUMN1 . ROW1) TIMESTAMP1) (WINDOW2 BUFFER-POS2 (COLUMN2 . ROW2) TIMESTAMP2)) For a drag event, the name of the symbol EVENT-TYPE contains the prefix `drag-'. The second and third elements of the event give the starting and ending position of the drag. Aside from that, the data have the same meanings as in a click event (*note Click Events::.). You can access the second element of any mouse event in the same way, with no need to distinguish drag events from others. The `drag-' prefix follows the modifier key prefixes such as `C-' and `M-'. If `read-key-sequence' receives a drag event which has no key binding, and the corresponding click event does have a binding, it changes the drag event into a click event at the drag's starting position. This means that you don't have to distinguish between click and drag events unless you want to. File: elisp, Node: Button-Down Events, Next: Motion Events, Prev: Drag Events, Up: Input Events Button-Down Events ------------------ Click and drag events happen when the user releases a mouse button. They cannot happen earlier, because there is no way to distinguish a click from a drag until the button is released. If you want to take action as soon as a button is pressed, you need to handle "button-down" events.(1). These occur as soon as a button is pressed. They are represented by lists which look exactly like click events (*note Click Events::.), except that the name of EVENT-TYPE contains the prefix `down-'. The `down-' prefix follows the modifier key prefixes such as `C-' and `M-'. The function `read-key-sequence', and the Emacs command loop, ignore any button-down events that don't have command bindings. This means that you need not worry about defining button-down events unless you want them to do something. The usual reason to define a button-down event is so that you can track mouse motion (by reading motion events) until the button is released. *Note Motion Events::. ---------- Footnotes ---------- (1) Button-down is the conservative antithesis of drag. File: elisp, Node: Motion Events, Next: Focus Events, Prev: Button-Down Events, Up: Input Events Motion Events ------------- Emacs sometimes generates "mouse motion" events to describe motion of the mouse without any button activity. Mouse motion events are represented by lists that look like this: (mouse-movement (WINDOW BUFFER-POS (COLUMN . ROW) TIMESTAMP)) The second element of the list describes the current position of the mouse, just as in a click event (*note Click Events::.). The special form `track-mouse' enables generation of motion events within its body. Outside of `track-mouse' forms, Emacs does not generate events for mere motion of the mouse, and these events do not appear. - Special Form: track-mouse BODY... This special form executes BODY, with generation of mouse motion events enabled. Typically BODY would use `read-event' to read the motion events and modify the display accordingly. When the user releases the button, that generates a click event. Normally BODY should return when it sees the click event, and discard the event. File: elisp, Node: Focus Events, Next: Event Examples, Prev: Motion Events, Up: Input Events Focus Events ------------ Window systems provide general ways for the user to control which window gets keyboard input. This choice of window is called the "focus". When the user does something to switch between Emacs frames, that generates a "focus event". The normal definition of a focus event, in the global keymap, is to select a new frame within Emacs, as the user would expect. *Note Input Focus::. Focus events are represented in Lisp as lists that look like this: (switch-frame NEW-FRAME) where NEW-FRAME is the frame switched to. In X windows, most window managers are set up so that just moving the mouse into a window is enough to set the focus there. Emacs appears to do this, because it changes the cursor to solid in the new frame. However, there is no need for the Lisp program to know about the focus change until some other kind of input arrives. So Emacs generates the focus event only when the user actually types a keyboard key or presses a mouse button in the new frame; just moving the mouse between frames does not generate a focus event. A focus event in the middle of a key sequence would garble the sequence. So Emacs never generates a focus event in the middle of a key sequence. If the user changes focus in the middle of a key sequence--that is, after a prefix key--then Emacs reorders the events so that the focus event comes either before or after the multi-event key sequence, and not within it. File: elisp, Node: Event Examples, Next: Classifying Events, Prev: Focus Events, Up: Input Events Event Examples -------------- If the user presses and releases the left mouse button over the same location, that generates a sequence of events like this: (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) Or, while holding the control key down, the user might hold down the second mouse button, and drag the mouse from one line to the next. That produces two events, as shown here: (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) (#<window 18 on NEWS> 3510 (0 . 28) -729648)) Or, while holding down the meta and shift keys, the user might press the second mouse button on the window's mode line, and then drag the mouse into another window. That produces the following pair of events: (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) -453816))