428
+ − 1
+ − 2 @node Keystrokes, Pull-down Menus, Frame, Top
+ − 3 @chapter Keystrokes, Key Sequences, and Key Bindings
+ − 4
+ − 5 @iftex
+ − 6 This chapter discusses the character set Emacs uses for input commands
+ − 7 and inside files. You have already learned that the more frequently
+ − 8 used Emacs commands are bound to keys. For example, @kbd{Control-f} is
+ − 9 bound to @code{forward-char}. The following issues are covered:
+ − 10
+ − 11 @itemize @bullet
+ − 12 @item
+ − 13 How keystrokes can be represented
+ − 14 @item
+ − 15 How you can create key sequences from keystrokes
+ − 16 @item
+ − 17 How you can add to the available modifier keys by customizing your
+ − 18 keyboard: for example, you could have the
+ − 19 @key{Capslock} key be understood as the @key{Super} key by Emacs. A
+ − 20 @key{Super} key is used like @key{Control} or @key{Meta} in that you hold
+ − 21 it while typing another key.
+ − 22 @end itemize
+ − 23
+ − 24 You will also learn how to customize existing key bindings and
+ − 25 create new ones.
+ − 26 @end iftex
+ − 27
+ − 28 @menu
+ − 29 * Intro to Keystrokes:: Keystrokes as building blocks of key sequences.
+ − 30 * Representing Keystrokes:: Using lists of modifiers and keysyms to
+ − 31 represent keystrokes.
+ − 32 * Key Sequences:: Combine key strokes into key sequences you can
+ − 33 bind to commands.
+ − 34 * String Key Sequences:: Available for upward compatibility.
+ − 35 * Meta Key:: Using @key{ESC} to represent @key{Meta}
+ − 36 * Super and Hyper Keys:: Adding modifier keys on certain keyboards.
+ − 37 * Character Representation:: How characters appear in Emacs buffers.
+ − 38 * Commands:: How commands are bound to key sequences.
3171
+ − 39 * Non-Latin keyboards:: Commands on keyboards where one can't type Latin.
428
+ − 40 @end menu
+ − 41
+ − 42 @node Intro to Keystrokes, Representing Keystrokes, Keystrokes, Keystrokes
+ − 43 @section Keystrokes as Building Blocks of Key Sequences
+ − 44 @cindex character set
+ − 45 @cindex ASCII
+ − 46 @cindex keystroke
+ − 47
+ − 48 Earlier versions of Emacs used only the ASCII character set,
+ − 49 which defines 128 different character codes. Some of these codes are
+ − 50 assigned graphic symbols like @samp{a} and @samp{=}; the rest are
+ − 51 control characters, such as @kbd{Control-a} (also called @kbd{C-a}).
+ − 52 @kbd{C-a} means you hold down the @key{CTRL} key and then press
+ − 53 @kbd{a}.@refill
+ − 54
+ − 55 Keybindings in XEmacs are not restricted to the set of
+ − 56 keystrokes that can be represented in ASCII. XEmacs can tell the
+ − 57 difference between, for example, @kbd{Control-h}, @kbd{Control-Shift-h},
+ − 58 and @kbd{Backspace}.
+ − 59
+ − 60 @cindex modifier key
+ − 61 @cindex keysym
+ − 62 @kindex meta key
+ − 63 @kindex control key
+ − 64 @kindex hyper key
+ − 65 @kindex super key
+ − 66 @kindex shift key
+ − 67 @kindex button1
+ − 68 @kindex button2
+ − 69 @kindex button3
+ − 70 @kindex button1up
+ − 71 @kindex button2up
+ − 72 @kindex button3up
+ − 73
+ − 74 A keystroke is like a piano chord: you get it by simultaneously
+ − 75 striking several keys. To be more precise, a keystroke consists
+ − 76 of a possibly empty set of modifiers followed by a single
+ − 77 @dfn{keysym}. The set of modifiers is small; it consists of
+ − 78 @kbd{Control}, @kbd{Meta}, @kbd{Super}, @kbd{Hyper}, and @kbd{Shift}.
+ − 79
+ − 80 The rest of the keys on your keyboard, along with the mouse buttons,
+ − 81 make up the set of keysyms. A keysym is usually what is printed on the
+ − 82 keys on your keyboard. Here is a table of some of the symbolic names
+ − 83 for keysyms:
+ − 84 @table @kbd
+ − 85 @item a,b,c...
+ − 86 alphabetic keys
+ − 87 @item f1,f2...
+ − 88 function keys
+ − 89 @item button1
+ − 90 left mouse button
+ − 91 @item button2
+ − 92 middle mouse button
+ − 93 @item button3
+ − 94 right mouse button
+ − 95 @item button1up
+ − 96 upstroke on the left mouse button
+ − 97 @item button2up
+ − 98 upstroke on the middle mouse button
+ − 99 @item button3up
+ − 100 upstroke on the right mouse button
+ − 101 @item return
+ − 102 Return key
+ − 103 @end table
+ − 104
+ − 105 @vindex keyboard-translate-table
+ − 106 Use the variable @code{keyboard-translate-table} only if you are on a
+ − 107 dumb tty, as it cannot handle input that cannot be represented as ASCII.
+ − 108 The value of this variable is a string used as a translate table for
+ − 109 keyboard input or @code{nil}. Each character is looked up in this
+ − 110 string and the contents used instead. If the string is of length
+ − 111 @code{n}, character codes @code{N} and up are untranslated. If you are
+ − 112 running Emacs under X, you should do the translations with the
+ − 113 @code{xmodmap} program instead.
+ − 114
+ − 115
+ − 116 @node Representing Keystrokes, Key Sequences, Intro to Keystrokes, Keystrokes
+ − 117 @comment node-name, next, previous, up
+ − 118 @subsection Representing Keystrokes
+ − 119 @kindex hyper key
+ − 120 @kindex super key
+ − 121 @findex read-key-sequence
+ − 122
+ − 123 XEmacs represents keystrokes as lists. Each list consists of
+ − 124 an arbitrary combination of modifiers followed by a single keysym at the
+ − 125 end of the list. If the keysym corresponds to an ASCII character, you
+ − 126 can use its character code. (A keystroke may also be represented by an
+ − 127 event object, as returned by the @code{read-key-sequence} function;
+ − 128 non-programmers need not worry about this.)
+ − 129
+ − 130 The following table gives some examples of how to list representations
+ − 131 for keystrokes. Each list consists of sets of modifiers followed by
+ − 132 keysyms:
+ − 133
+ − 134 @table @kbd
+ − 135 @item (control a)
+ − 136 Pressing @key{CTRL} and @kbd{a} simultaneously.
+ − 137 @item (control ?a)
+ − 138 Another way of writing the keystroke @kbd{C-a}.
+ − 139 @item (control 65)
+ − 140 Yet another way of writing the keystroke @kbd{C-a}.
+ − 141 @item (break)
+ − 142 Pressing the @key{BREAK} key.
+ − 143 @item (control meta button2up)
+ − 144 Release the middle mouse button, while pressing @key{CTRL} and
+ − 145 @key{META}.
+ − 146 @end table
442
+ − 147 @cindex shift modifier
428
+ − 148 Note: As you define keystrokes, you can use the @kbd{shift} key only
+ − 149 as a modifier with characters that do not have a second keysym on the
+ − 150 same key, such as @kbd{backspace} and @kbd{tab}. It is an error to
+ − 151 define a keystroke using the @key{shift} modifier with keysyms such as
+ − 152 @kbd{a} and @kbd{=}. The correct forms are @kbd{A} and @kbd{+}.
+ − 153
+ − 154 @node Key Sequences, String Key Sequences, Representing Keystrokes, Keystrokes
+ − 155 @subsection Representing Key Sequences
+ − 156
+ − 157 A @dfn{complete key sequence} is a sequence of keystrokes that Emacs
+ − 158 understands as a unit. Key sequences are significant because you can
+ − 159 bind them to commands. Note that not all sequences of keystrokes are
+ − 160 possible key sequences. In particular, the initial keystrokes in a key
+ − 161 sequence must make up a @dfn{prefix key sequence}.
+ − 162
+ − 163 Emacs represents a key sequence as a vector of keystrokes. Thus, the
+ − 164 schematic representation of a complete key sequence is as follows:
+ − 165
+ − 166 @example
442
+ − 167 [(modifier .. modifier keysym) ... (modifier .. modifier keysym)]
428
+ − 168 @end example
+ − 169
+ − 170 Here are some examples of complete key sequences:
+ − 171
+ − 172 @table @kbd
440
+ − 173 @item [(control c) (control a)]
428
+ − 174 Typing @kbd{C-c} followed by @kbd{C-a}
440
+ − 175 @item [(control c) (control 65)]
428
+ − 176 Typing @kbd{C-c} followed by @kbd{C-a}. (Using the ASCII code
+ − 177 for the character `a')@refill
+ − 178 @item [(control c) (break)]
+ − 179 Typing @kbd{C-c} followed by the @kbd{break} character.@refill
+ − 180 @end table
+ − 181
+ − 182 @kindex C-c
+ − 183 @kindex C-x
+ − 184 @kindex C-h
+ − 185 @kindex ESC
+ − 186 @cindex prefix key sequence
+ − 187
+ − 188 A @dfn{prefix key sequence} is the beginning of a series of longer
+ − 189 sequences that are valid key sequences; adding any single keystroke to
+ − 190 the end of a prefix results in a valid key sequence. For example,
+ − 191 @kbd{control-x} is standardly defined as a prefix. Thus there is a
+ − 192 two-character key sequence starting with @kbd{C-x} for each valid
+ − 193 keystroke, giving numerous possibilities. Here are some samples:
+ − 194
+ − 195 @itemize @bullet
+ − 196 @item
+ − 197 @kbd{[(control x) (c)]}
+ − 198 @item
+ − 199 @kbd{[(control x) (control c)]}
+ − 200 @end itemize
+ − 201
+ − 202 Adding one character to a prefix key does not have to form a complete
+ − 203 key. It could make another, longer prefix. For example, @kbd{[(control
+ − 204 x) (\4)]} is itself a prefix that leads to any number of different
+ − 205 three-character keys, including @kbd{[(control x) (\4) (f)]},
+ − 206 @kbd{[(control x) (\4) (b)]} and so on. It would be possible to define
+ − 207 one of those three-character sequences as a prefix, creating a series of
+ − 208 four-character keys, but we did not define any of them this way.@refill
+ − 209
+ − 210 By contrast, the two-character sequence @kbd{[(control f) (control
+ − 211 k)]} is not a key, because the @kbd{(control f)} is a complete key
+ − 212 sequence in itself. You cannot give @kbd{[(control f (control k)]} an
+ − 213 independent meaning as a command while @kbd{(control f)} is a complete
+ − 214 sequence, because Emacs would understand @key{C-f C-k} as two
+ − 215 commands.@refill
+ − 216
+ − 217 The predefined prefix key sequences in Emacs are @kbd{(control c)},
+ − 218 @kbd{(control x)}, @kbd{(control h)}, @kbd{[(control x) (\4)]}, and
+ − 219 @kbd{escape}. You can customize Emacs and could make new prefix keys or
+ − 220 eliminate the default key sequences. @xref{Key Bindings}. For example,
+ − 221 if you redefine @kbd{(control f)} as a prefix, @kbd{[(control f)
+ − 222 (control k)]} automatically becomes a valid key sequence (complete,
+ − 223 unless you define it as a prefix as well). Conversely, if you remove
+ − 224 the prefix definition of @kbd{[(control x) (\4)]}, @kbd{[(control x)
+ − 225 (\4) (f)]} (or @kbd{[(control x) (\4) @var{anything}]}) is no longer a
+ − 226 valid key sequence.
+ − 227
+ − 228 Note that the above paragraphs uses \4 instead of simply 4, because \4
+ − 229 is the symbol whose name is "4", and plain 4 is the integer 4, which
+ − 230 would have been interpreted as the ASCII value. Another way of
+ − 231 representing the symbol whose name is "4" is to write ?4, which would be
+ − 232 interpreted as the number 52, which is the ASCII code for the character
+ − 233 "4". We could therefore actually have written 52 directly, but that is
+ − 234 far less clear.
+ − 235
+ − 236 @node String Key Sequences, Meta Key, Key Sequences, Keystrokes
+ − 237 @comment node-name, next, previous, up
+ − 238 @subsection String Key Sequences
+ − 239 For backward compatibility, you may also represent a key sequence using
+ − 240 strings. For example, we have the following equivalent representations:
+ − 241
+ − 242 @table @kbd
+ − 243 @item "\C-c\C-c"
+ − 244 @code{[(control c) (control c)]}
+ − 245 @item "\e\C-c"
+ − 246 @code{[(meta control c)]}
+ − 247 @end table
+ − 248
+ − 249 @kindex LFD
+ − 250 @kindex TAB
+ − 251
+ − 252 @node Meta Key, Super and Hyper Keys, String Key Sequences, Keystrokes
+ − 253 @comment node-name, next, previous, up
+ − 254 @subsection Assignment of the @key{META} Key
+ − 255
+ − 256 @kindex META
+ − 257 @kindex ESC
+ − 258 Not all terminals have the complete set of modifiers.
+ − 259 Terminals that have a @key{Meta} key allow you to type Meta characters
+ − 260 by just holding that key down. To type @kbd{Meta-a}, hold down
+ − 261 @key{META} and press @kbd{a}. On those terminals, the @key{META} key
+ − 262 works like the @key{SHIFT} key. Such a key is not always labeled
+ − 263 @key{META}, however, as this function is often a special option for a
+ − 264 key with some other primary purpose.@refill
+ − 265
+ − 266 If there is no @key{META} key, you can still type Meta characters
+ − 267 using two-character sequences starting with @key{ESC}. To enter
+ − 268 @kbd{M-a}, you could type @kbd{@key{ESC} a}. To enter @kbd{C-M-a}, you
+ − 269 would type @kbd{ESC C-a}. @key{ESC} is allowed on terminals with
+ − 270 Meta keys, too, in case you have formed a habit of using it.@refill
+ − 271
+ − 272 If you are running under X and do not have a @key{META} key, it
+ − 273 is possible to reconfigure some other key to be a @key{META}
+ − 274 key. @xref{Super and Hyper Keys}. @refill
+ − 275
+ − 276 @vindex meta-flag
+ − 277 Emacs believes the terminal has a @key{META} key if the variable
+ − 278 @code{meta-flag} is non-@code{nil}. Normally this is set automatically
+ − 279 according to the termcap entry for your terminal type. However, sometimes
+ − 280 the termcap entry is wrong, and then it is useful to set this variable
+ − 281 yourself. @xref{Variables}, for how to do this.
+ − 282
+ − 283 Note: If you are running under the X window system, the setting of
+ − 284 the @code{meta-flag} variable is irrelevant.
+ − 285
+ − 286 @node Super and Hyper Keys, Character Representation, Meta Key, Keystrokes
+ − 287 @comment node-name, next, previous, up
+ − 288 @subsection Assignment of the @key{SUPER} and @key{HYPER} Keys
+ − 289 @kindex hyper key
+ − 290 @kindex super key
+ − 291
+ − 292 Most keyboards do not, by default, have @key{SUPER} or @key{HYPER}
+ − 293 modifier keys. Under X, you can simulate the @key{SUPER} or
+ − 294 @key{HYPER} key if you want to bind keys to sequences using @kbd{super}
+ − 295 and @kbd{hyper}. You can use the @code{xmodmap} program to do this.
+ − 296
+ − 297 For example, to turn your @key{CAPS-LOCK} key into a @key{SUPER} key,
+ − 298 do the following:
+ − 299
+ − 300 Create a file called @code{~/.xmodmap}. In this file, place the lines
+ − 301
+ − 302 @example
440
+ − 303 remove Lock = Caps_Lock
+ − 304 keysym Caps_Lock = Super_L
+ − 305 add Mod2 = Super_L
428
+ − 306 @end example
+ − 307
+ − 308 The first line says that the key that is currently called @code{Caps_Lock}
+ − 309 should no longer behave as a ``lock'' key. The second line says that
+ − 310 this should now be called @code{Super_L} instead. The third line says that
+ − 311 the key called @code{Super_L} should be a modifier key, which produces the
+ − 312 @code{Mod2} modifier.
+ − 313
+ − 314 To create a @key{META} or @key{HYPER} key instead of a @key{SUPER} key,
+ − 315 replace the word @code{Super} above with @code{Meta} or @code{Hyper}.
+ − 316
+ − 317 Just after you start up X, execute the command @code{xmodmap /.xmodmap}.
+ − 318 You can add this command to the appropriate initialization file to have
+ − 319 the command executed automatically.@refill
+ − 320
+ − 321 If you have problems, see the documentation for the @code{xmodmap}
+ − 322 program. The X keyboard model is quite complicated, and explaining
+ − 323 it is beyond the scope of this manual. However, we reprint the
+ − 324 following description from the X Protocol document for your convenience:
+ − 325
+ − 326 @cindex keysyms
+ − 327 @cindex keycode
+ − 328
+ − 329 A list of keysyms is associated with each keycode. If that list
+ − 330 (ignoring trailing @code{NoSymbol} entries) is a single keysym @samp{K},
+ − 331 then the list is treated as if it were the list
+ − 332 @code{``K NoSymbol K NoSymbol''}. If the list (ignoring trailing
+ − 333 @code{NoSymbol} entries) is a pair of keysyms @samp{K1 K2}, then the
+ − 334 list is treated as if it were the list @code{``K1 K2 K1 K2''}. If the
+ − 335 list (ignoring trailing @code{NoSymbol} entries) is a triple of keysyms
+ − 336 @samp{K1 K2 K3}, then the list is treated as if it were the list
+ − 337 @code{``K1 K2 K3 NoSymbol''}.
+ − 338
+ − 339 The first four elements of the list are split into two groups of
+ − 340 keysyms. Group 1 contains the first and second keysyms; Group 2 contains
+ − 341 third and fourth keysyms. Within each group, if the second element of
+ − 342 the group is NoSymbol, then the group should be treated as if the second
+ − 343 element were the same as the first element, except when the first
+ − 344 element is an alphabetic keysym @samp{K} for which both lowercase and
+ − 345 uppercase forms are defined. In that case, the group should be treated
+ − 346 as if the first element were the lowercase form of @samp{K} and the second
+ − 347 element were the uppercase form of @samp{K}.
+ − 348
+ − 349 The standard rules for obtaining a keysym from a KeyPress event make use of
+ − 350 only the Group 1 and Group 2 keysyms; no interpretation of other keysyms in
+ − 351 the list is given here. (That is, the last four keysyms are unused.)
+ − 352
+ − 353 Which group to use is determined by modifier state. Switching between
+ − 354 groups is controlled by the keysym named @code{Mode_switch}. Attach that
+ − 355 keysym to some keycode and attach that keycode to any one of the
+ − 356 modifiers Mod1 through Mod5. This modifier is called the @dfn{group
+ − 357 modifier}. For any keycode, Group 1 is used when the group modifier is
+ − 358 off, and Group 2 is used when the group modifier is on.
+ − 359
+ − 360 Within a group, which keysym to use is also determined by modifier
+ − 361 state. The first keysym is used when the @code{Shift} and @code{Lock}
+ − 362 modifiers are off. The second keysym is used when the @code{Shift}
+ − 363 modifier is on, or when the @code{Lock} modifier is on and the second
+ − 364 keysym is uppercase alphabetic, or when the @code{Lock} modifier is on
+ − 365 and is interpreted as @code{ShiftLock}. Otherwise, when the @code{Lock}
+ − 366 modifier is on and is interpreted as @code{CapsLock}, the state of the
+ − 367 @code{Shift} modifier is applied first to select a keysym,
+ − 368 but if that keysym is lower-case alphabetic, then the corresponding
+ − 369 upper-case keysym is used instead.
+ − 370
+ − 371 In addition to the above information on keysyms, we also provide the
+ − 372 following description of modifier mapping from the InterClient
+ − 373 Communications Conventions Manual:
+ − 374
+ − 375 @cindex modifier mapping
+ − 376
+ − 377 X11 supports 8 modifier bits, of which 3 are pre-assigned to
+ − 378 @code{Shift}, @code{Lock}, and @code{Control}. Each modifier bit is
+ − 379 controlled by the state of a set of keys, and these sets are specified
+ − 380 in a table accessed by @code{GetModifierMapping()} and
+ − 381 @code{SetModifierMapping()}.
+ − 382
+ − 383 A client needing to use one of the pre-assigned modifiers should assume
+ − 384 that the modifier table has been set up correctly to control these
+ − 385 modifiers. The @code{Lock} modifier should be interpreted as @code{Caps
+ − 386 Lock} or @code{Shift Lock} according to whether the keycodes in its
+ − 387 controlling set include @code{XK_Caps_Lock} or @code{XK_Shift_Lock}.
+ − 388
+ − 389 Clients should determine the meaning of a modifier bit from the keysyms
+ − 390 being used to control it.
+ − 391
+ − 392 A client needing to use an extra modifier, for example @code{Meta}, should:
+ − 393
+ − 394 @enumerate
+ − 395 @item
+ − 396 Scan the existing modifier mappings.
+ − 397
+ − 398 @enumerate
+ − 399 @item
+ − 400 If it finds a modifier that contains a keycode whose set of keysyms
+ − 401 includes @code{XK_Meta_L} or @code{XK_Meta_R}, it should use that
+ − 402 modifier bit.
+ − 403
+ − 404 @item
+ − 405 If there is no existing modifier controlled by @code{XK_Meta_L} or
+ − 406 @code{XK_Meta_R}, it should select an unused modifier bit (one with
+ − 407 an empty controlling set) and:
+ − 408 @end enumerate
+ − 409
+ − 410 @item
+ − 411 If there is a keycode with @code{XL_Meta_L} in its set of keysyms,
+ − 412 add that keycode to the set for the chosen modifier, and then:
+ − 413
+ − 414 @enumerate
+ − 415 @item
+ − 416 If there is a keycode with @code{XL_Meta_R} in its set of keysyms,
+ − 417 add that keycode to the set for the chosen modifier, and then:
+ − 418
+ − 419 @item
+ − 420 If the controlling set is still empty, interact with the user to
+ − 421 select one or more keys to be @code{Meta}.
+ − 422 @end enumerate
+ − 423
+ − 424
+ − 425 @item
+ − 426 If there are no unused modifier bits, ask the user to take corrective action.
+ − 427 @end enumerate
+ − 428
+ − 429 This means that the @code{Mod1} modifier does not necessarily mean
+ − 430 @code{Meta}, although some applications (such as twm and emacs 18)
+ − 431 assume that. Any of the five unassigned modifier bits could mean
+ − 432 @code{Meta}; what matters is that a modifier bit is generated by a
+ − 433 keycode which is bound to the keysym @code{Meta_L} or @code{Meta_R}.
+ − 434
+ − 435 Therefore, if you want to make a @key{META} key, the right way
+ − 436 is to make the keycode in question generate both a @code{Meta} keysym
+ − 437 and some previously-unassigned modifier bit.
+ − 438
+ − 439 @node Character Representation, Commands, Super and Hyper Keys, Keystrokes
+ − 440 @comment node-name, next, previous, up
+ − 441 @section Representation of Characters
+ − 442
+ − 443 This section briefly discusses how characters are represented in Emacs
+ − 444 buffers. @xref{Key Sequences}, for information on representing key
+ − 445 sequences to create key bindings.
+ − 446
4264
+ − 447 Printable characters (letters, numbers, punctuation and so on) in
+ − 448 XEmacs buffers are displayed as such. @key{LFD} (line feed, character
+ − 449 code @samp{\012} (octal)) is the same as a newline character; it is
+ − 450 displayed by starting a new line. @key{TAB} is displayed by moving to
+ − 451 the next tab stop column (usually every 8 spaces). Other control
+ − 452 characters below #x20 (hexadecimal) are displayed as a caret (@samp{^})
+ − 453 followed by the non-control version of the character; thus, @kbd{C-a} is
+ − 454 displayed as @samp{^A}. Characters between (hexadecimal) #x80 and #xA0
+ − 455 are displayed with octal escape sequences; thus, character code 243
+ − 456 (octal), also called @kbd{M-#} when used as an input character, is
+ − 457 displayed as @samp{\243}.
428
+ − 458
+ − 459 The variable @code{ctl-arrow} may be used to alter this behavior.
4264
+ − 460 @xref{Display Vars}. As a rule, its value limits octal display to those
+ − 461 characters in the range just mentioned, and otherwise characters are
+ − 462 treated as printable, and will be displayed as themselves when the
+ − 463 relevant fonts are available.
428
+ − 464
3171
+ − 465 @node Commands, Non-Latin keyboards, Character Representation, Keystrokes
428
+ − 466 @section Keys and Commands
+ − 467
+ − 468 @cindex binding
+ − 469 @cindex customization
+ − 470 @cindex keymap
+ − 471 @cindex function
+ − 472 @cindex command
+ − 473 This manual is full of passages that tell you what particular keys do.
+ − 474 But Emacs does not assign meanings to keys directly. Instead, Emacs
+ − 475 assigns meanings to @dfn{functions}, and then gives keys their meanings
+ − 476 by @dfn{binding} them to functions.
+ − 477
+ − 478 A function is a Lisp object that can be executed as a program. Usually
+ − 479 it is a Lisp symbol that has been given a function definition; every
+ − 480 symbol has a name, usually made of a few English words separated by
+ − 481 dashes, such as @code{next-line} or @code{forward-word}. It also has a
+ − 482 @dfn{definition}, which is a Lisp program. Only some functions can be the
+ − 483 bindings of keys; these are functions whose definitions use
+ − 484 @code{interactive} to specify how to call them interactively. Such
+ − 485 functions are called @dfn{commands}, and their names are @dfn{command
+ − 486 names}. More information on this subject will appear in the @i{XEmacs
+ − 487 Lisp Reference Manual}.
+ − 488
+ − 489 The bindings between keys and functions are recorded in various tables
+ − 490 called @dfn{keymaps}. @xref{Key Bindings}, for more information on key
+ − 491 sequences you can bind commands to. @xref{Keymaps}, for information on
+ − 492 creating keymaps.
+ − 493
+ − 494 When we say ``@kbd{C-n} moves down vertically one line'' we are
+ − 495 glossing over a distinction that is irrelevant in ordinary use but is
+ − 496 vital in understanding how to customize Emacs. The function
+ − 497 @code{next-line} is programmed to move down vertically. @kbd{C-n}
+ − 498 has this effect @i{because} it is bound to that function. If you rebind
+ − 499 @kbd{C-n} to the function @code{forward-word} then @kbd{C-n} will move
+ − 500 forward by words instead. Rebinding keys is a common method of
+ − 501 customization.@refill
+ − 502
+ − 503 The rest of this manual usually ignores this subtlety to keep
+ − 504 things simple. To give the customizer the information needed, we often
+ − 505 state the name of the command that really does the work in parentheses
+ − 506 after mentioning the key that runs it. For example, we will say that
+ − 507 ``The command @kbd{C-n} (@code{next-line}) moves point vertically
+ − 508 down,'' meaning that @code{next-line} is a command that moves vertically
+ − 509 down and @kbd{C-n} is a key that is standardly bound to it.
+ − 510
+ − 511 @cindex variables
+ − 512 While we are on the subject of information for customization only,
+ − 513 it's a good time to tell you about @dfn{variables}. Often the
+ − 514 description of a command will say, ``To change this, set the variable
+ − 515 @code{mumble-foo}.'' A variable is a name used to remember a value.
+ − 516 Most of the variables documented in this manual exist just to facilitate
+ − 517 customization: some command or other part of Emacs uses the variable
+ − 518 and behaves differently depending on its setting. Until you are interested in
+ − 519 customizing, you can ignore the information about variables. When you
+ − 520 are ready to be interested, read the basic information on variables, and
+ − 521 then the information on individual variables will make sense.
+ − 522 @xref{Variables}.
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+ − 523
+ − 524 @node Non-Latin keyboards, ,Commands, Keystrokes
+ − 525
+ − 526 @cindex russian
+ − 527 @cindex greek
+ − 528 @cindex ``russian c-x''
+ − 529 @cindex try-alternate-layouts-for-commands
+ − 530
+ − 531 If your computer has a keyboard designed for a language like Russian or
+ − 532 Greek, where you have to go to some trouble to type Roman-alphabet
+ − 533 characters, then typing @kbd{C-f} to call @code{forward-character} is
+ − 534 very inconvenient.
+ − 535
+ − 536 To address this, XEmacs allows you to pretend that your keyboard has a
+ − 537 US layout for such commands. That is, you can type @kbd{C-Cyrillic_che
+ − 538 C-Cyrillic_a} and XEmacs will work out that it should call the command
+ − 539 that @kbd{C-x C-f} is bound to@footnote{You can, of course, override
+ − 540 this with an explicit binding for @kbd{C-Cyrillic_che C-Cyrillic_a} to
+ − 541 something else.}. Function keys, like @key{F1},
+ − 542 @key{Shift} or @key{Control} are not handled by this, just alphanumeric
+ − 543 characters and punctuation.
+ − 544
+ − 545 The main user variable associated with this functionality is
+ − 546 @code{try-alternate-layouts-for-commands}. Setting this to @code{nil}
+ − 547 inhibits this translation, which would be appropriate if your keyboard
+ − 548 can handle the Roman alphabet but doesn't have the US layout, and you
+ − 549 want to avoid the possible confusion.
+ − 550
+ − 551 If @code{try-alternate-layouts-for-commands} is @code{t} but this
+ − 552 functionality doesn't work for you under X11, check the value of the
+ − 553 variable @code{x-us-keymap-description}. This is a hardware-specific
+ − 554 map from key codes to the US layout, and can be initialized from the
+ − 555 output of @code{xmodmap -pke}; see the documentation for that variable
+ − 556 and for @code{x-us-keymap-first-keycode}.
+ − 557
