From 96a6857705884d96b9026e80d2bc551d9079cee2 Mon Sep 17 00:00:00 2001 From: Stefan Monnier Date: Thu, 15 Nov 2012 09:20:45 -0500 Subject: [PATCH] * doc/lispref/keymaps.texi (Translation Keymaps): Backport subsection "Interaction with normal keymaps". Fixes: debbugs:12868 --- doc/lispref/ChangeLog | 5 +++++ doc/lispref/keymaps.texi | 45 ++++++++++++++++++++++++++++------------ 2 files changed, 37 insertions(+), 13 deletions(-) diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog index 68d7bee2b64..89b456f5c22 100644 --- a/doc/lispref/ChangeLog +++ b/doc/lispref/ChangeLog @@ -1,3 +1,8 @@ +2012-11-15 Stefan Monnier + + * keymaps.texi (Translation Keymaps): Add a subsection "Interaction + with normal keymaps" (bug#12868). + 2012-11-15 Glenn Morris * display.texi (Face Attributes): Fix :underline COLOR description. diff --git a/doc/lispref/keymaps.texi b/doc/lispref/keymaps.texi index f6d571ecc68..d01ecba4bed 100644 --- a/doc/lispref/keymaps.texi +++ b/doc/lispref/keymaps.texi @@ -1559,14 +1559,11 @@ sequence, to translate certain event sequences into others. being read, as it is read, against @code{input-decode-map}, then @code{local-function-key-map}, and then against @code{key-translation-map}. -@defvar input-decode-map -This variable holds a keymap that describes the character sequences sent -by function keys on an ordinary character terminal. This keymap has the -same structure as other keymaps, but is used differently: it specifies -translations to make while reading key sequences, rather than bindings -for key sequences. +These keymaps have the same structure as other keymaps, but they are used +differently: they specify translations to make while reading key sequences, +rather than bindings for key sequences. -If @code{input-decode-map} ``binds'' a key sequence @var{k} to a vector +If one of these keymaps ``binds'' a key sequence @var{k} to a vector @var{v}, then when @var{k} appears as a subsequence @emph{anywhere} in a key sequence, it is replaced with the events in @var{v}. @@ -1581,6 +1578,10 @@ Thus, typing @kbd{C-c @key{PF1}} sends the character sequence @kbd{C-c this back into @kbd{C-c @key{PF1}}, which it returns as the vector @code{[?\C-c pf1]}. +@defvar input-decode-map +This variable holds a keymap that describes the character sequences sent +by function keys on an ordinary character terminal. + The value of @code{input-decode-map} is usually set up automatically according to the terminal's Terminfo or Termcap entry, but sometimes those need help from terminal-specific Lisp files. Emacs comes with @@ -1655,8 +1656,6 @@ to turn the character that follows into a Hyper character: (let ((symbol (if (symbolp e) e (car e)))) (setq symbol (intern (concat string (symbol-name symbol)))) -@end group -@group (if (symbolp e) symbol (cons symbol (cdr e))))) @@ -1666,10 +1665,30 @@ to turn the character that follows into a Hyper character: @end example If you have enabled keyboard character set decoding using -@code{set-keyboard-coding-system}, decoding is done after the -translations listed above. @xref{Terminal I/O Encoding}. However, in -future Emacs versions, character set decoding may be done at an -earlier stage. +@code{set-keyboard-coding-system}, decoding is done before the +translations listed above. @xref{Terminal I/O Encoding}. + +@subsection Interaction with normal keymaps + +The end of a key sequence is detected when that key sequence either is bound +to a command, or when Emacs determines that no additional event can lead +to a sequence that is bound to a command. + +This means that, while @code{input-decode-map} and @code{key-translation-map} +apply regardless of whether the original key sequence would have a binding, the +presence of such a binding can still prevent translation from taking place. +For example, let us return to our VT100 example above and add a binding for +@kbd{C-c @key{ESC}} to the global map; now when the user hits @kbd{C-c +@key{PF1}} Emacs will fail to decode @kbd{C-c @key{ESC} O P} into @kbd{C-c +@key{PF1}} because it will stop reading keys right after @kbd{C-x @key{ESC}}, +leaving @kbd{O P} for later. This is in case the user really hit @kbd{C-c +@key{ESC}}, in which case Emacs should not sit there waiting for the next key +to decide whether the user really pressed @kbd{@key{ESC}} or @kbd{@key{PF1}}. + +For that reason, it is better to avoid binding commands to key sequences where +the end of the key sequence is a prefix of a key translation. The main such +problematic suffixes/prefixes are @kbd{@key{ESC}}, @kbd{M-O} (which is really +@kbd{@key{ESC} O}) and @kbd{M-[} (which is really @kbd{@key{ESC} [}). @node Key Binding Commands @section Commands for Binding Keys -- 2.39.2