bug#10942: 24.0.94; (emacs) `Modifier Keys'

[Drew Adams]

The menu at (emacs) `Key Bindings' says that node `Modifier Keys'
explains "Using modifier keys in key bindings."
 
Yet one of the most important things to know about "using modifier keys
in key bindings" is missing from that node.  Instead, it is said in node
`Init Rebinding', and it is easy to miss there:
 
Using a string "only works for ASCII characters and Meta-modified ASCII
characters."
 
A reader will naturally look for such info in node `Modifier Keys',
especially after encountering the error message "Invalid modifier in
string" (which, unfortunately, does not tell you which string is meant).
An index search of "modifier" will lead the reader to `Modifier Keys'.
 
That error message shows up if a user (starting with Emacs 22) tries to
use something like "\C-\M-~" with, e.g., `define-key'.
 
Given that error message, a user is likely to wonder what gives?  Which
of the bindings I wrote uses an invalid modifier?  And just what _is_ an
invalid modifier - which modifier is invalid, where?
 
But our user will find the answers only after first _locating_ the
sentence cited above, which is not so easy, and second, carefully
interpreting it as implying that using both Control and Meta modifiers
together with an ASCII character is not valid.
 
This info belongs in the node about using modifier keys.  It is short
enough that it could be repeated in both nodes, or a cross reference
could be added _from_ the init-file node _to_ the modifier-keys node.
 

In GNU Emacs 24.0.94.1 (i386-mingw-nt5.1.2600)
 of 2012-02-26 on MARVIN
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include'