diff options
| -rw-r--r-- | lispref/commands.texi | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/lispref/commands.texi b/lispref/commands.texi index fc9ed30aee3..e95b5599ad3 100644 --- a/lispref/commands.texi +++ b/lispref/commands.texi @@ -178,6 +178,31 @@ form that is evaluated to get a list of arguments to pass to the command. @cindex argument evaluation form +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 @emph{not} to do: + +@smallexample +(interactive + (list (region-beginning) (region-end) + (read-string "Foo: " nil 'my-history))) +@end smallexample + +@noindent +Here's how to avoid the problem, by examining point and the mark only +after reading the keyboard input: + +@smallexample +(interactive + (let ((string (read-string "Foo: " nil 'my-history))) + (list (region-beginning) (region-end) string))) +@end smallexample + @item @cindex argument prompt It may be a string; then its contents should consist of a code character |