@c Copyright (C) 1990, 1991, 1992, 1993, 1995, 1998 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/tips
-@node Tips, GNU Emacs Internals, Calendar, Top
+@node Tips, GNU Emacs Internals, System Interface, Top
@appendix Tips and Conventions
@cindex tips
@cindex standards of coding style
prefix. This helps avoid name conflicts.
This recommendation applies even to names for traditional Lisp
-primitives that are not primitives in Emacs Lisp---even to @code{cadr}.
-Believe it or not, there is more than one plausible way to define
-@code{cadr}. Play it safe; append your name prefix to produce a name
-like @code{foo-cadr} or @code{mylib-cadr} instead.
+primitives that are not primitives in Emacs Lisp---even to
+@code{copy-list}. Believe it or not, there is more than one plausible
+way to define @code{copy-list}. Play it safe; append your name prefix
+to produce a name like @code{foo-copy-list} or @code{mylib-copy-list}
+instead.
If you write a function that you think ought to be added to Emacs under
a certain name, such as @code{twiddle-files}, don't call it by that name
in your program. Call it @code{mylib-twiddle-files} in your program,
-and send mail to @samp{bug-gnu-emacs@@prep.ai.mit.edu} suggesting we add
+and send mail to @samp{bug-gnu-emacs@@gnu.org} suggesting we add
it to Emacs. If and when we do, we can change the name easily enough.
If one prefix is insufficient, your package may use two or three
@end example
@noindent
-(And @var{bar} should contain @code{(provide '@var{bar})}, to make the
-@code{require} work.) This will cause @var{bar} to be loaded when you
-byte-compile @var{foo}. Otherwise, you risk compiling @var{foo} without
-the necessary macro loaded, and that would produce compiled code that
-won't work right. @xref{Compiling Macros}.
+(And the library @var{bar} should contain @code{(provide '@var{bar})},
+to make the @code{require} work.) This will cause @var{bar} to be
+loaded when you byte-compile @var{foo}. Otherwise, you risk compiling
+@var{foo} without the necessary macro loaded, and that would produce
+compiled code that won't work right. @xref{Compiling Macros}.
Using @code{eval-when-compile} avoids loading @var{bar} when
the compiled version of @var{foo} is @emph{used}.
name that ends in @samp{-flag}.
@item
+@cindex reserved keys
+@cindex keys, reserved
Please do not define @kbd{C-c @var{letter}} as a key in your major
modes. These sequences are reserved for users; they are the
@strong{only} sequences reserved for users, so do not block them.
character, a digit, or certain punctuation characters. These sequences
are reserved for major modes.
-Changing all the major modes in Emacs 18 so they would follow this
-convention was a lot of work. Abandoning this convention would make
-that work go to waste, and inconvenience users.
+Changing all the Emacs major modes to follow this convention was a lot
+of work. Abandoning this convention would make that work go to waste,
+and inconvenience users.
@item
Sequences consisting of @kbd{C-c} followed by @kbd{@{}, @kbd{@}},
@item
Do not bind a key sequence ending in @key{ESC} except following
-another @key{ESC}. (That is, it is ok to bind a sequence ending in
+another @key{ESC}. (That is, it is OK to bind a sequence ending in
@kbd{@key{ESC} @key{ESC}}.)
The reason for this rule is that a non-prefix binding for @key{ESC} in
any context prevents recognition of escape sequences as function keys in
that context.
+@item
+Anything which acts like a temporary mode or state which the user can
+enter and leave should define @kbd{@key{ESC} @key{ESC}} of
+@kbd{@key{ESC} @key{ESC} @key{ESC}} as a way to escape.
+
+For a state which accepts ordinary Emacs commands, or more generally any
+kind of state in which @key{ESC} followed by a function key or arrow key
+is potentially meaningful, then you must not define @kbd{@key{ESC}
+@key{ESC}}, since that would preclude recognizing an escape sequence
+after @key{ESC}. In these states, you should define @kbd{@key{ESC}
+@key{ESC} @key{ESC}} as the way to escape. Otherwise, define
+@kbd{@key{ESC} @key{ESC}} instead.
+
@item
Applications should not bind mouse events based on button 1 with the
shift key held down. These events include @kbd{S-mouse-1},
In some other systems there is a convention of choosing variable names
that begin and end with @samp{*}. We don't use that convention in Emacs
Lisp, so please don't use it in your programs. (Emacs uses such names
-only for program-generated buffers.) The users will find Emacs more
+only for special-purpose buffers.) The users will find Emacs more
coherent if all libraries use the same conventions.
@item
If you bind a variable in one function, and use it or set it in another
function, the compiler warns about the latter function unless the
variable has a definition. But often these variables have short names,
-and it is not clean for Lisp packages to define such variables names.
+and it is not clean for Lisp packages to define such variable names.
Therefore, you should rename the variable to start with the name prefix
used for the other functions and variables in your package.
Don't make a habit of putting close-parentheses on lines by themselves;
Lisp programmers find this disconcerting. Once in a while, when there
is a sequence of many consecutive close-parentheses, it may make sense
-to split them in one or two significant places.
+to split the sequence in one or two significant places.
@item
Please put a copyright notice on the file if you give copies to anyone.
@cindex profiling
@cindex timing programs
@cindex @file{profile.el}
-Use the @file{profile} library to profile your program. See the file
-@file{profile.el} for instructions.
+@cindex @file{elp.el}
+Profile your program with the @file{profile} library or the @file{elp}
+library. See the files @file{profile.el} and @file{elp.el} for
+instructions.
@item
Use iteration rather than recursion whenever possible.
handled specially.
For example, the following input will show you that @code{aref} is
-compiled specially (@pxref{Array Functions}) while @code{elt} is not
-(@pxref{Sequence Functions}):
+compiled specially (@pxref{Array Functions}):
@example
@group
(get 'aref 'byte-compile)
@result{} byte-compile-two-args
@end group
-
-@group
-(get 'elt 'byte-compile)
- @result{} nil
-@end group
@end example
@item
-If calling a small function accounts for a substantial part of your
+If calling a small function accounts for a substantial part of your
program's running time, make the function inline. This eliminates
the function call overhead. Since making a function inline reduces
the flexibility of changing the program, don't do it unless it gives
@node Documentation Tips
@section Tips for Documentation Strings
- Here are some tips for the writing of documentation strings.
+@tindex checkdoc-minor-mode
+@findex checkdoc-minor-mode
+ Here are some tips and conventions for the writing of documentation
+strings. You can check many of these conventions by running the command
+@kbd{M-x checkdoc-minor-mode}.
@itemize @bullet
@item
@item
For consistency, phrase the verb in the first sentence of a
-documentation string as an infinitive with ``to'' omitted. For
+function's documentation string as an infinitive with ``to'' omitted. For
instance, use ``Return the cons of A and B.'' in preference to ``Returns
the cons of A and B@.'' Usually it looks good to do likewise for the
rest of the first paragraph. Subsequent paragraphs usually look better
When a documentation string refers to a Lisp symbol, write it as it
would be printed (which usually means in lower case), with single-quotes
around it. For example: @samp{lambda}. There are two exceptions: write
-t and nil without single-quotes. (In this manual, we normally do use
-single-quotes for those symbols.)
+t and nil without single-quotes. (In this manual, we use a different
+convention, with single-quotes for all symbols.)
@end ifinfo
+Help mode automatically creates a hyperlink when a documentation string
+uses a symbol name inside single quotes, if the symbol has either a
+function or a variable definition. You do not need to do anything
+special to make use of this feature. However, when a symbol has both a
+function definition and a variable definition, and you want to refer to
+just one of them, you can specify which one by writing one of the words
+@samp{variable}, @samp{option}, @samp{function}, or @samp{command},
+immediately before the symbol name. (Case makes no difference in
+recognizing these indicator words.) For example, if you write
+
+@example
+This function sets the variable `buffer-file-name'.
+@end example
+
+@noindent
+then the hyperlink will refer only to the variable documentation of
+@code{buffer-file-name}, and not to its function documentation.
+
+If a symbol has a function definition and/or a variable definition, but
+those are irrelevant to the use of the symbol that you are documenting,
+you can write the word @samp{symbol} before the symbol name to prevent
+making any hyperlink. For example,
+
+@example
+If the argument KIND-OF-RESULT is the symbol `list',
+this function returns a list of all the objects
+that satisfy the criterion.
+@end example
+
+@noindent
+does not make a hyperlink to the documentation, irrelevant here, of the
+function @code{list}.
+
@item
Don't write key sequences directly in documentation strings. Instead,
use the @samp{\\[@dots{}]} construct to stand for them. For example,
@end group
@end smallexample
-Every function that has no documentation string (because it is use only
-internally within the package it belongs to), should have instead a
-two-semicolon comment right before the function, explaining what the
-function does and how to call it properly. Explain precisely what each
-argument means and how the function interprets its possible values.
+Every function that has no documentation string (presumably one that is
+used only internally within the package it belongs to), should have
+instead a two-semicolon comment right before the function, explaining
+what the function does and how to call it properly. Explain precisely
+what each argument means and how the function interprets its possible
+values.
@item ;;;
Comments that start with three semicolons, @samp{;;;}, should start at
@noindent
The indentation commands of the Lisp modes in Emacs, such as @kbd{M-;}
-(@code{indent-for-comment}) and @key{TAB} (@code{lisp-indent-line})
+(@code{indent-for-comment}) and @key{TAB} (@code{lisp-indent-line}),
automatically indent comments according to these conventions,
depending on the number of semicolons. @xref{Comments,,
Manipulating Comments, emacs, The GNU Emacs Manual}.
;; Keywords: docs
;; This file is part of GNU Emacs.
-@var{copying permissions}@dots{}
+@dots{}
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
@end group
@end smallexample
@item Keywords
This line lists keywords for the @code{finder-by-keyword} help command.
+Please use that command to see a list of the meaningful keywords.
+
This field is important; it's how people will find your package when
they're looking for things by topic area. To separate the keywords, you
can use spaces, commas, or both.
@table @samp
@item ;;; Commentary:
This begins introductory comments that explain how the library works.
-It should come right after the copying permissions.
+It should come right after the copying permissions, terminated by a
+@samp{Change Log}, @samp{History} or @samp{Code} comment line. This
+text is used by the Finder package, so it should make sense in that
+context.
+
+@item ;;; Documentation
+This has been used in some files in place of @samp{;;; Commentary:},
+but @samp{;;; Commentary:} is preferred.
-@item ;;; Change log:
+@item ;;; Change Log:
This begins change log information stored in the library file (if you
store the change history there). For most of the Lisp
files distributed with Emacs, the change history is kept in the file
@file{ChangeLog} and not in the source file at all; these files do
-not have a @samp{;;; Change log:} line.
+not have a @samp{;;; Change Log:} line.
@item ;;; Code:
This begins the actual code of the program.