@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1998, 1999
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/internals
@node GNU Emacs Internals, Standard Errors, Tips, Top
internal aspects of GNU Emacs that may be of interest to C programmers.
@menu
-* Building Emacs:: How to preload Lisp libraries into Emacs.
+* Building Emacs:: How to the dumped Emacs is made.
* Pure Storage:: A kludge to make preloaded Lisp functions sharable.
* Garbage Collection:: Reclaiming space for Lisp objects no longer used.
+* Memory Usage:: Info about total size of Lisp objects made so far.
* Writing Emacs Primitives:: Writing C code for Emacs.
* Object Internals:: Data formats of buffers, windows, processes.
@end menu
-@node Building Emacs, Pure Storage, GNU Emacs Internals, GNU Emacs Internals
+@node Building Emacs
@appendixsec Building Emacs
@cindex building Emacs
@pindex temacs
the real runnable Emacs executable. These arguments direct
@file{temacs} to evaluate the Lisp files specified in the file
@file{loadup.el}. These files set up the normal Emacs editing
-environment, resulting in an Emacs which is still impure but no longer
+environment, resulting in an Emacs that is still impure but no longer
bare.
It takes a substantial time to load the standard Lisp files. Luckily,
you don't have to do this each time you run Emacs; @file{temacs} can
-dump out an executable program called @file{emacs} which has these files
+dump out an executable program called @file{emacs} that has these files
preloaded. @file{emacs} starts more quickly because it does not need to
load the files. This is the Emacs executable that is normally
installed.
Some operating systems don't support dumping. On those systems, you
must start Emacs with the @samp{temacs -l loadup} command each time you
-use it. This takes a long time, but since you need to start Emacs once
-a day at most---or once a week if you never log out---the extra time is
-not too severe a problem.
+use it. This takes a substantial time, but since you need to start
+Emacs once a day at most---or once a week if you never log out---the
+extra time is not too severe a problem.
@cindex @file{site-load.el}
+
You can specify additional files to preload by writing a library named
-@file{site-load.el} which loads them. You may need to increase the
-value of @code{PURESIZE}, in @file{src/puresize.h}, to make room for the
-additional files. (Try adding increments of 20000 until it is big
-enough.) However, the advantage of preloading additional files
-decreases as machines get faster. On modern machines, it is usually not
-advisable.
+@file{site-load.el} that loads them. You may need to add a definition
+
+@example
+#define SITELOAD_PURESIZE_EXTRA @var{n}
+@end example
+
+@noindent
+to make @var{n} added bytes of pure space to hold the additional files.
+(Try adding increments of 20000 until it is big enough.) However, the
+advantage of preloading additional files decreases as machines get
+faster. On modern machines, it is usually not advisable.
+
+ After @file{loadup.el} reads @file{site-load.el}, it finds the
+documentation strings for primitive and preloaded functions (and
+variables) in the file @file{etc/DOC} where they are stored, by calling
+@code{Snarf-documentation} (@pxref{Accessing Documentation}).
@cindex @file{site-init.el}
- You can specify other things to be done in Lisp just before dumping by
-putting them in a library named @file{site-init.el}. However, if these
-things might alter the behavior that users expect from an ordinary
-unmodified Emacs, it is better to do them in @file{default.el}, so that
-users can override them if they wish. @xref{Start-up Summary}.
-
- Before @file{emacs} is dumped, the documentation strings for primitive
-and preloaded functions (and variables) need to be found in the file
-where they are stored. This is done by calling
-@code{Snarf-documentation} (@pxref{Accessing Documentation}). These
-strings were moved out of @file{emacs} to make it smaller.
-@xref{Documentation Basics}.
+ You can specify other Lisp expressions to execute just before dumping
+by putting them in a library named @file{site-init.el}. This file is
+executed after the documentation strings are found.
+
+ If you want to preload function or variable definitions, there are
+three ways you can do this and make their documentation strings
+accessible when you subsequently run Emacs:
+
+@itemize @bullet
+@item
+Arrange to scan these files when producing the @file{etc/DOC} file,
+and load them with @file{site-load.el}.
+
+@item
+Load the files with @file{site-init.el}, then copy the files into the
+installation directory for Lisp files when you install Emacs.
+
+@item
+Specify a non-@code{nil} value for
+@code{byte-compile-dynamic-docstrings} as a local variable in each of these
+files, and load them with either @file{site-load.el} or
+@file{site-init.el}. (This method has the drawback that the
+documentation strings take up space in Emacs all the time.)
+@end itemize
+
+ It is not advisable to put anything in @file{site-load.el} or
+@file{site-init.el} that would alter any of the features that users
+expect in an ordinary unmodified Emacs. If you feel you must override
+normal features for your site, do it with @file{default.el}, so that
+users can override your changes if they wish. @xref{Startup Summary}.
@defun dump-emacs to-file from-file
@cindex unexec
- This function dumps the current state of Emacs into an executable file
+This function dumps the current state of Emacs into an executable file
@var{to-file}. It takes symbols from @var{from-file} (this is normally
the executable file @file{temacs}).
-If you use this function in an Emacs that was already dumped, you must
-set @code{command-line-processed} to @code{nil} first for good results.
-@xref{Command Line Arguments}.
+If you want to use this function in an Emacs that was already dumped,
+you must run Emacs with @samp{-batch}.
@end defun
-@deffn Command emacs-version
- This function returns a string describing the version of Emacs that is
-running. It is useful to include this string in bug reports.
-
-@example
-@group
-(emacs-version)
- @result{} "GNU Emacs 19.22.1 of Fri Feb 27 1994 \
-on slug (berkeley-unix)"
-@end group
-@end example
-
-Called interactively, the function prints the same information in the
-echo area.
-@end deffn
-
-@defvar emacs-build-time
- The value of this variable is the time at which Emacs was built at the
-local site.
-
-@example
-@group
-emacs-build-time
- @result{} "Fri Feb 27 14:55:57 1994"
-@end group
-@end example
-@end defvar
-
-@defvar emacs-version
-The value of this variable is the version of Emacs being run. It is a
-string such as @code{"19.22.1"}.
-@end defvar
-
-@node Pure Storage, Garbage Collection, Building Emacs, GNU Emacs Internals
+@node Pure Storage
@appendixsec Pure Storage
@cindex pure storage
- There are two types of storage in GNU Emacs Lisp for user-created Lisp
-objects: @dfn{normal storage} and @dfn{pure storage}. Normal storage is
-where all the new data which is created during an Emacs session is kept;
-see the following section for information on normal storage. Pure
-storage is used for certain data in the preloaded standard Lisp files:
-data that should never change during actual use of Emacs.
+ Emacs Lisp uses two kinds of storage for user-created Lisp objects:
+@dfn{normal storage} and @dfn{pure storage}. Normal storage is where
+all the new data created during an Emacs session are kept; see the
+following section for information on normal storage. Pure storage is
+used for certain data in the preloaded standard Lisp files---data that
+should never change during actual use of Emacs.
Pure storage is allocated only while @file{temacs} is loading the
standard preloaded Lisp libraries. In the file @file{emacs}, it is
-marked as read-only (on operating systems which permit this), so that
+marked as read-only (on operating systems that permit this), so that
the memory space can be shared by all the Emacs jobs running on the
machine at once. Pure storage is not expandable; a fixed amount is
allocated when Emacs is compiled, and if that is not sufficient for the
-preloaded libraries, @file{temacs} crashes. If that happens, you will
-have to increase the compilation parameter @code{PURESIZE} in the file
+preloaded libraries, @file{temacs} crashes. If that happens, you must
+increase the compilation parameter @code{PURESIZE} in the file
@file{src/puresize.h}. This normally won't happen unless you try to
preload additional libraries or add features to the standard ones.
@defun purecopy object
- This function makes a copy of @var{object} in pure storage and returns
-it. It copies strings by simply making a new string with the same
+This function makes a copy in pure storage of @var{object}, and returns
+it. It copies a string by simply making a new string with the same
characters in pure storage. It recursively copies the contents of
-vectors and cons cells. It does not make copies of symbols, or any
-other objects, but just returns them unchanged. It signals an error if
+vectors and cons cells. It does not make copies of other objects such
+as symbols, but just returns them unchanged. It signals an error if
asked to copy markers.
-This function is used only while Emacs is being built and dumped; it is
-called only in the file @file{emacs/lisp/loaddefs.el}.
+This function is a no-op except while Emacs is being built and dumped;
+it is usually called only in the file @file{emacs/lisp/loaddefs.el}, but
+a few packages call it just in case you decide to preload them.
@end defun
@defvar pure-bytes-used
- The value of this variable is the number of bytes of pure storage
+The value of this variable is the number of bytes of pure storage
allocated so far. Typically, in a dumped Emacs, this number is very
close to the total amount of pure storage available---if it were not,
we would preallocate less.
@end defvar
@defvar purify-flag
- This variable determines whether @code{defun} should make a copy of the
+This variable determines whether @code{defun} should make a copy of the
function definition in pure storage. If it is non-@code{nil}, then the
function definition is copied into pure storage.
- This flag is @code{t} while loading all of the basic functions for
+This flag is @code{t} while loading all of the basic functions for
building Emacs initially (allowing those functions to be sharable and
-non-collectible). It is set to @code{nil} when Emacs is saved out
-as @file{emacs}. The flag is set and reset in the C sources.
+non-collectible). Dumping Emacs as an executable always writes
+@code{nil} in this variable, regardless of the value it actually has
+before and after dumping.
- You should not change this flag in a running Emacs.
+You should not change this flag in a running Emacs.
@end defvar
-@node Garbage Collection, Writing Emacs Primitives, Pure Storage, GNU Emacs Internals
+@node Garbage Collection
@appendixsec Garbage Collection
@cindex garbage collector
@cindex memory allocation
When a program creates a list or the user defines a new function (such
-as by loading a library), then that data is placed in normal storage.
-If normal storage runs low, then Emacs asks the operating system to
+as by loading a library), that data is placed in normal storage. If
+normal storage runs low, then Emacs asks the operating system to
allocate more memory in blocks of 1k bytes. Each block is used for one
-type of Lisp object, so symbols, cons cells, markers, etc.@: are
-segregated in distinct blocks in memory. (Vectors, buffers and certain
-other editing types, which are fairly large, are allocated in individual
-blocks, one per object, while strings are packed into blocks of 8k
-bytes.)
-
- It is quite common to use some storage for a while, then release it
-by, for example, killing a buffer or deleting the last pointer to an
+type of Lisp object, so symbols, cons cells, markers, etc., are
+segregated in distinct blocks in memory. (Vectors, long strings,
+buffers and certain other editing types, which are fairly large, are
+allocated in individual blocks, one per object, while small strings are
+packed into blocks of 8k bytes.)
+
+ It is quite common to use some storage for a while, then release it by
+(for example) killing a buffer or deleting the last pointer to an
object. Emacs provides a @dfn{garbage collector} to reclaim this
abandoned storage. (This name is traditional, but ``garbage recycler''
might be a more intuitive metaphor for this facility.)
- The garbage collector operates by scanning all the objects that have
-been allocated and marking those that are still accessible to Lisp
-programs. To begin with, all the symbols, their values and associated
-function definitions, and any data presently on the stack, are
-accessible. Any objects which can be reached indirectly through other
-accessible objects are also accessible.
+ The garbage collector operates by finding and marking all Lisp objects
+that are still accessible to Lisp programs. To begin with, it assumes
+all the symbols, their values and associated function definitions, and
+any data presently on the stack, are accessible. Any objects that can
+be reached indirectly through other accessible objects are also
+accessible.
- When this is finished, all inaccessible objects are garbage. No
+ When marking is finished, all objects still unmarked are garbage. No
matter what the Lisp program or the user does, it is impossible to refer
-to them, since there is no longer a way to reach them. Their
-space might as well be reused, since no one will notice. That is what
-the garbage collector arranges to do.
+to them, since there is no longer a way to reach them. Their space
+might as well be reused, since no one will miss them. The second
+(``sweep'') phase of the garbage collector arranges to reuse them.
+
+@c ??? Maybe add something describing weak hash tables here?
@cindex free list
- Unused cons cells are chained together onto a @dfn{free list} for
-future allocation; likewise for symbols and markers. The accessible
-strings are compacted so they are contiguous in memory; then the rest of
-the space formerly occupied by strings is made available to the string
-creation functions. Vectors, buffers, windows and other large objects
-are individually allocated and freed using @code{malloc}.
+ The sweep phase puts unused cons cells onto a @dfn{free list}
+for future allocation; likewise for symbols and markers. It compacts
+the accessible strings so they occupy fewer 8k blocks; then it frees the
+other 8k blocks. Vectors, buffers, windows, and other large objects are
+individually allocated and freed using @code{malloc} and @code{free}.
@cindex CL note---allocate more storage
@quotation
-@b{Common Lisp note:} unlike other Lisps, GNU Emacs Lisp does not
+@b{Common Lisp note:} Unlike other Lisps, GNU Emacs Lisp does not
call the garbage collector when the free list is empty. Instead, it
simply requests the operating system to allocate more storage, and
processing continues until @code{gc-cons-threshold} bytes have been
@end quotation
@deffn Command garbage-collect
- This command runs a garbage collection, and returns information on
+This command runs a garbage collection, and returns information on
the amount of space in use. (Garbage collection can also occur
spontaneously if you use more than @code{gc-cons-threshold} bytes of
Lisp data since the previous garbage collection.)
- @code{garbage-collect} returns a list containing the following
+@code{garbage-collect} returns a list containing the following
information:
-@smallexample
+@example
@group
((@var{used-conses} . @var{free-conses})
(@var{used-syms} . @var{free-syms})
- (@var{used-markers} . @var{free-markers})
- @var{used-string-chars}
+@end group
+ (@var{used-miscs} . @var{free-miscs})
+ @var{used-string-chars}
@var{used-vector-slots}
- (@var{used-floats} . @var{free-floats}))
+ (@var{used-floats} . @var{free-floats})
+ (@var{used-intervals} . @var{free-intervals})
+ (@var{used-strings} . @var{free-strings}))
+@end example
+
+Here is an example:
+@example
+@group
(garbage-collect)
- @result{} ((3435 . 2332) (1688 . 0)
- (57 . 417) 24510 3839 (4 . 1))
+ @result{} ((106886 . 13184) (9769 . 0)
+ (7731 . 4651) 347543 121628
+ (31 . 94) (1273 . 168)
+ (25474 . 3569))
@end group
-@end smallexample
+@end example
Here is a table explaining each element:
The number of symbols for which space has been obtained from the
operating system, but that are not currently being used.
-@item used-markers
-The number of markers in use.
+@item used-miscs
+The number of miscellaneous objects in use. These include markers and
+overlays, plus certain objects not visible to users.
-@item free-markers
-The number of markers for which space has been obtained from the
-operating system, but that are not currently being used.
+@item free-miscs
+The number of miscellaneous objects for which space has been obtained
+from the operating system, but that are not currently being used.
@item used-string-chars
The total size of all strings, in characters.
@c Emacs 19 feature
The number of floats for which space has been obtained from the
operating system, but that are not currently being used.
+
+@item used-intervals
+The number of intervals in use. Intervals are an internal
+data structure used for representing text properties.
+
+@item free-intervals
+The number of intervals for which space has been obtained
+from the operating system, but that are not currently being used.
+
+@item used-strings
+The number of strings in use.
+
+@item free-strings
+The number of string headers for which the space was obtained from the
+operating system, but which are currently not in use. (A string
+object consists of a header and the storage for the string text
+itself; the latter is only allocated when the string is created.)
@end table
@end deffn
+@defopt garbage-collection-messages
+If this variable is non-@code{nil}, Emacs displays a message at the
+beginning and end of garbage collection. The default value is
+@code{nil}, meaning there are no such messages.
+@end defopt
+
@defopt gc-cons-threshold
- The value of this variable is the number of bytes of storage that must
+The value of this variable is the number of bytes of storage that must
be allocated for Lisp objects after one garbage collection in order to
-request another garbage collection. A cons cell counts as eight bytes,
+trigger another garbage collection. A cons cell counts as eight bytes,
a string as one byte per character plus a few bytes of overhead, and so
-on. (Space allocated to the contents of buffers does not count.) Note
-that the new garbage collection does not happen immediately when the
-threshold is exhausted, but only the next time the Lisp evaluator is
+on; space allocated to the contents of buffers does not count. Note
+that the subsequent garbage collection does not happen immediately when
+the threshold is exhausted, but only the next time the Lisp evaluator is
called.
- The initial threshold value is 100,000. If you specify a larger
+The initial threshold value is 400,000. If you specify a larger
value, garbage collection will happen less often. This reduces the
amount of time spent garbage collecting, but increases total memory use.
-You may want to do this when running a program which creates lots of
+You may want to do this when running a program that creates lots of
Lisp data.
- You can make collections more frequent by specifying a smaller value,
+You can make collections more frequent by specifying a smaller value,
down to 10,000. A value less than 10,000 will remain in effect only
until the subsequent garbage collection, at which time
@code{garbage-collect} will set the threshold back to 10,000.
@end defopt
+ The value return by @code{garbage-collect} describes the amount of
+memory used by Lisp data, broken down by data type. By contrast, the
+function @code{memory-limit} provides information on the total amount of
+memory Emacs is currently using.
+
@c Emacs 19 feature
@defun memory-limit
This function returns the address of the last byte Emacs has allocated,
memory usage.
@end defun
-@node Writing Emacs Primitives, Object Internals, Garbage Collection, GNU Emacs Internals
+@node Memory Usage
+@section Memory Usage
+
+ These functions and variables give information about the total amount
+of memory allocation that Emacs has done, broken down by data type.
+Note the difference between these and the values returned by
+@code{(garbage-collect)}; those count objects that currently exist, but
+these count the number or size of all allocations, including those for
+objects that have since been freed.
+
+@defvar cons-cells-consed
+The total number of cons cells that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar floats-consed
+The total number of floats that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar vector-cells-consed
+The total number of vector cells that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar symbols-consed
+The total number of symbols that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar string-chars-consed
+The total number of string characters that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar misc-objects-consed
+The total number of miscellaneous objects that have been allocated so
+far in this Emacs session. These include markers and overlays, plus
+certain objects not visible to users.
+@end defvar
+
+@defvar intervals-consed
+The total number of intervals that have been allocated so far
+in this Emacs session.
+@end defvar
+
+@defvar strings-consed
+The total number of strings that have been allocated so far in this
+Emacs session.
+@end defvar
+
+@node Writing Emacs Primitives
@appendixsec Writing Emacs Primitives
@cindex primitive function internals
@smallexample
@group
DEFUN ("or", For, Sor, 0, UNEVALLED, 0,
- "Eval args until one of them yields non-NIL, then return that value.\n\
-The remaining args are not evalled at all.\n\
+ doc: /* Eval args until one of them yields non-nil, then return that value.
+The remaining args are not evalled at all.
+If all args return nil, return nil.
@end group
@group
-If all args return NIL, return NIL.")
+usage: (or CONDITIONS ...) */)
(args)
Lisp_Object args;
@{
@end group
@group
- if (NULL(args))
+ if (NILP (args))
return Qnil;
args_left = args;
do
@{
val = Feval (Fcar (args_left));
- if (!NULL (val))
+ if (!NILP (val))
break;
args_left = Fcdr (args_left);
@}
- while (!NULL(args_left));
+ while (!NILP (args_left));
@end group
@group
@end smallexample
Let's start with a precise explanation of the arguments to the
-@code{DEFUN} macro. Here are the general names for them:
+@code{DEFUN} macro. Here is a template for them:
@example
DEFUN (@var{lname}, @var{fname}, @var{sname}, @var{min}, @var{max}, @var{interactive}, @var{doc})
@table @var
@item lname
-This is the name of the Lisp symbol to define with this
-function; in the example above, it is @code{or}.
+This is the name of the Lisp symbol to define as the function name; in
+the example above, it is @code{or}.
@item fname
This is the C function name for this function. This is
@samp{S}.
@item min
-This is the minimum number of arguments that the function requires. For
-@code{or}, no arguments are required.
+This is the minimum number of arguments that the function requires. The
+function @code{or} allows a minimum of zero arguments.
@item max
-This is the maximum number of arguments that the function accepts.
-Alternatively, it can be @code{UNEVALLED}, indicating a special form
-that receives unevaluated arguments. A function with the equivalent of
-an @code{&rest} argument would have @code{MANY} in this position. Both
-@code{UNEVALLED} and @code{MANY} are macros. This argument must be one
-of these macros or a number at least as large as @var{min}. It may not
-be greater than six.
+This is the maximum number of arguments that the function accepts, if
+there is a fixed maximum. Alternatively, it can be @code{UNEVALLED},
+indicating a special form that receives unevaluated arguments, or
+@code{MANY}, indicating an unlimited number of evaluated arguments (the
+equivalent of @code{&rest}). Both @code{UNEVALLED} and @code{MANY} are
+macros. If @var{max} is a number, it may not be less than @var{min} and
+it may not be greater than seven.
@item interactive
This is an interactive specification, a string such as might be used as
the argument of @code{interactive} in a Lisp function. In the case of
@code{or}, it is 0 (a null pointer), indicating that @code{or} cannot be
-called interactively. A value of @code{""} indicates an interactive
-function taking no arguments.
+called interactively. A value of @code{""} indicates a function that
+should receive no arguments when called interactively.
@item doc
-This is the documentation string. It is written just like a
-documentation string for a function defined in Lisp, except you must
-write @samp{\n\} at the end of each line. In particular, the first line
-should be a single sentence.
+This is the documentation string. It uses C comment syntax rather
+than C string syntax because comment syntax requires nothing special
+to include multiple lines. The @samp{doc:} identifies the comment
+that follows as the documentation string. The @samp{/*} and @samp{*/}
+delimiters that begin and end the comment are not part of the
+documentation string.
+
+If the last line of the documentation string begins with the keyword
+@samp{usage:}, the rest of the line is treated as the argument list
+for documentation purposes. This way, you can use different argument
+names in the documentation string from the ones used in the C code.
+
+All the usual rules for documentation strings in Lisp code
+(@pxref{Documentation Tips}) apply to C code documentation strings
+too.
@end table
- After the call to the @code{DEFUN} macro, you must write the list
-of argument names that every C function must have, followed by
-ordinary C declarations for them. Normally, all the arguments must
-be declared as @code{Lisp_Object}. If the function has no upper limit
-on the number of arguments in Lisp, then in C it receives two arguments:
-the number of Lisp arguments, and the address of a block containing their
-values. These have types @code{int} and @w{@code{Lisp_Object *}}.
+ After the call to the @code{DEFUN} macro, you must write the argument
+name list that every C function must have, followed by ordinary C
+declarations for the arguments. For a function with a fixed maximum
+number of arguments, declare a C argument for each Lisp argument, and
+give them all type @code{Lisp_Object}. When a Lisp function has no
+upper limit on the number of arguments, its implementation in C actually
+receives exactly two arguments: the first is the number of Lisp
+arguments, and the second is the address of a block containing their
+values. They have types @code{int} and @w{@code{Lisp_Object *}}.
Within the function @code{For} itself, note the use of the macros
@code{GCPRO1} and @code{UNGCPRO}. @code{GCPRO1} is used to ``protect''
@code{UNGCPRO} cancels the protection of the variables that are
protected in the current function. It is necessary to do this explicitly.
- For most data types, it suffices to know that one pointer to the
-object is protected; as long as the object is not recycled, all pointers
-to it remain valid. This is not so for strings, because the garbage
-collector can move them. When a string is moved, any pointers to it
-that the garbage collector does not know about will not be properly
-relocated. Therefore, all pointers to strings must be protected across
-any point where garbage collection may be possible.
-
- The macro @code{GCPRO1} protects just one local variable. If you
-want to protect two, use @code{GCPRO2} instead; repeating @code{GCPRO1}
-will not work. There are also @code{GCPRO3} and @code{GCPRO4}.
-
- In addition to using these macros, you must declare the local
-variables such as @code{gcpro1} which they implicitly use. If you
-protect two variables, with @code{GCPRO2}, you must declare
-@code{gcpro1} and @code{gcpro2}, as it uses them both. Alas, we can't
-explain all the tricky details here.
-
- Defining the C function is not enough; you must also create the
-Lisp symbol for the primitive and store a suitable subr object
-in its function cell. This is done by adding code to an initialization
-routine. The code looks like this:
+ For most data types, it suffices to protect at least one pointer to
+the object; as long as the object is not recycled, all pointers to it
+remain valid. This is not so for strings, because the garbage collector
+can move them. When the garbage collector moves a string, it relocates
+all the pointers it knows about; any other pointers become invalid.
+Therefore, you must protect all pointers to strings across any point
+where garbage collection may be possible.
+
+ The macro @code{GCPRO1} protects just one local variable. If you want
+to protect two, use @code{GCPRO2} instead; repeating @code{GCPRO1} will
+not work. Macros @code{GCPRO3} and @code{GCPRO4} also exist.
+
+ These macros implicitly use local variables such as @code{gcpro1}; you
+must declare these explicitly, with type @code{struct gcpro}. Thus, if
+you use @code{GCPRO2}, you must declare @code{gcpro1} and @code{gcpro2}.
+Alas, we can't explain all the tricky details here.
+
+ You must not use C initializers for static or global variables unless
+the variables are never written once Emacs is dumped. These variables
+with initializers are allocated in an area of memory that becomes
+read-only (on certain operating systems) as a result of dumping Emacs.
+@xref{Pure Storage}.
+
+ Do not use static variables within functions---place all static
+variables at top level in the file. This is necessary because Emacs on
+some operating systems defines the keyword @code{static} as a null
+macro. (This definition is used because those systems put all variables
+declared static in a place that becomes read-only after dumping, whether
+they have initializers or not.)
+
+ Defining the C function is not enough to make a Lisp primitive
+available; you must also create the Lisp symbol for the primitive and
+store a suitable subr object in its function cell. The code looks like
+this:
@example
defsubr (&@var{subr-structure-name});
@end example
@noindent
-@var{subr-structure-name} is the name you used as the third argument to
-@code{DEFUN}.
-
- If you are adding a primitive to a file that already has Lisp
-primitives defined in it, find the function (near the end of the file)
-named @code{syms_of_@var{something}}, and add that function call to it.
-If the file doesn't have this function, or if you create a new file, add
-to it a @code{syms_of_@var{filename}} (e.g., @code{syms_of_myfile}).
-Then find the spot in @file{emacs.c} where all of these functions are
-called, and add a call to @code{syms_of_@var{filename}} there.
-
- This function @code{syms_of_@var{filename}} is also the place to
-define any C variables which are to be visible as Lisp variables.
-@code{DEFVAR_LISP} is used to make a C variable of type
-@code{Lisp_Object} visible in Lisp. @code{DEFVAR_INT} is used to make a
-C variable of type @code{int} visible in Lisp with a value that is an
-integer.
-
- Here is another function, with more complicated arguments. This comes
-from the code for the X Window System, and it demonstrates the use of
-macros and functions to manipulate Lisp objects.
+Here @var{subr-structure-name} is the name you used as the third
+argument to @code{DEFUN}.
+
+ If you add a new primitive to a file that already has Lisp primitives
+defined in it, find the function (near the end of the file) named
+@code{syms_of_@var{something}}, and add the call to @code{defsubr}
+there. If the file doesn't have this function, or if you create a new
+file, add to it a @code{syms_of_@var{filename}} (e.g.,
+@code{syms_of_myfile}). Then find the spot in @file{emacs.c} where all
+of these functions are called, and add a call to
+@code{syms_of_@var{filename}} there.
+
+@vindex byte-boolean-vars
+ The function @code{syms_of_@var{filename}} is also the place to define
+any C variables that are to be visible as Lisp variables.
+@code{DEFVAR_LISP} makes a C variable of type @code{Lisp_Object} visible
+in Lisp. @code{DEFVAR_INT} makes a C variable of type @code{int}
+visible in Lisp with a value that is always an integer.
+@code{DEFVAR_BOOL} makes a C variable of type @code{int} visible in Lisp
+with a value that is either @code{t} or @code{nil}. Note that variables
+defined with @code{DEFVAR_BOOL} are automatically added to the list
+@code{byte-boolean-vars} used by the byte compiler.
+
+ If you define a file-scope C variable of type @code{Lisp_Object},
+you must protect it from garbage-collection by calling @code{staticpro}
+in @code{syms_of_@var{filename}}, like this:
+
+@example
+staticpro (&@var{variable});
+@end example
+
+ Here is another example function, with more complicated arguments.
+This comes from the code in @file{window.c}, and it demonstrates the use
+of macros and functions to manipulate Lisp objects.
@smallexample
@group
DEFUN ("coordinates-in-window-p", Fcoordinates_in_window_p,
Scoordinates_in_window_p, 2, 2,
"xSpecify coordinate pair: \nXExpression which evals to window: ",
- "Return non-nil if POSITIONS is in WINDOW.\n\
- \(POSITIONS is a list, (SCREEN-X SCREEN-Y)\)\n\
+ "Return non-nil if COORDINATES is in WINDOW.\n\
+COORDINATES is a cons of the form (X . Y), X and Y being distances\n\
+...
@end group
@group
- Returned value is list of positions expressed\n\
- relative to window upper left corner.")
- (coordinate, window)
- register Lisp_Object coordinate, window;
+If they are on the border between WINDOW and its right sibling,\n\
+ `vertical-line' is returned.")
+ (coordinates, window)
+ register Lisp_Object coordinates, window;
@{
- register Lisp_Object xcoord, ycoord;
+ int x, y;
@end group
@group
- if (!CONSP (coordinate)) wrong_type_argument (Qlistp, coordinate);
- CHECK_WINDOW (window, 2);
- xcoord = Fcar (coordinate);
- ycoord = Fcar (Fcdr (coordinate));
- CHECK_NUMBER (xcoord, 0);
- CHECK_NUMBER (ycoord, 1);
+ CHECK_LIVE_WINDOW (window, 0);
+ CHECK_CONS (coordinates, 1);
+ x = XINT (Fcar (coordinates));
+ y = XINT (Fcdr (coordinates));
@end group
+
@group
- if ((XINT (xcoord) < XINT (XWINDOW (window)->left))
- || (XINT (xcoord) >= (XINT (XWINDOW (window)->left)
- + XINT (XWINDOW (window)->width))))
+ switch (coordinates_in_window (XWINDOW (window), &x, &y))
@{
+ case 0: /* NOT in window at all. */
return Qnil;
- @}
- XFASTINT (xcoord) -= XFASTINT (XWINDOW (window)->left);
@end group
+
@group
- if (XINT (ycoord) == (screen_height - 1))
- return Qnil;
+ case 1: /* In text part of window. */
+ return Fcons (make_number (x), make_number (y));
@end group
+
@group
- if ((XINT (ycoord) < XINT (XWINDOW (window)->top))
- || (XINT (ycoord) >= (XINT (XWINDOW (window)->top)
- + XINT (XWINDOW (window)->height)) - 1))
- @{
- return Qnil;
- @}
+ case 2: /* In mode line of window. */
+ return Qmode_line;
+@end group
+
+@group
+ case 3: /* On right border of window. */
+ return Qvertical_line;
@end group
+
@group
- XFASTINT (ycoord) -= XFASTINT (XWINDOW (window)->top);
- return (Fcons (xcoord, Fcons (ycoord, Qnil)));
+ default:
+ abort ();
+ @}
@}
@end group
@end smallexample
- Note that you cannot directly call functions defined in Lisp as, for
-example, the primitive function @code{Fcons} is called above. You must
-create the appropriate Lisp form, protect everything from garbage
-collection, and @code{Feval} the form, as was done in @code{For} above.
+ Note that C code cannot call functions by name unless they are defined
+in C. The way to call a function written in Lisp is to use
+@code{Ffuncall}, which embodies the Lisp function @code{funcall}. Since
+the Lisp function @code{funcall} accepts an unlimited number of
+arguments, in C it takes two: the number of Lisp-level arguments, and a
+one-dimensional array containing their values. The first Lisp-level
+argument is the Lisp function to call, and the rest are the arguments to
+pass to it. Since @code{Ffuncall} can call the evaluator, you must
+protect pointers from garbage collection around the call to
+@code{Ffuncall}.
+
+ The C functions @code{call0}, @code{call1}, @code{call2}, and so on,
+provide handy ways to call a Lisp function conveniently with a fixed
+number of arguments. They work by calling @code{Ffuncall}.
@file{eval.c} is a very good file to look through for examples;
@file{lisp.h} contains the definitions for some important macros and
functions.
-@node Object Internals, , Writing Emacs Primitives, GNU Emacs Internals
+ If you define a function which is side-effect free, update the code in
+@file{byte-opt.el} which binds @code{side-effect-free-fns} and
+@code{side-effect-and-error-free-fns} to include it. This will help the
+optimizer.
+
+@node Object Internals
@appendixsec Object Internals
@cindex object internals
GNU Emacs Lisp manipulates many different types of data. The actual
-data are stored in a heap and the only access that programs have to it is
-through pointers. Pointers are thirty-two bits wide in most
+data are stored in a heap and the only access that programs have to it
+is through pointers. Pointers are thirty-two bits wide in most
implementations. Depending on the operating system and type of machine
-for which you compile Emacs, twenty-four to twenty-six bits are used to
-address the object, and the remaining six to eight bits are used for a
+for which you compile Emacs, twenty-eight bits are used to address the
+object, and the remaining four bits are used for a GC mark bit and the
tag that identifies the object's type.
- Because all access to data is through tagged pointers, it is always
-possible to determine the type of any object. This allows variables to
-be untyped, and the values assigned to them to be changed without regard
-to type. Function arguments also can be of any type; if you want a
-function to accept only a certain type of argument, you must check the
-type explicitly using a suitable predicate (@pxref{Type Predicates}).
+ Because Lisp objects are represented as tagged pointers, it is always
+possible to determine the Lisp data type of any object. The C data type
+@code{Lisp_Object} can hold any Lisp object of any data type. Ordinary
+variables have type @code{Lisp_Object}, which means they can hold any
+type of Lisp value; you can determine the actual data type only at run
+time. The same is true for function arguments; if you want a function
+to accept only a certain type of argument, you must check the type
+explicitly using a suitable predicate (@pxref{Type Predicates}).
@cindex type checking internals
@menu
* Process Internals:: Components of a process structure.
@end menu
-@node Buffer Internals, Window Internals, Object Internals, Object Internals
+@node Buffer Internals
@appendixsubsec Buffer Internals
@cindex internals, of buffer
@cindex buffer internals
We describe them here, naming them by the names used in the C code.
Many are accessible indirectly in Lisp programs via Lisp primitives.
+Two structures are used to represent buffers in C. The
+@code{buffer_text} structure contains fields describing the text of a
+buffer; the @code{buffer} structure holds other fields. In the case
+of indirect buffers, two or more @code{buffer} structures reference
+the same @code{buffer_text} structure.
+
+Here is a list of the @code{struct buffer_text} fields:
+
@table @code
-@item name
-The buffer name is a string which names the buffer. It is guaranteed to
-be unique. @xref{Buffer Names}.
+@item beg
+This field contains the actual address of the buffer contents.
+
+@item gpt
+This holds the character position of the gap in the buffer.
+
+@item z
+This field contains the character position of the end of the buffer
+text.
+
+@item gpt_byte
+Contains the byte position of the gap.
+
+@item z_byte
+Holds the byte position of the end of the buffer text.
+
+@item gap_size
+Contains the size of buffer's gap.
+
+@item modiff
+This field counts buffer-modification events for this buffer. It is
+incremented for each such event, and never otherwise changed.
+
+@item save_modiff
+Contains the previous value of @code{modiff}, as of the last time a
+buffer was visited or saved in a file.
+
+@item overlay_modiff
+Counts modifications to overlays analogous to @code{modiff}.
+
+@item beg_unchanged
+Holds the number of characters at the start of the text that are known
+to be unchanged since the last redisplay that finished.
+
+@item end_unchanged
+Holds the number of characters at the end of the text that are known to
+be unchanged since the last redisplay that finished.
+
+@item unchanged_modified
+Contains the value of @code{modiff} at the time of the last redisplay
+that finished. If this value matches @code{modiff},
+@code{beg_unchanged} and @code{end_unchanged} contain no useful
+information.
+
+@item overlay_unchanged_modified
+Contains the value of @code{overlay_modiff} at the time of the last
+redisplay that finished. If this value matches @code{overlay_modiff},
+@code{beg_unchanged} and @code{end_unchanged} contain no useful
+information.
+
+@item markers
+The markers that refer to this buffer. This is actually a single
+marker, and successive elements in its marker @code{chain} are the other
+markers referring to this buffer text.
-@item save_modified
-This field contains the time when the buffer was last saved, as an integer.
-@xref{Buffer Modification}.
+@item intervals
+Contains the interval tree which records the text properties of this
+buffer.
+@end table
+
+The fields of @code{struct buffer} are:
+
+@table @code
+@item next
+Points to the next buffer, in the chain of all buffers including killed
+buffers. This chain is used only for garbage collection, in order to
+collect killed buffers properly. Note that vectors, and most kinds of
+objects allocated as vectors, are all on one chain, but buffers are on a
+separate chain of their own.
+
+@item own_text
+This is a @code{struct buffer_text} structure. In an ordinary buffer,
+it holds the buffer contents. In indirect buffers, this field is not
+used.
+
+@item text
+This points to the @code{buffer_text} structure that is used for this
+buffer. In an ordinary buffer, this is the @code{own_text} field above.
+In an indirect buffer, this is the @code{own_text} field of the base
+buffer.
+
+@item pt
+Contains the character position of point in a buffer.
+
+@item pt_byte
+Contains the byte position of point in a buffer.
+
+@item begv
+This field contains the character position of the beginning of the
+accessible range of text in the buffer.
+
+@item begv_byte
+This field contains the byte position of the beginning of the
+accessible range of text in the buffer.
+
+@item zv
+This field contains the character position of the end of the
+accessible range of text in the buffer.
+
+@item zv_byte
+This field contains the byte position of the end of the
+accessible range of text in the buffer.
+
+@item base_buffer
+In an indirect buffer, this points to the base buffer. In an ordinary
+buffer, it is null.
+
+@item local_var_flags
+This field contains flags indicating that certain variables are local in
+this buffer. Such variables are declared in the C code using
+@code{DEFVAR_PER_BUFFER}, and their buffer-local bindings are stored in
+fields in the buffer structure itself. (Some of these fields are
+described in this table.)
@item modtime
This field contains the modification time of the visited file. It is
-set when the file is written or read. Every time the buffer is written
-to the file, this field is compared to the modification time of the
-file. @xref{Buffer Modification}.
+set when the file is written or read. Before writing the buffer into a
+file, this field is compared to the modification time of the file to see
+if the file has changed on disk. @xref{Buffer Modification}.
@item auto_save_modified
This field contains the time when the buffer was last auto-saved.
+@item auto_save_failure_time
+The time at which we detected a failure to auto-save, or -1 if we didn't
+have a failure.
+
@item last_window_start
This field contains the @code{window-start} position in the buffer as of
the last time the buffer was displayed in a window.
-@item undodata
-This field points to the buffer's undo stack. @xref{Undo}.
+@item clip_changed
+This flag is set when narrowing changes in a buffer.
+
+@item prevent_redisplay_optimizations_p
+this flag indicates that redisplay optimizations should not be used
+to display this buffer.
+
+@item undo_list
+This field points to the buffer's undo list. @xref{Undo}.
+
+@item name
+The buffer name is a string that names the buffer. It is guaranteed to
+be unique. @xref{Buffer Names}.
+
+@item filename
+The name of the file visited in this buffer, or @code{nil}.
+
+@item directory
+The directory for expanding relative file names.
+
+@item save_length
+Length of the file this buffer is visiting, when last read or saved.
+This and other fields concerned with saving are not kept in the
+@code{buffer_text} structure because indirect buffers are never saved.
-@item syntax_table_v
+@item auto_save_file_name
+File name used for auto-saving this buffer. This is not in the
+@code{buffer_text} because it's not used in indirect buffers at all.
+
+@item read_only
+Non-@code{nil} means this buffer is read-only.
+
+@item mark
+This field contains the mark for the buffer. The mark is a marker,
+hence it is also included on the list @code{markers}. @xref{The Mark}.
+
+@item local_var_alist
+This field contains the association list describing the buffer-local
+variable bindings of this buffer, not including the built-in
+buffer-local bindings that have special slots in the buffer object.
+(Those slots are omitted from this table.) @xref{Buffer-Local
+Variables}.
+
+@item major_mode
+Symbol naming the major mode of this buffer, e.g., @code{lisp-mode}.
+
+@item mode_name
+Pretty name of major mode, e.g., @code{"Lisp"}.
+
+@item mode_line_format
+Mode line element that controls the format of the mode line. If this
+is @code{nil}, no mode line will be displayed.
+
+@item header_line_format
+This field is analoguous to @code{mode_line_format} for the mode
+line displayed at the top of windows.
+
+@item keymap
+This field holds the buffer's local keymap. @xref{Keymaps}.
+
+@item abbrev_table
+This buffer's local abbrevs.
+
+@item syntax_table
This field contains the syntax table for the buffer. @xref{Syntax Tables}.
+@item category_table
+This field contains the category table for the buffer.
+
+@item case_fold_search
+The value of @code{case-fold-search} in this buffer.
+
+@item tab_width
+The value of @code{tab-width} in this buffer.
+
+@item fill_column
+The value of @code{fill-column} in this buffer.
+
+@item left_margin
+The value of @code{left-margin} in this buffer.
+
+@item auto_fill_function
+The value of @code{auto-fill-function} in this buffer.
+
@item downcase_table
This field contains the conversion table for converting text to lower case.
-@xref{Case Table}.
+@xref{Case Tables}.
@item upcase_table
This field contains the conversion table for converting text to upper case.
-@xref{Case Table}.
+@xref{Case Tables}.
@item case_canon_table
This field contains the conversion table for canonicalizing text for
-case-folding search. @xref{Case Table}.
+case-folding search. @xref{Case Tables}.
@item case_eqv_table
This field contains the equivalence table for case-folding search.
-@xref{Case Table}.
+@xref{Case Tables}.
+
+@item truncate_lines
+The value of @code{truncate-lines} in this buffer.
+
+@item ctl_arrow
+The value of @code{ctl-arrow} in this buffer.
+
+@item selective_display
+The value of @code{selective-display} in this buffer.
+
+@item selective_display_ellipsis
+The value of @code{selective-display-ellipsis} in this buffer.
+
+@item minor_modes
+An alist of the minor modes of this buffer.
+
+@item overwrite_mode
+The value of @code{overwrite_mode} in this buffer.
+
+@item abbrev_mode
+The value of @code{abbrev-mode} in this buffer.
@item display_table
This field contains the buffer's display table, or @code{nil} if it doesn't
have one. @xref{Display Tables}.
-@item markers
-This field contains the chain of all markers that point into the
-buffer. At each deletion or motion of the buffer gap, all of these
-markers must be checked and perhaps updated. @xref{Markers}.
+@item save_modified
+This field contains the time when the buffer was last saved, as an integer.
+@xref{Buffer Modification}.
-@item backed_up
-This field is a flag which tells whether a backup file has been made
-for the visited file of this buffer.
+@item mark_active
+This field is non-@code{nil} if the buffer's mark is active.
-@item mark
-This field contains the mark for the buffer. The mark is a marker,
-hence it is also included on the list @code{markers}. @xref{The Mark}.
+@item overlays_before
+This field holds a list of the overlays in this buffer that end at or
+before the current overlay center position. They are sorted in order of
+decreasing end position.
-@item local_var_alist
-This field contains the association list containing all of the variables
-local in this buffer, and their values. The function
-@code{buffer-local-variables} returns a copy of this list.
-@xref{Buffer-Local Variables}.
+@item overlays_after
+This field holds a list of the overlays in this buffer that end after
+the current overlay center position. They are sorted in order of
+increasing beginning position.
-@item mode_line_format
-This field contains a Lisp object which controls how to display the mode
-line for this buffer. @xref{Mode Line Format}.
+@item overlay_center
+This field holds the current overlay center position. @xref{Overlays}.
+
+@item enable_multibyte_characters
+This field holds the buffer's local value of
+@code{enable-multibyte-characters}---either @code{t} or @code{nil}.
+
+@item buffer_file_coding_system
+The value of @code{buffer-file-coding-system} in this buffer.
+
+@item file_format
+The value of @code{buffer-file-format} in this buffer.
+
+@item pt_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records point for this buffer when the
+buffer is not current.
+
+@item begv_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records @code{begv} for this buffer
+when the buffer is not current.
+
+@item zv_marker
+In an indirect buffer, or a buffer that is the base of an indirect
+buffer, this holds a marker that records @code{zv} for this buffer when
+the buffer is not current.
+
+@item file_truename
+The truename of the visited file, or @code{nil}.
+
+@item invisibility_spec
+The value of @code{buffer-invisibility-spec} in this buffer.
+
+@item last_selected_window
+This is the last window that was selected with this buffer in it, or @code{nil}
+if that window no longer displays this buffer.
+
+@item display_count
+This field is incremented each time the buffer is displayed in a window.
+
+@item left_margin_width
+The value of @code{left-margin-width} in this buffer.
+
+@item right_margin_width
+The value of @code{right-margin-width} in this buffer.
+
+@item indicate_empty_lines
+Non-@code{nil} means indicate empty lines (lines with no text) with a
+small bitmap in the fringe, when using a window system that can do it.
+
+@item display_time
+This holds a time stamp that is updated each time this buffer is
+displayed in a window.
+
+@item scroll_up_aggressively
+The value of @code{scroll-up-aggressively} in this buffer.
+
+@item scroll_down_aggressively
+The value of @code{scroll-down-aggressively} in this buffer.
@end table
-@node Window Internals, Process Internals, Buffer Internals, Object Internals
+@node Window Internals
@appendixsubsec Window Internals
@cindex internals, of window
@cindex window internals
@table @code
@item frame
- The frame that this window is on.
+The frame that this window is on.
@item mini_p
- Non-@code{nil} if this window is a minibuffer window.
+Non-@code{nil} if this window is a minibuffer window.
+
+@item parent
+Internally, Emacs arranges windows in a tree; each group of siblings has
+a parent window whose area includes all the siblings. This field points
+to a window's parent.
+
+Parent windows do not display buffers, and play little role in display
+except to shape their child windows. Emacs Lisp programs usually have
+no access to the parent windows; they operate on the windows at the
+leaves of the tree, which actually display buffers.
+
+The following four fields also describe the window tree structure.
+
+@item hchild
+In a window subdivided horizontally by child windows, the leftmost child.
+Otherwise, @code{nil}.
+
+@item vchild
+In a window subdivided vertically by child windows, the topmost child.
+Otherwise, @code{nil}.
+
+@item next
+The next sibling of this window. It is @code{nil} in a window that is
+the rightmost or bottommost of a group of siblings.
+
+@item prev
+The previous sibling of this window. It is @code{nil} in a window that
+is the leftmost or topmost of a group of siblings.
+
+@item left
+This is the left-hand edge of the window, measured in columns. (The
+leftmost column on the screen is @w{column 0}.)
+
+@item top
+This is the top edge of the window, measured in lines. (The top line on
+the screen is @w{line 0}.)
@item height
- The height of the window, measured in lines.
+The height of the window, measured in lines.
@item width
- The width of the window, measured in columns.
+The width of the window, measured in columns. This width includes the
+scroll bar and fringes, and/or the separator line on the right of the
+window (if any).
@item buffer
- The buffer which the window is displaying. This may change often during
+The buffer that the window is displaying. This may change often during
the life of the window.
-@item dedicated
- Non-@code{nil} if this window is dedicated to its buffer.
-
@item start
- The position in the buffer which is the first character to be displayed
+The position in the buffer that is the first character to be displayed
in the window.
@item pointm
@cindex window point internals
- This is the value of point in the current buffer when this window is
+This is the value of point in the current buffer when this window is
selected; when it is not selected, it retains its previous value.
-@item left
- This is the left-hand edge of the window, measured in columns. (The
-leftmost column on the screen is @w{column 0}.)
+@item force_start
+If this flag is non-@code{nil}, it says that the window has been
+scrolled explicitly by the Lisp program. This affects what the next
+redisplay does if point is off the screen: instead of scrolling the
+window to show the text around point, it moves point to a location that
+is on the screen.
-@item top
- This is the top edge of the window, measured in lines. (The top line on
-the screen is @w{line 0}.)
+@item frozen_window_start_p
+This field is set temporarily to 1 to indicate to redisplay that
+@code{start} of this window should not be changed, even if point
+gets invisible.
-@item next
- This is the window that is the next in the chain of siblings.
+@item start_at_line_beg
+Non-@code{nil} means current value of @code{start} was the beginning of a line
+when it was chosen.
-@item prev
- This is the window that is the previous in the chain of siblings.
+@item too_small_ok
+Non-@code{nil} means don't delete this window for becoming ``too small''.
-@item force_start
- This is a flag which, if non-@code{nil}, says that the window has been
-scrolled explicitly by the Lisp program. At the next redisplay, if
-point is off the screen, instead of scrolling the window to show the
-text around point, point will be moved to a location that is on the
-screen.
+@item height_fixed_p
+This field is temporarily set to 1 to fix the height of the selected
+window when the echo area is resized.
+
+@item use_time
+This is the last time that the window was selected. The function
+@code{get-lru-window} uses this field.
+
+@item sequence_number
+A unique number assigned to this window when it was created.
+
+@item last_modified
+The @code{modiff} field of the window's buffer, as of the last time
+a redisplay completed in this window.
+
+@item last_overlay_modified
+The @code{overlay_modiff} field of the window's buffer, as of the last
+time a redisplay completed in this window.
+
+@item last_point
+The buffer's value of point, as of the last time a redisplay completed
+in this window.
+
+@item last_had_star
+A non-@code{nil} value means the window's buffer was ``modified'' when the
+window was last updated.
+
+@item vertical_scroll_bar
+This window's vertical scroll bar.
+
+@item left_margin_width
+The width of the left margin in this window, or @code{nil} not to
+specify it (in which case the buffer's value of @code{left-margin-width}
+is used.
+
+@item right_margin_width
+Likewise for the right margin.
+
+@ignore
+@item last_mark_x
+@item last_mark_y
+???Not used.
+@end ignore
+
+@item window_end_pos
+This is computed as @code{z} minus the buffer position of the last glyph
+in the current matrix of the window. The value is only valid if
+@code{window_end_valid} is not @code{nil}.
+
+@item window_end_bytepos
+The byte position corresponding to @code{window_end_pos}.
+
+@item window_end_vpos
+The window-relative vertical position of the line containing
+@code{window_end_pos}.
+
+@item window_end_valid
+This field is set to a non-@code{nil} value if @code{window_end_pos} is truly
+valid. This is @code{nil} if nontrivial redisplay is preempted since in that
+case the display that @code{window_end_pos} was computed for did not get
+onto the screen.
+
+@item redisplay_end_trigger
+If redisplay in this window goes beyond this buffer position, it runs
+run the @code{redisplay-end-trigger-hook}.
+
+@ignore
+@item orig_height
+@item orig_top
+??? Are temporary storage areas.
+@end ignore
+
+@item cursor
+A structure describing where the cursor is in this window.
+
+@item last_cursor
+The value of @code{cursor} as of the last redisplay that finished.
+
+@item phys_cursor
+A structure describing where the cursor of this window physically is.
+
+@item phys_cursor_type
+The type of cursor that was last displayed on this window.
+
+@item phys_cursor_on_p
+This field is non-zero if the cursor is physically on.
+
+@item cursor_off_p
+Non-zero means the cursor in this window is logically on.
+
+@item last_cursor_off_p
+This field contains the value of @code{cursor_off_p} as of the time of
+the last redisplay.
+
+@item must_be_updated_p
+This is set to 1 during redisplay when this window must be updated.
@item hscroll
- This is the number of columns that the display in the window is scrolled
+This is the number of columns that the display in the window is scrolled
horizontally to the left. Normally, this is 0.
-@item use_time
- This is the last time that the window was selected. The function
-@code{get-lru-window} uses this field.
+@item vscroll
+Vertical scroll amount, in pixels. Normally, this is 0.
+
+@item dedicated
+Non-@code{nil} if this window is dedicated to its buffer.
@item display_table
- The window's display table, or @code{nil} if none is specified for it.
+The window's display table, or @code{nil} if none is specified for it.
+
+@item update_mode_line
+Non-@code{nil} means this window's mode line needs to be updated.
+
+@item base_line_number
+The line number of a certain position in the buffer, or @code{nil}.
+This is used for displaying the line number of point in the mode line.
+
+@item base_line_pos
+The position in the buffer for which the line number is known, or
+@code{nil} meaning none is known.
+
+@item region_showing
+If the region (or part of it) is highlighted in this window, this field
+holds the mark position that made one end of that region. Otherwise,
+this field is @code{nil}.
+
+@item column_number_displayed
+The column number currently displayed in this window's mode line, or @code{nil}
+if column numbers are not being displayed.
+
+@item current_matrix
+A glyph matrix describing the current display of this window.
+
+@item desired_matrix
+A glyph matrix describing the desired display of this window.
@end table
-@node Process Internals, , Window Internals, Object Internals
+@node Process Internals
@appendixsubsec Process Internals
@cindex internals, of process
@cindex process internals
A flag, non-@code{nil} if this is really a child process.
It is @code{nil} for a network connection.
-@item flags
-A symbol indicating the state of the process. Possible values include
-@code{run}, @code{stop}, @code{closed}, etc.
-
-@item reason
-An integer, the Unix signal number that the process received that
-caused the process to terminate or stop. If the process has exited,
-then this is the exit code it specified.
-
@item mark
-A marker indicating the position of end of last output from this process
-inserted into the buffer. This is usually the end of the buffer.
+A marker indicating the position of the end of the last output from this
+process inserted into the buffer. This is often but not always the end
+of the buffer.
@item kill_without_query
-A flag, non-@code{nil} meaning this process should not cause
-confirmation to be needed if Emacs is killed.
+If this is non-@code{nil}, killing Emacs while this process is still
+running does not ask for confirmation about killing the process.
+
+@item raw_status_low
+@itemx raw_status_high
+These two fields record 16 bits each of the process status returned by
+the @code{wait} system call.
+
+@item status
+The process status, as @code{process-status} should return it.
+
+@item tick
+@itemx update_tick
+If these two fields are not equal, a change in the status of the process
+needs to be reported, either by running the sentinel or by inserting a
+message in the process buffer.
+
+@item pty_flag
+Non-@code{nil} if communication with the subprocess uses a @sc{pty};
+@code{nil} if it uses a pipe.
+
+@item infd
+The file descriptor for input from the process.
+
+@item outfd
+The file descriptor for output to the process.
+
+@item subtty
+The file descriptor for the terminal that the subprocess is using. (On
+some systems, there is no need to record this, so the value is
+@code{nil}.)
+
+@item tty_name
+The name of the terminal that the subprocess is using,
+or @code{nil} if it is using pipes.
+
+@item decode_coding_system
+Coding-system for decoding the input from this process.
+
+@item decoding_buf
+A working buffer for decoding.
+
+@item decoding_carryover
+Size of carryover in decoding.
+
+@item encode_coding_system
+Coding-system for encoding the output to this process.
+
+@item encoding_buf
+A working buffer for enecoding.
+
+@item encoding_carryover
+Size of carryover in encoding.
+
+@item inherit_coding_system_flag
+Flag to set @code{coding-system} of the process buffer from the
+coding system used to decode process output.
@end table
HCoop / bpt / emacs.git / blobdiff