Avoid unnecessary rounding errors in timestamps

[emacs.git] / doc / emacs / msdos.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985-1987, 1993-1995, 1997, 2000-2017 Free Software
@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Microsoft Windows
@appendix Emacs and Microsoft Windows/MS-DOS
@cindex Microsoft Windows
@cindex MS-Windows, Emacs peculiarities

  This section describes peculiarities of using Emacs on Microsoft
Windows.  Some of these peculiarities are also relevant to Microsoft's
older MS-DOS operating system.
However, Emacs features that are relevant @emph{only} to MS-DOS are
described in a separate
@iftex
manual (@pxref{MS-DOS,,, emacs-xtra, Specialized Emacs Features}).
@end iftex
@ifnottex
section (@pxref{MS-DOS}).
@end ifnottex


  The behavior of Emacs on MS-Windows is reasonably similar to what is
documented in the rest of the manual, including support for long file
names, multiple frames, scroll bars, mouse menus, and subprocesses.
However, a few special considerations apply, and they are described
here.

@menu
* Windows Startup::     How to start Emacs on Windows.
* Text and Binary::     Text files use CRLF to terminate lines.
* Windows Files::       File-name conventions on Windows.
* ls in Lisp::          Emulation of @code{ls} for Dired.
* Windows HOME::        Where Emacs looks for your @file{.emacs} and
                          where it starts up.
* Windows Keyboard::    Windows-specific keyboard features.
* Windows Mouse::       Windows-specific mouse features.
* Windows Processes::   Running subprocesses on Windows.
* Windows Printing::    How to specify the printer on MS-Windows.
* Windows Fonts::       Specifying fonts on MS-Windows.
* Windows Misc::        Miscellaneous Windows features.
@ifnottex
* MS-DOS::              Using Emacs on MS-DOS.
@end ifnottex
@end menu

@node Windows Startup
@section How to Start Emacs on MS-Windows
@cindex starting Emacs on MS-Windows

  There are several ways of starting Emacs on MS-Windows:

@enumerate
@item
@pindex runemacs.exe
@cindex desktop shortcut, MS-Windows
@cindex start directory, MS-Windows
@cindex directory where Emacs starts on MS-Windows
From the desktop shortcut icon: either double-click the left mouse
button on the icon, or click once, then press @key{RET}.  The desktop
shortcut should specify as its ``Target'' (in the ``Properties'' of
the shortcut) the full absolute file name of @file{runemacs.exe},
@emph{not} of @file{emacs.exe}.  This is because @file{runemacs.exe}
hides the console window that would have been created if the target of
the shortcut were @file{emacs.exe} (which is a console program, as far
as Windows is concerned).  If you use this method, Emacs starts in the
directory specified by the shortcut.  To control where that is,
right-click on the shortcut, select ``Properties'', and in the
``Shortcut'' tab modify the ``Start in'' field to your liking.

@item
From the Command Prompt window, by typing @kbd{emacs @key{RET}} at the
prompt.  The Command Prompt window where you did that will not be
available for invoking other commands until Emacs exits.  In this
case, Emacs will start in the current directory of the Windows shell.

@item
From the Command Prompt window, by typing @kbd{runemacs @key{RET}} at
the prompt.  The Command Prompt window where you did that will be
immediately available for invoking other commands.  In this case,
Emacs will start in the current directory of the Windows shell.

@item
@cindex invoking Emacs from Windows Explorer
@pindex emacsclient.exe
@pindex emacsclientw.exe
Via @file{emacsclient.exe} or @file{emacsclientw.exe}, which allow you
to invoke Emacs from other programs, and to reuse a running Emacs
process for serving editing jobs required by other programs.
@xref{Emacs Server}.  The difference between @file{emacsclient.exe}
and @file{emacsclientw.exe} is that the former is a console program,
while the latter is a Windows GUI program.  Both programs wait for
Emacs to signal that the editing job is finished, before they exit and
return control to the program that invoked them.  Which one of them to
use in each case depends on the expectations of the program that needs
editing services.  If that program is itself a console (text-mode)
program, you should use @file{emacsclient.exe}, so that any of its
messages and prompts appear in the same command window as those of the
invoking program.  By contrast, if the invoking program is a GUI
program, you will be better off using @file{emacsclientw.exe}, because
@file{emacsclient.exe} will pop up a command window if it is invoked
from a GUI program.  A notable situation where you would want
@file{emacsclientw.exe} is when you right-click on a file in the
Windows Explorer and select ``Open With'' from the pop-up menu.  Use
the @samp{--alternate-editor=} or @samp{-a} options if Emacs might not
be running (or not running as a server) when @command{emacsclient} is
invoked---that will always give you an editor.  When invoked via
@command{emacsclient}, Emacs will start in the current directory of
the program that invoked @command{emacsclient}.
@end enumerate

@cindex emacsclient, on MS-Windows
Note that, due to limitations of MS-Windows, Emacs cannot have both
GUI and text-mode frames in the same session.  It also cannot open
text-mode frames on more than a single @dfn{Command Prompt} window,
because each Windows program can have only one console at any given
time.  For these reasons, if you invoke @command{emacsclient} with the
@option{-c} option, and the Emacs server runs in a text-mode session,
Emacs will always create a new text-mode frame in the same
@dfn{Command Prompt} window where it was started; a GUI frame will be
created only if the server runs in a GUI session.  Similarly, if you
invoke @command{emacsclient} with the @option{-t} option, Emacs will
create a GUI frame if the server runs in a GUI session, or a text-mode
frame when the session runs in text mode in a @dfn{Command Prompt}
window.  @xref{emacsclient Options}.

@node Text and Binary
@section Text Files and Binary Files
@cindex text and binary files on MS-DOS/MS-Windows

  GNU Emacs uses newline characters to separate text lines.  This is the
convention used on GNU, Unix, and other Posix-compliant systems.

@cindex end-of-line conversion on MS-DOS/MS-Windows
  By contrast, MS-DOS and MS-Windows normally use carriage-return linefeed,
a two-character sequence, to separate text lines.  (Linefeed is the same
character as newline.)  Therefore, convenient editing of typical files
with Emacs requires conversion of these end-of-line (EOL) sequences.
And that is what Emacs normally does: it converts carriage-return
linefeed into newline when reading files, and converts newline into
carriage-return linefeed when writing files.  The same mechanism that
handles conversion of international character codes does this conversion
also (@pxref{Coding Systems}).

@cindex cursor location, on MS-DOS
@cindex point location, on MS-DOS
  One consequence of this special format-conversion of most files is
that character positions as reported by Emacs (@pxref{Position Info}) do
not agree with the file size information known to the operating system.

  In addition, if Emacs recognizes from a file's contents that it uses
newline rather than carriage-return linefeed as its line separator, it
does not perform EOL conversion when reading or writing that file.
Thus, you can read and edit files from GNU and Unix systems on MS-DOS
with no special effort, and they will retain their Unix-style
end-of-line convention after you edit them.

  The mode line indicates whether end-of-line translation was used for
the current buffer.  If MS-DOS end-of-line translation is in use for the
buffer, the MS-Windows build of Emacs displays a backslash @samp{\} after
the coding system mnemonic near the beginning of the mode line
(@pxref{Mode Line}).  If no EOL translation was performed, the string
@samp{(Unix)} is displayed instead of the backslash, to alert you that the
file's EOL format is not the usual carriage-return linefeed.

@cindex DOS-to-Unix conversion of files
  To visit a file and specify whether it uses DOS-style or Unix-style
end-of-line, specify a coding system (@pxref{Text Coding}).  For
example, @kbd{C-x @key{RET} c unix @key{RET} C-x C-f foobar.txt}
visits the file @file{foobar.txt} without converting the EOLs; if some
line ends with a carriage-return linefeed pair, Emacs will display
@samp{^M} at the end of that line.  Similarly, you can direct Emacs to
save a buffer in a specified EOL format with the @kbd{C-x @key{RET} f}
command.  For example, to save a buffer with Unix EOL format, type
@kbd{C-x @key{RET} f unix @key{RET} C-x C-s}.  If you visit a file
with DOS EOL conversion, then save it with Unix EOL format, that
effectively converts the file to Unix EOL style, like the
@code{dos2unix} program.

@cindex untranslated file system
@findex add-untranslated-filesystem
  When you use NFS, Samba, or some other similar method to access file
systems that reside on computers using GNU or Unix systems, Emacs
should not perform end-of-line translation on any files in these file
systems---not even when you create a new file.  To request this,
designate these file systems as @dfn{untranslated} file systems by
calling the function @code{add-untranslated-filesystem}.  It takes one
argument: the file system name, including a drive letter and
optionally a directory.  For example,

@example
(add-untranslated-filesystem "Z:")
@end example

@noindent
designates drive Z as an untranslated file system, and

@example
(add-untranslated-filesystem "Z:\\foo")
@end example

@noindent
designates directory @file{\foo} on drive Z as an untranslated file
system.

  Most often you would use @code{add-untranslated-filesystem} in your
@file{.emacs} file, or in @file{site-start.el} so that all the users at
your site get the benefit of it.

@findex remove-untranslated-filesystem
  To countermand the effect of @code{add-untranslated-filesystem}, use
the function @code{remove-untranslated-filesystem}.  This function takes
one argument, which should be a string just like the one that was used
previously with @code{add-untranslated-filesystem}.

  Designating a file system as untranslated does not affect character
set conversion, only end-of-line conversion.  Essentially, it directs
Emacs to create new files with the Unix-style convention of using
newline at the end of a line.  @xref{Coding Systems}.

@node Windows Files
@section File Names on MS-Windows
@cindex file names on MS-Windows

  MS-Windows and MS-DOS normally use a backslash, @samp{\}, to
separate name units within a file name, instead of the slash used on
other systems.  Emacs on MS-DOS/MS-Windows permits use of either slash or
backslash, and also knows about drive letters in file names.

@cindex file-name completion, on MS-Windows
  On MS-DOS/MS-Windows, file names are case-insensitive, so Emacs by
default ignores letter-case in file names during completion.

@vindex w32-get-true-file-attributes
  The variable @code{w32-get-true-file-attributes} controls whether
Emacs should issue additional system calls to determine more
accurately file attributes in primitives like @code{file-attributes}
and @code{directory-files-and-attributes}.  These additional calls are
needed to report correct file ownership, link counts and file types
for special files such as pipes.  Without these system calls, file
ownership will be attributed to the current user, link counts will be
always reported as 1, and special files will be reported as regular
files.

  If the value of this variable is @code{local} (the default), Emacs
will issue these additional system calls only for files on local fixed
drives.  Any other non-@code{nil} value means do this even for
removable and remote volumes, where this could potentially slow down
Dired and other related features.  The value of @code{nil} means never
issue those system calls.  Non-@code{nil} values are more useful on
NTFS volumes, which support hard links and file security, than on FAT,
FAT32, and exFAT volumes.

@cindex file names, invalid characters on MS-Windows
  Unlike Unix, MS-Windows file systems restrict the set of characters
that can be used in a file name.  The following characters are not
allowed:

@itemize @bullet
@item
Shell redirection symbols @samp{<}, @samp{>}, and @samp{|}.

@item
Colon @samp{:} (except after the drive letter).

@item
Forward slash @samp{/} and backslash @samp{\} (except as directory
separators).

@item
Wildcard characters @samp{*} and @samp{?}.

@item
Control characters whose codepoints are 1 through 31 decimal.  In
particular, newlines in file names are not allowed.

@item
The null character, whose codepoint is zero (this limitation exists on
Unix filesystems as well).
@end itemize

@noindent
In addition, referencing any file whose name matches a DOS character
device, such as @file{NUL} or @file{LPT1} or @file{PRN} or @file{CON},
with or without any file-name extension, will always resolve to those
character devices, in any directory.  Therefore, only use such file
names when you want to use the corresponding character device.

@node ls in Lisp
@section Emulation of @code{ls} on MS-Windows
@cindex Dired, and MS-Windows/MS-DOS
@cindex @code{ls} emulation

  Dired normally uses the external program @code{ls}
to produce the directory listing displayed in Dired
buffers (@pxref{Dired}).  However, MS-Windows and MS-DOS systems don't
come with such a program, although several ports of @sc{gnu} @code{ls}
are available.  Therefore, Emacs on those systems @emph{emulates}
@code{ls} in Lisp, by using the @file{ls-lisp.el} package.  While
@file{ls-lisp.el} provides a reasonably full emulation of @code{ls},
there are some options and features peculiar to that emulation;
@iftex
for more details, see the documentation of the variables whose names
begin with @code{ls-lisp}.
@end iftex
@ifnottex
they are described in this section.

  The @code{ls} emulation supports many of the @code{ls} switches, but
it doesn't support all of them.  Here's the list of the switches it
does support: @option{-A}, @option{-a}, @option{-B}, @option{-C},
@option{-c}, @option{-G}, @option{-g}, @option{-h}, @option{-i}, @option{-n},
@option{-R}, @option{-r}, @option{-S}, @option{-s}, @option{-t}, @option{-U},
@option{-u}, and @option{-X}.  The @option{-F} switch is partially
supported (it appends the character that classifies the file, but does
not prevent symlink following).

@vindex ls-lisp-use-insert-directory-program
  On MS-Windows and MS-DOS, @file{ls-lisp.el} is preloaded when Emacs
is built, so the Lisp emulation of @code{ls} is always used on those
platforms.  If you have a ported @code{ls}, setting
@code{ls-lisp-use-insert-directory-program} to a non-@code{nil} value
will revert to using an external program named by the variable
@code{insert-directory-program}.

@vindex ls-lisp-ignore-case
  By default, @file{ls-lisp.el} uses a case-sensitive sort order for
the directory listing it produces; this is so the listing looks the
same as on other platforms.  If you wish that the files be sorted in
case-insensitive order, set the variable @code{ls-lisp-ignore-case} to
a non-@code{nil} value.

@vindex ls-lisp-dirs-first
  By default, files and subdirectories are sorted together, to emulate
the behavior of @code{ls}.  However, native MS-Windows/MS-DOS file
managers list the directories before the files; if you want that
behavior, customize the option @code{ls-lisp-dirs-first} to a
non-@code{nil} value.

@vindex ls-lisp-verbosity
  The variable @code{ls-lisp-verbosity} controls the file attributes
that @file{ls-lisp.el} displays.  The value should be a list that
contains one or more of the symbols @code{links}, @code{uid}, and
@code{gid}.  @code{links} means display the count of different file
names that are associated with (a.k.a.@: @dfn{links to}) the file's
data; this is only useful on NTFS volumes.  @code{uid} means display
the numerical identifier of the user who owns the file.  @code{gid}
means display the numerical identifier of the file owner's group.  The
default value is @code{(links uid gid)} i.e., all the 3 optional
attributes are displayed.

@vindex ls-lisp-emulation
  The variable @code{ls-lisp-emulation} controls the flavor of the
@code{ls} emulation by setting the defaults for the 3 options
described above: @code{ls-lisp-ignore-case},
@code{ls-lisp-dirs-first}, and @code{ls-lisp-verbosity}.  The value of
this option can be one of the following symbols:

@table @code
@item GNU
@itemx nil
Emulate @sc{gnu} systems; this is the default.  This sets
@code{ls-lisp-ignore-case} and @code{ls-lisp-dirs-first} to
@code{nil}, and @code{ls-lisp-verbosity} to @code{(links uid gid)}.
@item UNIX
Emulate Unix systems.  Like @code{GNU}, but sets
@code{ls-lisp-verbosity} to @code{(links uid)}.
@item MacOS
Emulate macOS@.  Sets @code{ls-lisp-ignore-case} to @code{t}, and
@code{ls-lisp-dirs-first} and @code{ls-lisp-verbosity} to @code{nil}.
@item MS-Windows
Emulate MS-Windows.  Sets @code{ls-lisp-ignore-case} and
@code{ls-lisp-dirs-first} to @code{t}, and @code{ls-lisp-verbosity} to
@code{(links)} on Windows NT/2K/XP/2K3 and to @code{nil} on Windows 9X@.
Note that the default emulation is @emph{not} @code{MS-Windows}, even
on Windows, since many users of Emacs on those platforms prefer the
@sc{gnu} defaults.
@end table

@noindent
Any other value of @code{ls-lisp-emulation} means the same as @code{GNU}.
Customizing this option calls the function @code{ls-lisp-set-options} to
update the 3 dependent options as needed.  If you change the value of
this variable without using customize after @file{ls-lisp.el} is loaded
(note that it is preloaded on MS-Windows and MS-DOS), you can call that
function manually for the same result.

@vindex ls-lisp-support-shell-wildcards
  The variable @code{ls-lisp-support-shell-wildcards} controls how
file-name patterns are supported: if it is non-@code{nil} (the
default), they are treated as shell-style wildcards; otherwise they
are treated as Emacs regular expressions.

@vindex ls-lisp-format-time-list
  The variable @code{ls-lisp-format-time-list} defines how to format
the date and time of files.  @emph{The value of this variable is
ignored}, unless Emacs cannot determine the current locale.  (However,
if the value of @code{ls-lisp-use-localized-time-format} is
non-@code{nil}, Emacs obeys @code{ls-lisp-format-time-list} even if
the current locale is available; see below.)

The value of @code{ls-lisp-format-time-list} is a list of 2 strings.
The first string is used if the file was modified within the current
year, while the second string is used for older files.  In each of
these two strings you can use @samp{%}-sequences to substitute parts
of the time.  For example:
@lisp
("%b %e %H:%M" "%b %e  %Y")
@end lisp

@noindent
Note that the strings substituted for these @samp{%}-sequences depend
on the current locale.  @xref{Time Parsing,,, elisp, The Emacs Lisp
Reference Manual}, for more about format time specs.

@vindex ls-lisp-use-localized-time-format
  Normally, Emacs formats the file time stamps in either traditional
or ISO-style time format.  However, if the value of the variable
@code{ls-lisp-use-localized-time-format} is non-@code{nil}, Emacs
formats file time stamps according to what
@code{ls-lisp-format-time-list} specifies.  The @samp{%}-sequences in
@code{ls-lisp-format-time-list} produce locale-dependent month and day
names, which might cause misalignment of columns in Dired display.
@end ifnottex

@node Windows HOME
@section HOME and Startup Directories on MS-Windows
@cindex HOME directory on MS-Windows

  The Windows equivalent of @code{HOME} is the @dfn{user-specific
application data directory}.  The actual location depends on the
Windows version; typical values are @file{C:\Documents and
Settings\@var{username}\Application Data} on Windows 2000/XP/2K3,
@file{C:\Users\@var{username}\AppData\Roaming} on Windows
Vista/7/2008, and either @file{C:\WINDOWS\Application Data} or
@file{C:\WINDOWS\Profiles\@var{username}\Application Data} on Windows
9X/ME@.  If this directory does not exist or cannot be accessed, Emacs
falls back to @file{C:\} as the default value of @code{HOME}.

  You can override this default value of @code{HOME} by explicitly
setting the environment variable @env{HOME} to point to any directory
on your system.  @env{HOME} can be set either from the command shell
prompt or from @samp{Properties} dialog of @samp{My Computer}.
@code{HOME} can also be set in the system registry,
@pxref{MS-Windows Registry}.

  For compatibility with older versions of Emacs@footnote{
Older versions of Emacs didn't check the application data directory.
}, if there is a file named @file{.emacs} in @file{C:\}, the root
directory of drive @file{C:}, and @env{HOME} is set neither in the
environment nor in the Registry, Emacs will treat @file{C:\} as the
default @code{HOME} location, and will not look in the application
data directory, even if it exists.  Note that only @file{.emacs} is
looked for in @file{C:\}; the older name @file{_emacs} (see below) is
not.  This use of @file{C:\.emacs} to define @code{HOME} is
deprecated.

  Whatever the final place is, Emacs sets the internal value of the
@env{HOME} environment variable to point to it, and it will use that
location for other files and directories it normally looks for or
creates in your home directory.

  You can always find out what Emacs thinks is your home directory's
location by typing @kbd{C-x d ~/ @key{RET}}.  This should present the
list of files in the home directory, and show its full name on the
first line.  Likewise, to visit your init file, type @kbd{C-x C-f
~/.emacs @key{RET}} (assuming the file's name is @file{.emacs}).

@cindex init file @file{.emacs} on MS-Windows
  The home directory is where your init file is stored.  It can have
any name mentioned in @ref{Init File}.

@cindex @file{_emacs} init file, MS-Windows
  Because MS-DOS does not allow file names with leading dots, and
older Windows systems made it hard to create files with such names,
the Windows port of Emacs supports an init file name @file{_emacs}, if
such a file exists in the home directory and @file{.emacs} does not.
This name is considered obsolete.

@node Windows Keyboard
@section Keyboard Usage on MS-Windows
@cindex keyboard, MS-Windows

  This section describes the Windows-specific features related to
keyboard input in Emacs.

@cindex MS-Windows keyboard shortcuts
  Many key combinations (known as ``keyboard shortcuts'') that have
conventional uses in MS-Windows programs conflict with traditional
Emacs key bindings.  (These Emacs key bindings were established years
before Microsoft was founded.)  Examples of conflicts include
@kbd{C-c}, @kbd{C-x}, @kbd{C-z}, @kbd{C-a}, and @kbd{W-@key{SPC}}.
You can redefine some of them with meanings more like the MS-Windows
meanings by enabling CUA Mode (@pxref{CUA Bindings}).

@iftex
@inforef{Windows Keyboard, , emacs}, for information about additional
Windows-specific variables in this category.
@end iftex
@ifnottex
@vindex w32-alt-is-meta
@cindex @code{Alt} key (MS-Windows)
  By default, the key labeled @key{Alt} is mapped as the @key{META}
key.  If you wish it to produce the @code{Alt} modifier instead, set
the variable @code{w32-alt-is-meta} to a @code{nil} value.

@findex w32-register-hot-key
@findex w32-unregister-hot-key
  MS-Windows reserves certain key combinations, such as
@kbd{@key{Alt}-@key{TAB}} and a number of Windows key combinations,
for its own use.  These key combinations are intercepted by the system
before Emacs can see them.  Also, on Windows 10, all Windows key
combinations are reserved by the system in such a way that they are
never propagated to applications, even if the system does not
currently define a hotkey on the specific combination.  You can use
the @code{w32-register-hot-key} function to allow a key sequence to be
seen by Emacs instead of being grabbed by Windows.  When registered as
a hot key, the key combination is pulled out of the system's input
queue before it is handled by Windows, effectively overriding the
special meaning of that key sequence for Windows.  The override is
only effective when Emacs is active; with other applications on the
foreground the keys behave normally.

  The argument to @code{w32-register-hot-key} must be a single key with a
single modifier, in vector form that would be acceptable to
@code{define-key}.  The control and shift modifiers have no effect on the
argument.  The meta modifier is interpreted as the @key{Alt} key if
@code{w32-alt-is-meta} is @code{t} (the default), and the super and hyper
modifiers are interpreted according to the bindings of
@code{w32-lwindow-modifier} and @code{w32-rwindow-modifier}.  Additionally, a
modifier with the trailing dash but with no key indicates that all
Windows defined hotkeys for that modifier are to be overridden in the
favor of Emacs.

@kindex M-TAB@r{, (MS-Windows)}
@cindex @kbd{M-@key{TAB}} vs @kbd{@key{Alt}-@key{TAB}} (MS-Windows)
@cindex @kbd{@key{Alt}-@key{TAB}} vs @kbd{M-@key{TAB}} (MS-Windows)
  For example, @code{(w32-register-hot-key [M-tab])} lets you use
@kbd{M-@key{TAB}} normally in Emacs; for instance, to complete the
word or symbol at point at top level, or to complete the current
search string against previously sought strings during incremental
search.  @code{(w32-register-hot-key [s-])} with
@code{w32-lwindow-modifier} bound to @code{super} disables all the
Windows' own Windows key based shortcuts.@footnote{There is one known
exception: The combination @kbd{@key{Windows}-@key{L}} that locks the
workstation is handled by the system on a lower level.  For this
reason, @code{w32-register-hot-key} cannot override this key
combination - it always locks the computer.}

  Note that @code{w32-register-hot-key} checks the
@code{w32-[lr]window-modifier} values at the time of the function
call.  Thus, you can set @code{w32-lwindow-modifier} as @code{super},
then call @code{(w32-register-hot-key [s-r])}, and finally set
@code{w32-rwindow-modifier} as @code{super} as well.  The result is
that the left Windows key together with @key{R} invokes whichever
function you have bound for the combination in Emacs, and the right
Windows key and @key{R} opens the Windows @code{Run} dialog.

  The hotkey registrations always also include all the shift and
control modifier combinations for the given hotkey; that is,
registering @kbd{s-@key{a}} as a hotkey gives you @kbd{S-s-@key{a}},
@kbd{C-s-@key{a}} and @kbd{C-S-s-@key{a}} as well.

  On Windows 98 and ME, the hotkey registration is more restricted.
The desired hotkey must always be fully specified, and
@code{w32-phantom-key-code} can be customized to achieve desired
results.

  The function @code{w32-unregister-hot-key} reverses the effect of
@code{w32-register-hot-key} for its argument key sequence.

@vindex w32-capslock-is-shiftlock
  By default, the @key{CapsLock} key only affects normal character
keys (it converts lower-case characters to their upper-case
variants).  However, if you set the variable
@code{w32-capslock-is-shiftlock} to a non-@code{nil} value, the
@key{CapsLock} key will affect non-character keys as well, as if you
pressed the @key{Shift} key while typing the non-character key.

@vindex w32-enable-caps-lock
  If the variable @code{w32-enable-caps-lock} is set to a @code{nil}
value, the @key{CapsLock} key produces the symbol @code{capslock}
instead of the shifted version of they keys.  The default value is
@code{t}.

@vindex w32-enable-num-lock
@cindex keypad keys (MS-Windows)
  Similarly, if @code{w32-enable-num-lock} is @code{nil}, the
@key{NumLock} key will produce the symbol @code{kp-numlock}.  The
default is @code{t}, which causes @key{NumLock} to work as expected:
toggle the meaning of the keys on the numeric keypad.
@end ifnottex

@vindex w32-apps-modifier
  The variable @code{w32-apps-modifier} controls the effect of the
@key{Apps} key (usually located between the right @key{Alt} and the
right @key{Ctrl} keys).  Its value can be one of the symbols
@code{hyper}, @code{super}, @code{meta}, @code{alt}, @code{control},
or @code{shift} for the respective modifier, or @code{nil} to appear
as the key @code{apps}.  The default is @code{nil}.

@vindex w32-lwindow-modifier
@vindex w32-rwindow-modifier
@vindex w32-scroll-lock-modifier
  The variable @code{w32-lwindow-modifier} determines the effect of
the left Windows key (usually labeled with @key{start} and the Windows
logo).  If its value is @code{nil} (the default), the key will produce
the symbol @code{lwindow}.  Setting it to one of the symbols
@code{hyper}, @code{super}, @code{meta}, @code{alt}, @code{control},
or @code{shift} will produce the respective modifier.  A similar
variable @code{w32-rwindow-modifier} controls the effect of the right
Windows key, and @code{w32-scroll-lock-modifier} does the same for the
@key{ScrLock} key.  If these variables are set to @code{nil}, the
right Windows key produces the symbol @code{rwindow} and @key{ScrLock}
produces the symbol @code{scroll}.  If you want @key{ScrLock} to
produce the same effect as in other applications, i.e.@: toggle the
Scroll Lock @acronym{LED} indication on the keyboard, set
@code{w32-scroll-lock-modifier} to @code{t} or any non-@code{nil}
value other than the above modifier symbols.

@vindex w32-pass-alt-to-system
@cindex Windows system menu
@cindex @code{Alt} key invokes menu (Windows)
  Emacs compiled as a native Windows application normally turns off
the Windows feature that tapping the @key{Alt} key invokes the Windows
menu.  The reason is that the @key{Alt} serves as @key{META} in Emacs.
When using Emacs, users often press the @key{META} key temporarily and
then change their minds; if this has the effect of bringing up the
Windows menu, it alters the meaning of subsequent commands.  Many
users find this frustrating.

  You can re-enable Windows's default handling of tapping the @key{Alt}
key by setting @code{w32-pass-alt-to-system} to a non-@code{nil}
value.

@ifnottex
@vindex w32-pass-lwindow-to-system
@vindex w32-pass-rwindow-to-system
  The variables @code{w32-pass-lwindow-to-system} and
@code{w32-pass-rwindow-to-system} determine whether the respective
keys are passed to Windows or swallowed by Emacs.  If the value is
@code{nil}, the respective key is silently swallowed by Emacs,
otherwise it is passed to Windows.  The default is @code{t} for both
of these variables.  Passing each of these keys to Windows produces
its normal effect: for example, @kbd{@key{Lwindow}} opens the
@code{Start} menu, etc.

@vindex w32-recognize-altgr
@kindex AltGr @r{(MS-Windows)}
@cindex AltGr key (MS-Windows)
  The variable @code{w32-recognize-altgr} controls whether the
@key{AltGr} key (if it exists on your keyboard), or its equivalent,
the combination of the right @key{Alt} and left @key{Ctrl} keys
pressed together, is recognized as the @key{AltGr} key.  The default
is @code{t}, which means these keys produce @code{AltGr}; setting it
to @code{nil} causes @key{AltGr} or the equivalent key combination to
be interpreted as the combination of @key{Ctrl} and @key{META}
modifiers.
@end ifnottex

@node Windows Mouse
@section Mouse Usage on MS-Windows
@cindex mouse, and MS-Windows

  This section describes the Windows-specific variables related to
the mouse.

@vindex w32-mouse-button-tolerance
@cindex simulation of middle mouse button
  The variable @code{w32-mouse-button-tolerance} specifies the
time interval, in milliseconds, for faking middle mouse button press
on 2-button mice.  If both mouse buttons are depressed within this
time interval, Emacs generates a middle mouse button click event
instead of a double click on one of the buttons.

@vindex w32-pass-extra-mouse-buttons-to-system
  If the variable @code{w32-pass-extra-mouse-buttons-to-system} is
non-@code{nil}, Emacs passes the fourth and fifth mouse buttons to
Windows.

@vindex w32-swap-mouse-buttons
  The variable @code{w32-swap-mouse-buttons} controls which of the 3
mouse buttons generates the @kbd{mouse-2} events.  When it is
@code{nil} (the default), the middle button generates @kbd{mouse-2}
and the right button generates @kbd{mouse-3} events.  If this variable
is non-@code{nil}, the roles of these two buttons are reversed.

@node Windows Processes
@section Subprocesses on Windows 9X/ME and Windows NT/2K/XP/Vista/7/8/10
@cindex subprocesses on MS-Windows

@cindex DOS applications, running from Emacs
  Emacs compiled as a native Windows application (as opposed to the DOS
version) includes full support for asynchronous subprocesses.
In the Windows version, synchronous and asynchronous subprocesses work
fine on both
Windows 9X/ME and Windows NT/2K/XP/Vista/7/8/10 as long as you run
only 32-bit or 64-bit Windows
applications.  However, when you run a DOS application in a subprocess,
you may encounter problems or be unable to run the application at all;
and if you run two DOS applications at the same time in two
subprocesses, you may have to reboot your system.

Since the standard command interpreter (and most command line utilities)
on Windows 9X are DOS applications, these problems are significant when
using that system.  But there's nothing we can do about them; only
Microsoft can fix them.

If you run just one DOS application subprocess, the subprocess should
work as expected as long as it is ``well-behaved'' and does not perform
direct screen access or other unusual actions.  If you have a CPU
monitor application, your machine will appear to be 100% busy even when
the DOS application is idle, but this is only an artifact of the way CPU
monitors measure processor load.

You must terminate the DOS application before you start any other DOS
application in a different subprocess.  Emacs is unable to interrupt or
terminate a DOS subprocess.  The only way you can terminate such a
subprocess is by giving it a command that tells its program to exit.

If you attempt to run two DOS applications at the same time in separate
subprocesses, the second one that is started will be suspended until the
first one finishes, even if either or both of them are asynchronous.

@cindex kill DOS application
If you can go to the first subprocess, and tell it to exit, the second
subprocess should continue normally.  However, if the second subprocess
is synchronous, Emacs itself will be hung until the first subprocess
finishes.  If it will not finish without user input, then you have no
choice but to reboot if you are running on Windows 9X@.  If you are
running on Windows NT/2K/XP, you can use a process viewer application to kill
the appropriate instance of NTVDM instead (this will terminate both DOS
subprocesses).

If you have to reboot Windows 9X in this situation, do not use the
@code{Shutdown} command on the @code{Start} menu; that usually hangs the
system.  Instead, type @kbd{@key{Ctrl}-@key{Alt}-@key{DEL}} and then choose
@code{Shutdown}.  That usually works, although it may take a few minutes
to do its job.

@vindex w32-quote-process-args
  The variable @code{w32-quote-process-args} controls how Emacs quotes
the process arguments.  Non-@code{nil} means quote with the @code{"}
character.  If the value is a character, Emacs uses that character to escape
any quote characters that appear; otherwise it chooses a suitable escape
character based on the type of the program.

@vindex w32-pipe-buffer-size
  The variable @code{w32-pipe-buffer-size} controls the size of the
buffer Emacs requests from the system when it creates pipes for
communications with subprocesses.  The default value is zero, which
lets the OS choose the size.  Any valid positive value will request a
buffer of that size in bytes.  This can be used to tailor
communications with subprocesses to programs that exhibit unusual
behavior with respect to buffering pipe I/O.

@ifnottex
@findex w32-shell-execute
  The function @code{w32-shell-execute} can be useful for writing
customized commands that run MS-Windows applications registered to
handle a certain standard Windows operation for a specific type of
document or file.  This function is a wrapper around the Windows
@code{ShellExecute} API@.  See the MS-Windows API documentation for
more details.
@end ifnottex

@node Windows Printing
@section Printing and MS-Windows

  Printing commands, such as @code{lpr-buffer} (@pxref{Printing}) and
@code{ps-print-buffer} (@pxref{PostScript}) work in MS-DOS and
MS-Windows by sending the output to one of the printer ports, if a
Posix-style @code{lpr} program is unavailable.  The same Emacs
variables control printing on all systems, but in some cases they have
different default values on MS-DOS and MS-Windows.

  Emacs on MS Windows attempts to determine your default printer
automatically (using the function @code{default-printer-name}).
But in some rare cases this can fail, or you may wish to use a different
printer from within Emacs.  The rest of this section explains how to
tell Emacs which printer to use.

@vindex printer-name@r{, (MS-DOS/MS-Windows)}
  If you want to use your local printer, then set the Lisp variable
@code{lpr-command} to @code{""} (its default value on Windows) and
@code{printer-name} to the name of the printer port---for example,
@code{"PRN"}, the usual local printer port, or @code{"LPT2"}, or
@code{"COM1"} for a serial printer.  You can also set
@code{printer-name} to a file name, in which case ``printed'' output
is actually appended to that file.  If you set @code{printer-name} to
@code{"NUL"}, printed output is silently discarded (sent to the system
null device).

  You can also use a printer shared by another machine by setting
@code{printer-name} to the UNC share name for that printer---for
example, @code{"//joes_pc/hp4si"}.  (It doesn't matter whether you use
forward slashes or backslashes here.)  To find out the names of shared
printers, run the command @samp{net view} from the command prompt to
obtain a list of servers, and @samp{net view @var{server-name}} to see
the names of printers (and directories) shared by that server.
Alternatively, click the @samp{Network Neighborhood} icon on your
desktop, and look for machines that share their printers via the
network.

@cindex @samp{net use}, and printing on MS-Windows
@cindex networked printers (MS-Windows)
  If the printer doesn't appear in the output of @samp{net view}, or
if setting @code{printer-name} to the UNC share name doesn't produce a
hardcopy on that printer, you can use the @samp{net use} command to
connect a local print port such as @code{"LPT2"} to the networked
printer.  For example, typing @kbd{net use LPT2: \\joes_pc\hp4si}@footnote{
Note that the @samp{net use} command requires the UNC share name to be
typed with the Windows-style backslashes, while the value of
@code{printer-name} can be set with either forward- or backslashes.}
causes Windows to @dfn{capture} the @code{LPT2} port and redirect the
printed material to the printer connected to the machine @code{joes_pc}.
After this command, setting @code{printer-name} to @code{"LPT2"}
should produce the hardcopy on the networked printer.

  With some varieties of Windows network software, you can instruct
Windows to capture a specific printer port such as @code{"LPT2"}, and
redirect it to a networked printer via the @w{@code{Control
Panel->Printers}} applet instead of @samp{net use}.

  If you set @code{printer-name} to a file name, it's best to use an
absolute file name.  Emacs changes the working directory according to
the default directory of the current buffer, so if the file name in
@code{printer-name} is relative, you will end up with several such
files, each one in the directory of the buffer from which the printing
was done.

  If the value of @code{printer-name} is correct, but printing does
not produce the hardcopy on your printer, it is possible that your
printer does not support printing plain text (some cheap printers omit
this functionality).  In that case, try the PostScript print commands,
described below.

@findex print-buffer @r{(MS-DOS)}
@findex print-region @r{(MS-DOS)}
@vindex lpr-headers-switches @r{(MS-DOS)}
  The commands @code{print-buffer} and @code{print-region} call the
@code{pr} program, or use special switches to the @code{lpr} program, to
produce headers on each printed page.  MS-DOS and MS-Windows don't
normally have these programs, so by default, the variable
@code{lpr-headers-switches} is set so that the requests to print page
headers are silently ignored.  Thus, @code{print-buffer} and
@code{print-region} produce the same output as @code{lpr-buffer} and
@code{lpr-region}, respectively.  If you do have a suitable @code{pr}
program (for example, from GNU Coreutils), set
@code{lpr-headers-switches} to @code{nil}; Emacs will then call
@code{pr} to produce the page headers, and print the resulting output as
specified by @code{printer-name}.

@vindex print-region-function @r{(MS-DOS)}
@cindex lpr usage under MS-DOS
@vindex lpr-command @r{(MS-DOS)}
@vindex lpr-switches @r{(MS-DOS)}
  Finally, if you do have an @code{lpr} work-alike, you can set the
variable @code{lpr-command} to @code{"lpr"}.  Then Emacs will use
@code{lpr} for printing, as on other systems.  (If the name of the
program isn't @code{lpr}, set @code{lpr-command} to the appropriate value.)
The variable @code{lpr-switches} has its standard meaning
when @code{lpr-command} is not @code{""}.  If the variable
@code{printer-name} has a string value, it is used as the value for the
@code{-P} option to @code{lpr}, as on Unix.

@findex ps-print-buffer @r{(MS-DOS)}
@findex ps-spool-buffer @r{(MS-DOS)}
@vindex ps-printer-name @r{(MS-DOS)}
@vindex ps-lpr-command @r{(MS-DOS)}
@vindex ps-lpr-switches @r{(MS-DOS)}
  A parallel set of variables, @code{ps-lpr-command},
@code{ps-lpr-switches}, and @code{ps-printer-name} (@pxref{PostScript
Variables}), defines how PostScript files should be printed.  These
variables are used in the same way as the corresponding variables
described above for non-PostScript printing.  Thus, the value of
@code{ps-printer-name} is used as the name of the device (or file) to
which PostScript output is sent, just as @code{printer-name} is used
for non-PostScript printing.  (There are two distinct sets of
variables in case you have two printers attached to two different
ports, and only one of them is a PostScript printer.)

@cindex Ghostscript, use for PostScript printing
  The default value of the variable @code{ps-lpr-command} is @code{""},
which causes PostScript output to be sent to the printer port specified
by @code{ps-printer-name}; but @code{ps-lpr-command} can also be set to
the name of a program which will accept PostScript files.  Thus, if you
have a non-PostScript printer, you can set this variable to the name of
a PostScript interpreter program (such as Ghostscript).  Any switches
that need to be passed to the interpreter program are specified using
@code{ps-lpr-switches}.  (If the value of @code{ps-printer-name} is a
string, it will be added to the list of switches as the value for the
@code{-P} option.  This is probably only useful if you are using
@code{lpr}, so when using an interpreter typically you would set
@code{ps-printer-name} to something other than a string so it is
ignored.)

  For example, to use Ghostscript for printing on the system's default
printer, put this in your @file{.emacs} file:

@example
(setq ps-printer-name t)
(setq ps-lpr-command "D:/gs6.01/bin/gswin32c.exe")
(setq ps-lpr-switches '("-q" "-dNOPAUSE" "-dBATCH"
                        "-sDEVICE=mswinpr2"
                        "-sPAPERSIZE=a4"))
@end example

@noindent
(This assumes that Ghostscript is installed in the
@file{D:/gs6.01} directory.)

@node Windows Fonts
@section Specifying Fonts on MS-Windows
@cindex font specification (MS Windows)

  Starting with Emacs 23, fonts are specified by their name, size
and optional properties.  The format for specifying fonts comes from the
fontconfig library used in modern Free desktops:

@example
  [Family[-PointSize]][:Option1=Value1[:Option2=Value2[...]]]
@end example

  The old XLFD based format is also supported for backwards compatibility.

@cindex font backend selection (MS-Windows)
  Emacs 23 and later supports a number of font backends.  Currently,
the @code{gdi} and @code{uniscribe} backends are supported on Windows.
The @code{gdi} font backend is available on all versions of Windows,
and supports all fonts that are natively supported by Windows.  The
@code{uniscribe} font backend is available on Windows 2000 and later,
and supports TrueType and OpenType fonts.  Some languages requiring
complex layout can only be properly supported by the Uniscribe
backend.  By default, both backends are enabled if supported, with
@code{uniscribe} taking priority over @code{gdi}.  To override that
and use the GDI backend even if Uniscribe is available, invoke Emacs
with the @kbd{-xrm Emacs.fontBackend:gdi} command-line argument, or
add a @code{Emacs.fontBackend} resource with the value @code{gdi} in
the Registry under either the
@samp{HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs} or the
@samp{HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs} key (@pxref{Resources}).

@cindex font properties (MS Windows)
@noindent
Optional properties common to all font backends on MS-Windows are:

@table @code

@vindex font-weight-table @r{(MS-Windows)}
@item weight
Specifies the weight of the font.  Special values @code{light},
@code{medium}, @code{demibold}, @code{bold}, and @code{black} can be specified
without @code{weight=} (e.g., @kbd{Courier New-12:bold}).  Otherwise,
the weight should be a numeric value between 100 and 900, or one of the
named weights in @code{font-weight-table}.  If unspecified, a regular font
is assumed.

@vindex font-slant-table @r{(MS-Windows)}
@item slant
Specifies whether the font is italic.  Special values
@code{roman}, @code{italic} and @code{oblique} can be specified
without @code{slant=} (e.g., @kbd{Courier New-12:italic}).
Otherwise, the slant should be a numeric value, or one of the named
slants in @code{font-slant-table}.  On Windows, any slant above 150 is
treated as italics, and anything below as roman.

@item family
Specifies the font family, but normally this will be specified
at the start of the font name.

@item pixelsize
Specifies the font size in pixels.  This can be used instead
of the point size specified after the family name.

@item adstyle
Specifies additional style information for the font.
On MS-Windows, the values @code{mono}, @code{sans}, @code{serif},
@code{script} and @code{decorative} are recognized.  These are most useful
as a fallback with the font family left unspecified.

@vindex w32-charset-info-alist
@item registry
Specifies the character set registry that the font is
expected to cover.  Most TrueType and OpenType fonts will be Unicode fonts
that cover several national character sets, but you can narrow down the
selection of fonts to those that support a particular character set by
using a specific registry from @code{w32-charset-info-alist} here.

@item spacing
Specifies how the font is spaced.  The @code{p} spacing specifies
a proportional font, and @code{m} or @code{c} specify a monospaced font.

@item foundry
Not used on Windows, but for informational purposes and to
prevent problems with code that expects it to be set, is set internally to
@code{raster} for bitmapped fonts, @code{outline} for scalable fonts,
or @code{unknown} if the type cannot be determined as one of those.
@end table

@cindex font properties (MS Windows gdi backend)
Options specific to @code{GDI} fonts:

@table @code

@cindex font scripts (MS Windows)
@cindex font Unicode subranges (MS Windows)
@item script
Specifies a Unicode subrange the font should support.

The following scripts are recognized on Windows: @code{latin}, @code{greek},
@code{coptic}, @code{cyrillic}, @code{armenian}, @code{hebrew}, @code{arabic},
@code{syriac}, @code{nko}, @code{thaana}, @code{devanagari}, @code{bengali},
@code{gurmukhi}, @code{gujarati}, @code{oriya}, @code{tamil}, @code{telugu},
@code{kannada}, @code{malayam}, @code{sinhala}, @code{thai}, @code{lao},
@code{tibetan}, @code{myanmar}, @code{georgian}, @code{hangul},
@code{ethiopic}, @code{cherokee}, @code{canadian-aboriginal}, @code{ogham},
@code{runic}, @code{khmer}, @code{mongolian}, @code{symbol}, @code{braille},
@code{han}, @code{ideographic-description}, @code{cjk-misc}, @code{kana},
@code{bopomofo}, @code{kanbun}, @code{yi}, @code{byzantine-musical-symbol},
@code{musical-symbol}, and @code{mathematical}.

@cindex font antialiasing (MS Windows)
@item antialias
Specifies the antialiasing method.  The value @code{none} means no
antialiasing, @code{standard} means use standard antialiasing,
@code{subpixel} means use subpixel antialiasing (known as Cleartype on
Windows), and @code{natural} means use subpixel antialiasing with
adjusted spacing between letters.  If unspecified, the font will use
the system default antialiasing.
@end table

@node Windows Misc
@section Miscellaneous Windows-specific features

  This section describes miscellaneous Windows-specific features.

@vindex w32-use-visible-system-caret
@cindex screen reader software, MS-Windows
  The variable @code{w32-use-visible-system-caret} is a flag that
determines whether to make the system caret visible.  The default when
no screen reader software is in use is @code{nil}, which means Emacs
draws its own cursor to indicate the position of point.  A
non-@code{nil} value means Emacs will indicate point location with the
system caret; this facilitates use of screen reader software, and is
the default when such software is detected when running Emacs.
When this variable is non-@code{nil}, other variables affecting the
cursor display have no effect.

@iftex
@inforef{Windows Misc, , emacs}, for information about additional
Windows-specific variables in this category.
@end iftex

@ifnottex
@vindex w32-grab-focus-on-raise
@cindex frame focus policy, MS-Windows
  The variable @code{w32-grab-focus-on-raise}, if set to a
non-@code{nil} value causes a frame to grab focus when it is raised.
The default is @code{t}, which fits well with the Windows default
click-to-focus policy.
@end ifnottex

@ifnottex
@include msdos-xtra.texi
@end ifnottex