@c This is part of the Emacs manual.
@c Copyright (C) 2000-2018 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Mac OS / GNUstep
@appendix Emacs and macOS / GNUstep
@cindex macOS
@cindex Macintosh
@cindex GNUstep

  This section describes the peculiarities of using Emacs built with
the GNUstep libraries on GNU/Linux or other operating systems, or on
macOS with native window system support.  On macOS, Emacs can be
built either without window system support, with X11, or with the
Cocoa interface; this section only applies to the Cocoa build.  This
does not support versions before macOS 10.6.

  GNUstep is free software; macOS is not.  Because it is a non-free
operating system, macOS denies its users the freedom that every computer
user deserves.  That is an injustice.  For your freedom's sake, we
urge you to switch to a free operating system.

  We support GNU Emacs on proprietary operating systems because
we hope this taste of freedom will inspire users to escape from them.

  For various historical and technical reasons, Emacs uses the term
@samp{Nextstep} internally, instead of ``Cocoa'' or ``macOS''; for
instance, most of the commands and variables described in this section
begin with @samp{ns-}, which is short for @samp{Nextstep}.  NeXTstep
was an application interface released by NeXT Inc.@: during the 1980s,
of which Cocoa is a direct descendant.  Apart from Cocoa, there is
another NeXTstep-style system: GNUstep, which is free software.  As of
this writing, Emacs GNUstep support is in alpha status (@pxref{GNUstep
Support}), but we hope to improve it in the future.

@menu
* Mac / GNUstep Basics::        Basic Emacs usage under GNUstep or macOS.
* Mac / GNUstep Customization:: Customizations under GNUstep or macOS.
* Mac / GNUstep Events::        How window system events are handled.
* GNUstep Support::             Details on status of GNUstep support.
@end menu

@node Mac / GNUstep Basics
@section Basic Emacs usage under macOS and GNUstep

@cindex modifier keys (macOS)
  By default, the @key{Alt} and @key{Option} keys are the same as
@key{Meta}.  The Mac @key{Cmd} key is the same as @key{Super}, and
Emacs provides a set of key bindings using this modifier key that mimic
other Mac / GNUstep applications (@pxref{Mac / GNUstep Events}).  You
can change these bindings in the usual way (@pxref{Key Bindings}).

@vindex ns-alternate-modifier
@vindex ns-right-alternate-modifier
  The variable @code{ns-right-alternate-modifier} controls the
behavior of the right @key{Alt} and @key{Option} keys.  These keys
behave like the left-hand keys if the value is @code{left} (the
default).  A value of @code{control}, @code{meta}, @code{alt},
@code{super}, or @code{hyper} makes them behave like the corresponding
modifier keys; a value of @code{left} means be the same key as
@code{ns-alternate-modifier}; a value of @code{none} tells Emacs to
ignore them, in which case you get the default behavior of macOS
accentuation system from the right @key{Option} key.

  @kbd{S-mouse-1} adjusts the region to the click position,
just like @kbd{mouse-3} (@code{mouse-save-then-kill}); it does not pop
up a menu for changing the default face, as @kbd{S-mouse-1} normally
does (@pxref{Text Scale}).  This change makes Emacs behave more like
other Mac / GNUstep applications.

  When you open or save files using the menus, or using the
@kbd{Cmd-o} and @kbd{Cmd-S} bindings, Emacs uses graphical file
dialogs to read file names.  However, if you use the regular Emacs key
sequences, such as @kbd{C-x C-f}, Emacs uses the minibuffer to read
file names.

@cindex copy/paste to/from primary selection (macOS)
  On GNUstep, in an X-windows environment you need to use @kbd{Cmd-c}
instead of one of the @kbd{C-w} or @kbd{M-w} commands to transfer text
to the X primary selection; otherwise, Emacs will use the
clipboard selection.  Likewise, @kbd{Cmd-y} (instead of @kbd{C-y})
yanks from the X primary selection instead of the kill-ring or
clipboard.


@subsection Grabbing environment variables

@c How is this any different to launching from a window manager menu
@c in GNU/Linux?  These are sometimes not login shells either.
@cindex environment variables (macOS)
Many programs which may run under Emacs, like latex or man, depend on the
settings of environment variables.  If Emacs is launched from the shell, it
will automatically inherit these environment variables and its subprocesses
will inherit them from it.  But if Emacs is launched from the Finder it
is not a descendant of any shell, so its environment variables haven't been
set, which often causes the subprocesses it launches to behave differently than
they would when launched from the shell.

For the PATH and MANPATH variables, a system-wide method
of setting PATH is recommended on macOS, using the
@file{/etc/paths} files and the @file{/etc/paths.d} directory.

@node Mac / GNUstep Customization
@section Mac / GNUstep Customization

There are a few customization options that are specific to the
Nextstep port.  For example, they affect things such as the modifier
keys and the fullscreen behavior.  To see all such options, use
@kbd{M-x customize-group @key{RET} ns @key{RET}}.

@subsection Font Panel

@findex ns-popup-font-panel
The standard Mac / GNUstep font panel is accessible with @kbd{M-x
ns-popup-font-panel} and will set the default font in the frame most
recently used or clicked on.

@c  To make the setting permanent, use @samp{Save Options} in the
@c Options menu, or run @code{menu-bar-options-save}.

@cindex Core Text, on macOS
@cindex font backend, on macOS
In macOS, Emacs uses a Core Text based font backend
by default.  If you prefer the older font style, enter the following
at the command-line before starting Emacs:

@example
% defaults write org.gnu.Emacs FontBackend ns
@end example


@node Mac / GNUstep Events
@section Windowing System Events under macOS / GNUstep
@cindex events on macOS

  Nextstep applications receive a number of special events which have
no X equivalent.  These are sent as specially defined key events, which
do not correspond to any sequence of keystrokes.  Under Emacs, these
key events can be bound to functions just like ordinary
keystrokes.  Here is a list of these events.

@table @key
@item ns-open-file
@vindex ns-pop-up-frames
This event occurs when another Nextstep application requests that
Emacs open a file.  A typical reason for this would be a user
double-clicking a file in the Finder application.  By default, Emacs
responds to this event by opening a new frame and visiting the file in
that frame (@code{ns-find-file}).  As an exception, if the selected
buffer is the @file{*scratch*} buffer, Emacs visits the file in the
selected frame.

You can change how Emacs responds to a @code{ns-open-file} event by
changing the variable @code{ns-pop-up-frames}.  Its default value,
@samp{fresh}, is what we have just described.  A value of @code{t}
means to always visit the file in a new frame.  A value of @code{nil}
means to always visit the file in the selected frame.

@item ns-open-temp-file
This event occurs when another application requests that Emacs open a
temporary file.  By default, this is handled by just generating a
@code{ns-open-file} event, the results of which are described above.

@item ns-open-file-line
Some applications, such as ProjectBuilder and gdb, request not only a
particular file, but also a particular line or sequence of lines in
the file.  Emacs handles this by visiting that file and highlighting
the requested line (@code{ns-open-file-select-line}).

@item ns-drag-n-drop
This event occurs when a user drags an object from another application
into an Emacs frame.  The default behavior is to open a file in the
window under the mouse, or to insert text at point of the window under
the mouse.  It may sometimes be necessary to use the @key{Meta} key in
conjunction with dragging to force text insertion.

@item ns-change-font
This event occurs when the user selects a font in a Nextstep font
panel (which can be opened with @kbd{Cmd-t}).  The default behavior is
to adjust the font of the selected frame
(@code{ns-respond-to-changefont}).  The name and size of the selected
font are stored in the variables @code{ns-input-font} and
@code{ns-input-fontsize}, respectively.

@item ns-power-off
This event occurs when the user logs out and Emacs is still running, or when
``Quit Emacs'' is chosen from the application menu.
The default behavior is to save all file-visiting buffers.
@end table

@cindex using Nextstep services (macOS)
  Emacs also allows users to make use of Nextstep services, via a set
of commands whose names begin with @samp{ns-service-} and end with the
name of the service.  Type @kbd{M-x ns-service-@key{TAB}} to
see a list of these commands.  These functions either operate on
marked text (replacing it with the result) or take a string argument
and return the result as a string.  You can also use the Lisp function
@code{ns-perform-service} to pass arbitrary strings to arbitrary
services and receive the results back.  Note that you may need to
restart Emacs to access newly-available services.

@node GNUstep Support
@section GNUstep Support

Emacs can be built and run under GNUstep, but there are still
issues to be addressed.  Interested developers should contact
@ifnothtml
@email{emacs-devel@@gnu.org}.
@end ifnothtml
@ifhtml
@url{https://lists.gnu.org/mailman/listinfo/emacs-devel, the
emacs-devel mailing list}.
@end ifhtml