@c -*-texinfo-*-
@c This is part of the XEmacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. 
@c See the file lispref.texi for copying conditions.
@setfilename ../../info/x-windows.texinfo
@node X-Windows, ToolTalk Support, System Interface, Top
@chapter Functions Specific to the X Window System
@cindex X
@cindex X-Windows

@c This section is largely different from the one in FSF Emacs.

XEmacs provides the concept of @dfn{devices}, which generalizes
connections to an X server, a TTY device, etc.  Most information about
an X server that XEmacs is connected to can be determined through
general console and device functions.  @xref{Consoles and Devices}.
However, there are some features of the X Window System that do not
generalize well, and they are covered specially here.

@menu
* X Selections::                Transferring text to and from other X clients.
* X Server::                    Information about the X server connected to
                                  a particular device.
* X Miscellaneous::             Other X-specific functions and variables.
@end menu

@node X Selections
@section X Selections
@cindex selection (for X windows)

The X server records a set of @dfn{selections} which permit transfer of
data between application programs.  The various selections are
distinguished by @dfn{selection types}, represented in XEmacs by
symbols.  X clients including XEmacs can read or set the selection for
any given type.

@defun x-own-selection data &optional type
This function sets a ``selection'' in the X server.  It takes two
arguments: a value, @var{data}, and the selection type @var{type} to
assign it to.  @var{data} may be a string, a cons of two markers, or an
extent.  In the latter cases, the selection is considered to be the text
between the markers, or between the extent's endpoints.

Each possible @var{type} has its own selection value, which changes
independently.  The usual values of @var{type} are @code{PRIMARY} and
@code{SECONDARY}; these are symbols with upper-case names, in accord
with X Windows conventions.  The default is @code{PRIMARY}.

(In FSF Emacs, this function is called @code{x-set-selection} and
takes different arguments.)
@end defun

@defun x-get-selection
This function accesses selections set up by XEmacs or by other X
clients.  It returns the value of the current primary selection.
@end defun

@defun x-disown-selection &optional secondary-p
Assuming we own the selection, this function disowns it.  If
@var{secondary-p} is non-@code{nil}, the secondary selection instead of
the primary selection is discarded.
@end defun

@cindex cut buffer
The X server also has a set of numbered @dfn{cut buffers} which can
store text or other data being moved between applications.  Cut buffers
are considered obsolete, but XEmacs supports them for the sake of X
clients that still use them.

@defun x-get-cutbuffer &optional n
This function returns the contents of cut buffer number @var{n}. (This
function is called @code{x-get-cut-buffer} in FSF Emacs.)
@end defun

@defun x-store-cutbuffer string
This function stores @var{string} into the first cut buffer (cut buffer
0), moving the other values down through the series of cut buffers,
kill-ring-style. (This function is called @code{x-set-cut-buffer} in FSF
Emacs.)
@end defun

@node X Server
@section X Server

This section describes how to access and change the overall status of
the X server XEmacs is using.

@menu
* Resources::                   Getting resource values from the server.
* Server Data::                 Getting info about the X server.
* Grabs::                       Restricting access to the server by other apps.
@end menu

@node Resources
@subsection Resources

@defun default-x-device
This function return the default X device for resourcing.  This is the
first-created X device that still exists.
@end defun

@defun x-get-resource name class type &optional locale device noerror
This function retrieves a resource value from the X resource manager.

@itemize @bullet
@item
The first arg is the name of the resource to retrieve, such as
@samp{"font"}.

@item
The second arg is the class of the resource to retrieve, like
@samp{"Font"}.

@item
The third arg should be one of the symbols @code{string},
@code{integer}, @code{natnum}, or @code{boolean}, specifying the type of
object that the database is searched for.

@item
The fourth arg is the locale to search for the resources on, and can
currently be a a buffer, a frame, a device, or the symbol @code{global}.
If omitted, it defaults to @code{global}.

@item
The fifth arg is the device to search for the resources on. (The
resource database for a particular device is constructed by combining
non-device- specific resources such any command-line resources specified
and any app-defaults files found [or the fallback resources supplied by
XEmacs, if no app-defaults file is found] with device-specific resources
such as those supplied using @samp{xrdb}.) If omitted, it defaults to
the device of @var{locale}, if a device can be derived (i.e. if
@var{locale} is a frame or device), and otherwise defaults to the value
of @code{default-x-device}.

@item
The sixth arg @var{noerror}, if non-@code{nil}, means do not signal an
error if a bogus resource specification was retrieved (e.g. if a
non-integer was given when an integer was requested).  In this case, a
warning is issued instead.
@end itemize

The resource names passed to this function are looked up relative to the
locale.

If you want to search for a subresource, you just need to specify the
resource levels in @var{name} and @var{class}.  For example, @var{name}
could be @samp{"modeline.attributeFont"}, and @var{class}
@samp{"Face.AttributeFont"}.

Specifically,

@enumerate
@item
If @var{locale} is a buffer, a call

@example
    @code{(x-get-resource "foreground" "Foreground" 'string @var{some-buffer})}
@end example

is an interface to a C call something like

@example
    @code{XrmGetResource (db, "xemacs.buffer.@var{buffer-name}.foreground",
                        "Emacs.EmacsLocaleType.EmacsBuffer.Foreground",
                        "String");}
@end example

@item
If @var{locale} is a frame, a call

@example
    @code{(x-get-resource "foreground" "Foreground" 'string @var{some-frame})}
@end example

is an interface to a C call something like
@example

    @code{XrmGetResource (db, "xemacs.frame.@var{frame-name}.foreground",
                        "Emacs.EmacsLocaleType.EmacsFrame.Foreground",
                        "String");}
@end example

@item
If @var{locale} is a device, a call

@example
    @code{(x-get-resource "foreground" "Foreground" 'string @var{some-device})}
@end example

is an interface to a C call something like

@example
    @code{XrmGetResource (db, "xemacs.device.@var{device-name}.foreground",
                        "Emacs.EmacsLocaleType.EmacsDevice.Foreground",
                        "String");}
@end example

@item
If @var{locale} is the symbol @code{global}, a call

@example
    @code{(x-get-resource "foreground" "Foreground" 'string 'global)}
@end example

is an interface to a C call something like

@example
    @code{XrmGetResource (db, "xemacs.foreground",
                        "Emacs.Foreground",
                        "String");}
@end example
@end enumerate

Note that for @code{global}, no prefix is added other than that of the
application itself; thus, you can use this locale to retrieve arbitrary
application resources, if you really want to.

The returned value of this function is @code{nil} if the queried
resource is not found.  If @var{type} is @code{string}, a string is
returned, and if it is @code{integer}, an integer is returned.  If
@var{type} is @code{boolean}, then the returned value is the list
@code{(t)} for true, @code{(nil)} for false, and is @code{nil} to mean
``unspecified''.
@end defun

@defun x-put-resource resource-line &optional device
This function adds a resource to the resource database for @var{device}.
@var{resource-line} specifies the resource to add and should be a
standard resource specification.
@end defun

@defvar x-emacs-application-class
This variable holds The X application class of the XEmacs process.  This
controls, among other things, the name of the ``app-defaults'' file that
XEmacs will use.  For changes to this variable to take effect, they must
be made before the connection to the X server is initialized, that is,
this variable may only be changed before XEmacs is dumped, or by setting
it in the file @file{lisp/term/x-win.el}.

By default, this variable is nil at startup.  When the connection
to the X server is first initialized, the X resource database will
be consulted and the value will be set according to whether any
resources are found for the application class ``XEmacs''.
@end defvar

@node Server Data
@subsection Data about the X Server

  This section describes functions and a variable that you can use to
get information about the capabilities and origin of the X server
corresponding to a particular device.  The device argument is generally
optional and defaults to the selected device.

@defun x-server-version &optional device 
This function returns the list of version numbers of the X server
@var{device} is on.  The returned value is a list of three integers: the
major and minor version numbers of the X protocol in use, and the
vendor-specific release number.
@end defun

@defun x-server-vendor &optional device
This function returns the vendor supporting the X server @var{device} is
on.
@end defun

@defun x-display-visual-class &optional device
This function returns the visual class of the display @var{device} is
on.  The value is one of the symbols @code{static-gray},
@code{gray-scale}, @code{static-color}, @code{pseudo-color},
@code{true-color}, and @code{direct-color}. (Note that this is different
from previous versions of XEmacs, which returned @code{StaticGray},
@code{GrayScale}, etc.)
@end defun

@node Grabs
@subsection Restricting Access to the Server by Other Apps

@defun x-grab-keyboard &optional device
This function grabs the keyboard on the given device (defaulting to the
selected one).  So long as the keyboard is grabbed, all keyboard events
will be delivered to XEmacs---it is not possible for other X clients to
eavesdrop on them.  Ungrab the keyboard with @code{x-ungrab-keyboard}
(use an @code{unwind-protect}).  Returns @code{t} if the grab was
successful; @code{nil} otherwise.
@end defun

@defun x-ungrab-keyboard &optional device
This function releases a keyboard grab made with @code{x-grab-keyboard}.
@end defun

@defun x-grab-pointer &optional device cursor ignore-keyboard
This function grabs the pointer and restricts it to its current window.
If optional @var{device} argument is @code{nil}, the selected device
will be used.  If optional @var{cursor} argument is non-@code{nil},
change the pointer shape to that until @code{x-ungrab-pointer} is called
(it should be an object returned by the @code{make-cursor} function).
If the second optional argument @var{ignore-keyboard} is non-@code{nil},
ignore all keyboard events during the grab.  Returns @code{t} if the
grab is successful, @code{nil} otherwise.
@end defun

@defun x-ungrab-pointer &optional device
This function releases a pointer grab made with @code{x-grab-pointer}.
If optional first arg @var{device} is @code{nil} the selected device is
used.  If it is @code{t} the pointer will be released on all X devices.
@end defun

@node X Miscellaneous
@section Miscellaneous X Functions and Variables

@defvar x-bitmap-file-path
This variable holds a list of the directories in which X bitmap files
may be found.  If @code{nil}, this is initialized from the
@samp{"*bitmapFilePath"} resource.  This is used by the
@code{make-image-instance} function (however, note that if the
environment variable @samp{XBMLANGPATH} is set, it is consulted first).
@end defvar

@defvar x-library-search-path
This variable holds the search path used by @code{read-color} to find
@file{rgb.txt}.
@end defvar

@defun x-valid-keysym-name-p keysym
This function returns true if @var{keysym} names a keysym that the X
library knows about.  Valid keysyms are listed in the files
@file{/usr/include/X11/keysymdef.h} and in
@file{/usr/lib/X11/XKeysymDB}, or whatever the equivalents are on your
system.
@end defun

@defun x-window-id &optional frame
This function returns the ID of the X11 window.  This gives us a chance
to manipulate the Emacs window from within a different program.  Since
the ID is an unsigned long, we return it as a string.
@end defun

@defvar x-allow-sendevents
If non-@code{nil}, synthetic events are allowed.  @code{nil} means
they are ignored.  Beware: allowing XEmacs to process SendEvents opens a
big security hole.
@end defvar

@defun x-debug-mode arg &optional device
With a true arg, make the connection to the X server synchronous.  With
false, make it asynchronous.  Synchronous connections are much slower,
but are useful for debugging. (If you get X errors, make the connection
synchronous, and use a debugger to set a breakpoint on
@code{x_error_handler}.  Your backtrace of the C stack will now be
useful.  In asynchronous mode, the stack above @code{x_error_handler}
isn't helpful because of buffering.)  If @var{device} is not specified,
the selected device is assumed.

Calling this function is the same as calling the C function
@code{XSynchronize}, or starting the program with the @samp{-sync}
command line argument.
@end defun

@defvar x-debug-events
If non-zero, debug information about events that XEmacs sees is
displayed.  Information is displayed on stderr.  Currently defined
values are:

@itemize @bullet
@item
1 == non-verbose output
@item
2 == verbose output
@end itemize
@end defvar