1 \input texinfo @c -*-texinfo-*-
2 @setfilename ../../info/dbus
4 @settitle Using of D-Bus
5 @c @setchapternewpage odd
9 Copyright @copyright{} 2007, 2008 Free Software Foundation, Inc.
12 Permission is granted to copy, distribute and/or modify this document
13 under the terms of the GNU Free Documentation License, Version 1.2 or
14 any later version published by the Free Software Foundation; with no
15 Invariant Sections, with the Front-Cover texts being ``A GNU Manual'',
16 and with the Back-Cover Texts as in (a) below. A copy of the license
17 is included in the section entitled ``GNU Free Documentation License''.
19 (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
20 modify this GNU manual. Buying copies from the FSF supports it in
21 developing GNU and promoting software freedom.''
27 * D-Bus: (dbus). Using D-Bus in Emacs.
31 @node Top, Overview, (dir), (dir)
32 @top D-Bus integration in Emacs
34 This manual documents an API for usage of D-Bus in
35 Emacs.@footnote{D-Bus is not enabled by default. You must run
36 @command{./configure --with-dbus} in Emacs' top level directory,
37 before you compile Emacs.} D-Bus is a message bus system, a simple
38 way for applications to talk to one another. An overview of D-Bus can
39 be found at @uref{http://dbus.freedesktop.org/}.
44 * Overview:: An overview of D-Bus.
45 * Inspection:: Inspection of D-Bus services.
46 * Type Conversion:: Mapping Lisp types and D-Bus types.
47 * Synchronous Methods:: Calling methods in a blocking way.
48 * Asynchronous Methods:: Calling methods non-blocking.
49 * Receiving Method Calls:: Offering own methods.
50 * Signals:: Sending and receiving signals.
51 * Errors and Events:: Errors and events.
52 * GNU Free Documentation License:: The license for this documentation.
57 @chapter An overview of D-Bus
60 D-Bus is an inter-process communication mechanism for applications
61 residing on the same host. The communication is based on
62 @dfn{messages}. Data in the messages is carried in a structured way,
63 it is not just a byte stream.
65 The communication is connection oriented to two kinds of message
66 buses: a so called @dfn{system bus}, and a @dfn{session bus}. On a
67 given machine, there is always one single system bus for miscellaneous
68 system-wide communication, like changing of hardware configuration.
69 On the other hand, the session bus is always related to a single
72 Every client application, which is connected to a bus, registers under
73 a @dfn{unique name} at the bus. This name is used for identifying the
74 client application. Such a unique name starts always with a colon,
75 and looks like @samp{:1.42}.
77 Additionally, a client application can register itself to a so called
78 @dfn{known name}, which is a series of identifiers separated by dots,
79 as in @samp{org.gnu.Emacs}. If several applications register to the
80 same known name, these registrations are queued, and only the first
81 application which has registered for the known name is reachable via
82 this name. If this application disconnects from the bus, the next
83 queued unique name becomes the owner of this known name.
85 An application can install one or several objects under its name.
86 Such objects are identified by an @dfn{object path}, which looks
87 similar to paths in a filesystem. An example of such an object path
88 could be @samp{/org/gnu/Emacs/}.
90 Applications might send a request to an object, that means sending a
91 message with some data as input parameters, and receiving a message
92 from that object with the result of this message, the output
93 parameters. Such a request is called @dfn{method} in D-Bus.
95 The other form of communication are @dfn{signals}. The underlying
96 message is emitted from an object and will be received by all other
97 applications which have registered for such a signal.
99 All methods and signals an object supports are called @dfn{interface}
100 of the object. Interfaces are specified under a hierarchical name in
101 D-Bus; an object can support several interfaces. Such an interface
102 name could be @samp{org.gnu.Emacs.TextEditor} or
103 @samp{org.gnu.Emacs.FileManager}.
107 @chapter Inspection of D-Bus services.
111 * Bus names:: Discovering D-Bus names.
112 * Introspection:: Knowing the details of D-Bus services.
113 * Nodes and Interfaces:: Detecting object paths and interfaces.
114 * Methods and Signal:: Applying the functionality.
115 * Properties and Annotations:: What else to know about interfaces.
116 * Arguments and Signatures:: The final details.
123 There are several basic functions which inspect the buses for
124 registered names. Internally they use the basic interface
125 @samp{org.freedesktop.DBus}, which is supported by all objects of a bus.
127 @defun dbus-list-activatable-names
128 This function returns the D-Bus service names, which can be activated.
129 An activatable service is described in a service registration file.
130 Under GNU/Linux, such files are located at
131 @file{/usr/share/dbus-1/services/}.
133 The result is a list of strings, which is @code{nil} when there are no
134 activatable service names at all.
137 @defun dbus-list-names bus
138 All service names, which are registered at D-Bus @var{bus}, are
139 returned. The result is a list of strings, which is @code{nil} when
140 there are no registered service names at all. Well known names are
141 strings like @samp{org.freedesktop.DBus}. Names starting with
142 @samp{:} are unique names for services.
144 @var{bus} must be either the symbol @code{:system} or the symbol
148 @defun dbus-list-known-names bus
149 Retrieves all services which correspond to a known name in @var{bus}.
150 A service has a known name if it doesn't start with @samp{:}. The
151 result is a list of strings, which is @code{nil} when there are no
154 @var{bus} must be either the symbol @code{:system} or the symbol
158 @defun dbus-list-queued-owners bus service
159 For a given service, registered at D-Bus @var{bus} under the name
160 @var{service}, all queued unique names are returned. The result is a
161 list of strings, or @code{nil} when there are no queued names for
162 @var{service} at all.
164 @var{bus} must be either the symbol @code{:system} or the symbol
165 @code{:session}. @var{service} must be a known service name as
169 @defun dbus-get-name-owner bus service
170 For a given service, registered at D-Bus @var{bus} under the name
171 @var{service}, the unique name of the name owner is returned. The
172 result is a string, or @code{nil} when there exist no name owner of
175 @var{bus} must be either the symbol @code{:system} or the symbol
176 @code{:session}. @var{service} must be a known service name as
180 @defun dbus-ping bus service
181 Check whether the service name @var{service} is registered at D-Bus
182 @var{bus}. @var{service} might not have been started yet. The result
183 is either @code{t} or @code{nil}.
185 @var{bus} must be either the symbol @code{:system} or the symbol
186 @code{:session}. @var{service} must be a string. Example:
190 "%s screensaver on board."
192 ((dbus-ping :session "org.gnome.ScreenSaver") "Gnome")
193 ((dbus-ping :session "org.freedesktop.ScreenSaver") "KDE")
198 @defun dbus-get-unique-name bus
199 The unique name, under which Emacs is registered at D-Bus @var{bus},
200 is returned as string.
202 @var{bus} must be either the symbol @code{:system} or the symbol
208 @section Knowing the details of D-Bus services.
210 D-Bus services publish their interfaces. This can be retrieved and
211 analyzed during runtime, in order to understand the used
214 The resulting introspection data are in XML format. The root
215 introspection element is always a @code{node} element. It might have
216 a @code{name} attribute, which denotes the (absolute) object path an
217 interface is introspected.
219 The root @code{node} element may have @code{node} and @code{interface}
220 children. A child @code{node} element must have a @code{name}
221 attribute, this case it is the relative object path to the root
224 An @code{interface} element has just one attribute, @code{name}, which
225 is the full name of that interface. The default interface
226 @samp{org.freedesktop.DBus.Introspectable} is always present. Example:
229 <node name="/org/bluez">
230 <interface name="org.freedesktop.DBus.Introspectable">
233 <interface name="org.bluez.Manager">
236 <interface name="org.bluez.Database">
239 <interface name="org.bluez.Security">
242 <node name="service_audio"/>
243 <node name="service_input"/>
244 <node name="service_network"/>
245 <node name="service_serial"/>
249 Children of an @code{interface} element can be @code{method},
250 @code{signal} and @code{property} elements. A @code{method} element
251 stands for a D-Bus method of the surrounding interface. The element
252 itself has a @code{name} attribute, showing the method name. Children
253 elements @code{arg} stand for the arguments of a method. Example:
256 <method name="ResolveHostName">
257 <arg name="interface" type="i" direction="in"/>
258 <arg name="protocol" type="i" direction="in"/>
259 <arg name="name" type="s" direction="in"/>
260 <arg name="aprotocol" type="i" direction="in"/>
261 <arg name="flags" type="u" direction="in"/>
262 <arg name="interface" type="i" direction="out"/>
263 <arg name="protocol" type="i" direction="out"/>
264 <arg name="name" type="s" direction="out"/>
265 <arg name="aprotocol" type="i" direction="out"/>
266 <arg name="address" type="s" direction="out"/>
267 <arg name="flags" type="u" direction="out"/>
271 @code{arg} elements can have the attributes @code{name}, @code{type}
272 and @code{direction}. The @code{name} attribute is optional. The
273 @code{type} attribute stands for the @dfn{signature} of the argument
274 in D-Bus. For a discussion of D-Bus types and their Lisp
275 representation see @ref{Type Conversion}.@footnote{D-Bus signatures
276 are explained in the D-Bus specification
277 @uref{http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-signatures}.}
278 The @code{direction} attribute of an @code{arg} element can be only
279 @samp{in} or @samp{out}; in case it is omitted, it defaults to
282 A @code{signal} element of an @code{interface} has a similar
283 structure. The @code{direction} attribute of an @code{arg} child
284 element can be only @samp{out} here; which is also the default value.
288 <signal name="StateChanged">
289 <arg name="state" type="i"/>
290 <arg name="error" type="s"/>
294 A @code{property} element has no @code{arg} child
295 element. It just has the attributes @code{name}, @code{type} and
296 @code{access}, which are all mandatory. The @code{access} attribute
297 allows the values @samp{readwrite}, @samp{read}, and @samp{write}.
301 <property name="Status" type="u" direction="read"/>
304 @code{annotation} elements can be children of @code{interface},
305 @code{method}, @code{signal}, and @code{property} elements. Unlike
306 properties, which can change their values during lifetime of a D-Bus
307 object, annotations are static. Often they are used for code
308 generators of D-Bus langugae bindings. Example:
311 <annotation name="de.berlios.Pinot.GetStatistics" value="pinotDBus"/>
314 Annotations have just @code{name} and @code{value} attributes, both
317 @defun dbus-introspect bus service path
318 This function returns all interfaces and sub-nodes of @var{service},
319 registered at object path @var{path} at bus @var{bus}.
321 @var{bus} must be either the symbol @code{:system} or the symbol
322 @code{:session}. @var{service} must be a known service name, and
323 @var{path} must be a valid object path. The last two parameters are
324 strings. The result, the introspection data, is a string in XML
329 :system "org.freedesktop.Hal"
330 "/org/freedesktop/Hal/devices/computer")
332 @result{} "<!DOCTYPE node PUBLIC
333 "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
334 "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
336 <interface name="org.freedesktop.Hal.Device">
337 <method name="GetAllProperties">
338 <arg name="properties" direction="out" type="a@{sv@}"/>
341 <signal name="PropertyModified">
342 <arg name="num_updates" type="i"/>
343 <arg name="updates" type="a(sbb)"/>
350 This example informs us, that the service @samp{org.freedesktop.Hal}
351 at object path @samp{/org/freedesktop/Hal/devices/computer} offers the
352 interface @samp{org.freedesktop.Hal.Device} (and 2 other interfaces
353 not documented here). This interface contains the method
354 @samp{GetAllProperties}, which needs no input parameters, but returns
355 as output parameter an array of dictionary entries (key-value pairs).
356 Every dictionary entry has a string as key, and a variant as value.
358 The interface offers also a signal, which returns 2 parameters: an
359 integer, and an array consisting of elements which are a struct of a
360 string and 2 boolean values.@footnote{ The interfaces of the service
361 @samp{org.freedesktop.Hal} are described at
362 @uref{http://people.freedesktop.org/~david/hal-spec/hal-spec.html#interfaces}.}
365 @defun dbus-introspect-xml bus service path
366 This function has the same intention as function
367 @code{dbus-introspect}. The returned value is a parsed XML tree,
368 which can be used for further analysis. Example:
372 :session "org.freedesktop.xesam.searcher"
373 "/org/freedesktop/xesam/searcher/main")
375 @result{} (node ((name . "/org/freedesktop/xesam/searcher/main"))
376 (interface ((name . "org.freedesktop.xesam.Search"))
377 (method ((name . "GetHitData"))
378 (arg ((name . "search") (type . "s") (direction . "in")))
379 (arg ((name . "hit_ids") (type . "au") (direction . "in")))
380 (arg ((name . "fields") (type . "as") (direction . "in")))
381 (arg ((name . "hit_data") (type . "aav") (direction . "out")))
384 (signal ((name . "HitsAdded"))
385 (arg ((name . "search") (type . "s")))
386 (arg ((name . "count") (type . "u")))
394 @defun dbus-introspect-get-attribute object attribute
395 It returns the @var{attribute} value of a D-Bus introspection
396 @var{object}. @var{object} can be every subtree of a parsed XML tree
397 as retrieved with @code{dbus-introspect-xml}. @var{attribute} must be
398 a string according to the attribute names in the D-Bus specification.
402 (dbus-introspect-get-attribute
403 (dbus-introspect-xml :system "org.freedesktop.SystemToolsBackends"
404 "/org/freedesktop/SystemToolsBackends/UsersConfig")
407 @result{} "/org/freedesktop/SystemToolsBackends/UsersConfig"
410 If @var{object} has no @var{attribute}, the function returns nil.
414 @node Nodes and Interfaces
415 @section Detecting object paths and interfaces.
417 The first elements, to be introspected for a D-Bus object, are further
418 object paths and interfaces.
420 @defun dbus-introspect-get-node-names bus service path
421 All node names of @var{service} in D-Bus @var{bus} at object path
422 @var{path} are returned as list of strings. Example:
425 (dbus-introspect-get-node-names
426 :session "org.gnome.seahorse" "/org/gnome/seahorse")
428 @result{} ("crypto" "keys")
431 The node names stand for further object paths of the D-Bus
432 @var{service}, relative to @var{path}. In the example,
433 @samp{/org/gnome/seahorse/crypto} and @samp{/org/gnome/seahorse/keys}
434 are also object paths of the D-Bus service @samp{org.gnome.seahorse}.
437 @defun dbus-introspect-get-all-nodes bus service path
438 This function returns all node names of @var{service} in D-Bus
439 @var{bus} at object path @var{path}. It returns a list of strings
440 with all object paths of @var{service}, starting at @var{path}.
444 (dbus-introspect-get-all-nodes :session "org.gnome.seahorse" "/")
446 @result{} ("/" "/org" "/org/gnome" "/org/gnome/seahorse"
447 "/org/gnome/seahorse/crypto"
448 "/org/gnome/seahorse/keys"
449 "/org/gnome/seahorse/keys/openpgp"
450 "/org/gnome/seahorse/keys/openpgp/local"
451 "/org/gnome/seahorse/keys/openssh"
452 "/org/gnome/seahorse/keys/openssh/local")
456 @defun dbus-introspect-get-interface-names bus service path
457 There will be returned a list strings of all interface names of
458 @var{service} in D-Bus @var{bus} at object path @var{path}. This list
459 will contain the default interface @samp{org.freedesktop.DBus.Introspectable}.
461 Another default interface is @samp{org.freedesktop.DBus.Properties}.
462 If present, @code{interface} elements can also have @code{property}
466 (dbus-introspect-get-interface-names
467 :system "org.freedesktop.Hal"
468 "/org/freedesktop/Hal/devices/computer")
470 @result{} ("org.freedesktop.DBus.Introspectable"
471 "org.freedesktop.Hal.Device"
472 "org.freedesktop.Hal.Device.SystemPowerManagement"
473 "org.freedesktop.Hal.Device.CPUFreq")
477 @defun dbus-introspect-get-interface bus service path interface
478 Return @var{interface} of @var{service} in D-Bus @var{bus} at object
479 path @var{path}. The return value is an XML element. @var{interface}
480 must be a string, element of the list returned by
481 @code{dbus-introspect-get-interface-names}. Example:
484 (dbus-introspect-get-interface
485 :session "org.freedesktop.xesam.searcher"
486 "/org/freedesktop/xesam/searcher/main"
487 "org.freedesktop.xesam.Search")
489 @result{} (interface ((name . "org.freedesktop.xesam.Search"))
490 (method ((name . "GetHitData"))
491 (arg ((name . "search") (type . "s") (direction . "in")))
492 (arg ((name . "hit_ids") (type . "au") (direction . "in")))
493 (arg ((name . "fields") (type . "as") (direction . "in")))
494 (arg ((name . "hit_data") (type . "aav") (direction . "out")))
497 (signal ((name . "HitsAdded"))
498 (arg ((name . "search") (type . "s")))
499 (arg ((name . "count") (type . "u")))
506 With these functions, it is possible to retrieve all introspection
507 data from a running system:
510 (with-current-buffer (switch-to-buffer "*introspect*")
512 (dolist (service (dbus-list-known-names :session))
513 (dolist (path (dbus-introspect-get-all-nodes :session service "/"))
514 ;; We want to introspect only elements, which have more than
515 ;; the default interface "org.freedesktop.DBus.Introspectable".
517 "org.freedesktop.DBus.Introspectable"
518 (dbus-introspect-get-interface-names :session service path))
519 (insert (message "\nservice: \"%s\" path: \"%s\"\n" service path)
520 (dbus-introspect :session service path))
525 @node Methods and Signal
526 @section Applying the functionality.
528 Methods and signals are the communicatione means to D-Bus. The
529 following functions return their specifications.
531 @defun dbus-introspect-get-method-names bus service path interface
532 Return a list of strings of all method names of @var{interface} of
533 @var{service} in D-Bus @var{bus} at object path @var{path}. Example:
536 (dbus-introspect-get-method-names
537 :session "org.freedesktop.xesam.searcher"
538 "/org/freedesktop/xesam/searcher/main"
539 "org.freedesktop.xesam.Search")
541 @result{} ("GetState" "StartSearch" "GetHitCount" "GetHits" "NewSession"
542 "CloseSession" "GetHitData" "SetProperty" "NewSearch"
543 "GetProperty" "CloseSearch")
547 @defun dbus-introspect-get-method bus service path interface method
548 This function returns @var{method} of @var{interface} as XML element.
549 It must be located at @var{service} in D-Bus @var{bus} at object path
550 @var{path}. @var{method} must be a string, element of the list
551 returned by @code{dbus-introspect-get-method-names}. Example:
554 (dbus-introspect-get-method
555 :session "org.freedesktop.xesam.searcher"
556 "/org/freedesktop/xesam/searcher/main"
557 "org.freedesktop.xesam.Search" "GetHitData")
559 @result{} (method ((name . "GetHitData"))
560 (arg ((name . "search") (type . "s") (direction . "in")))
561 (arg ((name . "hit_ids") (type . "au") (direction . "in")))
562 (arg ((name . "fields") (type . "as") (direction . "in")))
563 (arg ((name . "hit_data") (type . "aav") (direction . "out")))
568 @defun dbus-introspect-get-signal-names bus service path interface
569 Return a list of strings of all signal names of @var{interface} of
570 @var{service} in D-Bus @var{bus} at object path @var{path}. Example:
573 (dbus-introspect-get-signal-names
574 :session "org.freedesktop.xesam.searcher"
575 "/org/freedesktop/xesam/searcher/main"
576 "org.freedesktop.xesam.Search")
578 @result{} ("StateChanged" "SearchDone" "HitsModified"
579 "HitsRemoved" "HitsAdded")
583 @defun dbus-introspect-get-signal bus service path interface signal
584 This function returns @var{signal} of @var{interface} as XML element.
585 It must be located at @var{service} in D-Bus @var{bus} at object path
586 @var{path}. @var{signal} must be a string, element of the list
587 returned by @code{dbus-introspect-get-signal-names}. Example:
590 (dbus-introspect-get-signal
591 :session "org.freedesktop.xesam.searcher"
592 "/org/freedesktop/xesam/searcher/main"
593 "org.freedesktop.xesam.Search" "HitsAdded")
595 @result{} (signal ((name . "HitsAdded"))
596 (arg ((name . "search") (type . "s")))
597 (arg ((name . "count") (type . "u")))
603 @node Properties and Annotations
604 @section What else to know about interfaces.
606 Interfaces can have properties. These can be exposed via the
607 @samp{org.freedesktop.DBus.Properties} interface@footnote{See
608 @uref{http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties}}.
609 That is, properties can be retrieved and changed during lifetime of an
612 Annotations, on the other hand, are static values for an element.
613 Often, they are used to instruct generators, how to generate code from
614 the interface for a given language binding.
616 @defun dbus-introspect-get-property-names bus service path interface
617 Return a list of strings with all property names of @var{interface} of
618 @var{service} in D-Bus @var{bus} at object path @var{path}. Example:
621 (dbus-introspect-get-property-names
622 :session "org.kde.kded" "/modules/networkstatus"
623 "org.kde.Solid.Networking.Client")
628 If an interface declares properties, the corresponding element supports
629 also the @samp{org.freedesktop.DBus.Properties} interface.
632 @defun dbus-introspect-get-property bus service path interface property
633 This function returns @var{property} of @var{interface} as XML element.
634 It must be located at @var{service} in D-Bus @var{bus} at object path
635 @var{path}. @var{property} must be a string, element of the list
636 returned by @code{dbus-introspect-get-property-names}.
638 A @var{property} value can be retrieved by the function
639 @code{dbus-introspect-get-attribute}. Example:
642 (dbus-introspect-get-property
643 :session "org.kde.kded" "/modules/networkstatus"
644 "org.kde.Solid.Networking.Client" "Status")
646 @result{} (property ((access . "read") (type . "u") (name . "Status")))
648 (dbus-introspect-get-attribute
649 (dbus-introspect-get-property
650 :session "org.kde.kded" "/modules/networkstatus"
651 "org.kde.Solid.Networking.Client" "Status")
658 @defun dbus-get-property bus service path interface property
659 This function returns the value of @var{property} of @var{interface}.
660 It will be checked at @var{bus}, @var{service}, @var{path}. The
661 result can be any valid D-Bus value, or nil if there is no
662 @var{property}. Example:
666 :session "org.kde.kded" "/modules/networkstatus"
667 "org.kde.Solid.Networking.Client" "Status")
673 @defun dbus-set-property bus service path interface property value
674 Set value of @var{property} of @var{interface} to @var{value}. It
675 will be checked at @var{bus}, @var{service}, @var{path}. When the
676 value has been set successful, the result is @var{value}. Otherwise,
677 @code{nil} is returned. Example:
681 :session "org.kde.kaccess" "/MainApplication"
682 "com.trolltech.Qt.QApplication" "doubleClickInterval" 500)
688 @defun dbus-get-all-properties bus service path interface
689 This function returns all properties of @var{interface}. It will be
690 checked at @var{bus}, @var{service}, @var{path}. The result is a list
691 of cons. Every cons contains the name of the property, and its value.
692 If there are no properties, @code{nil} is returned. Example:
695 (dbus-get-all-properties
696 :session "org.kde.kaccess" "/MainApplication"
697 "com.trolltech.Qt.QApplication")
699 @result{} (("cursorFlashTime" . 1000) ("doubleClickInterval" . 500)
700 ("keyboardInputInterval" . 400) ("wheelScrollLines" . 3)
701 ("globalStrut" 0 0) ("startDragTime" . 500)
702 ("startDragDistance" . 4) ("quitOnLastWindowClosed" . t)
707 @defun dbus-introspect-get-annotation-names bus service path interface &optional name
708 Return a list of all annotation names as list of strings. If
709 @var{name} is @code{nil}, the annotations are children of
710 @var{interface}, otherwise @var{name} must be a @code{method},
711 @code{signal}, or @code{property} XML element, where the annotations
715 (dbus-introspect-get-annotation-names
716 :session "de.berlios.Pinot" "/de/berlios/Pinot"
717 "de.berlios.Pinot" "GetStatistics")
719 @result{} ("de.berlios.Pinot.GetStatistics")
722 Default annotation names@footnote{See
723 @uref{http://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format}}
727 @item org.freedesktop.DBus.Deprecated
728 Whether or not the entity is deprecated; defaults to @code{nil}
730 @item org.freedesktop.DBus.GLib.CSymbol
731 The C symbol; may be used for @code{methods} and @code{interfaces}
733 @item org.freedesktop.DBus.Method.NoReply
734 If set, don't expect a reply to the @code{method} call; defaults to @code{nil}
738 @defun dbus-introspect-get-annotation bus service path interface name annotation
739 Return annotation @var{ANNOTATION} as XML object. If @var{name} is
740 @code{nil}, @var{ANNOTATION} is a child of @var{interface}, otherwise
741 @var{name} must be the name of a @code{method}, @code{signal}, or
742 @code{property} XML element, where the @var{ANNOTATION} belongs to.
744 An attribute value can be retrieved by
745 @code{dbus-introspect-get-attribute}. Example:
748 (dbus-introspect-get-annotation
749 :session "de.berlios.Pinot" "/de/berlios/Pinot"
750 "de.berlios.Pinot" "GetStatistics"
751 "de.berlios.Pinot.GetStatistics")
753 @result{} (annotation ((name . "de.berlios.Pinot.GetStatistics")
754 (value . "pinotDBus")))
756 (dbus-introspect-get-attribute
757 (dbus-introspect-get-annotation
758 :session "de.berlios.Pinot" "/de/berlios/Pinot"
759 "de.berlios.Pinot" "GetStatistics"
760 "de.berlios.Pinot.GetStatistics")
763 @result{} "pinotDBus"
768 @node Arguments and Signatures
769 @section The final details.
771 Methods and signals have arguments. They are described in the
772 @code{arg} XML elements.
774 @defun dbus-introspect-get-argument-names bus service path interface name
775 Return a list of all argument names as list of strings. @var{name}
776 must be a @code{method} or @code{signal} XML element. Example:
779 (dbus-introspect-get-argument-names
780 :session "org.freedesktop.xesam.searcher"
781 "/org/freedesktop/xesam/searcher/main"
782 "org.freedesktop.xesam.Search" "GetHitData")
784 @result{} ("search" "hit_ids" "fields" "hit_data")
787 Argument names are optional; the function can return @code{nil}
788 therefore, even if the method or signal has arguments.
791 @defun dbus-introspect-get-argument bus service path interface name arg
792 Return argument @var{ARG} as XML object. @var{name}
793 must be a @code{method} or @code{signal} XML element. Example:
796 (dbus-introspect-get-argument
797 :session "org.freedesktop.xesam.searcher"
798 "/org/freedesktop/xesam/searcher/main"
799 "org.freedesktop.xesam.Search" "GetHitData" "search")
801 @result{} (arg ((name . "search") (type . "s") (direction . "in")))
805 @defun dbus-introspect-get-signature bus service path interface name &optional direction
806 Return signature of a @code{method} or @code{signal}, represented by
807 @var{name}, as string.
809 If @var{name} is a @code{method}, @var{direction} can be either
810 @samp{in} or @samp{out}. If @var{direction} is @code{nil}, @samp{in}
813 If @var{name} is a @code{signal}, and @var{direction} is
814 non-@code{nil}, @var{direction} must be @samp{out}. Example:
817 (dbus-introspect-get-signature
818 :session "org.freedesktop.xesam.searcher"
819 "/org/freedesktop/xesam/searcher/main"
820 "org.freedesktop.xesam.Search" "GetHitData" "in")
824 (dbus-introspect-get-signature
825 :session "org.freedesktop.xesam.searcher"
826 "/org/freedesktop/xesam/searcher/main"
827 "org.freedesktop.xesam.Search" "HitsAdded")
834 @node Type Conversion
835 @chapter Mapping Lisp types and D-Bus types.
836 @cindex type conversion
838 D-Bus method calls and signals accept usually several arguments as
839 parameters, either as input parameter, or as output parameter. Every
840 argument belongs to a D-Bus type.
842 Such arguments must be mapped between the value encoded as a D-Bus
843 type, and the corresponding type of Lisp objects. The mapping is
844 applied Lisp object @expansion{} D-Bus type for input parameters, and
845 D-Bus type @expansion{} Lisp object for output parameters.
848 @section Input parameters.
850 Input parameters for D-Bus methods and signals occur as arguments of a
851 Lisp function call. The following mapping to D-Bus types is
852 applied, when the corresponding D-Bus message is created:
855 @multitable {@code{t} and @code{nil}} {@expansion{}} {DBUS_TYPE_BOOLEAN}
856 @item Lisp type @tab @tab D-Bus type
858 @item @code{t} and @code{nil} @tab @expansion{} @tab DBUS_TYPE_BOOLEAN
859 @item number @tab @expansion{} @tab DBUS_TYPE_UINT32
860 @item integer @tab @expansion{} @tab DBUS_TYPE_INT32
861 @item float @tab @expansion{} @tab DBUS_TYPE_DOUBLE
862 @item string @tab @expansion{} @tab DBUS_TYPE_STRING
863 @item list @tab @expansion{} @tab DBUS_TYPE_ARRAY
867 Other Lisp objects, like symbols or hash tables, are not accepted as
870 If it is necessary to use another D-Bus type, a corresponding type
871 symbol can be preceeded to the corresponding Lisp object. Basic D-Bus
872 types are represented by the type symbols @code{:byte},
873 @code{:boolean}, @code{:int16}, @code{:uint16}, @code{:int32},
874 @code{:uint32}, @code{:int64}, @code{:uint64}, @code{:double},
875 @code{:string}, @code{:object-path} and @code{:signature}.
881 (dbus-call-method @dots{} @var{NUMBER} @var{STRING})
887 (dbus-call-method @dots{} :uint32 @var{NUMBER} :string @var{STRING})
893 (dbus-call-method @dots{} :int32 @var{NUMBER} :signature @var{STRING})
896 The value for a byte D-Bus type can be any integer in the range 0
897 through 255. If a character is used as argument, modifiers
898 represented outside this range are stripped of. For example,
899 @code{:byte ?x} is equal to @code{:byte ?\M-x}, but it is not equal to
900 @code{:byte ?\C-x} or @code{:byte ?\M-\C-x}.
902 A D-Bus compound type is always represented as a list. The @sc{car}
903 of this list can be the type symbol @code{:array}, @code{:variant},
904 @code{:struct} or @code{:dict-entry}, which would result in a
905 corresponding D-Bus container. @code{:array} is optional, because
906 this is the default compound D-Bus type for a list.
908 The objects being elements of the list are checked according to the
909 D-Bus compound type rules.
912 @item An array must contain only elements of the same D-Bus type. It
915 @item A variant must contain only one single element.
917 @item A dictionary entry must be element of an array, and it must
918 contain only a key-value pair of two elements, with a basic D-Bus type
921 @item There is no restriction for structs.
924 If an empty array needs an element D-Bus type other than string, it
925 can contain exactly one element of D-Bus type @code{:signature}. The
926 value of this element (a string) is used as the signature of the
927 elements of this array. Example:
931 :session "org.freedesktop.Notifications"
932 "/org/freedesktop/Notifications"
933 "org.freedesktop.Notifications" "Notify"
934 "GNU Emacs" ;; Application name.
935 0 ;; No replacement of other notifications.
937 "Notification summary" ;; Summary.
939 "This is a test notification, raised from %s" (emacs-version))
940 '(:array) ;; No actions (empty array of strings).
941 '(:array :signature "@{sv@}") ;; No hints
942 ;; (empty array of dictionary entries).
943 ':int32 -1) ;; Default timeout.
949 @section Output parameters.
951 Output parameters of D-Bus methods and signals are mapped to Lisp
955 @multitable {DBUS_TYPE_OBJECT_PATH} {@expansion{}} {@code{t} or @code{nil}}
956 @item D-Bus type @tab @tab Lisp type
958 @item DBUS_TYPE_BOOLEAN @tab @expansion{} @tab @code{t} or @code{nil}
959 @item DBUS_TYPE_BYTE @tab @expansion{} @tab number
960 @item DBUS_TYPE_UINT16 @tab @expansion{} @tab number
961 @item DBUS_TYPE_INT16 @tab @expansion{} @tab number
962 @item DBUS_TYPE_UINT32 @tab @expansion{} @tab number or float
963 @item DBUS_TYPE_INT32 @tab @expansion{} @tab number or float
964 @item DBUS_TYPE_UINT64 @tab @expansion{} @tab number or float
965 @item DBUS_TYPE_INT64 @tab @expansion{} @tab number or float
966 @item DBUS_TYPE_DOUBLE @tab @expansion{} @tab float
967 @item DBUS_TYPE_STRING @tab @expansion{} @tab string
968 @item DBUS_TYPE_OBJECT_PATH @tab @expansion{} @tab string
969 @item DBUS_TYPE_SIGNATURE @tab @expansion{} @tab string
970 @item DBUS_TYPE_ARRAY @tab @expansion{} @tab list
971 @item DBUS_TYPE_VARIANT @tab @expansion{} @tab list
972 @item DBUS_TYPE_STRUCT @tab @expansion{} @tab list
973 @item DBUS_TYPE_DICT_ENTRY @tab @expansion{} @tab list
977 A float object in case of @code{DBUS_TYPE_UINT32},
978 @code{DBUS_TYPE_INT32}, @code{DBUS_TYPE_UINT64} and
979 @code{DBUS_TYPE_INT6432} is returned, when the C value exceeds the
980 Emacs number size range.
982 The resulting list of the last 4 D-Bus compound types contains as
983 elements the elements of the D-Bus container, mapped according to the
986 The signal @code{PropertyModified}, discussed as example in
987 @ref{Inspection}, would offer as Lisp data the following object
988 (@var{BOOL} stands here for either @code{nil} or @code{t}):
991 (@var{NUMBER} ((@var{STRING} @var{BOOL} @var{BOOL}) (@var{STRING} @var{BOOL} @var{BOOL}) @dots{}))
995 @node Synchronous Methods
996 @chapter Calling methods in a blocking way.
997 @cindex method calls, synchronous
998 @cindex synchronous method calls
1000 Methods can be called synchronously (@dfn{blocking}) or asynchronously
1001 (@dfn{non-blocking}).
1003 At D-Bus level, a method call consist of two messages: one message
1004 which carries the input parameters to the object owning the method to
1005 be called, and a reply message returning the resulting output
1006 parameters from the object.
1008 @defun dbus-call-method bus service path interface method &optional :timeout timeout &rest args
1009 This function calls @var{method} on the D-Bus @var{bus}. @var{bus} is
1010 either the symbol @code{:system} or the symbol @code{:session}.
1012 @var{service} is the D-Bus service name to be used. @var{path} is the
1013 D-Bus object path, @var{service} is registered at. @var{interface} is
1014 an interface offered by @var{service}. It must provide @var{method}.
1016 If the parameter @code{:timeout} is given, the following integer
1017 @var{timeout} specifies the maximum number of milliseconds the method
1018 call must return. The default value is 25.000. If the method call
1019 doesn't return in time, a D-Bus error is raised (@pxref{Errors and
1022 All other arguments args are passed to @var{method} as arguments.
1023 They are converted into D-Bus types as described in @ref{Type
1026 The function returns the resulting values of @var{method} as a list of
1027 Lisp objects, according to the type conversion rules described in
1028 @ref{Type Conversion}. Example:
1032 :session "org.gnome.seahorse" "/org/gnome/seahorse/keys/openpgp"
1033 "org.gnome.seahorse.Keys" "GetKeyField"
1034 "openpgp:657984B8C7A966DD" "simple-name")
1036 @result{} (t ("Philip R. Zimmermann"))
1039 If the result of the method call is just one value, the converted Lisp
1040 object is returned instead of a list containing this single Lisp
1045 :system "org.freedesktop.Hal"
1046 "/org/freedesktop/Hal/devices/computer"
1047 "org.freedesktop.Hal.Device" "GetPropertyString"
1048 "system.kernel.machine")
1053 With the @code{dbus-introspect} function it is possible to explore the
1054 interfaces of @samp{org.freedesktop.Hal} service. It offers the
1055 interfaces @samp{org.freedesktop.Hal.Manager} for the object at the
1056 path @samp{/org/freedesktop/Hal/Manager} as well as the interface
1057 @samp{org.freedesktop.Hal.Device} for all objects prefixed with the
1058 path @samp{/org/freedesktop/Hal/devices}. With the methods
1059 @samp{GetAllDevices} and @samp{GetAllProperties}, it is simple to
1060 emulate the @code{lshal} command on GNU/Linux systems:
1065 :system "org.freedesktop.Hal"
1066 "/org/freedesktop/Hal/Manager"
1067 "org.freedesktop.Hal.Manager" "GetAllDevices"))
1068 (message "\nudi = %s" device)
1071 :system "org.freedesktop.Hal" device
1072 "org.freedesktop.Hal.Device" "GetAllProperties"))
1074 (car properties) (or (caar (cdr properties)) ""))))
1076 @print{} "udi = /org/freedesktop/Hal/devices/computer
1077 info.addons = (\"hald-addon-acpi\")
1078 info.bus = \"unknown\"
1079 info.product = \"Computer\"
1080 info.subsystem = \"unknown\"
1081 info.udi = \"/org/freedesktop/Hal/devices/computer\"
1082 linux.sysfs_path_device = \"(none)\"
1083 power_management.acpi.linux.version = \"20051216\"
1084 power_management.can_suspend_to_disk = t
1085 power_management.can_suspend_to_ram = \"\"
1086 power_management.type = \"acpi\"
1087 smbios.bios.release_date = \"11/07/2001\"
1088 system.chassis.manufacturer = \"COMPAL\"
1089 system.chassis.type = \"Notebook\"
1090 system.firmware.release_date = \"03/19/2005\"
1095 @defun dbus-call-method-non-blocking bus service path interface method &optional :timeout timeout &rest args
1096 Call @var{method} on the D-Bus @var{bus}, but don't block the event queue.
1097 This is necessary for communicating to registered D-Bus methods,
1098 which are running in the same Emacs process.
1100 The arguments are the same as in @code{dbus-call-method}. Example:
1103 (dbus-call-method-non-blocking
1104 :system "org.freedesktop.Hal"
1105 "/org/freedesktop/Hal/devices/computer"
1106 "org.freedesktop.Hal.Device" "GetPropertyString"
1107 "system.kernel.machine")
1114 @node Asynchronous Methods
1115 @chapter Calling methods non-blocking.
1116 @cindex method calls, asynchronous
1117 @cindex asynchronous method calls
1119 @defun dbus-call-method-asynchronously bus service path interface method handler &optional :timeout timeout &rest args
1120 This function calls @var{method} on the D-Bus @var{bus}
1121 asynchronously. @var{bus} is either the symbol @code{:system} or the
1122 symbol @code{:session}.
1124 @var{service} is the D-Bus service name to be used. @var{path} is the
1125 D-Bus object path, @var{service} is registered at. @var{interface} is
1126 an interface offered by @var{service}. It must provide @var{method}.
1128 @var{handler} is a Lisp function, which is called when the
1129 corresponding return message has arrived.
1131 If the parameter @code{:timeout} is given, the following integer
1132 @var{timeout} specifies the maximum number of milliseconds a reply
1133 message must arrive. The default value is 25.000. If there is no
1134 reply message in time, a D-Bus error is raised (@pxref{Errors and
1137 All other arguments args are passed to @var{method} as arguments.
1138 They are converted into D-Bus types as described in @ref{Type
1141 The function returns a key into the hash table
1142 @code{dbus-registered-functions-table}. The corresponding entry in
1143 the hash table is removed, when the return message has been arrived,
1144 and @var{handler} is called. Example:
1147 (dbus-call-method-asynchronously
1148 :system "org.freedesktop.Hal"
1149 "/org/freedesktop/Hal/devices/computer"
1150 "org.freedesktop.Hal.Device" "GetPropertyString" 'message
1151 "system.kernel.machine")
1153 @result{} (:system 2)
1160 @node Receiving Method Calls
1161 @chapter Offering own methods.
1162 @cindex method calls, returning
1163 @cindex returning method calls
1165 Emacs can also offer own methods, which can be called by other
1166 applications. These methods could be an implementation of an
1167 interface of a well known service, like @samp{org.freedesktop.TextEditor}.
1169 It could be also an implementation of an own interface. In this case,
1170 the service name must be @samp{org.gnu.Emacs}. The object path shall
1171 begin with @samp{/org/gnu/Emacs/@strong{Application}/}, and the
1172 interface name shall be @code{org.gnu.Emacs.@strong{Application}}.
1173 @samp{@strong{Application}} is the name of the application which
1174 provides the interface.
1176 @defun dbus-register-method bus service path interface method handler
1177 With this function, an application registers @var{method} on the D-Bus
1180 @var{bus} is either the symbol @code{:system} or the symbol
1183 @var{service} is the D-Bus service name of the D-Bus object
1184 @var{method} is registered for. It must be a known name.
1186 @var{path} is the D-Bus object path @var{service} is
1189 @var{interface} is the interface offered by @var{service}. It must
1190 provide @var{method}.
1192 @var{handler} is a Lisp function to be called when when a @var{method}
1193 call is is received. It must accept as arguments the input arguments
1194 of @var{method}. @var{handler} must return a list, which elements are
1195 used as arguments for the reply message of @var{method}. This list
1196 can be composed like the input parameters in @ref{Type Conversion}.
1198 The default D-Bus timeout when waiting for a message reply is 25
1199 seconds. This value could be even smaller, depending on the calling
1200 client. Therefore, @var{handler} shall not last longer than
1201 absolutely necessary.
1203 @code{dbus-register-method} returns a Lisp object, which can be used
1204 as argument in @code{dbus-unregister-object} for removing the
1205 registration for @var{method}. Example:
1208 (defun my-dbus-method-handler (filename)
1210 (if (find-file filename)
1211 (setq result '(:boolean t))
1212 (setq result '(:boolean nil)))
1215 @result{} my-dbus-method-handler
1217 (dbus-register-method
1218 :session "org.freedesktop.TextEditor" "/org/freedesktop/TextEditor"
1219 "org.freedesktop.TextEditor" "OpenFile"
1220 'my-dbus-method-handler)
1222 @result{} ((:session "org.freedesktop.TextEditor" "OpenFile")
1223 ("org.freedesktop.TextEditor" "/org/freedesktop/TextEditor"
1224 my-dbus-method-handler))
1227 If you invoke the method @samp{org.freedesktop.TextEditor.OpenFile}
1228 from another D-Bus application with a filename as parameter, the file
1229 is opened in Emacs, and the method returns either @var{true} or
1230 @var{false}, indicating the success if the method. As test tool one
1231 could use the command line tool @code{dbus-send} in a shell:
1234 # dbus-send --session --print-reply \
1235 --dest="org.freedesktop.TextEditor" \
1236 "/org/freedesktop/TextEditor" \
1237 "org.freedesktop.TextEditor.OpenFile" string:"/etc/hosts"
1239 @print{} method return sender=:1.22 -> dest=:1.23 reply_serial=2
1243 You can indicate an error by raising the Emacs signal
1244 @code{dbus-error}. The handler above could be changed like this:
1247 (defun my-dbus-method-handler (&rest args)
1248 (unless (and (= (length args) 1) (stringp (car args)))
1249 (signal 'dbus-error (list (format "Wrong argument list: %S" args))))
1251 (find-file (car args))
1252 (error (signal 'dbus-error (cdr err))))
1255 @result{} my-dbus-method-handler
1261 # dbus-send --session --print-reply \
1262 --dest="org.freedesktop.TextEditor" \
1263 "/org/freedesktop/TextEditor" \
1264 "org.freedesktop.TextEditor.OpenFile" \
1265 string:"/etc/hosts" string:"/etc/passwd"
1267 @print{} Error org.freedesktop.DBus.Error.Failed:
1268 Wrong argument list: ("/etc/hosts" "/etc/passwd")
1274 @chapter Sending and receiving signals.
1277 Signals are broadcast messages. They carry input parameters, which
1278 are received by all objects which have registered for such a signal.
1280 @defun dbus-send-signal bus service path interface signal &rest args
1281 This function is similar to @code{dbus-call-method}. The difference
1282 is, that there are no returning output parameters.
1284 The function emits @var{signal} on the D-Bus @var{bus}. @var{bus} is
1285 either the symbol @code{:system} or the symbol @code{:session}. It
1286 doesn't matter whether another object has registered for @var{signal}.
1288 @var{service} is the D-Bus service name of the object the signal is
1289 emitted from. @var{path} is the corresponding D-Bus object path,
1290 @var{service} is registered at. @var{interface} is an interface
1291 offered by @var{service}. It must provide @var{signal}.
1293 All other arguments args are passed to @var{signal} as arguments.
1294 They are converted into D-Bus types as described in @ref{Type
1295 Conversion}. Example:
1299 :session "org.gnu.Emacs" "/org/gnu/Emacs"
1300 "org.gnu.Emacs.FileManager" "FileModified" "/home/albinus/.emacs")
1304 @defun dbus-register-signal bus service path interface signal handler &rest args
1305 With this function, an application registers for @var{signal} on the
1308 @var{bus} is either the symbol @code{:system} or the symbol
1311 @var{service} is the D-Bus service name used by the sending D-Bus
1312 object. It can be either a known name or the unique name of the D-Bus
1313 object sending the signal. In case of a unique name, signals won't be
1314 received any longer once the object owning this unique name has
1315 disappeared, and a new queued object has replaced it.
1317 When @var{service} is @code{nil}, related signals from all D-Bus
1318 objects shall be accepted.
1320 @var{path} is the corresponding D-Bus object path, @var{service} is
1321 registered at. It can also be @code{nil} if the path name of incoming
1322 signals shall not be checked.
1324 @var{interface} is an interface offered by @var{service}. It must
1325 provide @var{signal}.
1327 @var{handler} is a Lisp function to be called when the @var{signal} is
1328 received. It must accept as arguments the output parameters
1329 @var{signal} is sending.
1331 All other arguments @var{args}, if specified, must be strings. They
1332 stand for the respective arguments of @var{signal} in their order, and
1333 are used for filtering as well. A @code{nil} argument might be used
1334 to preserve the order.
1336 @code{dbus-register-signal} returns a Lisp object, which can be used
1337 as argument in @code{dbus-unregister-object} for removing the
1338 registration for @var{signal}. Example:
1341 (defun my-dbus-signal-handler (device)
1342 (message "Device %s added" device))
1344 @result{} my-dbus-signal-handler
1346 (dbus-register-signal
1347 :system "org.freedesktop.Hal" "/org/freedesktop/Hal/Manager"
1348 "org.freedesktop.Hal.Manager" "DeviceAdded"
1349 'my-dbus-signal-handler)
1351 @result{} ((:system "org.freedesktop.Hal.Manager" "DeviceAdded")
1352 ("org.freedesktop.Hal" "/org/freedesktop/Hal/Manager"
1356 As we know from the introspection data of interface
1357 @samp{org.freedesktop.Hal.Manager}, the signal @samp{DeviceAdded}
1358 provides one single parameter, which is mapped into a Lisp string.
1359 The callback function @code{my-dbus-signal-handler} must define one
1360 single string argument therefore. Plugging an USB device to your
1361 machine, when registered for signal @samp{DeviceAdded}, will show you
1362 which objects the GNU/Linux @code{hal} daemon adds.
1365 @defun dbus-unregister-object object
1366 Unregister @var{object} from the the D-Bus. @var{object} must be the
1367 result of a preceding @code{dbus-register-signal} or
1368 @code{dbus-register-method} call. It returns @code{t} if @var{object}
1369 has been unregistered, @code{nil} otherwise.
1373 @node Errors and Events
1374 @chapter Errors and events.
1378 Input parameters of @code{dbus-call-method},
1379 @code{dbus-call-method-non-blocking},
1380 @code{dbus-call-method-asynchronously}, and
1381 @code{dbus-register-signal} are checked for correct D-Bus types. If
1382 there is a type mismatch, the Lisp error @code{wrong-type-argument}
1383 @code{D-Bus ARG} is raised.
1385 All errors raised by D-Bus are signaled with the error symbol
1386 @code{dbus-error}. If possible, error messages from D-Bus are
1387 appended to the @code{dbus-error}.
1389 @defspec dbus-ignore-errors forms@dots{}
1390 This executes @var{forms} exactly like a @code{progn}, except that
1391 @code{dbus-error} errors are ignored during the @var{forms}. These
1392 errors can be made visible when variable @code{dbus-debug} is set to
1396 Incoming D-Bus messages are handled as Emacs events (see @pxref{Misc
1397 Events, , , elisp}). The generated event has this form:
1400 (dbus-event @var{bus} @var{type} @var{serial} @var{service} @var{path} @var{interface} @var{member} @var{handler}
1404 @var{bus} identifies the D-Bus the message is coming from. It is
1405 either the symbol @code{:system} or the symbol @code{:session}.
1407 @var{type} is the D-Bus message type which has caused the event. It
1408 can be @code{dbus-message-type-invalid},
1409 @code{dbus-message-type-method-call},
1410 @code{dbus-message-type-method-return},
1411 @code{dbus-message-type-error}, or @code{dbus-message-type-signal}.
1412 @var{serial} is the serial number of the received D-Bus message.
1414 @var{service} and @var{path} are the unique name and the object path
1415 of the D-Bus object emitting the message. @var{interface} and
1416 @var{member} denote the message which has been sent.
1418 @var{handler} is the callback function which has been registered for
1419 this message (see @pxref{Signals}). When a @code{dbus-event} event
1420 arrives, @var{handler} is called with @var{args} as arguments.
1422 In order to inspect the @code{dbus-event} data, you could extend the
1423 definition of the callback function in @ref{Signals}:
1426 (defun my-dbus-signal-handler (&rest args)
1427 (message "my-dbus-signal-handler: %S" last-input-event))
1430 There exist convenience functions which could be called inside a
1431 callback function in order to retrieve the information from the event.
1433 @defun dbus-event-bus-name event
1434 Returns the bus name @var{event} is coming from.
1435 The result is either the symbol @code{:system} or the symbol @code{:session}.
1438 @defun dbus-event-message-type event
1439 Returns the message type of the corresponding D-Bus message. The
1443 @defun dbus-event-serial-number event
1444 Returns the serial number of the corresponding D-Bus message.
1445 The result is a number.
1448 @defun dbus-event-service-name event
1449 Returns the unique name of the D-Bus object @var{event} is coming from.
1452 @defun dbus-event-path-name event
1453 Returns the object path of the D-Bus object @var{event} is coming from.
1456 @defun dbus-event-interface-name event
1457 Returns the interface name of of the D-Bus object @var{event} is coming from.
1460 @defun dbus-event-member-name event
1461 Returns the member name of of the D-Bus object @var{event} is coming
1462 from. It is either a signal name or a method name.
1465 D-Bus errors are not propagated during event handling, because it is
1466 usually not desired. D-Bus errors in events can be made visible by
1467 setting the variable @code{dbus-debug} to @code{t}.
1470 @node GNU Free Documentation License
1471 @appendix GNU Free Documentation License
1472 @include doclicense.texi
1479 arch-tag: 2eeec19d-0caf-44e0-a193-329d7f9951d8