Merge branch 'dbus-1.4'

[platform/upstream/dbus.git] / README

diff --git a/README b/README
index 0eb45e3..bd2921a 100644 (file)
--- a/README
+++ b/README
@@ -1,74 +1,111 @@
-D-BUS is a simple IPC library based on messages.
+Sections in this file describe:
+ - introduction and overview
+ - low-level vs. high-level API
+ - version numbers
+ - options to the configure script
+ - ABI stability policy
+
+Introduction
+===
+
+D-Bus is a simple system for interprocess communication and coordination.

 
 

-See also the file HACKING for notes of interest to developers working on D-BUS.
+The "and coordination" part is important; D-Bus provides a bus daemon that does things like:
+ - notify applications when other apps exit
+ - start services on demand
+ - support single-instance applications

 
 See http://www.freedesktop.org/software/dbus/ for lots of documentation, 
 mailing lists, etc.
 
 
 See http://www.freedesktop.org/software/dbus/ for lots of documentation, 
 mailing lists, etc.
 

-Note
+See also the file HACKING for notes of interest to developers working on D-Bus.
+
+If you're considering D-Bus for use in a project, you should be aware
+that D-Bus was designed for a couple of specific use cases, a "system
+bus" and a "desktop session bus." These are documented in more detail
+in the D-Bus specification and FAQ available on the web site.
+
+If your use-case isn't one of these, D-Bus may still be useful, but
+only by accident; so you should evaluate carefully whether D-Bus makes
+sense for your project.
+
+Note: low-level API vs. high-level binding APIs

 ===
 
 ===
 

-A core concept of the D-BUS implementation is that "libdbus" is
-intended to be a low-level API, similar to Xlib. Most programmers are
-intended to use the bindings to GLib, Qt, Python, Mono, Java, or
-whatever. These bindings have varying levels of completeness.
+A core concept of the D-Bus implementation is that "libdbus" is
+intended to be a low-level API. Most programmers are intended to use
+the bindings to GLib, Qt, Python, Mono, Java, or whatever. These
+bindings have varying levels of completeness and are maintained as
+separate projects from the main D-Bus package. The main D-Bus package
+contains the low-level libdbus, the bus daemon, and a few command-line
+tools such as dbus-launch.

 
 

-Configuration flags
+If you use the low-level API directly, you're signing up for some
+pain. Think of the low-level API as analogous to Xlib or GDI, and the
+high-level API as analogous to Qt/GTK+/HTML.
+
+Version numbers

 ===
 
 ===
 

-These are the dbus-specific configuration flags that can be given to
-the ./configure program.
-
-  --enable-qt             enable Qt-friendly client library (note: Qt4)
-  --enable-qt-debug       enable Qt-friendly client library, linked to debug
-                          Qt libraries
-  --enable-qt3            enable Qt3-friendly client library
-  --enable-glib           enable GLib-friendly client library
-  --enable-gtk            enable GTK-requiring executables
-  --enable-tests          enable unit test code
-  --enable-ansi           enable -ansi -pedantic gcc flags
-  --enable-verbose-mode   support verbose debug mode
-  --enable-asserts        include assertion checks
-  --enable-checks         include sanity checks on public API
-  --enable-xml-docs       build XML documentation (requires xmlto)
-  --enable-doxygen-docs   build DOXYGEN documentation (requires Doxygen)
-  --enable-gcov           compile with coverage profiling instrumentation (gcc only)
-  --enable-abstract-sockets
-                          use abstract socket namespace (linux only)
-  --enable-gcj            build gcj bindings
-  --enable-mono           build mono bindings
-  --enable-mono-docs      build mono docs
-  --enable-python         build python bindings
-  --enable-selinux        build with SELinux support
-  --enable-dnotify        build with dnotify support (linux only)
-
-  --with-qt-moc=<path>              moc for Qt
-  --with-qt3-moc=<path>             moc for Qt3
-  --with-xml=libxml/expat           XML library to use
-  --with-init-scripts=redhat        Style of init scripts to install
-  --with-session-socket-dir=dirname Where to put sockets for the per-login-session message bus
-  --with-test-socket-dir=dirname    Where to put sockets for make check
-  --with-system-pid-file=pidfile    PID file for systemwide daemon
-  --with-system-socket=filename     UNIX domain socket for systemwide daemon
-  --with-console-auth-dir=dirname   directory to check for console ownerhip
-  --with-dbus-user=<user>           User for running the DBUS daemon (messagebus)
-  --with-gnu-ld                     assume the C compiler uses GNU ld [default=no]
-  --with-tags[=TAGS]                include additional configurations [automatic]
-  --with-x                          use the X Window System
+D-Bus uses the common "Linux kernel" versioning system, where
+even-numbered minor versions are stable and odd-numbered minor
+versions are development snapshots.

 
 

+So for example, development snapshots: 1.1.1, 1.1.2, 1.1.3, 1.3.4
+Stable versions: 1.0, 1.0.1, 1.0.2, 1.2.1, 1.2.3

 
 

-API/ABI Policy
+All pre-1.0 versions were development snapshots.
+
+Development snapshots make no ABI stability guarantees for new ABI
+introduced since the last stable release. Development snapshots are
+likely to have more bugs than stable releases, obviously.
+
+Configuration 

 ===
 
 ===
 

-D-BUS API/ABI and protocol necessarily remain in flux until we are
-sure it will meet the various needs it's intended to meet. This means
-we need to see some significant sample usage in the contexts of GNOME,
-KDE, desktop applications, and systemwide uses such as print queue
-monitoring, hotplug events, or whatever. We need the flexibility to
-incorporate feedback from this sample usage.
+dbus could be build by using autotools or cmake. 

 
 

-Once we feel confident in the protocol and the API, we will release a 
-version 1.0. At that point, the intent is:
+When using autotools the configure step is initiated by running ./configure 
+with our without additional configuration flags. 
+
+When using cmake the configure step is initiated by running the cmake 
+program with our without additional configuration flags. 
+
+Configuration flags
+===
+
+When using autotools, run "./configure --help" to see the possible
+configuration options and environment variables.
+
+When using the cmake build system the dbus-specific configuration flags that can be given 
+to the cmake program are these (use -D<key>=<value> on command line)
+
+    CMAKE_BUILD_TYPE                   set dbus build mode - one of Debug|Release|RelWithDebInfo|MinSizeRel
+    DBUS_BUILD_TESTS                   enable unit test code  default=ON
+    DBUS_BUILD_X11                     Build with X11 autolaunch support default=ON
+    HAVE_CONSOLE_OWNER_FILE            enable console owner file (solaris only) ) default=ON
+    DBUS_DISABLE_ASSERTS               Disable assertion checking default=OFF
+    DBUS_DISABLE_CHECKS                Disable public API sanity checking default=OFF
+    DBUS_ENABLE_ABSTRACT_SOCKETS       enable support for abstract sockets (linux only) default=ON
+    DBUS_ENABLE_ANSI                   enable -ansi -pedantic gcc flags default=OFF
+    DBUS_ENABLE_DNOTIFY                build with dnotify support (linux only) default=ON
+    DBUS_ENABLE_VERBOSE_MODE           support verbose debug mode default=ON
+    DBUS_ENABLE_DOXYGEN_DOCS           build DOXYGEN documentation (requires Doxygen) default=ON
+    DBUS_GCOV_ENABLED                  compile with coverage profiling instrumentation (gcc only) default=OFF
+    DBUS_INSTALL_SYSTEM_LIBS           install required system libraries default (windows only) =OFF
+    DBUS_USE_EXPAT                     Use expat (== ON) or libxml2 (==OFF) default=ON [1]
+    DBUS_USE_NONCE_TCP_DEFAULT_ADDRESS Use nonce tcp default address default=OFF
+    DBUS_USE_OUTPUT_DEBUG_STRING       enable win32 debug port for message output default=OFF
+    
+    [1] requires installed development package of the related dependency 
+
+    
+API/ABI Policy
+===
+
+Now that D-Bus has reached version 1.0, the objective is that all
+applications dynamically linked to libdbus will continue working
+indefinitely with the most recent system and session bus daemons.

 
  - The protocol will never be broken again; any message bus should 
    work with any client forever. However, extensions are possible
 
  - The protocol will never be broken again; any message bus should 
    work with any client forever. However, extensions are possible


@@ -79,23 +116,47 @@ version 1.0. At that point, the intent is:
    it will always be possible to compile against and use the older 
    API, and apps will always get the API they expect.
 
    it will always be possible to compile against and use the older 
    API, and apps will always get the API they expect.
 

-Until 1.0 is released, feedback that requires API changes may be
-incorporated into D-BUS. This may break the API, the ABI, the
-protocol, or all three.
+Interfaces can and probably will be _added_. This means both new
+functions and types in libdbus, and new methods exported to
+applications by the bus daemon.
+
+The above policy is intended to make D-Bus as API-stable as other
+widely-used libraries (such as GTK+, Qt, Xlib, or your favorite
+example). If you have questions or concerns they are very welcome on
+the D-Bus mailing list.
+
+NOTE ABOUT DEVELOPMENT SNAPSHOTS AND VERSIONING
+
+Odd-numbered minor releases (1.1.x, 1.3.x, 2.1.x, etc. -
+major.minor.micro) are devel snapshots for testing, and any new ABI
+they introduce relative to the last stable version is subject to
+change during the development cycle.
+
+Any ABI found in a stable release, however, is frozen.
+
+ABI will not be added in a stable series if we can help it. i.e. the
+ABI of 1.2.0 and 1.2.5 you can expect to be the same, while the ABI of
+1.4.x may add more stuff not found in 1.2.x.
+
+NOTE ABOUT STATIC LINKING
+
+We are not yet firmly freezing all runtime dependencies of the libdbus
+library. For example, the library may read certain files as part of
+its implementation, and these files may move around between versions.

 
 

-To avoid a huge soname, the plan is to increment the soname only
-between official stable releases, not with every development snapshot.
-Versions numbered 0.x are considered development snapshots.
+As a result, we don't yet recommend statically linking to
+libdbus. Also, reimplementations of the protocol from scratch might
+have to work to stay in sync with how libdbus behaves.

 
 

-Until 1.0 is released, you have to define -DDBUS_API_SUBJECT_TO_CHANGE
-just as a safety check to be sure everyone is aware of this API/ABI
-policy and has the right expectations.
+To lock things down and declare static linking and reimplementation to
+be safe, we'd like to see all the internal dependencies of libdbus
+(for example, files read) well-documented in the specification, and
+we'd like to have a high degree of confidence that these dependencies
+are supportable over the long term and extensible where required.

 
 

-We do need people to test the APIs, so please do use the development
-snapshots of D-BUS. They are intended to work and we do actively
-address bugs.
+NOTE ABOUT HIGH-LEVEL BINDINGS

 
 

-However, if you're shipping a commercial binary-only application that
-needs to keep running on M future versions of N operating systems, you
-might want to include your own copy of D-BUS rather than relying on
-the installed copy, for example.
+Note that the high-level bindings are _separate projects_ from the
+main D-Bus package, and have their own release cycles, levels of
+maturity, and ABI stability policies. Please consult the documentation
+for your binding.