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start at general description.

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Mon Oct 30 11:13:12 2000  Tim Janik  <timj@gtk.org>

        * gobject/tmpl/signals.sgml: start at general description.

        * gobject/gobject-docs.sgml: added introduction.
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docs/reference/ChangeLog
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@ -1,3 +1,9 @@
Mon Oct 30 11:13:12 2000 Tim Janik <timj@gtk.org>
* gobject/tmpl/signals.sgml: start at general description.
* gobject/gobject-docs.sgml: added introduction.
Mon Oct 30 06:01:43 2000 Tim Janik <timj@gtk.org>
* gobject/gobject-sections.txt: opened up a new section on signals.

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@ -14,9 +14,54 @@
<title>GObject Reference Manual</title>
</bookinfo>
<preface>
<title>Introduction</title>
<para>
Most modern programming languages come with their own native object
systems and additional fundamental algorithmic language constructs.
Just as GLib serves as an implementation of such fundamental
types and algorithms (linked lists, hash tables and so forth), the
GLib Object System provides the required implementations of a
flexible extensible and intentionally easy to map (into other
languages) object oriented framework for C.
The substantial elements that are provided can be summarized as:
<variablelist>
<varlistentry><term></term><listitem><para>
* A generic type system to register arbitrary single-inherited
flat and deep derived types as well as interfaces for
structured types.
It takes care of creation, initialization and memory management
of the assorted object and class structures, maintains
parent/child relationships and deals with dynamic implementations
of such types. That is, their type specific implementations are
relocatable/unloadable during runtime.
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
* A collection of fundamental type implementations, such as integers,
doubles, enums and structured types, to name a few.
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
* A sample fundamental type implementation to base object hirachies
upon - the GObject fundamental type.
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
* A signal system that allowes very flexible user customization of
virtual/overridable object methods and can serve as a powerfull
notification mechanism.
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
* An extensible parameter/value system, supporting all the provided
fundamental types that can be used to generically handle object
properties or otherwise parameterized types.
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
</variablelist>
</para>
</preface>
<reference>
<title>API Reference</title>
&gobject-types;
&gobject-objects;
&gobject-enumerations-flags;
@ -26,6 +71,6 @@
&gobject-param-specs;
&gobject-standard-params;
&gobject-signals;
</reference>
</book>

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docs/reference/gobject/tmpl/signals.sgml
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@ -7,7 +7,62 @@ as general purpose notification mechanism.
<!-- ##### SECTION Long_Description ##### -->
<para>
The basic concept of the signal system is that of the @emission of a signal.
Signals are introduced per-type and are identified through strings.
Signals introduced for a parent type are availale in derived types as well,
so basically they are a per-type facility that is inherited.
A signal emission mainly involves invocation of a certain set of callbacks in
precisely defined manner. There are two main categories of such callbacks,
per-object
<footnote><para> Although signals can deal with any kind of type, i'm
referring to those types as "@object @types" in the following, simply
because that is the context most users will encounter signals in.
</para></footnote>
ones and user provided ones.
The per-object callbacks are most often referred to as "object method
handler" or "default (signal) handler", while user provided callbacks are
usually just called "signal handler".
The object method handler is provided at signal creation time (this most
frequently happens at the end of an object class' creation), while user
provided handlers are frequently @connected and @disconnected to/from a certain
signal on certain object instances.
</para>
<para>
A signal emission consists of five stages, unless prematurely stopped:
<variablelist>
<varlistentry><term></term><listitem><para>
1 - Invocation of the object method handler for @G_SIGNAL_RUN_FIRST signals
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
2 - Invocation of normal user-provided signal handlers (@after flag @FALSE)
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
3 - Invocation of the object method handler for @G_SIGNAL_RUN_LAST signals
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
4 - Invocation of user provided signal handlers, connected with an @after flag of @TRUE
</para></listitem></varlistentry>
<varlistentry><term></term><listitem><para>
5 - Invocation of the object method handler for @G_SIGNAL_RUN_CLEANUP signals
</para></listitem></varlistentry>
</variablelist>
The user provided signal handlers are called in the order they were
connected in.
All handlers may prematurely stop a signal emission, and any number of
handlers may be connected, disconnected, blocked or unblocked during
a signal emission.
There are certain criteria for skipping user handlers in stages 2 and 4
of a signal emission.
First, user handlers may be @blocked, blocked handlers are omitted
during callback invocation, to return from the "blocked" state, a
handler has to get unblocked exactly the same amount of times
it has been blocked before.
Second, upon emission of a @G_SIGNAL_DETAILED signal, an additional
"detail" argument passed in to g_signal_emit() has to match the detail
argument of the signal handler currently subject to invocation.
Specification of no detail argument for signal handlers (omission of the
detail part of the signal specification upon connection) serves as a
wildcard and matches any detail argument passed in to emission.
</para>
<!-- ##### SECTION See_Also ##### -->
@ -21,27 +76,27 @@ The @GSignalInvocationHint structure is used to pass on additional information
to callbacks during a signal emission.
</para>
@signal_id: The signal id of the signal invoking the callback
@detail: The detail passed on for this emission
@run_type: The stage the signal emission is currently in, this
field will contain either of @G_SIGNAL_RUN_FIRST,
@signal_id: The signal id of the signal invoking the callback
@detail: The detail passed on for this emission
@run_type: The stage the signal emission is currently in, this
field will contain one of @G_SIGNAL_RUN_FIRST,
@G_SIGNAL_RUN_LAST or @G_SIGNAL_RUN_CLEANUP.
<!-- ##### USER_FUNCTION GSignalAccumulator ##### -->
<para>
The signal accumulator is a special callback function that can be used
to collect return values of the various callbacks that are called
during a signal emission. The signal accumulator is at signal creation
time, if it is left NULL, no accumulation of callback return values is
perfomed, the return value of the signal emission is the value returned
by the last callback.
during a signal emission. The signal accumulator is specified at signal
creation time, if it is left NULL, no accumulation of callback return
values is perfomed. The return value of signal emissions is then the
value returned by the last callback.
</para>
@ihint: Signal invokation hint, see @GSignalInvocationHint
@return_accu: Accumulator to collect callback return values in, this
@ihint: Signal invokation hint, see @GSignalInvocationHint
@return_accu: Accumulator to collect callback return values in, this
is the return value of the current signal emission
@return_value: The return value of the most recent callback function
@Returns: The accumulator function returns whether signal emission
@return_value: The return value of the most recent callback function
@Returns: The accumulator function returns whether the signal emission
should be aborted. Returning @FALSE means to abort the
current emission and @TRUE is returned for continuation.
@ -95,7 +150,7 @@ by the last callback.
<!-- ##### STRUCT GSignalQuery ##### -->
<para>
A structure holding in-depth information for a specific signal. It is
filled in by the @g_signal_query() function.
filled in by the g_signal_query() function.
</para>
@signal_id: The signal id of the signal being querried, or 0 if the
@ -107,7 +162,11 @@ filled in by the @g_signal_query() function.
@n_params: The number of parameters that user callbacks take
@param_types: The individual parameter types for user callbacks, note that the
effective callback signature is:
@return_type callback (gpointer data1, @[parameters], gpointer data2);
<msgtext><programlisting>
@return_type callback (@gpointer data1,
[@param_types param_names,]
@gpointer data2);
</programlisting></msgtext>
<!-- ##### FUNCTION g_signal_newv ##### -->
<para>
@ -175,7 +234,7 @@ be considered constant and have to be left untouched.
<para>
List the signals by id, that a certain instance or interface type
created. Further information about the signals can be aquired through
@g_signal_query().
g_signal_query().
</para>
@itype: Instance or interface type