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><H1
><A
NAME="GTK-SIGNAL-MARSHALLERS"
>Signal Marshallers</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN9134"
></A
><H2
>Name</H2
>Signal Marshallers -- Functions to adapt C structures to native calling convention.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN9137"
></A
><H2
>Synopsis</H2
><TABLE
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><PRE
CLASS="SYNOPSIS"
> #include <gtk/gtk.h>
#define <A
HREF="gtk-signal-marshallers.html#GTK-SIGNAL-DEFAULT-MARSHALLER"
>gtk_signal_default_marshaller</A
> </PRE
></TD
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><DIV
CLASS="REFSECT1"
><A
NAME="AEN9141"
></A
><H2
>Description</H2
><DIV
CLASS="REFSECT2"
><A
NAME="AEN9143"
></A
><H3
>What are Signal Marshallers?</H3
><P
>Marshals are functions which all have the same prototype:
they take a <A
HREF="gtkobject.html"
>GtkObject</A
>, a <A
HREF="gtk-types.html#GTKSIGNALFUNC"
>GtkSignalFunc</A
>, a <A
HREF=../glib/glib-basic-types.html#GPOINTER
>gpointer</A>,
and an array of argument values.
The functions are names gtk_marshall_RETURNTYPE__PARAMTYPE1_PARAMTYPE2....</P
><P
>They then call a native function: the GtkObject is the first
parameter passed in. The arguments are passed in the native
calling convention: chars, shorts, ints, longs may be packed
on the stack, or tucked in registers: it doesn't matter
because the same calling convention will be generated
inside the gtkmarshal code as is expected where you define
your handlers.</P
><P
>So the function named:
<TABLE
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><TD
><PRE
CLASS="PROGRAMLISTING"
>gtk_marshal_BOOL__POINTER_INT_INT_UINT(GtkObject*, GtkSignalFunc, gpointer, GtkArg*);</PRE
></TD
></TR
></TABLE
>
will call the <A
HREF="gtk-types.html#GTKSIGNALFUNC"
>GtkSignalFunc</A
> assuming it was a function with signature:
<TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>gboolean sigfunc(gpointer,gint,gint,guint);</PRE
></TD
></TR
></TABLE
></P
></DIV
><HR><DIV
CLASS="REFSECT2"
><A
NAME="AEN9154"
></A
><H3
>Writing Custom Marshals</H3
><P
>Marshals are primarily used as arguments to <A
HREF="gtk-signals.html#GTK-SIGNAL-NEW"
>gtk_signal_new</A
>().
Sometimes, you may find that a marshaller you need isn't available
in the standard list. Then you have to write your own.</P
><P
>If you wish to define a signal with a new type of argument list.
Suppose you want 2 pointers and 2 integers.
You would write:
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><PRE
CLASS="PROGRAMLISTING"
>typedef int (*GtkSignal_INT__POINTER_POINTER_INT_INT)(
gpointer, gpointer, gint, gint
);
void marshal_INT__POINTER_POINTER_INT_INT(GtkObject* object,
GtkSignalFunc func,
gpointer func_data,
GtkArg* args)
{
GtkSignal_NONE__POINTER_POINTER_INT_INT rfunc;
gint* return_val;
return_val = GTK_RETLOC_INT(args[4]);
rfunc = (GtkSignal_INT__POINTER_POINTER_INT_INT)func;
*return_val = (*rfunc)(object,
GTK_VALUE_POINTER(args[0]),
GTK_VALUE_POINTER(args[1]),
GTK_VALUE_INT(args[2]),
GTK_VALUE_INT(args[3]),
func_data);
}</PRE
></TD
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></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN9160"
></A
><H2
>Details</H2
><DIV
CLASS="REFSECT2"
><A
NAME="AEN9162"
></A
><H3
><A
NAME="GTK-SIGNAL-DEFAULT-MARSHALLER"
></A
>gtk_signal_default_marshaller</H3
><TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#define gtk_signal_default_marshaller gtk_marshal_NONE__NONE</PRE
></TD
></TR
></TABLE
><P
>A marshaller that returns void and takes no extra parameters.</P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN9167"
></A
><H2
>See Also</H2
><P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>GtkSignal</DT
><DD
><P
>The signal handling functions (of which marshallers are
really an implementation detail).</P
></DD
></DL
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