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Marshals are functions which all have the same prototype: they take a GtkObject, a GtkSignalFunc, a gpointer, and an array of argument values. The functions are names gtk_marshall_RETURNTYPE__PARAMTYPE1_PARAMTYPE2....
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.
So the function named:
gtk_marshal_BOOL__POINTER_INT_INT_UINT(GtkObject*, GtkSignalFunc, gpointer, GtkArg*); |
gboolean sigfunc(gpointer,gint,gint,guint); |
Marshals are primarily used as arguments to gtk_signal_new(). Sometimes, you may find that a marshaller you need isn't available in the standard list. Then you have to write your own.
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:
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);
} |