## GIArgInfo

GIArgInfo — Struct representing an argument

## Synopsis

    #define             GI_IS_ARG_INFO                      (info)
    typedef             GIArgInfo;
    enum                GIDirection;
    enum                GIScopeType;
    enum                GITransfer;
    GIDirection         g_arg_info_get_direction            (GIArgInfo *info);
    gboolean            g_arg_info_is_caller_allocates      (GIArgInfo *info);
    gboolean            g_arg_info_is_return_value          (GIArgInfo *info);
    gboolean            g_arg_info_is_optional              (GIArgInfo *info);
    gboolean            g_arg_info_may_be_null              (GIArgInfo *info);
    GITransfer          g_arg_info_get_ownership_transfer   (GIArgInfo *info);
    GIScopeType         g_arg_info_get_scope                (GIArgInfo *info);
    gint                g_arg_info_get_closure              (GIArgInfo *info);
    gint                g_arg_info_get_destroy              (GIArgInfo *info);
    GITypeInfo *        g_arg_info_get_type                 (GIArgInfo *info);
    void                g_arg_info_load_type                (GIArgInfo *info,
                                                             GITypeInfo *type);

## Description

GIArgInfo represents an argument. An argument is always part of a GICallableInfo.

## Struct hierarchy

      GIBaseInfo
       +----GIArgInfo

## Details

### GI_IS_ARG_INFO()

    #define             GI_IS_ARG_INFO(info)

### GIArgInfo

    typedef GIBaseInfo GIArgInfo;

Represents an argument.

### enum GIDirection

    typedef enum {
      GI_DIRECTION_IN,
      GI_DIRECTION_OUT,
      GI_DIRECTION_INOUT
    } GIDirection;

The direction of a GIArgInfo.

`GI_DIRECTION_IN` | in argument.
`GI_DIRECTION_OUT` | out argument.
`GI_DIRECTION_INOUT` | in and out argument.

### enum GIScopeType

    typedef enum {
      GI_SCOPE_TYPE_INVALID,
      GI_SCOPE_TYPE_CALL,
      GI_SCOPE_TYPE_ASYNC,
      GI_SCOPE_TYPE_NOTIFIED
    } GIScopeType;

Scope type of a GIArgInfo representing callback, determines how the callback is invoked and is used to decided when the invoke structs can be freed.

`GI_SCOPE_TYPE_INVALID` | The argument is not of callback type.
`GI_SCOPE_TYPE_CALL` | The callback and associated user_data is only used during the call to this function.
`GI_SCOPE_TYPE_ASYNC` | The callback and associated user_data is only used until the callback is invoked, and the callback. is invoked always exactly once.
`GI_SCOPE_TYPE_NOTIFIED` | The callback and and associated user_data is used until the caller is notfied via the destroy_notify.

### enum GITransfer

    typedef enum {
      GI_TRANSFER_NOTHING,
      GI_TRANSFER_CONTAINER,
      GI_TRANSFER_EVERYTHING
    } GITransfer;

The transfer is the exchange of data between two parts, from the callee to the caller. The callee is either a function/method/signal or an object/interface where a property is defined. The caller is the side accessing a property or calling a function. GITransfer specifies who's responsible for freeing the resources after the ownership transfer is complete. In case of a containing type such as a list, an array or a hash table the container itself is specified differently from the items within the container itself. Each container is freed differently, check the documentation for the types themselves for information on how to free them.

`GI_TRANSFER_NOTHING` | transfer nothing from the callee (function or the type instance the property belongs to) to the caller. The callee retains the ownership of the transfer and the caller doesn't need to do anything to free up the resources of this transfer.
`GI_TRANSFER_CONTAINER` | transfer the container (list, array, hash table) from the callee to the caller. The callee retains the ownership of the individual items in the container and the caller has to free up the container resources (`g_list_free()`/`g_hash_table_destroy()` etc) of this transfer.
`GI_TRANSFER_EVERYTHING` | transfer everything, eg the container and its contents from the callee to the caller. This is the case when the callee creates a copy of all the data it returns. The caller is responsible for cleaning up the container and item resources of this transfer.

### g_arg_info_get_direction ()

    GIDirection         g_arg_info_get_direction            (GIArgInfo *info);

Obtain the direction of the argument. Check GIDirection for possible direction values.

`info` : | a GIArgInfo
Returns : | the direction

### g_arg_info_is_caller_allocates ()

    gboolean            g_arg_info_is_caller_allocates      (GIArgInfo *info);

Obtain if the argument is a pointer to a struct or object that will receive an output of a function. The default assumption for `GI_DIRECTION_OUT` arguments which have allocation is that the callee allocates; if this is `TRUE`, then the caller must allocate.

`info` : | a GIArgInfo
Returns : | `TRUE` if caller is required to have allocated the argument

### g_arg_info_is_return_value ()

    gboolean            g_arg_info_is_return_value          (GIArgInfo *info);

Obtain if the argument is a return value. It can either be a parameter or a return value.

`info` : | a GIArgInfo
Returns : | `TRUE` if it is a return value

### g_arg_info_is_optional ()

    gboolean            g_arg_info_is_optional              (GIArgInfo *info);

Obtain if the argument is optional.

`info` : | a GIArgInfo
Returns : | `TRUE` if it is an optional argument

### g_arg_info_may_be_null ()

    gboolean            g_arg_info_may_be_null              (GIArgInfo *info);

Obtain if the argument accepts `NULL`.

`info` : | a GIArgInfo
Returns : | `TRUE` if it accepts `NULL`

### g_arg_info_get_ownership_transfer ()

    GITransfer          g_arg_info_get_ownership_transfer   (GIArgInfo *info);

Obtain the ownership transfer for this argument. GITransfer contains a list of possible values.

`info` : | a GIArgInfo
Returns : | the transfer

### g_arg_info_get_scope ()

    GIScopeType         g_arg_info_get_scope                (GIArgInfo *info);

Obtain the scope type for this argument. The scope type explains how a callback is going to be invoked, most importantly when the resources required to invoke it can be freed. GIScopeType contains a list of possible values.

`info` : | a GIArgInfo
Returns : | the scope type

### g_arg_info_get_closure ()

    gint                g_arg_info_get_closure              (GIArgInfo *info);

Obtain the index of the user data argument. This is only valid for arguments which are callbacks.

`info` : | a GIArgInfo
Returns : | index of the user data argument or -1 if there is none

### g_arg_info_get_destroy ()

    gint                g_arg_info_get_destroy              (GIArgInfo *info);

Obtains the index of the GDestroyNotify argument. This is only valid for arguments which are callbacks.

`info` : | a GIArgInfo
Returns : | index of the GDestroyNotify argument or -1 if there is none

### g_arg_info_get_type ()

    GITypeInfo *        g_arg_info_get_type                 (GIArgInfo *info);

Obtain the type information for `info`.

`info` : | a GIArgInfo
Returns : | the GIArgInfo, free it with `g_base_info_unref()` when done. [transfer full]

### g_arg_info_load_type ()

    void                g_arg_info_load_type                (GIArgInfo *info,
                                                             GITypeInfo *type);

Obtain information about a the type of given argument `info`; this function is a variant of `g_arg_info_get_type()` designed for stack allocation.

The initialized `type` must not be referenced after `info` is deallocated.

`info` : | a GIArgInfo
`type` : | Initialized with information about type of `info`. [out caller-allocates]