GIArgInfo: GObject Introspection Reference Manual

## GIArgInfo GIArgInfo — Struct representing an argument |

## Functions

#define | GI_IS_ARG_INFO()
gint | g_arg_info_get_closure ()
gint | g_arg_info_get_destroy ()
GIDirection | g_arg_info_get_direction ()
GITransfer | g_arg_info_get_ownership_transfer ()
GIScopeType | g_arg_info_get_scope ()
GITypeInfo * | g_arg_info_get_type ()
void | g_arg_info_load_type ()
gboolean | g_arg_info_may_be_null ()
gboolean | g_arg_info_is_caller_allocates ()
gboolean | g_arg_info_is_optional ()
gboolean | g_arg_info_is_return_value ()
gboolean | g_arg_info_is_skip ()

## Types and Values

typedef | GIArgInfo
enum | GIDirection
enum | GIScopeType
enum | GITransfer

## Description

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

## Struct hierarchy

      GIBaseInfo
       +----GIArgInfo

## Functions

### GI_IS_ARG_INFO()

    #define             GI_IS_ARG_INFO(info)

Checks if `info` is a GIArgInfo.

#### Parameters

info | an info structure |

### 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.

#### Parameters

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.

#### Parameters

info | a GIArgInfo |

#### Returns

index of the GDestroyNotify argument or -1 if there is none

### 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.

#### Parameters

info | a GIArgInfo |

#### Returns

the direction

### 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.

#### Parameters

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.

#### Parameters

info | a GIArgInfo |

#### Returns

the scope type

### g_arg_info_get_type ()

    GITypeInfo *
    g_arg_info_get_type (GIArgInfo *info);

Obtain the type information for `info` .

#### Parameters

info | a GIArgInfo |

#### Returns

the GITypeInfo holding the type information for `info` , 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.

#### Parameters

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

### g_arg_info_may_be_null ()

    gboolean
    g_arg_info_may_be_null (GIArgInfo *info);

Obtain if the type of the argument includes the possibility of `NULL`. For 'in' values this means that `NULL` is a valid value. For 'out' values, this means that `NULL` may be returned.

See also `g_arg_info_is_optional()`.

#### Parameters

info | a GIArgInfo |

#### Returns

`TRUE` if the value may be `NULL`

### 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.

#### Parameters

info | a GIArgInfo |

#### Returns

`TRUE` if caller is required to have allocated the argument

### g_arg_info_is_optional ()

    gboolean
    g_arg_info_is_optional (GIArgInfo *info);

Obtain if the argument is optional. For 'out' arguments this means that you can pass `NULL` in order to ignore the result.

#### Parameters

info | a GIArgInfo |

#### Returns

`TRUE` if it is an optional 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.

#### Parameters

info | a GIArgInfo |

#### Returns

`TRUE` if it is a return value

### g_arg_info_is_skip ()

    gboolean
    g_arg_info_is_skip (GIArgInfo *info);

Obtain if an argument is only useful in C.

#### Parameters

info | a GIArgInfo |

#### Returns

`TRUE` if argument is only useful in C.

Since: 1.29.0

## Types and Values

### GIArgInfo

    typedef GIBaseInfo GIArgInfo;

Represents an argument.

### enum GIDirection

The direction of a GIArgInfo.

#### Members

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

### enum 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.

#### Members

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

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.

#### Members

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. |