Projects/Vala/Manual/GIR metadata format

GIR metadata format

Contents

GIR metadata format

The GIR format actually has a lot of information for generating bindings, but it's a different language than Vala. Therefore, it's almost impossible to directly map a whole .gir file into a Vala tree, hence the need of metadata. On the other side we might want to use directly .gir + .metadata instead of generating a .vapi, but .vapi is more humanly readable and faster to parse than the GIR, hence the need of vapigen for generating a .vapi.

Locating metadata

The filename of a metadata for a SomeLib.gir must be SomeLib.metadata. By default Vala looks for .metadata into the same directory of the .gir file, however it's possible to specify other directories using the --metadatadir option.

Comments

Comments in the metadata have the same syntax as in Vala code:

// this is a comment
/*
 * multi-line comment
 */

Syntax

Metadata information for each symbol must provided on different lines:

rule:
- pattern [ arguments ] [ newline relative-rules ] newline
relative-rules:
- . pattern [ arguments ] [ newline relative-rules ]
pattern:
- glob-style-pattern [ # selector ] [ . pattern ]
arguments:
- identifier [ = expression ] [ arguments ]
expression:
- null
  true
  false
  - expression
  integer-literal
  real-literal
  string-literal
  symbol
symbol:
- identifier [ . identifier ]

Patterns are tied to the GIR tree: if a class FooBar contains a method baz_method then it can be referenced in the metadata as FooBar.baz_method.
Selectors are used to specify a particular element name of the GIR tree, for example FooBar.baz_method#method will only select method elements whose name is baz_method. Useful to solve name collisions.
Given a namespace named Foo a special pattern Foo is available for setting general arguments.
If a GIR symbol matches multiple rules then all of them will be applied: if there are clashes among arguments, last written rules in the file take precedence.
If the expression for an argument is not provided, it's treated as true by default.
A relative rule is relative to the nearest preceding absolute rule. Metadata must contain at least one absolute rule. It's not possible to make a rule relative to another relative rule.

Valid arguments

Name	Applies to	Type	Description
skip	all	bool	Skip processing the symbol
hidden	all	bool	Process the symbol but hide from output
type	method, parameter, property, field, constant, alias	string	Complete Vala type
type_arguments	method, parameter, property, field, constant, alias	string	Vala type parameters for generics, separated by commas
cheader_filename	all including namespace	string	C headers separated by commas
name	all including namespace	string	Vala symbol name
owned	parameter	bool	Whether the parameter value should be owned
unowned	method, property, field, constant	bool	Whether the symbol is unowned
parent	all	string	Move the symbol to the specified container symbol. If no container exists, a new namespace will be created.
nullable	method, parameter, property, field, constant, alias	bool	Whether the type is nullable or not
deprecated	all	bool	Whether the symbol is deprecated or not
replacement	all	string	Deprecation replacement, implies `deprecated=true`
deprecated_since	all	string	Deprecated since version, implies `deprecated=true`
array	method, parameter, property, field, constant, alias	bool	Whether the type is an array or not
array_length_idx	parameter	int	The index of the C array length parameter
default	parameter	any	Default expression for the parameter
out	parameter	bool	Whether the parameter direction is out or not
ref	parameter	bool	Whether the parameter direction is ref or not
vfunc_name	method	string	Name of the C virtual function
virtual	method, signal, property	bool	Whether the symbol is virtual or not
abstract	method, signal, property	bool	Whether the symbol is abstract or not
scope	parameter (async method)	string	Scope of the delegate, in GIR terms
struct	record (detected as boxed compact class)	bool	Whether the boxed type must be threaten as struct instead of compact class
printf_format	method	bool	Add the [PrintfFormat] attribute to the method if true
array_length_field	field (array)	string	The name of the length field
sentinel	method	string	C expression of the last argument for varargs
closure	parameter	int	Specifies the index of the parameter representing the user data for this callback
errordomain	enumeration	bool	Whether the enumeration is an errordomain or not
destroys_instance	method	bool	Whether the instance is owned by the method
throws	method	string	Type of exception the method throws

Examples

Demonstrating...

Overriding Types

When you have the following expression:

typedef GList MyList;

where GList will hold integers, use type metadata as follows:

MyList type="GLib.List<int>"

The above metadata will generate the following code:

    public class MyList : GLib.List<int> {
        [CCode (has_construct_function = false)]
        protected MyList ();
        public static GLib.Type get_type ();
    }

Then you can use GLib.List or NameSpace.MyList as if equal.

Skipping Simbols

MySimbol skip

More Examples

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