Data.GI.Base.GVariant

This module contains some helper functions for dealing with GVariant values. The simplest way of dealing with them is by using the IsGVariant typeclass:

str <- fromGVariant variant :: IO (Maybe Text)

assuming that the variant is expected to contain a string in UTF8 encoding. The code becomes even shorter if the type checker can determine the return type for you:

readStringVariant :: GVariant -> IO Text
readStringVariant variant =
  fromGVariant variant >>= \case
     Nothing  -> error "Variant was not a string"
     Just str -> return str

Alternatively, you can use manually the gvariantFrom* and gvariantTo* family of functions.

Documentation

class IsGVariant a where

The typeclass for types that can be automatically marshalled into GVariant using toGVariant and fromGVariant.

Methods

toGVariant :: a -> IO GVariant

Convert a value of the given type into a GVariant.

fromGVariant :: GVariant -> IO (Maybe a)

Try to decode a GVariant into a target type. If the conversion fails we return Nothing. The type that was expected can be obtained by calling toGVariantFormatString, and the actual type as understood by the GVariant code can be obtained by calling gvariantToTypeString.

toGVariantFormatString :: a -> Text

The expected format string for this type (the argument is ignored).

Instances

IsGVariant Bool

IsGVariant Double

IsGVariant Int16

IsGVariant Int32

IsGVariant Int64

IsGVariant Word8

IsGVariant Word16

IsGVariant Word32

IsGVariant Word64

IsGVariant ()

The empty tuple GVariant, mostly useful for type checking.

IsGVariant ByteString

IsGVariant Text

IsGVariant GVariant

IsGVariant GVariantSignature

IsGVariant GVariantObjectPath

IsGVariant GVariantHandle

IsGVariant a => IsGVariant [a]

IsGVariant a => IsGVariant (Maybe a)

IsGVariant a => IsGVariant (GVariantSinglet a)

One element tuples.

(IsGVariant a, IsGVariant b) => IsGVariant (a, b)

(IsGVariant a, IsGVariantBasicType a, IsGVariant b) => IsGVariant (Map a b)

(IsGVariant a, IsGVariantBasicType a, IsGVariant b) => IsGVariant (GVariantDictEntry a b)

(IsGVariant a, IsGVariant b, IsGVariant c) => IsGVariant (a, b, c)

(IsGVariant a, IsGVariant b, IsGVariant c, IsGVariant d) => IsGVariant (a, b, c, d)

(IsGVariant a, IsGVariant b, IsGVariant c, IsGVariant d, IsGVariant e) => IsGVariant (a, b, c, d, e)

class Ord a => IsGVariantBasicType a

The typeclass for basic type GVariant types, i.e. those that are not containers.

Instances

IsGVariantBasicType Bool

IsGVariantBasicType Double

IsGVariantBasicType Int16

IsGVariantBasicType Int32

IsGVariantBasicType Int64

IsGVariantBasicType Word8

IsGVariantBasicType Word16

IsGVariantBasicType Word32

IsGVariantBasicType Word64

IsGVariantBasicType Text

IsGVariantBasicType GVariantSignature

IsGVariantBasicType GVariantObjectPath

IsGVariantBasicType GVariantHandle

noGVariant :: Maybe GVariant

An alias for Nothing :: Maybe GVariant to save some typing.

gvariantGetTypeString :: GVariant -> IO Text

Get the expected type of a GVariant, in GVariant notation. See https://developer.gnome.org/glib/stable/glib-GVariantType.html for the meaning of the resulting format string.

Type wrappers

Some GVariant types are isomorphic to Haskell types, but they carry some extra information. For example, there is a tuple singlet type, which is isomorphic to a single Haskell value with the added bit of information that it is wrapped in a tuple container. In order to use these values you can use the following wrappers, which allow the IsGVariant instance to disambiguate the requested type properly.

newtype GVariantSinglet a

Haskell has no notion of one element tuples, but GVariants do, so the following allows for marshalling one element tuples properly using fromGVariant and toGVariant. For instance, to construct a single element tuple containing a string, you could do

toGVariant (GVariantSinglet "Test")

Constructors

GVariantSinglet a

Instances

Eq a => Eq (GVariantSinglet a)

Show a => Show (GVariantSinglet a)

IsGVariant a => IsGVariant (GVariantSinglet a)

One element tuples.

data GVariantDictEntry key value

A DictEntry GVariant is isomorphic to a two-tuple. Wrapping the values into a GVariantDictentry allows the IsGVariant instance to do the right thing.

Constructors

GVariantDictEntry key value

Instances

(Eq key, Eq value) => Eq (GVariantDictEntry key value)

(Show key, Show value) => Show (GVariantDictEntry key value)

(IsGVariant a, IsGVariantBasicType a, IsGVariant b) => IsGVariant (GVariantDictEntry a b)

newtype GVariantHandle

Constructors

GVariantHandle Int32

Instances

Eq GVariantHandle

Ord GVariantHandle

Show GVariantHandle

IsGVariantBasicType GVariantHandle

IsGVariant GVariantHandle

data GVariantObjectPath

An object representing a DBus object path, which is a particular type of GVariant too. (Just a string with some specific requirements.) In order to construct/deconstruct a GVariantObjectPath one can use newGVariantObjectPath and gvariantObjectPathToText.

Instances

Eq GVariantObjectPath

Ord GVariantObjectPath

Show GVariantObjectPath

IsGVariantBasicType GVariantObjectPath

IsGVariant GVariantObjectPath

newGVariantObjectPath :: Text -> Maybe GVariantObjectPath

Try to construct a DBus object path. If the passed string is not a valid object path Nothing will be returned.

gvariantObjectPathToText :: GVariantObjectPath -> Text

Return the Text representation of a GVariantObjectPath.

data GVariantSignature

An object representing a DBus signature, which is a particular type of GVariant too. (Just a string with some specific requirements.) In order to construct/deconstruct a GVariantSignature one can use newGVariantSignature and gvariantSignatureToText.

Instances

Eq GVariantSignature

Ord GVariantSignature

Show GVariantSignature

IsGVariantBasicType GVariantSignature

IsGVariant GVariantSignature

newGVariantSignature :: Text -> Maybe GVariantSignature

Try to construct a DBus object path. If the passed string is not a valid DBus signature Nothing will be returned.

gvariantSignatureToText :: GVariantSignature -> Text

Return the Text representation of a GVariantSignature.

Manual memory management

wrapGVariantPtr :: Ptr GVariant -> IO GVariant

Take ownership of a passed in Ptr (typically created just for us, so if it is floating we sink it).

newGVariantFromPtr :: Ptr GVariant -> IO GVariant

Construct a Haskell wrapper for the given GVariant, without assuming ownership.

refGVariant :: GVariant -> IO (Ptr GVariant)

Add a reference to the given GVariant.

unrefGVariant :: GVariant -> IO ()

Remove a reference to the given GVariant.

Manual conversions

Basic types

The use of these should be fairly self-explanatory. If you want to convert a Haskell type into a GVariant, use gvariantTo*. If you want to convert a GVariant into a Haskell type, use gvariantFrom*. The conversion can fail if the GVariant is not of the expected type (if you want to convert a GVariant containing a Int16 into a Text value, say), in which case Nothing will be returned.

gvariantToBool :: GVariant -> IO (Maybe Bool)

gvariantFromBool :: Bool -> IO GVariant

gvariantToWord8 :: GVariant -> IO (Maybe Word8)

gvariantFromWord8 :: Word8 -> IO GVariant

gvariantToInt16 :: GVariant -> IO (Maybe Int16)

gvariantFromInt16 :: Int16 -> IO GVariant

gvariantToWord16 :: GVariant -> IO (Maybe Word16)

gvariantFromWord16 :: Word16 -> IO GVariant

gvariantToInt32 :: GVariant -> IO (Maybe Int32)

gvariantFromInt32 :: Int32 -> IO GVariant

gvariantToWord32 :: GVariant -> IO (Maybe Word32)

gvariantFromWord32 :: Word32 -> IO GVariant

gvariantToInt64 :: GVariant -> IO (Maybe Int64)

gvariantFromInt64 :: Int64 -> IO GVariant

gvariantToWord64 :: GVariant -> IO (Maybe Word64)

gvariantFromWord64 :: Word64 -> IO GVariant

gvariantToHandle :: GVariant -> IO (Maybe Int32)

Extract the DBus handle (an Int32) inside a GVariant.

gvariantFromHandle :: Int32 -> IO GVariant

Convert a DBus handle (an Int32) into a GVariant.

gvariantToDouble :: GVariant -> IO (Maybe Double)

gvariantFromDouble :: Double -> IO GVariant

gvariantToText :: GVariant -> IO (Maybe Text)

Decode an UTF-8 encoded string GVariant into Text.

gvariantFromText :: Text -> IO GVariant

Encode a Text into an UTF-8 encoded string GVariant.

gvariantToObjectPath :: GVariant -> IO (Maybe Text)

Extract a GVariantObjectPath from a GVariant, represented as its underlying Text representation.

gvariantFromObjectPath :: GVariantObjectPath -> IO GVariant

Construct a GVariant containing an object path. In order to build a GVariantObjectPath value see newGVariantObjectPath.

gvariantToSignature :: GVariant -> IO (Maybe Text)

Extract a GVariantSignature from a GVariant, represented as Text.

gvariantFromSignature :: GVariantSignature -> IO GVariant

Construct a GVariant containing an DBus signature. In order to build a GVariantSignature value see newGVariantSignature.

Container type conversions

gvariantToGVariant :: GVariant -> IO (Maybe GVariant)

Unbox a GVariant contained inside another GVariant.

gvariantFromGVariant :: GVariant -> IO GVariant

Box a GVariant inside another GVariant.

gvariantToBytestring :: GVariant -> IO (Maybe ByteString)

Extract a zero terminated list of bytes into a ByteString.

gvariantFromBytestring :: ByteString -> IO GVariant

Encode a ByteString into a list of bytes GVariant.

gvariantFromMaybe :: forall a. IsGVariant a => Maybe a -> IO GVariant

Convert a Maybe value into a corresponding GVariant of maybe type.

gvariantToMaybe :: forall a. IsGVariant a => GVariant -> IO (Maybe (Maybe a))

Try to decode a maybe GVariant into the corresponding Maybe type. If the conversion is successful this returns Just x, where x itself is of Maybe type. So, in particular, Just Nothing indicates a successful call, and means that the GVariant of maybe type was empty.

gvariantFromDictEntry :: (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => key -> value -> IO GVariant

Construct a GVariant of type DictEntry from the given key and value. The key must be a basic GVariant type, i.e. not a container. This is determined by whether it belongs to the IsGVariantBasicType typeclass. On the other hand value is an arbitrary GVariant, and in particular it can be a container type.

gvariantToDictEntry :: forall key value. (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => GVariant -> IO (Maybe (key, value))

Unpack a DictEntry variant into key and value, which are returned as a two element tuple in case of success.

gvariantFromMap :: (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => Map key value -> IO GVariant

Pack a Map into a GVariant for dictionary type, which is just an array of GVariantDictEntry.

gvariantToMap :: forall key value. (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => GVariant -> IO (Maybe (Map key value))

Unpack a GVariant into a Map. Notice that this assumes that all the elements in the GVariant array of GVariantDictEntry are of the same type, which is not necessary for a generic GVariant, so this is somewhat restrictive. For the general case it is necessary to use gvariantToList plus gvariantToDictEntry directly.

gvariantFromList :: forall a. IsGVariant a => [a] -> IO GVariant

Given a list of elements construct a GVariant array containing them.

gvariantToList :: forall a. IsGVariant a => GVariant -> IO (Maybe [a])

Unpack a GVariant array into its elements.

gvariantFromTuple :: [GVariant] -> IO GVariant

Given a list of GVariant, construct a GVariant tuple containing the elements in the list.

gvariantToTuple :: GVariant -> IO (Maybe [GVariant])

Extract the children of a GVariant tuple into a list.