Data.GI.Base.Overloading

Helpers for dealing with GObjects.

Type level inheritance

type family ParentTypes a :: [*]

The direct parents of this object: its direct parent type, if any, and the interfaces it implements. The interfaces inherited from parent types can be omitted.

type family IsDescendantOf parent descendant :: Constraint

Check that a type is in the list of GObjectParents of another GObject-derived type.

Equations

IsDescendantOf d d = () ~ ()

IsDescendantOf p d = CheckForAncestorType d p (ParentTypes d) ~ HasAncestor p d

Looking up attributes in parent types

type family AttributeList a :: [(Symbol, *)]

The list of attributes defined for a given type. Each element of the list is a tuple, with the first element of the tuple the name of the attribute, and the second the type encoding the information of the attribute. This type will be an instance of AttrInfo.

type family ResolveAttribute s o :: *

Return the type encoding the attribute information for a given type and attribute.

Equations

ResolveAttribute s o = FindElement s (AttributeList o) (UnknownAttribute "Error: could not find attribute" s "for object" o)

type family HasAttribute attr o

A constraint imposing that the given object has the given attribute.

Equations

HasAttribute attr o = IsElem attr (AttributeList o) HasAttribute (DoesNotHaveAttribute "Error: attribute" attr "not found for type" o) ~ HasAttribute

class HasAttr attr o

A constraint that enforces that the given type has a given attribute.

Instances

HasAttribute attr o => HasAttr attr o

Looking up signals in parent types

type family SignalList a :: [(Symbol, *)]

The list of signals defined for a given type. Each element of the list is a tuple, with the first element of the tuple the name of the signal, and the second the type encoding the information of the signal. This type will be an instance of SignalInfo.

type family ResolveSignal s o :: *

Return the type encoding the signal information for a given type and signal.

Equations

ResolveSignal s o = FindElement s (SignalList o) (UnknownSignal "Error: could not find signal" s "for object" o)

type family HasSignal s o

A constraint enforcing that the signal exists for the given object, or one of its ancestors.

Equations

HasSignal s o = IsElem s (SignalList o) HasSignal (DoesNotHaveSignal "Error: signal" s "not found for type" o) ~ HasSignal

Looking up methods in parent types

class MethodInfo i o s where

Class for types containing the information about an overloaded method of type `o -> s`.

Methods

overloadedMethod :: MethodProxy i -> o -> s

data MethodProxy a

Proxy for passing a type to overloadedMethod. We do not use Proxy directly since it clashes with types defined in the autogenerated bindings.

Constructors

MethodProxy

data MethodResolutionFailed label o

Datatype returned when the method is not found, hopefully making the resulting error messages somewhat clearer.

Overloaded labels

class IsLabelProxy x a where

Support for overloaded labels in ghc < 8.0. This is like the IsLabel class introduced in ghc 8.0 (for use with the OverloadedLabels extension) with the difference that the Proxy argument is lifted. (Using the unlifted Proxy# type in user code is a bit of a pain, hence the choice.)

Methods

fromLabelProxy :: Proxy x -> a

Instances

(~) Symbol a x => IsLabelProxy x (AttrLabelProxy a)

Support for overloaded labels.

(HasSignal slot object, (~) * info (ResolveSignal slot object)) => IsLabelProxy slot (SignalProxy object info)

Support for overloaded labels.