wlhs

This project aims to develop a set of Haskell bindings for wlroots (and some parts of libwayland) At the moment it focusses on low-level bindings, in the wlhs-bindings package.

Warning: this project has just begun! Currently, the bindings are highly incomplete. Please feel free to help us expand them!

Development

We currently target wlroots version 0.17.1.

There is a Nix development flake available, which may be accessed via nix develop. For direnv users, an .envrc file is also provided.

hsc2hs extensions

wlhs-bindings contains a custom Setup.hs, which extends hsc2hs files with some custom syntax. This is probably best illustrated by example:

<table> <tr> <th>Macro call</th> <th>Equivalent to</th> </tr> <tr> <td>

{{ struct
    include.h,
    wl_type_name
}}

</td> <td>

data {-# CTYPE "include.h" "struct wl_type_name" #-} WL_type_name
    deriving (Show)

(Note: requires {-# LANGUAGE EmptyDataDeriving #-})

</td> </tr> <td>

{{ struct
    include.h,
    wl_type_name,
    field1, Type1,
    field2, Type2,
    nested field, Type2,
    arrayfield, [3]Type3
}}

</td> <td>

data {-# CTYPE "include.h" "struct wl_type_name" #-} WL_type_name
    = WL_type_name
    { wl_type_name_field1 :: Type1
    , wl_type_name_field2 :: Type2
    , wl_type_name_nested_field :: Type2
    , wl_type_name_arrayfield :: [Type3]
    } deriving (Show)
    
instance Storable WL_type_name where
    alignment _ = #alignment struct wl_type_name
    sizeOf _ = #size struct wl_type_name
    peek ptr = WL_type_name
        <$> (#peek struct wl_type_name, field1) ptr
        <*> (#peek struct wl_type_name, field2) ptr
        <*> (#peek struct wl_type_name, nested.field) ptr
        <*> peekArray 3 ((#ptr struct wl_type_name, arrayfield) ptr)
    poke ptr t = do
        (#poke struct wl_type_name, field1) ptr (wl_type_name_field1 t)
        (#poke struct wl_type_name, field2) ptr (wl_type_name_field2 t)
        (#poke struct wl_type_name, nested.field) ptr (wl_type_name_nested_field t)
        pokeArray ((#ptr struct wl_type_name, nested.field) ptr) (wl_type_name_nested_field t)

</td> </tr> <tr> <td>

{{ enum
    WL_type_name,
    WLR_ENUM_VALUE_1,
    WLR_ENUM_VALUE_2
}}

</td> <td>

type WL_type_name = CInt

pattern WLR_ENUM_VALUE_1 :: (Eq a, Num a) => a
pattern WLR_ENUM_VALUE_1 = #const WLR_ENUM_VALUE_1 

pattern WLR_ENUM_VALUE_2 :: (Eq a, Num a) => a
pattern WLR_ENUM_VALUE_2 = #const WLR_ENUM_VALUE_2 

</td> </tr> </table>