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Internal.hs
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Internal.hs
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{-# LANGUAGE DeriveDataTypeable #-}
module Graphics.UI.Threepenny.Internal (
-- * Synopsis
-- | Internal core:
-- 'UI' monad, integrating FRP and JavaScript FFI. garbage collection
-- * Documentation
Window, disconnect,
startGUI,
UI, runUI, liftIOLater, askWindow,
FFI, FromJS, ToJS, JSFunction, JSObject, ffi,
runFunction, callFunction, ffiExport, debug,
Element, fromJSObject, getWindow,
mkElementNamespace, mkElement, delete, appendChild, clearChildren,
EventData, domEvent, unsafeFromJSON,
) where
import Control.Applicative (Applicative)
import Control.Monad
import Control.Monad.Fix
import Control.Monad.IO.Class
import qualified Control.Monad.Trans.RWS.Lazy as Monad
import Data.Dynamic (Typeable)
import qualified Data.Aeson as JSON
import qualified Foreign.JavaScript as JS
import qualified Foreign.RemotePtr as Foreign
import qualified Reactive.Threepenny as E
import Foreign.JavaScript hiding (runFunction, callFunction, debug, Window)
{-----------------------------------------------------------------------------
Custom Window type
------------------------------------------------------------------------------}
-- | The type 'Window' represents a browser window.
data Window = Window
{ jsWindow :: JS.Window -- JavaScript window
, eDisconnect :: E.Event () -- event that happens when client disconnects
, wEvents :: Foreign.Vendor Events -- events associated to 'Element's
}
-- | Start server for GUI sessions.
startGUI
:: Config -- ^ Server configuration.
-> (Window -> UI ()) -- ^ Action to run whenever a client browser connects.
-> IO ()
startGUI config init = JS.serve config $ \w -> do
-- set up disconnect event
(eDisconnect, handleDisconnect) <- E.newEvent
JS.onDisconnect w $ handleDisconnect ()
-- make window
wEvents <- Foreign.newVendor
let window = Window
{ jsWindow = w
, eDisconnect = eDisconnect
, wEvents = wEvents
}
-- run initialization
runUI window $ init window
-- | Event that occurs whenever the client has disconnected,
-- be it by closing the browser window or by exception.
--
-- Note: DOM Elements in a browser window that has been closed
-- can no longer be manipulated.
disconnect :: Window -> E.Event ()
disconnect = eDisconnect
{-----------------------------------------------------------------------------
Elements
------------------------------------------------------------------------------}
type Events = String -> E.Event JSON.Value
data Element = Element
{ toJSObject :: JS.JSObject -- corresponding JavaScript object
, elEvents :: Events -- FRP event mapping
, elWindow :: Window -- Window in which the element was created
} deriving (Typeable)
instance ToJS Element where
render = render . toJSObject
getWindow :: Element -> IO Window
getWindow = return . elWindow
-- | Convert JavaScript object into an element.
--
-- FIXME: For the purpose of garbage collection, this element
-- will always be reachable from the root.
fromJSObject :: JS.JSObject -> UI Element
fromJSObject el = do
window <- askWindow
liftIO $ do
Foreign.addReachable (JS.root $ jsWindow window) el
events <- getEvents el window
return $ Element el events window
-- | Add lazy FRP events to a JavaScript object.
addEvents :: JS.JSObject -> Window -> IO Events
addEvents el Window{ jsWindow = w, wEvents = wEvents } = do
-- Lazily create FRP events whenever they are needed.
let initializeEvent (name,_,handler) = do
handlerPtr <- JS.exportHandler w handler
-- make handler reachable from element
Foreign.addReachable el handlerPtr
JS.runFunction w $
ffi "Haskell.bind(%1,%2,%3)" el name handlerPtr
events <- E.newEventsNamed initializeEvent
-- Create new pointer and add reachability.
Foreign.withRemotePtr el $ \coupon _ -> do
ptr <- Foreign.newRemotePtr coupon events wEvents
Foreign.addReachable el ptr
return events
-- | Lookup or create lazy events for an a JavaScript object.
getEvents :: JS.JSObject -> Window -> IO Events
getEvents el window@Window{ wEvents = wEvents } = do
Foreign.withRemotePtr el $ \coupon _ -> do
mptr <- Foreign.lookup coupon wEvents
case mptr of
Nothing -> addEvents el window
Just p -> Foreign.withRemotePtr p $ \_ -> return
-- | Events may carry data. At the moment, they may return
-- a single JSON value, as defined in the "Data.Aeson" module.
type EventData = JSON.Value
-- | Convert event data to a Haskell value.
-- Throws an exception when the data cannot be converted.
unsafeFromJSON :: JSON.FromJSON a => EventData -> a
unsafeFromJSON x = let JSON.Success y = JSON.fromJSON x in y
-- | Obtain DOM event for a given element.
domEvent
:: String
-- ^ Event name. A full list can be found at
-- <http://www.w3schools.com/jsref/dom_obj_event.asp>.
-- Note that the @on@-prefix is not included,
-- the name is @click@ and so on.
-> Element -- ^ Element where the event is to occur.
-> E.Event EventData
domEvent name el = elEvents el name
-- | Make a new DOM element with a given tag name.
mkElement :: String -> UI Element
mkElement = mkElementNamespace Nothing
-- | Make a new DOM element with a namespace and a given tag name.
--
-- A namespace 'Nothing' corresponds to the default HTML namespace.
mkElementNamespace :: Maybe String -> String -> UI Element
mkElementNamespace namespace tag = do
window <- askWindow
let w = jsWindow window
liftIO $ do
el <- JS.callFunction w $ case namespace of
Nothing -> ffi "document.createElement(%1)" tag
Just ns -> ffi "document.createElementNS(%1,%2)" ns tag
events <- getEvents el window
return $ Element el events window
-- | Delete the given element.
delete :: Element -> UI ()
delete el = liftJSWindow $ \w -> do
JS.runFunction w $ ffi "$(%1).detach()" el
Foreign.destroy $ toJSObject el
-- | Remove all child elements.
clearChildren :: Element -> UI ()
clearChildren (Element el _ _) = liftJSWindow $ \w -> do
Foreign.withRemotePtr el $ \_ _ -> do
Foreign.clearReachable el
JS.runFunction w $ ffi "$(%1).contents().detach()" el
-- | Append a child element.
appendChild :: Element -> Element -> UI ()
appendChild (Element eParent _ _) (Element eChild _ _) = liftJSWindow $ \w -> do
-- FIXME: We have to stop the child being reachable from its
-- /previous/ parent.
Foreign.addReachable eParent eChild
JS.runFunction w $ ffi "$(%1).append($(%2))" eParent eChild
{-----------------------------------------------------------------------------
UI monad
------------------------------------------------------------------------------}
{- |
User interface elements are created and manipulated in the 'UI' monad.
This monad is essentially just a thin wrapper around the familiar 'IO' monad.
Use the 'liftIO' function to access 'IO' operations like reading
and writing from files.
There are several subtle reasons why Threepenny
uses a custom 'UI' monad instead of the standard 'IO' monad:
* More convenience when calling JavaScript.
The monad keeps track of a browser 'Window' context
in which JavaScript function calls are executed.
* Recursion for functional reactive programming.
-}
newtype UI a = UI { unUI :: Monad.RWST Window [IO ()] () IO a }
deriving (Typeable)
liftJSWindow :: (JS.Window -> IO a) -> UI a
liftJSWindow f = askWindow >>= liftIO . f . jsWindow
instance Functor UI where
fmap f = UI . fmap f . unUI
instance Applicative UI where
pure = return
(<*>) = ap
instance Monad UI where
return = UI . return
m >>= k = UI $ unUI m >>= unUI . k
instance MonadIO UI where
liftIO = UI . liftIO
instance MonadFix UI where
mfix f = UI $ mfix (unUI . f)
-- | Execute an 'UI' action in a particular browser window.
-- Also runs all scheduled 'IO' actions.
runUI :: Window -> UI a -> IO a
runUI window m = do
(a, _, actions) <- Monad.runRWST (unUI m) window ()
sequence_ actions
return a
-- | Retrieve current 'Window' context in the 'UI' monad.
askWindow :: UI Window
askWindow = UI Monad.ask
-- | Schedule an 'IO' action to be run later.
liftIOLater :: IO () -> UI ()
liftIOLater x = UI $ Monad.tell [x]
{-----------------------------------------------------------------------------
FFI
------------------------------------------------------------------------------}
-- | Run the given JavaScript function and carry on. Doesn't block.
--
-- The client window uses JavaScript's @eval()@ function to run the code.
runFunction :: JSFunction () -> UI ()
runFunction fun = liftJSWindow $ \w -> JS.runFunction w fun
-- | Run the given JavaScript function and wait for results. Blocks.
--
-- The client window uses JavaScript's @eval()@ function to run the code.
callFunction :: JSFunction a -> UI a
callFunction fun = liftJSWindow $ \w -> JS.callFunction w fun
-- | Export the given Haskell function so that it can be called
-- from JavaScript code.
--
-- FIXME: At the moment, the function is not garbage collected.
ffiExport :: JS.IsHandler a => a -> UI JSObject
ffiExport fun = liftJSWindow $ \w -> do
handlerPtr <- JS.exportHandler w fun
Foreign.addReachable (JS.root w) handlerPtr
return handlerPtr
-- | Print a message on the client console if the client has debugging enabled.
debug :: String -> UI ()
debug s = liftJSWindow $ \w -> JS.debug w s