Add requestFullscreen (#1525)

- [x] Add `requestFullscreen` to `Miso.FFI`

Author: dmjio

src/Miso/FFI.hs

@@ -101,6 +101,8 @@ module Miso.FFI
   , inline
     -- ** Scroll
   , scrollIntoView
+    -- ** Fullscreen
+  , requestFullscreen
     -- ** SplitMix32
   , splitmix32
     -- ** Math.random()

src/Miso/FFI/Internal.hs

@@ -79,6 +79,7 @@ module Miso.FFI.Internal
    , select
    , setSelectionRange
    , scrollIntoView
+   , requestFullscreen
    , alert
    , locationReload
    -- * CSS
@@ -563,6 +564,22 @@ scrollIntoView elId = do
   _ <- el # "scrollIntoView" $ ()
   pure ()
 -----------------------------------------------------------------------------
+-- | Calls @document.documentElement.requestFullscreen()@, falling back to
+-- @webkitRequestFullscreen@ for Safari.
+requestFullscreen :: IO ()
+{-# INLINABLE requestFullscreen #-}
+requestFullscreen = do
+  doc   <- jsg "document"
+  docEl <- doc ! "documentElement"
+  rfs   <- docEl ! "requestFullscreen"
+  undef <- isUndefined rfs
+  if not undef
+    then void $ docEl # "requestFullscreen" $ ()
+    else do
+      wrfs   <- docEl ! "webkitRequestFullscreen"
+      wundef <- isUndefined wrfs
+      when (not wundef) $ void $ docEl # "webkitRequestFullscreen" $ ()
+-----------------------------------------------------------------------------
 -- | Calls the @alert()@ function.
 alert :: MisoString -> IO ()
 {-# INLINABLE alert #-}