src/Reflex/Widget/Basic.hs · patch

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1{-# LANGUAGE CPP #-}

2{-# LANGUAGE ExplicitForAll #-}

3{-# LANGUAGE MultiParamTypeClasses #-}

4{-# LANGUAGE RecursiveDo #-}

5#ifdef USE_REFLEX_OPTIMIZER

6{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}

7#endif

9module Reflex.Widget.Basic where

11import Control.Monad.Fix (MonadFix)

12import Data.Map (Map)

13import Reflex.Class

14import Reflex.Patch.MapWithMove

17-- | Build sortable content in such a way that re-sorting it can cause minimal

18-- disruption to an existing context.

20-- Naively re-sorting a list of images would destroy every image and add them back

21-- in the new order. This framework is able to avoid that by preserving the

22-- identity of each image and simply moving it to the new location.

24-- Example:

26-- > let sortByFst = buttonA $> comparing fst

27-- > sortBySnd = buttonB $> comparing snd

28-- > sortEvent = leftmost [sortByFst, sortBySnd]

29-- > sortableList

30-- > (\k v -> text $ "\n" ++ show k ++ " " ++ v) -- show each element on a new line

31-- > (Map.fromList $ zip [0..] [(3, "a"), (2, "b"), (1, "c")])

32-- > sortEvent

33sortableList :: forall t m k v a. (MonadHold t m, MonadFix m, Adjustable t m, Ord k)

34 => (k -> v -> m a) -- ^ Function to render the content for each key/value pair

35 -> Map k v -- ^ The sortable list with an initial ordering determined by the @Map@ keys in ascending order

36 -> Event t (v -> v -> Ordering) -- ^ An event carrying a sort function for the list

37 -> m (Map k a)

38sortableList f m0 reSortFunc = do

39 rec let reSortPatch = attachWith (flip patchThatSortsMapWith) (currentIncremental m) reSortFunc

40 m <- holdIncremental m0 reSortPatch

41 (results, _) <- mapMapWithAdjustWithMove f m0 reSortPatch

42 pure results