src/Reflex/Widget/Basic.hs · reflex

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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)

14import Reflex.Class

15import Reflex.Adjustable.Class

16import Data.Patch.MapWithMove

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

20-- disruption to an existing context.

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

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

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

26-- Example:

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

29-- > sortBySnd = buttonB $> comparing snd

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

31-- > sortableList

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

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

34-- > sortEvent

35sortableList :: forall t m k v a. (MonadHold t m, MonadFix m, Adjustable t m, Ord k)

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

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

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

39 -> m (Map k a)

40sortableList f m0 reSortFunc = do

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

42 m <- holdIncremental m0 reSortPatch

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

44 pure results