1 files changed, 17 insertions(+), 15 deletions(-)

M src/Data/Text/ParagraphLayout/Internal/Plain.hs

@@ 2,10 2,12 @@ module Data.Text.ParagraphLayout.Internal.Plain (layoutPlain)
 where
 
 import Control.Applicative (ZipList (ZipList), getZipList)
+import Data.Foldable (toList)
 import Data.Int (Int32)
 import Data.List (mapAccumL)
 import Data.List.NonEmpty (NonEmpty ((:|)), nonEmpty, (<|))
 import qualified Data.List.NonEmpty as NonEmpty
+import Data.Maybe (catMaybes)
 import Data.Text.Foreign (lengthWord8)
 import Data.Text.Glyphize
     ( Buffer (..)


@@ 66,23 68,26 @@ spanToRunsWrapped s = map (WithSpan s) (spanToRuns s)
 layoutAndAlignLines :: Int32 -> NonEmpty (WithSpan Run) -> [WithSpan Fragment]
 layoutAndAlignLines maxWidth runs = frags
     where
-        frags = concat fragsInLines
+        frags = concatMap NonEmpty.toList fragsInLines
         (_, fragsInLines) = mapAccumL positionLineH originY canonicalLines
         canonicalLines = fmap canonicalOrder logicalLines
-        logicalLines = NonEmpty.filter (not . null) $ layoutLines maxWidth runs
+        logicalLines = nonEmptyItems $ layoutLines maxWidth runs
         originY = paragraphOriginY
 
+nonEmptyItems :: Foldable t => t [a] -> [NonEmpty a]
+nonEmptyItems = catMaybes . map nonEmpty . toList
+
 -- | Reorder the given fragments from logical order to whatever order HarfBuzz
 -- uses (LTR for horizontal text, TTB for vertical text), so that cluster order
 -- is preserved even across runs.
-canonicalOrder :: [WithSpan PF.ProtoFragment] -> [WithSpan PF.ProtoFragment]
-canonicalOrder [] = []
-canonicalOrder pfs@((WithSpan _ headPF) : _) = case PF.direction headPF of
+canonicalOrder :: NonEmpty (WithSpan PF.ProtoFragment) ->
+    NonEmpty (WithSpan PF.ProtoFragment)
+canonicalOrder pfs@((WithSpan _ headPF) :| _) = case PF.direction headPF of
     -- TODO: Use BiDi levels to control reversing.
     Just DirLTR -> pfs
-    Just DirRTL -> reverse pfs
+    Just DirRTL -> NonEmpty.reverse pfs
     Just DirTTB -> pfs
-    Just DirBTT -> reverse pfs
+    Just DirBTT -> NonEmpty.reverse pfs
     -- If no guess can be made, use LTR.
     -- TODO: Add explicit direction to input interface.
     Nothing -> pfs


@@ 111,16 116,13 @@ layoutLines maxWidth runs = case nonEmpty rest of
 -- @vertical-align: top@ in CSS.
 --
 -- TODO: For rich text, allow other types of vertical alignment.
-positionLineH :: Int32 -> [WithSpan PF.ProtoFragment] ->
-    (Int32, [WithSpan Fragment])
+positionLineH :: Int32 -> NonEmpty (WithSpan PF.ProtoFragment) ->
+    (Int32, NonEmpty (WithSpan Fragment))
 positionLineH originY pfs = (nextY, frags)
     where
-        -- A line with no fragments will be considered to have zero height.
-        -- This can happen when line breaking produces a line that contains
-        -- only spaces.
-        nextY = if null rects then originY else maximum $ map y_min rects
-        rects = map (\ (WithSpan _ r) -> fragmentRect r) frags
-        frags = snd $ mapAccumL (positionFragmentH originY) originX pfs
+        nextY = maximum $ fmap y_min rects
+        rects = fmap (\ (WithSpan _ r) -> fragmentRect r) frags
+        (_, frags) = mapAccumL (positionFragmentH originY) originX pfs
         originX = paragraphOriginX
 
 -- | Position the given horizontal fragment on a line,