6 files changed, 28 insertions(+), 14 deletions(-)

M .golden/paginatedParagraphLayout/spannedArabicFiller20em.golden
M .golden/paragraphLayout/arabicFiller20em.golden
M .golden/paragraphLayout/hardBreaksRTL.golden
M .golden/paragraphLayout/spannedArabicFiller20em.golden
M src/Data/Text/ParagraphLayout/Internal/BiDiLevels.hs
M src/Data/Text/ParagraphLayout/Internal/Plain.hs

@@ 180,7 180,7 @@
             { fragmentUserData = ()
             , fragmentLine = 2
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = -1500, x_size = 3213, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 240,7 240,7 @@
             { fragmentUserData = ()
             , fragmentLine = 3
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 14300, y_origin = 0, x_size = 4862, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 320,7 320,7 @@
             { fragmentUserData = ()
             , fragmentLine = 3
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = 0, x_size = 3898, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 339,7 339,7 @@
             { fragmentUserData = ()
             , fragmentLine = 4
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 12238, y_origin = -1500, x_size = 2357, y_size = -1500}
             , fragmentPen = (0, -1085)

@@ 6,7 6,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 1
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = 0, x_size = 19850, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 184,7 184,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 4
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = -4500, x_size = 14595, y_size = -1500}
             , fragmentPen = (0, -1085)

@@ 6,7 6,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 1
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = 0, x_size = 2808, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 137,7 137,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 9
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = -12000, x_size = 1960, y_size = -1500}
             , fragmentPen = (0, -1085)

@@ 180,7 180,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 2
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = -1500, x_size = 3213, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 200,7 200,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 3
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 14300, y_origin = -3000, x_size = 4862, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 280,7 280,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 3
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = SpacedEdge 0, boxEndEdge = NoEdge}
                 ]
             , fragmentRect = Rect {x_origin = 0, y_origin = -3000, x_size = 3898, y_size = -1500}
             , fragmentPen = (0, -1085)


@@ 299,7 299,7 @@ ParagraphLayout
             { fragmentUserData = ()
             , fragmentLine = 4
             , fragmentAncestorBoxes =
-                [ AncestorBox {boxUserData = (), boxLeftEdge = NoEdge, boxRightEdge = SpacedEdge 0, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
+                [ AncestorBox {boxUserData = (), boxLeftEdge = SpacedEdge 0, boxRightEdge = NoEdge, boxStartEdge = NoEdge, boxEndEdge = SpacedEdge 0}
                 ]
             , fragmentRect = Rect {x_origin = 12238, y_origin = -4500, x_size = 2357, y_size = -1500}
             , fragmentPen = (0, -1085)

@@ 3,6 3,7 @@ module Data.Text.ParagraphLayout.Internal.BiDiLevels
     , TextLevels (TextLevels)
     , WithLevel
     , dropLevels
+    , firstStrongDirection
     , headLevel
     , level
     , levelDirectionH

@@ 5,6 5,7 @@ where
 import Data.Text.Glyphize (Direction (DirLTR))
 
 import Data.Text.ParagraphLayout.Internal.AncestorBox
+import Data.Text.ParagraphLayout.Internal.BiDiLevels
 import Data.Text.ParagraphLayout.Internal.BoxOptions
 import Data.Text.ParagraphLayout.Internal.Fragment
 import Data.Text.ParagraphLayout.Internal.ParagraphOptions


@@ 29,7 30,8 @@ layoutPlain p@(P.Paragraph _ _ spans _) =
 -- Span indexes are added to the user data internally, then used to split the
 -- resulting fragments according to their corresponding spans.
 plainToRich :: P.Paragraph d -> R.Paragraph (Int, d)
-plainToRich (P.Paragraph arr off spans opts) = R.Paragraph arr off rootNode opts
+plainToRich p@(P.Paragraph arr off spans opts) =
+    R.Paragraph arr off rootNode opts
     where
         rootNode = RootBox rootBox
         rootBox = Box spanNodes baseOpts


@@ 39,11 41,22 @@ plainToRich (P.Paragraph arr off spans opts) = R.Paragraph arr off rootNode opts
             (boxFromPlain baseOpts i s)
             defaultBoxOptions
         indexedSpans = zip [0 ..] spans
-        baseOpts = (defaultTextOptions DirLTR)
+        baseOpts = (defaultTextOptions $ detectDirection p)
             { textFont = paragraphFont opts
             , textLineHeight = paragraphLineHeight opts
             }
 
+-- | Simplified autodetection of text direction for plain text,
+-- to provide temporary compatibility with the old interface which
+-- did not allow setting text direction explicitly.
+--
+-- Note that the detected direction carries over hard line breaks,
+-- which is not compliant with the Unicode Bidirectional Algorithm.
+detectDirection :: P.Paragraph d -> Direction
+detectDirection p = case firstStrongDirection (P.paragraphText p) of
+    Just dir -> dir
+    Nothing -> DirLTR
+
 -- | Convert a legacy `Span` to a rich text box with one text node inside.
 --
 -- Add the given index to the user data, so that it can be extracted later.