2 files changed, 27 insertions(+), 3 deletions(-)

M src/Data/Text/ParagraphLayout/Internal/Run.hs
M test/Data/Text/ParagraphLayout/Internal/RunSpec.hs

@@ 78,7 78,22 @@ considerNext z = case next z of
 data Merged a = Incompatible | Merged a
 
 spanToRuns :: ResolvedSpan d -> [Run]
-spanToRuns s = snd $ mapAccumL run 0 $ protoRuns zipper levels
+spanToRuns s
+    | Text.null (spanText s) = [emptyRun]
+    | otherwise = spanToRuns' s
+    where
+        emptyRun = Run
+            { runOffsetInSpan = 0
+            , runText = Text.empty
+            , runLevel = defaultLevel
+            , runDirection = levelDirectionH defaultLevel
+            , runScript = Nothing
+            , runHardBreak = False
+            }
+        defaultLevel = baseLevel $ spanBiDiLevels s
+
+spanToRuns' :: ResolvedSpan d -> [Run]
+spanToRuns' s = snd $ mapAccumL run 0 $ protoRuns zipper levels
     where
         wholeText = spanText s
         zipper = start wholeText

@@ 1,6 1,6 @@
 module Data.Text.ParagraphLayout.Internal.RunSpec (spec) where
 
-import Data.Text (Text, pack)
+import Data.Text (Text, empty, pack)
 import Data.Text.Glyphize (Direction (..), emptyFont)
 
 import Test.Hspec


@@ 49,7 49,16 @@ spec = do
         it "handles span with no text" $ do
             let inputSpan = sampleSpan englishEmpty allLTR
             let runs = spanToRuns inputSpan
-            runs `shouldBe` []
+            runs `shouldBe`
+                [ Run
+                    { runOffsetInSpan = 0
+                    , runText = empty
+                    , runLevel = 0
+                    , runDirection = DirLTR
+                    , runScript = Nothing
+                    , runHardBreak = False
+                    }
+                ]
         it "handles Czech hello" $ do
             let inputSpan = sampleSpan czechHello allLTR
             let runs = spanToRuns inputSpan