fix offsetMap computation to include cursor character

src/Data/Text/Zipper.hs

@@ -12,7 +12,7 @@ module Data.Text.Zipper where
 import           Prelude
 
 import Control.Exception (assert)
-import Control.Monad.State (evalState, forM, get, put, join)
+import Control.Monad.State (evalState, forM, get, put)
 import Data.Char (isSpace)
 import Data.Map (Map)
 import Data.Maybe (fromMaybe)
@@ -418,10 +418,13 @@ displayLinesWithAlignment alignment width tag cursorTag (TextZipper lb b a la) =
       linesBefore = map (wrapWithOffsetAndAlignment alignment width 0) $ reverse lb
       linesAfter :: [[WrappedLine]] -- The wrapped lines after the cursor line
       linesAfter = map (wrapWithOffsetAndAlignment alignment width 0) la
+
+      -- simulate trailing cursor character when computing OffsetMap
+      afterWithCursor = if T.null a then " " else a
       offsets :: OffsetMapWithAlignment
       offsets = offsetMapWithAlignmentInternal $ mconcat
         [ linesBefore
-        , [wrapWithOffsetAndAlignment alignment width 0 $ b <> a]
+        , [wrapWithOffsetAndAlignment alignment width 0 $ b <> afterWithCursor]
         , linesAfter
         ]
       flattenLines = concatMap (fmap _wrappedLines_text)

test/Data/Text/ZipperSpec.hs

@@ -88,6 +88,11 @@ spec =
     _displayLines_cursorPos dl4 `shouldBe` (5,0)
     _displayLines_cursorPos dl5 `shouldBe` (4,0)
     _displayLines_cursorPos dl6 `shouldBe` (4,0)
+  it "displayLines - offsetMap" $ do
+    let
+      dl0 = displayLinesWithAlignment TextAlignment_Left 5 () () (end $ fromText "aoeku")
+    _displayLines_cursorPos dl0 `shouldBe` (0,1)
+    Map.size (_displayLines_offsetMap dl0) `shouldBe` 2 -- cursor character is on second line
   it "displayLinesWithAlignment - spans" $ do
     let
       someText = top $ fromText "0123456789abcdefgh"