fill in todo where strIdx is in tl, in text-window.sml function 'getStartLineWithCursorCentered

fcore/text-window.sml

@@ -196,7 +196,7 @@ struct
       case stl of
         hd :: tl =>
           getCursorStartLine
-            (String.size hd - 1, str, lineNum, tl, maxW, halfH)
+            (String.size hd - 1, hd, lineNum, tl, maxW, halfH)
       | [] =>
           0
     else
@@ -212,22 +212,7 @@ struct
             (strPos - 1, str, lineNum, stl, maxW, halfH)
       end
 
-  (* Prerequisite: LineGap is moved to cursor *)
+  fun getLineNum (strIdx, lhd, bufferLine) =
-  fun getStartLineWithCursorCentered 
-    (lineGap: LineGap.t, cursorIdx, origLine, maxWidth, maxHeight) =
-      let
-        val {rightStrings, rightLines, idx = bufferIdx, line = bufferLine, leftStrings, ...} = lineGap
-      in
-        case (rightStrings, rightLines) of
-          (shd :: stl, lhd :: ltl) =>
-            let
-              (* convert absolute cursorIdx to idx relative to hd string *)
-              val strIdx = cursorIdx - bufferIdx
-            in
-              if strIdx < String.size shd then
-                (* strIdx is in hd *)
-                let
-                  val lineNum = 
     if Vector.length lhd = 0 then
       bufferLine
     else if Vector.length lhd = 1 then
@@ -250,13 +235,42 @@ struct
         else
           bufferLine + 1
       end
+
+  (* Prerequisite: LineGap is moved to cursor *)
+  fun getStartLineWithCursorCentered 
+    (lineGap: LineGap.t, cursorIdx, origLine, maxWidth, maxHeight) =
+      let
+        val {rightStrings, rightLines, idx = bufferIdx, line = bufferLine, leftStrings, ...} = lineGap
+      in
+        case (rightStrings, rightLines) of
+          (shd :: stl, lhd :: ltl) =>
+            let
+              (* convert absolute cursorIdx to idx relative to hd string *)
+              val strIdx = cursorIdx - bufferIdx
+            in
+              if strIdx < String.size shd then
+                (* strIdx is in hd *)
+                let
+                  val lineNum = getLineNum (strIdx, lhd, bufferLine)
                 in
                   getCursorStartLine 
                     (strIdx, shd, lineNum, leftStrings, maxWidth, maxHeight)
                 end
               else
-                (* todo: strIdx is in tl *)
+                (* strIdx is in tl *)
-                raise Match
+                case (stl, ltl) of
+                  (stlhd :: stltl, ltlhd :: _) =>
+                    let
+                      val strIdx = strIdx - String.size shd
+                      val bufferLine = bufferLine + Vector.length lhd
+                      val lineNum = getLineNum (strIdx, ltlhd, bufferLine)
+                      val leftStrings = shd :: leftStrings
+                    in
+                      getCursorStartLine 
+                        (strIdx, stlhd, lineNum, leftStrings, maxWidth, maxHeight)
+                    end
+                | (_, _) =>
+                    origLine
             end
         | (_, _) =>
             origLine