fix bugs in implementing and using text buffer. Some functions did not save the drawMsg to the app's state, which we means we didn't draw in those cases. The text builder functions also drew cursors on characters even when the cursor is not at this position. Both of these bugs are fixed.

fcore/normal-mode/normal-finish.sml

@@ -41,7 +41,7 @@ struct
         )
       val drawMsg = Vector.concat drawMsg
       val drawMsg = DRAW_TEXT drawMsg
-      val drawMsg = [DRAW drawMsg]
+      val msgs = DRAW drawMsg :: msgs
 
       val mode = NORMAL_MODE ""
     in
@@ -91,7 +91,7 @@ struct
 
       val newBuffer = LineGap.goToIdx (cursorIdx, buffer)
       val visualScrollColumn =
-        TextScroll.getScrollColumn (buffer, cursorIdx, windowWidth)
+        TextScroll.getScrollColumn (buffer, cursorIdx, newWidth)
       val newBuffer = LineGap.goToLine (startLine, newBuffer)
       val lineIdx = TextBuilderUtils.getLineAbsIdxFromBuffer (startLine, buffer)
 
@@ -99,15 +99,15 @@ struct
         ( startLine
         , cursorIdx
         , buffer
-        , windowWidth
-        , windowHeight
+        , newWidth
+        , newHeight
         , searchList
         , searchString
         , visualScrollColumn
         )
       val drawMsg = Vector.concat drawMsg
       val drawMsg = DRAW_TEXT drawMsg
-      val drawMsg = [DRAW drawMsg]
+      val msgs = [DRAW drawMsg]
     in
       NormalModeWith.bufferAndSize
         ( app
@@ -115,7 +115,7 @@ struct
         , newWidth
         , newHeight
         , searchList
-        , drawMsg
+        , msgs
         , bufferModifyTime
         , visualScrollColumn
         )
@@ -159,7 +159,7 @@ struct
         )
       val drawMsg = Vector.concat drawMsg
       val drawMsg = DRAW_TEXT drawMsg
-      val drawMsg = [DRAW drawMsg]
+      val msgs = DRAW drawMsg :: initialMsg
 
       val mode = NORMAL_MODE ""
     in
@@ -170,7 +170,7 @@ struct
         , mode
         , startLine
         , searchList
-        , drawMsg
+        , msgs
         , bufferModifyTime
         , visualScrollColumn
         )