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/text-builder/normal-mode-text-builder.sml

@@ -27,7 +27,6 @@ struct
             (* get relative index of line to start building from *)
             val strPos =
               Utils.getRelativeLineStartFromRightHead (startLine, curLine, lhd)
-              + 1
             (* get absolute idx of line *)
             val absIdx = curIdx + strPos
             val searchPos = BinSearch.equalOrMore (absIdx, searchList)

fcore/text-builder/text-builder-with-cursor.sml

@@ -207,8 +207,7 @@ struct
                 in Utils.makeCursorOnChr (chr, posX, posY, env) :: acc
                 end
               else
-                Utils.makeChr (chr, posX, posY, env)
-                :: Utils.makeCursor (posX, posY, env) :: acc
+                Utils.makeChr (chr, posX, posY, env) :: acc
           in
             build
               ( pos + 1

fcore/text-builder/text-builder-with-highlight.sml

@@ -270,8 +270,8 @@ struct
               let
                 val acc =
                   if absIdx = cursorIdx then
-                    Utils.makeCursor (posX, posY, env)
-                    :: Utils.makeCursorOnChr (chr, posX, posY, env) :: acc
+                    Utils.makeCursorOnChr (chr, posX, posY, env)
+                    :: Utils.makeCursor (posX, posY, env) :: acc
                   else if Utils.isInSearchRange (absIdx, searchPos, env) then
                     Utils.makeHighlightChr (chr, posX, posY, env)
                     :: Utils.makeHighlight (posX, posY, env) :: acc