draw cursor at newline linebreaks (only \n though and not \r\n)

fcore/cursor.sml

@@ -1,6 +1,29 @@
 structure Cursor =
 struct
-  (* Prerequisite: lineGap is moved to requested idx first *)
+  (* todo: viL does not handle \r\n pair right now
+   * but this is not a priority so it's okay *)
+  local
+    fun helpVilLf (hd, strIdx, bufferIdx, cursorIdx, tl) =
+      (* if we are in \n, 
+       * move cursor to character after newline 
+       * if possible *)
+      if strIdx < String.size hd - 3 then
+        (* we know it is safe to move cursorIdx by 2 
+         * if strIdx + 2 is before or at the end of the string. *)
+        cursorIdx + 2
+      else
+        (* we have to check the tl to see if it is not empty  
+         * so we know it is safe to move. *)
+        case tl of
+          _ :: _ => 
+            (* not empty, so we can increment by 2 *) 
+            cursorIdx + 2
+        | [] =>
+            (* empty, so return end of string which is \n *)
+            bufferIdx + String.size hd - 1
+  in
+    (* Prerequisite: lineGap is moved to requested idx first 
+     * todo: check if we are in a \r\n pair, but this is not a priority *)
     fun viL (lineGap: LineGap.t, cursorIdx) =
       let
         val {rightStrings, idx = bufferIdx, ...} = lineGap
@@ -8,38 +31,21 @@ struct
         case rightStrings of
           hd :: tl =>
             let
-            (* idx relative to this string *)
+              (* convert absolute cursorIdx to idx relative to hd string *)
               val strIdx = cursorIdx - bufferIdx
             in
               if strIdx < String.size hd - 2 then
-              (* increment if there is a character after where cursor is 
+                (case String.sub (hd, strIdx + 1) of
-               * but first, check if we are in a \r\n pair; 
+                   #"\n" => helpVilLf (hd, strIdx, bufferIdx, cursorIdx, tl)
-               * if we are, then increment cursor by 2 *)
+                 | _ => cursorIdx + 1)
-              if
-                String.size hd > strIdx + 2
-                andalso String.sub (hd, strIdx + 1) = #"\r"
-                andalso String.sub (hd, strIdx + 2) = #"\n"
-              then
-                (* increment cursor by 2 if we are inside \r\n pair *)
-                cursorIdx + 2
-              else
-                (* inccrement cursor by 1 if we are not inside \r\n pair *)
-                cursorIdx + 1
               else
                 (case tl of
-                 _ :: _ =>
+                   tlhd :: tltl =>
                      (* if there is another string after current head, we can increment cursorIdx 
-                    * however, first we need to check if next string is \r\n pair. *)
+                      * however, first we need to check if next char is \n. *)
-                   if
+                     (case String.sub (tlhd, 0) of
-                     String.size hd > strIdx + 2
+                        #"\n" => helpVilLf (tlhd, 0, bufferIdx, cursorIdx, tltl)
-                     andalso String.sub (hd, strIdx + 1) = #"\r"
+                      | _ => cursorIdx + 1)
-                     andalso String.sub (hd, strIdx + 2) = #"\n"
-                   then
-                     (* increment cursor by 2 if we are inside \r\n pair *)
-                     cursorIdx + 2
-                   else
-                     (* inccrement cursor by 1 if we are not inside \r\n pair *)
-                     cursorIdx + 1
                  | _ =>
                      (* if there is no string after current head, return original cursorIdx *)
                      cursorIdx)
@@ -49,3 +55,4 @@ struct
             cursorIdx
       end
   end
+end

fcore/text-builder.sml

@@ -316,11 +316,25 @@ struct
             )
       | #"\n" =>
           if posY + ySpace < windowHeight then
+            if absIdx <> cursorPos then
+              (* not in cursor position, so iterate like normal *)
               buildTextStringWithinCursor
                 ( pos + 1, str, acc, startX, posY + ySpace, startX
                 , windowWidth, windowHeight, fWindowWidth, fWindowHeight
                 , r, g, b, tl, absIdx + 1, cursorPos, cursorAcc, hr, hg, hb
                 )
+            else
+              (* in cursor position, so build cursorAcc 
+               * and call AfterCursor function *)
+              let
+                val cursorAcc = buildCursor (posX, posY, fWindowWidth, fWindowHeight, r, g ,b)
+              in
+                buildTextStringAfterCursor
+                  ( pos + 1, str, acc, startX, posY + ySpace, startX
+                  , windowWidth, windowHeight, fWindowWidth, fWindowHeight
+                  , r, g, b, tl, cursorAcc
+                  )
+              end
           else
             accToDrawMsg (acc, cursorAcc)
       | #"\r" =>

temp.txt

@@ -1,6 +1,8 @@
 signature TEXT_BUILDER =
+
 sig
   (* Prerequisite: LineGap is moved to requested line first. *)
   val build: int * int * LineGap.t * int * int
              -> MailboxType.t list
 enda
+