done coding functionality to create a string suitable for exporting

fcore/common-update.sml

@@ -10,7 +10,7 @@ struct
   fun getSaveSquaresMsg (model: app_type) =
     let
       val {canvasWidth, canvasHeight, squares, ...} = model
-      val str = CollisionTree.toString (squares, canvasWidth, canvasHeight)
+      val str = CollisionTree.toSaveString (squares, canvasWidth, canvasHeight)
       val msg = SAVE_SQUARES str
     in
       (model, [FILE msg])
@@ -19,9 +19,17 @@ struct
   fun getLoadSquaresMsg model =
     (model, [FILE LOAD_SQUARES])
 
-  (* unimplemented *)
-  fun getExportSquaresMsg model = (model, [])
+  fun getExportSquaresMsg (model: app_type) =
+    let
+      val {squares, canvasWidth, canvasHeight, ...} = model
+      val exportString =
+        CollisionTree.toExportString (squares, canvasWidth, canvasHeight)
+      val msg = EXPORT_SQUARES exportString
+    in
+      (model, [FILE msg])
+    end
 
+  (* unimplemented *)
   fun useSquaresInNormalMode (model, squares) = (model, [])
 
   fun squaresLoadError model = (model, [])

fcore/quad-tree.sml

@@ -457,7 +457,7 @@ struct
       toBintree tree
     end
 
-  fun toStringFolder ({x, ex, y, ey, data = {r, g, b, a}}, acc) =
+  fun toSaveStringFolder ({x, ex, y, ey, data = {r, g, b, a}}, acc) =
     let
       val item = String.concat
         [ "{"
@@ -482,14 +482,14 @@ struct
       item :: acc
     end
 
-  fun toString (squares, canvasWidth, canvasHeight) =
+  fun toSaveString (squares, canvasWidth, canvasHeight) =
     let
       val size = Int.max (canvasWidth, canvasHeight)
       val qtree = buildTree (0, 0, size, squares)
       val bintree = merge (qtree, squares)
 
       val initial = ["}"]
-      val acc = BinTree.foldr (toStringFolder, bintree, initial)
+      val acc = BinTree.foldr (toSaveStringFolder, bintree, initial)
       val acc =
         String.concat
           [Int.toString canvasWidth, " ", Int.toString canvasHeight, " { "]
@@ -582,7 +582,7 @@ struct
         , "     #[\n"
         ]
 
-      val footer = String.concat ["    end\n", "end\n"]
+      val footer = String.concat ["      ]\n", "    end\n", "end\n"]
     in
       String.concat [header, coords, footer]
     end

message-types/file-msg.sml

@@ -3,7 +3,7 @@ struct
   datatype t =
     SAVE_SQUARES of string
   | LOAD_SQUARES
-  | EXPORT_SQUARES of int vector vector
+  | EXPORT_SQUARES of string
   | LOAD_FILES of string
   | SELECT_PATH of string
 end