remove 'squares' field from app type, and refactor most functions in common-update.sml to use layer tree instead of squares vector

fcore/common-update.sml

@@ -10,17 +10,19 @@ struct
   fun resizeWindow (model, width, height, dots) =
     let
       val
-        { squares
-        , canvasWidth
+        { canvasWidth
         , canvasHeight
         , showGraph
         , arrowX
         , arrowY
         , xClickPoints
         , yClickPoints
+        , layerTree
         , ...
         } = model
+
       val maxSide = Int.max (canvasWidth, canvasHeight)
+      val squares = LayerTree.flatten (maxSide, layerTree)
 
       val squares = CollisionTree.toTriangles
         ( width
@@ -46,11 +48,12 @@ struct
 
   fun getSaveSquaresMsg (model: app_type) =
     let
-      val {canvasWidth, canvasHeight, squares, ...} = model
-      val str = CollisionTree.toSaveString (squares, canvasWidth, canvasHeight)
-      val msg = SAVE_SQUARES str
-    in
-      (model, [FILE msg])
+    (* todo: reimplement, saving each layer to a different line 
+    val {canvasWidth, canvasHeight, squares, ...} = model
+    val str = CollisionTree.toSaveString (squares, canvasWidth, canvasHeight)
+    val msg = SAVE_SQUARES str
+    *)
+    in raise Fail "todo common-update.sml: reimplement saving"
     end
 
   fun getLoadSquaresMsg model =
@@ -58,7 +61,11 @@ struct
 
   fun getExportSquaresMsg (model: app_type) =
     let
-      val {squares, canvasWidth, canvasHeight, ...} = model
+      val {layerTree, canvasWidth, canvasHeight, ...} = model
+
+      val maxSide = Int.max (canvasWidth, canvasHeight)
+      val squares = LayerTree.flatten (maxSide, layerTree)
+
       val exportString =
         CollisionTree.toExportString (squares, canvasWidth, canvasHeight)
       val msg = EXPORT_SQUARES exportString
@@ -68,7 +75,11 @@ struct
 
   fun getCollisionMsg (model: app_type) =
     let
-      val {squares, canvasWidth, canvasHeight, modalNum, ...} = model
+      val {layerTree, canvasWidth, canvasHeight, modalNum, ...} = model
+
+      val maxSide = Int.max (canvasWidth, canvasHeight)
+      val squares = LayerTree.flatten (maxSide, layerTree)
+
       val exportString =
         CollisionTree.toCollisionString
           (squares, canvasWidth, canvasHeight, modalNum)