begin coding functionality to move squares

fcore/app-type.sml

@@ -1,6 +1,6 @@
 structure AppType =
 struct
-  datatype app_mode = NORMAL_MODE | BROWSE_MODE
+  datatype app_mode = NORMAL_MODE | BROWSE_MODE | MOVE_MODE
 
   datatype file_browser_item = IS_FILE of string | IS_FOLDER of string
 

fcore/app-update.sml

@@ -6,4 +6,5 @@ struct
     case #mode model of
       NORMAL_MODE => NormalMode.update (model, inputMsg)
     | BROWSE_MODE => BrowseMode.update (model, inputMsg)
+    | MOVE_MODE => MoveMode.update (model, inputMsg)
 end

fcore/app-with.sml

@@ -145,6 +145,62 @@ struct
       }
     end
 
+  fun squares (app, newSquares) =
+    let
+      val
+        { mode
+        , squares
+        , arrowX
+        , arrowY
+        , canvasWidth
+        , canvasHeight
+        , windowWidth
+        , windowHeight
+        , xClickPoints
+        , yClickPoints
+
+        , showGraph
+        , mouseX
+        , mouseY
+        , openFilePath
+        , fileBrowser
+        , fileBrowserIdx
+        , r
+        , g
+        , b
+        , a
+        , modalNum
+        , undo
+        , redo
+        } = app
+    in
+      { mode = mode
+      , squares = newSquares
+      , arrowX = arrowX
+      , arrowY = arrowY
+      , canvasWidth = canvasWidth
+      , canvasHeight = canvasHeight
+      , windowWidth = windowWidth
+      , windowHeight = windowHeight
+      , xClickPoints = xClickPoints
+      , yClickPoints = yClickPoints
+
+      , showGraph = showGraph
+      , mouseX = mouseX
+      , mouseY = mouseY
+      , openFilePath = openFilePath
+      , fileBrowser = fileBrowser
+      , fileBrowserIdx = fileBrowserIdx
+      , r = r
+      , g = g
+      , b = b
+      , a = a
+      , modalNum = modalNum
+      , undo = undo
+      , redo = redo
+      }
+    end
+
   fun arrowX (app, arrowX) =
     let
       val

fcore/move-mode.sml

@@ -0,0 +1,35 @@
+structure MoveMode =
+struct
+  open AppType
+  open InputMessage
+
+  fun makeBlankYAxis length =
+    Vector.tabulate (length, fn _ => {r = 0, g = 0, b = 0, a = 0})
+
+  fun moveImageUp (model: app_type) =
+    let
+      val {squares, ...} = model
+
+      val squares =
+        Vector.mapi
+          (fn (idx, yAxis) =>
+             if idx + 1 < Vector.length squares then
+               Vector.sub (squares, idx + 1)
+             else
+               makeBlankYAxis (Vector.length yAxis)) squares
+
+      val model = AppWith.squares (model, squares)
+    in
+      (model, [])
+    end
+
+  fun update (model, inputMsg) =
+    case inputMsg of
+      ARROW_UP => moveImageUp model
+    (*
+    | ARROW_LEFT => moveImageLeft model
+    | ARROW_RIGHT => moveImageRight model
+    | ARROW_DOWN => moveImageDown model
+    *)
+    | _ => (model, [])
+end