add function to help change size of canvas

fcore/app-with.sml

@@ -10,6 +10,20 @@ struct
          else
            el) squares
 
+  fun changeSquaresSize (squares, newCanvasWidth, newCanvasHeight) =
+    Vector.tabulate (newCanvasWidth + 1, fn i =>
+      if i < Vector.length squares then
+        Vector.tabulate (newCanvasHeight + 1, fn ii =>
+          let
+            val yAxis = Vector.sub (squares, i)
+          in
+            if ii < Vector.length yAxis then Vector.sub (yAxis, ii)
+            else {r = 0, g = 0, b = 0, a = 0}
+          end)
+      else
+        Vector.tabulate (newCanvasHeight + 1, fn _ =>
+          {r = 0, g = 0, b = 0, a = 0}))
+
   fun addSquare (app, newX, newY, arrowX, arrowY) : app_type =
     let
       val