code function that indicates which area, if any, was clicked

functional-core/app-update.sml

@@ -1 +1,75 @@
-structure AppUpdate = struct end
+structure AppUpdate =
+struct
+  val clickPoints =
+   #[ 25
+    , 50
+    , 75
+    , 100
+    , 125
+    , 150
+    , 175
+    , 200
+    , 225
+    , 250
+    , 275
+    , 300
+    , 325
+    , 350
+    , 375
+    , 400
+    , 425
+    , 450
+    , 475
+    ]
+
+  local
+    fun getVerticalClickPos (idx, horizontalPos, mouseX, mouseY) =
+      if idx = Vector.length clickPoints then
+        #[]
+      else
+        let
+          val curVerticalPos = Vector.sub (clickPoints, idx)
+        in
+          if mouseY < curVerticalPos - 10 orelse mouseY > curVerticalPos + 10 then
+            getVerticalClickPos (idx + 1, horizontalPos, mouseX, mouseY)
+          else
+            let
+              val left = Real32.fromInt ((horizontalPos - 10) div 500)
+              val right = Real32.fromInt ((horizontalPos + 10) div 500)
+              val bottom = Real32.fromInt ((curVerticalPos - 10) div 500)
+              val top = Real32.fromInt ((curVerticalPos + 10) div 500)
+            in
+              val highlightSquare = #[
+                left, bottom, (* lower left *)
+                right, bottom, (* lower right *)
+                left, top, (* upper left *)
+
+                left, top, (* upper left *)
+                right, bottom, (* lower right *)
+                right, top (* upper right *)
+              ]
+            end
+        end
+
+    fun getHorizontalClickPos (idx, mouseX, mouseY) =
+      if idx = Vector.length clickPoints then
+        #[]
+      else
+        let
+          val curPos = Vector.sub (clickPoints, idx)
+        in
+          if mouseX < curPos - 10 orelse mouseX > curPos + 10 then
+            getHorizontalClickPos (idx + 1, mouseX, mouseY)
+          else
+            getVerticalClickPos (0, curPos, mouseX, mouseY)
+        end
+  in
+    (*
+     * This function returns a vector containing the position data of the
+     * clicked square.
+     * If a square wasn't found at the clicked position, 
+     * an empty vector is returned.
+     *)
+    fun getClickPos (mouseX, mouseY) = getHorizontalClickPos (0, mouseX, mouseY)
+  end
+end