begin refactoring AppUpdate structure

temp-squares/fcore/app-update.sml

@@ -0,0 +1,44 @@
+structure AppUpdate =
+struct
+  open AppType
+
+  open DrawMessage
+  open FileMessage
+  open InputMessage
+  open UpdateMessage
+
+  fun getDotVecFromIndices (model: app_type, hIdx, vIdx) =
+    let
+      val {windowWidth, windowHeight, xClickPoints, yClickPoints, ...} = model
+      val xpos = Vector.sub (xClickPoints, hIdx)
+      val ypos = Vector.sub (yClickPoints, vIdx)
+
+      val endXpos =
+        if hIdx + 1 = Vector.length xClickPoints then
+          xpos
+        else
+          Vector.sub (xClickPoints, hIdx + 1)
+
+      val endYpos =
+        if vIdx + 1 = Vector.length yClickPoints then
+          ypos
+        else
+          Vector.sub (yClickPoints, vIdx + 1)
+
+      val tl =
+        ClickPoints.getDrawDotRgb
+          (xpos, ypos, 1.0, 0.0, 0.0, windowWidth, windowHeight)
+      val tr =
+        ClickPoints.getDrawDotRgb
+          (endXpos, ypos, 1.0, 0.0, 0.0, windowWidth, windowHeight)
+      val bl =
+        ClickPoints.getDrawDotRgb
+          (xpos, endYpos, 1.0, 0.0, 0.0, windowWidth, windowHeight)
+      val br =
+        ClickPoints.getDrawDotRgb
+          (endXpos, endYpos, 1.0, 0.0, 0.0, windowWidth, windowHeight)
+    in
+      Vector.concat [tl, tr, bl, br]
+    end
+
+end