progress with refactoring

temp-squares/fcore/quad-tree.sml

@@ -225,8 +225,15 @@ struct
           foldWithDuplicates (f, br, acc)
         end
 
-  fun insertItemIntoTree (item, acc) =
-    BinTree.insert (item, acc)
+  fun insertItemIntoTree ignoreData (item, acc) =
+    if #data item = 0 then 
+      (* ignore specific data by not inserting it into tree.
+       * May later functorise this quad tree,
+       * and allow different types of data
+       * to be ignored/stored in #data field. *)
+      acc
+    else 
+      BinTree.insert (item, acc)
 
   fun toList qtree =
     let
@@ -234,4 +241,19 @@ struct
     in
       BinTree.toList (tree, [])
     end
+
+  fun toTriangles (windowWidth, windowHeight, squares, acc) =
+    case squares of
+      {x, y, ex, ey, data = _} :: tl =>
+        let
+          val startX = Ndc.fromPixelX (x, windowWidth, windowHeight)
+          val endX = Ndc.fromPixelX (ex, windowWidth, windowHeight)
+          val startY = Ndc.fromPixelY (y, windowWidth, windowHeight)
+          val endY = Ndc.fromPixelY (ey, windowWidth, windowHeight)
+
+          val acc = Ndc.ltrbToVertex (startX, startY, endX, endY) :: acc
+        in
+          toTriangles (windowWidth, windowHeight, tl, acc)
+        end
+    | [] => Vector.concat acc
 end