progress with refactoring

temp-squares/fcore/ndc.sml

@@ -1,6 +1,7 @@
 structure Ndc = 
 struct
   (* ndc = normalised device coordinates *)
+
   fun ltrbToVertex (left, top, right, bottom) =
     #[ left, bottom
      , right, bottom
@@ -20,4 +21,36 @@ struct
      , right, bottom, r, g, b
      , right, top, r, g, b
      ]
+
+  fun fromPixelX (xpos, windowWidth, windowHeight) =
+    let
+      val halfWidth = (Real32.fromInt windowWidth) / 2.0
+      val xpos = xpos - halfWidth
+    in
+      if windowWidth > windowHeight then
+        let
+          val difference = windowWidth - windowHeight
+          val offset = Real32.fromInt (difference div 2)
+        in
+          xpos / (halfWidth - offset)
+        end
+      else
+        xpos / halfWidth
+    end
+
+  fun fromPixelY (ypos, windowWidth, windowHeight) =
+    let
+      val halfHeight = (Real32.fromInt windowHeight) / 2.0
+      val ypos = ~(ypos - halfHeight)
+    in
+      if windowHeight > windowWidth then
+        let
+          val difference = windowHeight - windowWidth
+          val offset = Real32.fromInt (difference div 2)
+        in
+          ypos / (halfHeight - offset)
+        end
+      else
+        ypos / halfHeight
+    end
 end

temp-squares/fcore/quad-tree.sml

@@ -225,8 +225,15 @@ struct
           foldWithDuplicates (f, br, acc)
         end
 
-  fun insertItemIntoTree (item, acc) =
+  fun insertItemIntoTree ignoreData (item, acc) =
-    BinTree.insert (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