begin creating a string for collision data

fcore/quad-tree.sml

@@ -548,12 +548,36 @@ struct
 
       (* based on triangle order formed by `Ndc.ltrbToVertexRgb` function *)
       val item = String.concatWith ",\n"
-        [ x, ey, r, g, b
-        , ex, ey, r, g, b
-        , x, y, r, g, b
-        , x, y, r, g, b
-        , ex, ey, r, g, b
-        , ex, y, r, g, b
+        [ x
+        , ey
+        , r
+        , g
+        , b
+        , ex
+        , ey
+        , r
+        , g
+        , b
+        , x
+        , y
+        , r
+        , g
+        , b
+        , x
+        , y
+        , r
+        , g
+        , b
+        , ex
+        , ey
+        , r
+        , g
+        , b
+        , ex
+        , y
+        , r
+        , g
+        , b
         ]
     in
       item :: acc
@@ -598,4 +622,25 @@ struct
         , "end\n"
         ]
     end
+
+  (* functions for exporting a collision detection string *)
+  fun mapItem (item as {r, g, b, a}) =
+    if shouldIgnoreData item then item else {r = 1, g = 1, b = 1, a = 1}
+
+  fun mapGrid grid =
+    Vector.map (fn yAxis => Vector.map (fn item => mapItem item) yAxis) grid
+
+  fun toCollisionStringFolder ({x, ex, y, ey, data = _}, acc) =
+    let
+      val ex = if x = ex then ex + 1 else ex
+      val ey = if y = ey then ey + 1 else ey
+
+  fun toCollisionString (squares, canvasWidth, canvasHeight) =
+    let
+      val size = Int.max (canvasWidth, canvasHeight)
+      val qtree = buildTree (0, 0, size, squares)
+      val bintree = merge (qtree, squares)
+
+      val collisions = BinTree.foldr (toExportStringFolder, bintree, [])
+      val collisions = String.concatWith ",\n" coords
 end