From 131b16a751af282215ae0da5bc131e0a4c9489f4 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 29 Apr 2018 20:56:31 -0400
Subject: render: tiled: Invert Y coordinates of objects.

* chickadee/render/tiled.scm (load-tile-map): Invert Y coordinate for
objects.
---
 chickadee/render/tiled.scm | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/chickadee/render/tiled.scm b/chickadee/render/tiled.scm
index 802a9a2..3de534b 100644
--- a/chickadee/render/tiled.scm
+++ b/chickadee/render/tiled.scm
@@ -330,31 +330,35 @@
            (properties (map parse-property
                             ((sxpath '(properties property)) node))))
       (%make-tile-layer name width height tiles properties)))
-  (define (parse-polygon node)
+  (define (parse-polygon node pixel-height)
     (make-polygon
      (list->vector
       (map (lambda (s)
              (match (string-split s #\,)
                ((x y)
-                (vec2 (string->number x) (string->number y)))))
+                (vec2 (string->number x)
+                      (- pixel-height (string->number y))))))
            (string-split (attr node 'points) #\space)))))
-  (define (parse-object node)
+  (define (parse-object node pixel-height)
     (let* ((id (attr node 'id string->number))
            (name (attr node 'name))
            (type (attr node 'type string->symbol))
            (x (attr node 'x string->number))
-           (y (attr node 'y string->number))
+           (y (- pixel-height (attr node 'y string->number)))
            (width (attr node 'width string->number))
            (height (attr node 'height string->number))
            (shape (if (and width height)
                       (make-rect x y width height)
-                      (parse-polygon (car ((sxpath '(polygon)) node)))))
+                      (parse-polygon (car ((sxpath '(polygon)) node))
+                                     pixel-height)))
            (properties (map parse-property
                             ((sxpath '(properties property)) node))))
       (%make-map-object id name type shape properties)))
-  (define (parse-object-layer node)
+  (define (parse-object-layer node pixel-height)
     (let ((name (attr node 'name))
-          (objects (map parse-object ((sxpath '(object)) node)))
+          (objects (map (lambda (node)
+                          (parse-object node pixel-height))
+                        ((sxpath '(object)) node)))
           (properties (map parse-property
                            ((sxpath '(properties property)) node))))
       (%make-object-layer name objects properties)))
@@ -382,7 +386,7 @@
                               (('layer . _)
                                (parse-tile-layer node tilesets))
                               (('objectgroup . _)
-                               (parse-object-layer node))))
+                               (parse-object-layer node (* height tile-height)))))
                           layers))
                     (map parse-property properties)
                     (make-rect 0.0
-- 
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