gamnit: fix Y axis un `screen_to_ui`

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/gamnit/cameras.nit b/lib/gamnit/cameras.nit
index be7edcf..0756a38 100644 (file)
--- a/lib/gamnit/cameras.nit
+++ b/lib/gamnit/cameras.nit
@@ -234,7 +234,7 @@ class UICamera
 
                var wx = x.to_f * width / display.width.to_f - position.x
                var wy = y.to_f * height / display.height.to_f - position.y
-               return new Point[Float](wx, wy)
+               return new Point[Float](wx, -wy)
        end
 
        # Center of the screen, from the point of view of the camera, at z = 0