Add arrows signal.

* 2d/game.scm (arrows): New signal.

1 files changed, 12 insertions, 0 deletions

diff --git a/2d/game.scm b/2d/game.scm
index 72980fd..c2ad0bc 100644
--- a/2d/game.scm
+++ b/2d/game.scm
@@ -43,6 +43,7 @@
             window-size
             key-last-pressed
             key-down?
+            arrows
             mouse-position
             mouse-down?
             current-fps))
@@ -194,6 +195,17 @@ time in milliseconds that has passed since the last game update."
   "Return a signal for BUTTON."
   (signal-hash-ref mouse-signals button))
 
+(define arrows (signal-lift4 (lambda (up? down? left? right?)
+                               (let ((up (if up? -1 0))
+                                     (down (if down? 1 0))
+                                     (left (if left? -1 0))
+                                     (right (if right? 1 0)))
+                                 (vector2 (+ left right) (+ up down))))
+                             (key-down? 'up)
+                             (key-down? 'down)
+                             (key-down? 'left)
+                             (key-down? 'right)))
+
 (define (handle-event e)
   "Call the relevant callbacks for the event E."
   (case (SDL:event:type e)