[example] add gravity toggle

1 files changed, 30 insertions, 11 deletions

diff --git a/examples/09-ghoulspree.lisp b/examples/09-ghoulspree.lisp
index 05bd4a3..35986fa 100644
--- a/examples/09-ghoulspree.lisp
+++ b/examples/09-ghoulspree.lisp
@@ -11,7 +11,8 @@
 
 (defclass/std  ghoulspree (ww::application)
   ((ghouls-per-click :std 10)
-   (collision-on-p :std t)))
+   (collision-on-p :std t)
+   (gravity-on-p :std nil)))
 
 (defclass/std ghoul (ww:bitmap)
   ((dx dy dr :std)))
@@ -70,6 +71,10 @@ on which boundary VAL is outside of."
               dy2 tdy
               dr2 tdr)))))
 
+(defun apply-gravity-to (thing acc)
+  (with-slots (dx dy) thing
+    (decf dy acc)))
+
 (ww:defhandler moveghouls
     (ww:on-perframe (app)
       ;; first handle collisions
@@ -83,12 +88,17 @@ on which boundary VAL is outside of."
               (advance-pos g1)
               (advance-pos g2)
               (advance-pos g2))))
-      
       ;; then update positions and remove the out of bounds
-      (loop for ghoul in (ww:container-units app)
-            do (advance-pos ghoul)
-            when (out-of-bounds-p ghoul)
-              do (ww:drop-unit ghoul))))
+      (let ((gravity
+              (gravity-on-p app))
+            (accelleration
+              (/ 9.8 (ww:fps app)))) 
+        (loop for ghoul in (ww:container-units app)
+              do (advance-pos ghoul)
+              when gravity
+                do (apply-gravity-to ghoul accelleration)
+              when (out-of-bounds-p ghoul)
+                do (ww:drop-unit ghoul)))))
 
 (defun random-sign ()
   (if (zerop (random 2)) -1 1))
@@ -107,14 +117,23 @@ on which boundary VAL is outside of."
 
 
 (ww:defhandler toggle-collision
-    (ww:on-keydown ()
-      (format t "collision: ~a~%"
-              (setf (collision-on-p target)
-                    (not (collision-on-p target))))))
+    (ww:on-keydown (app scancode)
+      (case scancode
+        (:scancode-c 
+         (format t "collision: ~a~%"
+                 (setf (collision-on-p app)
+                       (not (collision-on-p app)))))
+        (:scancode-g
+         (format t "gravity: ~a~%"
+                 (setf (gravity-on-p app)
+                       (not (gravity-on-p app))))))))
+
 
 (defmethod ww::boot ((app ghoulspree))
   "Adds the intro text and sets up the start button handler."
-  (format t "Click to add ghouls to the screen.~%Press any key to toggle collision detection.~%")
+  (format t "Click to add ~a ghouls to the screen.~%" (ghouls-per-click app))
+  (format t "Press c to toggle collision handling.~%")
+  (format t "Press g to toggle gravity.~%")
 
   (ww:add-handler app #'add-ghouls)
   (ww:add-handler app #'moveghouls)