Add animations.

modules/game/animation.scm

@@ -0,0 +1,56 @@
+(define-module (game animation)
+  #:use-module (game tileset)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-9)
+  #:export (make-frame
+            frame?
+            frame-tile
+            frame-duration
+
+            make-animation
+            animation?
+            animation-tileset
+            animation-time
+            animation-frames
+            update-animation
+            draw-animation))
+
+(define-record-type <frame>
+  (make-frame tile duration)
+  frame?
+  (tile frame-tile)
+  (duration frame-duration))
+
+(define-record-type <animation>
+  (%make-animation tileset frames time frame-idx)
+  animation?
+  (tileset animation-tileset)
+  (frames animation-frames)
+  (time animation-time set-animation-time!)
+  (frame-idx animation-frame-idx set-animation-frame-idx!))
+
+(define (make-animation tileset frames)
+  (%make-animation tileset frames 0.0 0))
+
+(define (flonum? x)
+  (and (real? x) (inexact? x)))
+
+(define (update-animation anim dt)
+  (unless (flonum? dt)
+    (error "not a flonum" dt))
+  (match anim
+    (($ <animation> tileset frames (? flonum? time) idx)
+     (let ((time* (+ time dt)))
+       (match (vector-ref frames idx)
+         (($ <frame> tile duration)
+          (cond
+           ((>= time* duration)
+            (set-animation-frame-idx! anim (modulo (1+ idx) (vector-length frames)))
+            (set-animation-time! anim (- time* duration)))
+           (else
+            (set-animation-time! anim time*)))))))))
+
+(define (draw-animation context anim x y)
+  (match anim
+    (($ <animation> tileset frames time idx)
+     (draw-tile context tileset (frame-tile (vector-ref frames idx)) x y))))

modules/game/effects.scm

@@ -1,5 +1,6 @@
 (define-module (game effects)
   #:use-module (dom canvas)
+  #:use-module (game time)
   #:use-module (ice-9 match)
   #:use-module (math)
   #:use-module (srfi srfi-9)
@@ -24,9 +25,6 @@
 
 (define (ease:linear t) t)
 
-(define (current-time*)
-  (/ (exact->inexact (current-jiffy)) (jiffies-per-second)))
-
 (define-record-type <effect>
   (%make-effect type draw ease duration start)
   effect?

modules/game/time.scm

@@ -0,0 +1,6 @@
+(define-module (game time)
+  #:use-module (scheme time)
+  #:export (current-time*))
+
+(define (current-time*)
+  (/ (exact->inexact (current-jiffy)) (jiffies-per-second)))