From c370d37157de9428ece281793d5e741b75bfad1b Mon Sep 17 00:00:00 2001
From: Josha von Gizycki <mail@joshavg.de>
Date: Thu, 19 Oct 2017 16:58:25 +0200
Subject: [PATCH] new fps calculation, objects move with pixels per second
 speed

---
 src/cljs/topdown2d/core.cljs      | 32 ++++++++++++++++++++-----------
 src/cljs/topdown2d/demoscene.cljs |  9 +++++----
 src/cljs/topdown2d/objects.cljs   | 29 ++++++++++++++++++----------
 3 files changed, 45 insertions(+), 25 deletions(-)

diff --git a/src/cljs/topdown2d/core.cljs b/src/cljs/topdown2d/core.cljs
index 1fb108f..7815f53 100644
--- a/src/cljs/topdown2d/core.cljs
+++ b/src/cljs/topdown2d/core.cljs
@@ -8,10 +8,12 @@
 (def gamestate {
   :canvas (.getElementById js/document "gamecanvas")
   :2d (.getContext (.getElementById js/document "gamecanvas") "2d")
+  :target-fps 30
   :timing {
     :prev 0
     :now 0
     :fps 0
+    :elapsed 0
   }
   :dimensions {
     :w 600
@@ -31,17 +33,23 @@
 (aset (:2d gamestate) "font" "10px monospace")
 
 (defn set-timing [state timingkey]
-  (update-in state
+  (assoc-in state
     [:timing timingkey]
-    #(.now js/performance)))
+    (.now js/performance)))
 
 (defn set-fps [state]
-  (let [newstate (set-timing state :now)
-        now (get-in newstate [:timing :now])
-        prev (get-in newstate [:timing :prev])
-        duration (- now prev)
-        fps (/ 1000 duration)]
-    (update-in newstate [:timing :fps] (fn [] fps))))
+  (let [elapsed (get-in state [:timing :elapsed])
+        fps (/ 1 elapsed)]
+    (assoc-in state [:timing :fps] fps)))
+
+(defn set-elapsed-seconds [gamestate]
+  (assoc-in gamestate
+    [:timing :elapsed]
+    (/
+      (-
+        (get-in gamestate [:timing :now])
+        (get-in gamestate [:timing :prev]))
+      1000)))
 
 (defn update-scene [gamestate]
   (let [scenekey (:scene gamestate)
@@ -52,9 +60,11 @@
 
 (defn update-step [gamestate]
   (-> gamestate
+    (set-timing :now)
+    (set-elapsed-seconds)
     (set-fps)
-    (set-timing :prev)
-    (update-scene)))
+    (update-scene)
+    (set-timing :prev)))
 
 (defn draw-step [gamestate]
   (.clearRect (:2d gamestate)
@@ -77,7 +87,7 @@
       (fn []
         (.requestAnimationFrame js/window
           #(mainloop newstate)))
-      (/ 1000 30))))
+      (/ 1000 (:target-fps gamestate)))))
 
 (defn init-scenes []
   (assoc
diff --git a/src/cljs/topdown2d/demoscene.cljs b/src/cljs/topdown2d/demoscene.cljs
index 4c50d2d..305f6e9 100644
--- a/src/cljs/topdown2d/demoscene.cljs
+++ b/src/cljs/topdown2d/demoscene.cljs
@@ -13,7 +13,6 @@
         :y 50
         :w 10
         :h 10
-        :v 0
       }
       :box
       {
@@ -21,7 +20,7 @@
         :y 5
         :w 10
         :h 10
-        :v 5
+        :pps 100
         :d :?
       }
     }))
@@ -30,9 +29,11 @@
   (let [box (get-in scenedata [:data :box])
         dir (input/dirinput)
         box (assoc box :d dir)]
-    (update-in scenedata
+    (assoc-in scenedata
       [:data :box]
-      #(objects/move-inside-gamestate gamestate box))))
+      (objects/move-inside-gamestate
+        gamestate
+        box))))
 
 (defn draw [gamestate scenedata]
   (let [{{:keys [bumper box]} :data} scenedata
diff --git a/src/cljs/topdown2d/objects.cljs b/src/cljs/topdown2d/objects.cljs
index d28d67c..10c677f 100644
--- a/src/cljs/topdown2d/objects.cljs
+++ b/src/cljs/topdown2d/objects.cljs
@@ -9,21 +9,21 @@
       (< (+ x w) (+ cx cw))
       (< (+ y h) (+ cy ch)))))
 
-(defn moved-object [obj]
-  (let [{:keys [x y v d]} obj]
+(defn moved-object [obj pxs]
+  (let [{:keys [x y d]} obj]
     (cond
       (= d :w)
         (assoc obj
-          :x (- x v))
+          :x (- x pxs))
       (= d :e)
         (assoc obj
-          :x (+ x v))
+          :x (+ x pxs))
       (= d :n)
         (assoc obj
-          :y (- y v))
+          :y (- y pxs))
       (= d :s)
         (assoc obj
-          :y (+ y v))
+          :y (+ y pxs))
       :else obj)))
 
 (defn bump-in-wall [obj container]
@@ -36,14 +36,23 @@
       :s (update obj :y #(- (+ cy ch) h 1))
       :? obj)))
 
-(defn move-inside [obj container]
-  (let [moved (moved-object obj)]
+(defn pps->px [gamestate obj]
+  (let [prev (get-in gamestate [:timing :prev])
+        now (get-in gamestate [:timing :now])
+        secs (/ (- now prev) 1000)
+        pps (:pps obj)]
+    (* pps secs)))
+
+(defn move-inside [obj container pxs]
+  (let [moved (moved-object obj pxs)]
     (if (in? moved container)
       moved
       (bump-in-wall obj container))))
 
 (defn move-inside-gamestate [gamestate obj]
-  (let [container (assoc (:dimensions gamestate)
+  (let [pxs (pps->px gamestate obj)
+        container (assoc
+                    (:dimensions gamestate)
                     :x 0
                     :y 0)]
-    (move-inside obj container)))
+    (move-inside obj container pxs)))