Don't draw an error, use watch system

src/engine.clj

@@ -6,15 +6,10 @@
 
 (defonce ^:private last-error (atom nil))
 
-(reset! last-error (ex-info "something bad happened" {:reason "why"}))
-(reset! last-error nil)
-
-(defn- draw-error! [err]
-  (rl/clear-background!* rl/cornflower-blue)
-  (rl/draw-rectangle!* 10 10 300 30 (rl/color-seg 0xFF0000))
-  (rl/draw-text!* "Fix the code then left click anywhere with the mouse" 0 10 16 rl/white)
-  #_(rl/draw-text!* (str err) 50 100 20 rl/white)
-  (rl/draw-text!* "Error" 50 50 40 rl/white))
+(defn clear-error!
+  "Call from the REPL to resume the loop after an error froze it."
+  []
+  (reset! last-error nil))
 
 (defn run-game!
   [{:keys [title width height config-path init input update draw watch-fn]
@@ -24,19 +19,16 @@
   (rl/set-target-fps! 60)
   (let [state (atom (init (edn/read-string (slurp config-path))))]
     (while (not (rl/window-should-close?))
-      (rl/with-drawing!
-        (if @last-error
-          (do
-            (draw-error! @last-error)
-            (when (rl/mouse-button-released? rl/mouse-button-left)
-              (reset! last-error nil)))
+      (if @last-error
+        (Thread/sleep 50)
+        (rl/with-drawing!
           (try
             (swap! state input)
             (swap! state update)
             (draw @state)
             (w/watch! (watch-fn @state))
-            ;; TODO: Have Cider report this exception
             (catch Throwable t
               (println t)
-              (reset! last-error t))))))
+              (reset! last-error t)
+              (w/watch! (merge (watch-fn @state) {:error t})))))))
     (rl/close-window!)))

src/rl.clj

@@ -120,12 +120,14 @@
 
 ;;; --------------------------------------------------- macros
 
-(defmacro with-drawing! [& body]
+(defmacro with-drawing!
+  [& body]
   `(do
+     (begin-drawing!)
      (try
-       (begin-drawing!)
        ~@body
-       (end-drawing!))))
+       (finally
+         (end-drawing!)))))
 
 ;;; --------------------------------------------------- native value allocation