Handle timing data not being available on initial load

src/day8/re_frame/trace/subs.cljs

@@ -251,3 +251,9 @@
     (let [start-of-render (first (filter metam/request-animation-frame? traces))
           end-of-epoch (utils/last-in-vec traces)]
       (metam/elapsed-time start-of-render end-of-epoch))))
+
+(rf/reg-sub
+  :timing/data-available?
+  :<- [:traces/current-event-traces]
+  (fn [traces]
+    (not (empty? traces))))

src/day8/re_frame/trace/view/timing.cljs

@@ -7,14 +7,18 @@
   (:require-macros [day8.re-frame.trace.utils.macros :as macros]))
 
 (defn render []
-
-  [rc/v-box
-   :padding "12px 0px"
-   :children [[rc/label :label "Total Epoch Time"]
-              [rc/label :label (str @(rf/subscribe [:timing/total-epoch-time]) "ms")]
-              [rc/label :label "Animation Frames"]
-              [rc/label :label @(rf/subscribe [:timing/animation-frame-count])]
-              [rc/label :label "Event time"]
-              [rc/label :label (str @(rf/subscribe [:timing/event-processing-time]) "ms")]
-              [rc/label :label "Render/Subscription time"]
-              [rc/label :label (str @(rf/subscribe [:timing/render-time]) "ms")]]])
+  (let [timing-data-available? @(rf/subscribe [:timing/data-available?])]
+    (if timing-data-available?
+      [rc/v-box
+       :padding "12px 0px"
+       :children [[rc/label :label "Total Epoch Time"]
+                  [rc/label :label (str @(rf/subscribe [:timing/total-epoch-time]) "ms")]
+                  [rc/label :label "Animation Frames"]
+                  [rc/label :label @(rf/subscribe [:timing/animation-frame-count])]
+                  [rc/label :label "Event time"]
+                  [rc/label :label (str @(rf/subscribe [:timing/event-processing-time]) "ms")]
+                  [rc/label :label "Render/Subscription time"]
+                  [rc/label :label (str @(rf/subscribe [:timing/render-time]) "ms")]]]
+      [rc/v-box
+       :padding "12px 0px"
+       :children [[:h1 "No timing data available currently."]]])))